Symposium Organizers
Elisabetta Comini Brescia University
Perena Gouma State University of New York-Stony Brook
Luisa Torsi Universita di Bari
George Malliaras Ecole Nationale Supérieure des Mines de St. Etienne
K1: Inorganic Nanowires in Chemical Sensing
Session Chairs
Tuesday PM, April 06, 2010
Room 2007 (Moscone West)
9:00 AM - **K1.1
Metal Oxide Nanowires: Towards Chemical Sensors for Security.
Elisabetta Comini 1 , Guido Faglia 1 , Matteo Ferroni 1 , Andrea Ponzoni 1 , Giorgio Sberveglieri 1
1 , SENSOR, CNR-INFM, Brescia University, Brescia Italy
Show AbstractIncreasing concern on health hazard due to pollution or terrorist attacks encouraged an increasing research effort on gas sensing for real-time monitoring of all aspects of indoor and outdoor environments. Industrial requirements for a sensor are high sensitivity, high selectivity and good stability, together with low fabrication costs. Among all possible technological approaches, conductometric gas sensors based on metal oxide semiconductors are the most promising for the development of low cost and reliable sensors. It has been confirmed that the sensitivity of metal oxide is improved as the crystallite size is decreased down to nanometer scale, thanks to the increased surface to volume ratio and the grains carriers’ depletion. Unfortunately polycrystalline metal oxides suffer from grain coalescence induced by the high operating temperatures required to enhance chemical reactions. This affects sensor stability over long-term operation. On the contrary single crystalline nanosized metal oxide are stable materials and have the dimensions and surface to volume ratio necessary to obtain high chemical sensitivity. The better stoichiometry and greater crystallinity degree compared to polycrystalline oxides make these materials very promising for a better understanding of sensing principles and the development of a new generation of chemical sensors.After the first publication demonstrating the capability of nanowires to detect gaseous species, huge research activity was carried out as demonstrated by the high number of publications and conferences on this topic. The challenge is the integration into sensing platforms necessary for the exploitation in the sensor market. Concerning gas sensing application metal oxide nanowires demonstrate performace suited to detect chemical warfare agents (CWAs) simulants at concentrations close or lower than the toxicity values of the real CWAs. The results obtained on n-type and p-type metal oxide nanowires will be presented together with the possibility to use heterojuctions of metal oxides.
9:30 AM - K1.2
Gigantic Enhancement in Sensitivity Using Schottky Contacted Nanowire Nanosensor.
Te-Yu Wei 1 2 , Ping-Hung Yeh 1 3 , Shih-Yuan Lu 2 , Zhong Lin Wang 1
1 School of Materials Science and Engineering, Gerorgia Institute of Technology, Atlanta, Georgia, United States, 2 Department of Chemical Engineering, National Tsing Hua University, Hsinchu Taiwan, 3 Department of Physics, Tamkang University, Tansui Taiwan
Show AbstractA new single nanowire based nanosensor is demonstrated for illustrating its ultrahigh sensitivity for gas sensing. The device is composed of a single ZnO nanowire mounted on Pt electrodes with one end in Ohmic contact and the other end in Schottky contact. The Schottky contact functions as a “gate” that controls the current flowing through the entire system. By tuning the Schottky barrier height through the responsive variation of the surface chemisorbed gases and the amplification role played by the nanowire to Schottky barrier effect, an ultrahigh sensitivity of 32,000% was achieved using the Schottky contacted device operated in reverse bias mode at 275 oC for detection of 400 ppm CO, which is four orders of magnitude higher than that obtained using Ohmic contact device under the same conditions. In addition, the response time and reset time has been shorten by a factor of 7. The methodology and principle illustrated in the paper presents a new sensing mechanism that can be readily and extensively applied to other gas sensing systems.
9:45 AM - K1.3
Noble Metal/SnO2 Nanocrystals Coated Three Dimensional Nanowire Arrays for Highly Sensitive and Selective Gas Detection.
Jiajun Chen 1 , Kai Wang 1 , Weilie Zhou 1
1 AMRI/Chemistry, Advanced Materials Research Institute/UNO, New Orleans, Louisiana, United States
Show AbstractVertically aligned nanowire arrays provide several key features, including large surface area, high aspect ratio and three-dimensional (3D) architecture for efficient gas molecule absorption and desorption, making them extremely useful in creating highly sensitive gas sensors. In this presentation, we report a fabrication of 3D gas sensors based on noble metal/SnO2 nanocrystals coated well-aligned nanowire arrays. The gas sensors showed responses to some environmental toxic gases, such as NO2 and H2S, down to sub-ppm level at room-temperature. Different noble metal coatings were used to engineer the cross-reactive behaviors of the gas sensors. A device prototype consisting of three gas sensors was fabricated for selective detection of NO2, H2S, NH3, CO and H2 by using principle component analysis (PCA). The high sensitivity and selectivity are ascribed to the synergic effects of 3D device architecture, large surfaces of nanocrystals and activation of noble metal catalysts. The gas sensors with 3D architectures have great potential in gas detection and discrimination at high sensitivity.
10:00 AM - K1.4
A Calibration Method for Nanowire Biosensors to Suppress Device-to-device Variation.
Fumiaki Ishikawa 1 , Hsiao-Kang Chang 1 , Marco Curreli 2 , Rui Zhang 2 , Po-Chiang Chen 1 , Richard Cote 3 , Mark Thompson 2 , Chongwu Zhou 1
1 Electrical Engineering, University of Southern California, Los Angeles, California, United States, 2 Chemistry, University of Southern California, Los Angeles, California, United States, 3 , University of Miami, Miami, Florida, United States
Show AbstractBiological sensors based on nanowire/nanotube field effect transistors (FETs) are one of the most promising applications of bionanotechnology. As a proof of their promising capabilities, nanowire/nanotube sensors have been used to detect a large variety of biological molecules, to monitor enzymatic activities; and to observe cellular signaling/responses, with sensitivity and response time comparable or better than conventional techniques such as ELISA. However, a major challenge holding back the practical application of nanobiosensors to bio-analytical measurements is the device-to-device variation in the device properties such as conductance, threshold voltage, and transconductance. This variation results in unreliable detection, making quantitative analysis difficult, and thus must be addressed to bridge the gap between academic research and practical use of the technology. In this work we have developed an analytical method to calibrate nanowire biosensor responses that can suppress the device-to-device variation in sensing response significantly. The method is based on our discovery of a strong correlation between the biosensor gate dependence (dIds/dVg) and the absolute response (absolute change in current, delta I) in biosensing experiments. In2O3 nanowire based biosensors for streptavidin detection were used as the model system. Studying the liquid gate effect and ionic concentration dependence of strepavidin sensing indicates that electrostatic interaction is the dominant mechanism for sensing response. Based on this sensing mechanism and transistor physics, a linear correlation between the absolute sensor response (delta I) and the gate dependence (dIds/dVg) is predicted and confirmed experimentally. Using this correlation, a calibration method was developed where the absolute response is divided by dIds/dVg for each device, and the calibrated responses from different devices showed drastically reduced coefficient of variance. (from 59% for the absolute response to 25% for the calibrated response) Compared to the common normalization method in which conductance/resistance/current was normalized by the initial value, this calibration method was proved advantageous using a conventional transistor model. The method presented here substantially suppresses device-to-device variation, allowing the use of nanosensors in large arrays to get much more reliable sensing results.
10:15 AM - K1.5
Enhanced H2S Sensing Characteristics of SnO2 Nanowires Functionalized With CuO.
In-Sung Hwang 1 , Joong-Ki Choi 1 , Sun-Jung Kim 1 , Ki-Young Dong 1 , Byeong-Kwon Ju 1 , Jong-Heun Lee 1
1 , Korea University, Seoul Korea (the Republic of)
Show AbstractH2S is a colorless, toxic, and flammable gas produced from the coal, oil, and natural gas industries. Oxide semiconductors such as SnO2, ZnO,WO3, and In2O3 have been explored to detect trace concentrations of H2S. In order to enhance the sensitivity and selectivity to H2S further, various functional or catalytic materials were added. The compositionally modified sensing materials include CuO-doped SnO2, Fe-doped SnO2, Al-doped WO3 and La-doped In2O3. Among those reported materials, CuO-modified SnO2 is acknowledged as one of the most promising materials for the sensitive and selective detection of H2S.The promotion of H2S sensing by doping CuO is being explained by the establishment of a resistive p–n junction between CuO and SnO2 in air atmosphere, the conversion of the semiconducting CuO layer into metallic CuS upon exposure to H2S, and the high chemical affinity of the alkaline CuO toward the acidic H2S gas.In this study, the CuO-functionalized SnO2 nanowire (NW) sensors were fabricated by depositing a slurry containing SnO2 NWs on a substrate and subsequently dropping Cu nitrate aqueous solution. The CuO coating increased the gas responses to 20 ppm H2S up to ∼74-fold. The Ra/Rg value of the CuO-doped SnO2 NWs to 20 ppm H2S was as high as 809 at 300°C, while the cross-gas responses to 5 ppm NO2, 100 ppm CO, 200 ppm C2H5OH, and 100 ppm C3H8 were negligibly low (1.5 ~ 4.0). Moreover, the 90% response times to H2S were as short as 1~2 s at 300 ~ 400°C. The selective detection of H2S and enhancement of the gas response were attributed to the uniform distribution of the sensitizer (CuO) on the surface of the less agglomerated network of the SnO2 NWs.
K2: Organic Materials in Chemical Sensing
Session Chairs
Tuesday PM, April 06, 2010
Room 2007 (Moscone West)
11:00 AM - **K2.1
Organic and Carbon Nanotube Transistor Sensors.
Zhenan Bao 1
1 , Stanford University, Stanford, California, United States
Show AbstractOrganic semiconductor materials and carbon nanotubes are interesting alternatives to inorganic semiconductors in applications where low cost, flexible or transparent substrates, and large area format is required. Currently they have been incorporated into thin-film transistors, integrated display driver circuits, photovoltaics and radio frequency identification tags. In this talk, I will present recent results on materials design and fabrication of chemical and biological sensors using organic and carbon nanotube transistors. Approaches to reach high sensitivity and selectivity are discussed.
11:30 AM - K2.2
Solution Processed Chemical Sensors from Metallotetrabenzoporphyrin Organic Thin Film Transistors.
James Royer 1 , Sangyeob Lee 1 , Noboru Ono 3 , Jerzy Kanicki 2 , Andrew Kummel 1
1 Chemistry, UCSD, San Diego, California, United States, 3 Chemistry, Ehime University, Bunkyo-cho 2-5, Matsuyama, Japan, 2 Electrical Engineering and Computer Science, University of Michgan, Ann Arbor, Michigan, United States
Show AbstractA solution processed chemical sensor based on metallotetrabenzoporphyrin thin film transistors (TFTs) is reported. Metallotetrabenzoporphyrins (TBPs) are converted from a soluble tetrabicycloporphyrin precursor which is spin coated and then thermally annealed to form polycrystalline TBP films which exhibit p-type semiconductor characteristics and hole mobilities greater than 0.01 cm2/Vs. The sensor properties are comparable to similar organic TFT devices fabricated using ultra-thin vacuum evaporated films of metal phthalocyanines (MPcs); for ideal films, MPcs and TBPs have nearly identical gas adsorption properties since they both have metal atoms coordinated to four aromatic nitrogens. By operating the TBP sensors using a pulsed gate, the sensor current drift can be limited to less than 0.05% per hour. TBP TFT sensors exhibit high sensitivity (<100ppb detection limit) to the nerve agent simulant dimethyl methylphosophonate (DMMP), demonstrating the potential for technologically relevant sensing applications. The TBP sensors show over 100 times difference in response between small alcohols (e.g. methanol) and DMMP but nearly identical response to similar MPc vapor deposited sensors, demonstrating the inherent selectivity based on the interactions of the analyte with the central core the TBP molecule. TBPs can also be tailored for array based sensing by changing the metal atom or peripheral substituents, making TBPs an attractive candidate for low cost, low power chemical sensor applications.
11:45 AM - K2.3
NO2 Detection Sensitivity of SiC and Epitaxial Graphene on SiC.
Goutam Koley 1 , Muhammad Qazi 1 , Mvs Chandrashekhar 1 , Waliullah Nomani 1 , Virgil Shields 2 , Michael Spencer 2
1 Electrical Engineering, University of South Carolina, Columbia, South Carolina, United States, 2 , Cornell University , Ithaca, New York, United States
Show AbstractSiC is one of the commonly materials used in high temperature gas sensors in catalytic converter today. Most SiC gas sensors are in the form of schottky diodes or capacitive MIS devices where target molecules would dissociate on the catalyst metal surface and create a change in potential barrier across the interface. Despite its widespread application in high temperature gas sensors, SiC is still used as substrate material as gaseous adsorption on thin film semiconductor surfaces does not change the conductance of the overall film significantly. Consequently, research reports on molecular adsorption on SiC thin films and related electronic property changes are scarce. Nevertheless, theoretical calculations involving SiC nanotubes show that they can bind gaseous molecules and also reports on experimental evidences of H2 detection utilizing resistance change of 3C-SiC thin films are present. In this work, microcantilever based electrostatic force microscopy is applied to find out the surface work function (SWF) changes of wide area SiC thin films with the adsorption of NO2 molecules. Any sensitivity variation between Si and C faces of SiC and also between undoped and doped SiC is also discussed.The C-face of 6H-SiC shows an SWF change of 100 meV in 300 s with 15 ppm NO2 flow, while the Si-face shows better sensitivity with an SWF change of 139 meV in the same time. This difference is significant, and likely originates from the non-equivalence of the two faces of 6H-SiC in terms of surface free energy and surface polarization. Results of the SWF experiments on highly n+ doped 6H-SiC shows that for n+-doped 6H-SiC, the SWF of the C-face was found to increase much more than the Si-face, showing correspondingly higher NO2 sensitivity. Additionally, potentiometric measurements were performed on epitaxial graphene layers grown on SiC substrates to investigate whether a few mono-layers of graphene has any different effect on the sensitivity of the surface towards NO2. SWF changes of epitaxial graphene grown on both the Si and C-faces of 6H-SiC in response to 15 ppm NO2 were measured. Though we did not find any statistically significant variations in the rise response of the graphene surfaces, the decay of the SWF changes was found be slow in comparison to that of wide area SiC indicating that NO2 creates stronger chemical bond on graphene. We further measured the conductance change of epitaxial graphene layers with the flow of 15 ppm NO2 using Indium contacts. From the percentage conductance change of graphene grown on Si and C-faces of SiC, we find surprisingly that the adsorption of NO2 increases the conductance of the graphene grown on C-face whereas the conductance decreases on the other face. We believe this is due to the ambipolar nature of the charge carriers in graphene.
12:00 PM - K2.4
Hybrid Organic/Inorganic Ambipolar Thin Film Transistor Sensors.
Soumya Dutta 1 , Shannon Lewis 1 , Ananth Dodabalapur 1
1 Microelectronic Research Centre, University of Texas at Austin, Austin, Texas, United States
Show AbstractThin film transistor (TFT) based sensors are a promising approach to sense the chemical and biological species, ionic liquids, etc. In organic TFT chemical vapor sensors, numerous studies have shown that trapping of charges by polar analytes at grain boundaries and other device interfaces often results in a decrease in drain current (Id) [1-2]. An important limitation of organic TFT chemical sensors is that the ordinary bias stress effect ( which is a decrease in drain current with time due to charge trapping) in the absence of analytes is indistinguishable from drain curremt decrease due to analytes. On the other hand, in inorganic TFT sensors, the drain current increases substantially upon exposure to such polar analytes under highly saturated vapor condition at room temperature [3]. The drawback of inorganic TFT, on the other hand, is poor response to chemical analyte under unsaturated vapor condition at room temperature. In prior work, we reported on the four-terminal field-effect sensing device [4]. In this work, a novel hybrid ambipolar transistor structure, using zinc oxide as n-type inorganic semicondcutor and pentacene as p-type organic counterpart will be examined as a chemical vapor sensor. The device operates in four different modes depending on the combination of gate voltage and drain-source voltage. These are as follows: n-channel accumulation mode, p-channel diode mode, n-channel diode mode and p-channel accumulation mode. The p-channel accumulation mode behaves as typical organic TFT chemical sensors with decrease in Id upon delivering ethanol vapor. In contrast, n-channel diode mode responds quite differently with the same polar analyte. The diode current increases upon delivering analyte. The possible reason for the increase diode current is the trapping of holes (in the organic semiconductor layer) by the analyte molecules to perturb the electrostatic environment of the device, resulting in an increase in diode current. The base line current value is observed to be stable as the current mainly contributed by the n-channel zinc oxide, which is much more stable than the organic counterpart, whereas the response is solely due to the interaction between the polar analytes and the organic semiconductor. In this way, we separate the sensing and charge transport areas of the device and get a more stable response as a result. Stable responses are very important as we can then use amplifying circuits to enhance the magnitude of the response.References:[1]L. Torsi and A. Dodabalapur, Anal. Chem. 77, 380A (2005).[2]B. Crone, A. Dodabalapur, A. Gelperin, L. Torsi, H. E. Katz, A. J. Lovinger, and Z. Bao, Appl. Phys. Lett. 87, 2229 (2001).[3]S. Dutta and A. Dodabalapur, Sens. Actuator B (2009) [In press; doi:10.1016/j.snb.2009.07.056 ][4]Yeon Taek Jeong, B. H. Cobb, S. D. Lewis, A. Dodabalapur, S. Lu, A. Facchetti, and T. J. Marks, Appl. Phys. Lett. 93, 133304 (2008)
12:15 PM - K2.5
Evaluation of the Vapor and Chemical Sensing Mechanism for Organic Field Effect Transistors.
Davianne Duarte 1 , Ananth Dodabalapur 1
1 Electrical Engineering, University of Texas Austin, Austin, Texas, United States
Show AbstractField effect transistors (FETs) based on organic semiconductors have exhibited much promise for vapor and chemical/biochemical sensing. The initial sensing work for organic FETs was based on vapor sensing with studies suggesting the grain boundaries are key in determining sensor response [1]. Although work has been done with organic FETs under aqueous conditions for chemical sensing [2,3], the sensing mechanism by which an aqueous absorbed species produces a change in the OFET characteristics is still not well understood. The high polarizability of organic semiconductors makes them excellent sensors when they interact with dipoles such as polar analytes, ions, etc. Studies in our group comparing typical organic semiconductors such as pentacene with inorganic semiconductors such as zinc tin oxide clearly demonstrates the vapor sensing behavior of OFETs are related to charge trapping produced by polar analytes. This is not seen in inorganic thin film transistors. A previous proposal for the aqueous sensing mechanism includes one similar to vapor sensing where diffusion of the analyte to the semiconductor/dielectric interface results in an influence in the charge transfer via trapping and doping[3]. Other possibilities include perturbation of the charge channel by dipole fields and alteration of the space charge distribution at the organic semiconductor surface. In this work a comparison of the vapor and chemical sensing mechanisms was conducted utilizing copper phthalocyanine and oligothiophene FETs to elucidate on the physics occurring during sensing; with a closer analysis of data parameters such as shifts in the threshold voltage, mobility and effective carrier concentration. References:1. Crone, B.; Dodabalapur, A.; Gelperin, A.; Torsi, L.; Katz, H.E.; Lovinger, A. J. Applied Physics Letters 2001 78, 2229.2. Someya, T.; Dodabalapur, A; Gelperin, A.; Katz, H.E.; Bao, Z. Langmuir 2002, 18, 5299.3. Roberts, M.E.; Mannsfeld, C.B.; Queralto, N.; Reese, C.; Knoll, W.; Bao, Z. PNAS 2008, 105, 12134.
12:30 PM - K2.6
Nitroaromatic Vapor Sensing Utilizing Organic Filed-effect Transistors.
Thomas Dawidczyk 1 , Jia Huang 1 , Jia Sun 1 , Byung Jun Jung 1 , Howard Katz 1
1 Materials Science, Johns Hopkins University, Baltimore, Maryland, United States
Show AbstractOrganic field-effect transistors (OFETs) have potential applications in display drivers, radio frequency identification (RFID) tags, pressure mapping elements, and sensors. Some OFETs are environmentally sensitive making them attractive candidates for vapor sensing. Receptors can be incorporated to further enhance the sensitivity and/or selectivity. Analytes can bind to the receptors and alter the current flowing across the channel of the transistor, resulting in a change in source current for a drain and gate voltage. Electron deficient analytes such as trinitrotoluene (TNT) and dinitrotoluene (DNT), a by-product of TNT manufacturing, can potentially dope p-type (hole carrying) semiconductors and quench n-type (electron carrying) semiconductors. This doping/quenching effect is limited/enhanced by the dipole moment of the analyte, which will always decrease the current because of local electric fields. To further enhance the response time of the OFETs the film thickness should be minimized, so that the most of the film consists of the conduction channel. In this presentation, we report responses of varied OFETs to DNT and TNT. Small n-channel molecules used were N’N’-bis(pentafluoro phenylmethyl) naphthalenete-1,4,5,8-tracarboxylic diimide (C2PhF5 NTCDI ) and N,N’- bis (3,5-bis (trifluoromethyl) phenylmethyl) naphthalene-1,4,5,8-tetracarboxylic diimide (bis-CF3 NTCDI). 5,5’-bis(4-hexylphenyl)-2,2’-bithiophene (6PTTP6), 5,5’-bis(4-(6-hydroxyhexyloxy)phenyl)bithiophene (HO6OPT), alpha-sexithiophene, and 1,4 bis(5-phenylthiophen-2-yl)benzene (PTPTP) were used as p-channel small molecules; poly(3,3””-didodecylquaterthiophene) (PQT 12) was used as a p-type polymer. For p-type small molecule semiconductors the current decreased upon exposure to DNT, but the incorporation of a receptor actually increased the current when exposed to DNT. Electron conducting devices and the p-type polymer showed decreased current upon exposure to DNT, with the mobility and threshold voltage of each having a varying response. The varied responses show the ability to create an array that can sense for an analyte that will have its own fingerprint, with different responses to nitroaromatics.
12:45 PM - K2.7
Organic Thin-film Transistors for pH Detection.
Monia Demelas 1 2 , Massimo Barbaro 1 , Annalisa Bonfiglio 1 2
1 Dept. of Electric and Electronic Engineering, University of Cagliari, Cagliari Italy, 2 , S3-INFM-CNR, Modena Italy
Show AbstractA novel, flexible and ductile organic field-effect transistor (OFET) able to detect pH changes in chemical solutions has been realized and successfully tested. With respect to other organic pH sensors, which are based on an ISFET-like structure where the solution is deposited on top of the dielectric thus requiring proper choice of materials, in our approach the organic transistor is completely separated from the sensing active area and its gate is left floating. The gate is elongated and superposed on a fourth electrode (control-gate) to form a planar capacitor. Such control-gate is used to bias the transistor by capacitive coupling. The floating-gate is functionalized by deposition of a layer of thio-amines able to protonize proportionally to the pH value of the solution. A change in the pH of the solution in contact with the active area causes a change in the electric charge immobilized on it thus modifying the conducting properties of the channel. The structure does not need an Ag/AgCl counter-electrode since the control-gate is not in contact with the solution. Moreover, the sensing mechanism does depend on the choice of the dielectric and semiconductor material since the working principle is based on charge separation in the metal induced by the electric field. This structure also simplifies the realization of the fluidics since all the contactable electrodes (drain, source and control-gate) are on the same side of the substrate. With the same structure, other chemical species may be detected provided that a proper functionalization procedure is adopted.The device was realized on a PET sheet where a gold floating-gate electrode was patterned by a shadow mask. The electrode has a peculiar shape with a round active area for sensing purposes and a long finger acting as the actual gate of the transistor. The PET sheet was coated with parylene leaving exposed the active area. Parylene on the gate finger acts as dielectric for the OFET. Gold source/drain and control-gate electrodes where photolithographically patterned on the structure. The organic semiconductor (pentacene) was evaporated on the device in a bottom contact structure. Two transistors, sharing the same source and control-gate, were realized side by side in order to make differential measures. Finally, the floating-gate was functionalized with thio-amines.Experimental results have proved the working principle. The sensor active area was sequentially plunged in solutions with decreasing values of pH while the reference active area was always plunged in a solution at pH=7. The resulting drain currents were measured and relative percentage changes with respect to the initial values were computed and plotted. A decrease of more than 70% in the drain current of the sensor was obtained for a decrease of pH down to 2.5 while the output of the reference transistor remained unchanged. The process is reversible and the drain current level is restored when the initial solution is used.
K3: Inorganic Materials in Chemical Sensing I
Session Chairs
Tuesday PM, April 06, 2010
Room 2007 (Moscone West)
3:00 PM - K3.1
A DFT-based Insight into the Chemoresistive Sensing of Light Alkanes.
Mauro Epifani 1 , Joan Prades 2 4 , Elisabetta Comini 3 , Albert Cirera 2 , Pietro Siciliano 1 , Guido Faglia 3 , Joan Morante 2 4
1 Istituto per la Microelettronica e Microsistemi, Consiglio Nazionale delle Ricerche, Lecce Italy, 2 EME/XaRMAE/IN2UB, Departament d’Electrònica, Universitat de Barcelona, Barcelona Spain, 4 , Institut de Recerca en Energia de Catalunya (IREC), Barcelona Spain, 3 Dipartimento Chimica e Fisica per l’Ingegneria e i Materiali, CNR-INFM and Università di Brescia, Brescia Italy
Show AbstractThe improved gas-sensing properties of metal oxide nanocrystals are attributed to size effects in the interaction with the gaseous analytes, but the surface features of the sensing materials must also be considered for achieving a thorough understanding of the sensing performances. In this work we provide a basis for understanding the light alkanes (CnH2n+2, n ≤ 4) sensing by SnO2 nanocrystals prepared with a low temperature chemical route. Our approach consisted in first highlighting the main features of the alkane sensing tests carried out with SnO2 nanocrystals. We observed that: ai) the presence of humidity generally lowered the response with respect to dry air; b) the best operating temperature was 300 °C for all gases, when the response for propane and butane ranges over 2 orders of magnitude; c) the response did not follow a monotonic trend with increasing the alkyl chain length. For methane it was always the lowest, but it was maximum for propane. The response could reach up very high values for propane and butane, but even for methane appreciable responses were obtained for as low as 5 ppm concentration. It must be remarked that in other works comparable responses were obtained only with much higher gas concentrations.The second step was to consider the experimental surface chemistry of the sensing material for building up a model of the alkane-surface interaction. In the model, we considered, on the alkane side, that the generally supposed, rate-limiting first step in the sensing mechanisms is a dehydrogenation. On the SnO2 side, a completely reduced surface was used in the model, as indicated by experimental data. The reduced surface was modified by ionosorbed atomic oxygen onto the tin sites, as expected in the experimental conditions of the sensing tests. Finally, the resulting model was used for an ab initio DFT modelling of the energy balance involved in the supposed reaction. The model correctly predicts the trends of the gas response in the experimental tests, and in particular the inversion of the response between propane and butane. The latter is shown to be a peculiar consequence of the highly reduced surface of the SnO2 nanocrystals.
3:15 PM - K3.2
Nonaqueous Sol-gel Routes to Metal Oxides: Versatile Preparation Methods of Nanopowders and Films for Gas Sensing Applications.
Nicola Pinna 1 2 , Giovanni Neri 3
1 Department of Chemistry and CICECO, University of Aveiro, Aveiro Portugal, 2 World Class University (WCU) program of Chemical Convergence for Energy and Environment (C2E2), Department of Chemical and Biological Engineering, Seoul National University, Seoul Korea (the Republic of), 3 Deptartment of Industrial Chemistry and Materials Engineering, University of Messina, Messina Italy
Show AbstractIn order to sustain the positive trend observed in the last years in the growth of solid state gas sensors market and provide new applications in relevant technological fields, improvements in the sensors properties are required. Especially, better sensitivity and selectivity, faster response, together with low power consumption and high device reliability are sought. The sensor performance can be enhanced by decreasing the grain size of the sensing material.In this respect, our recent works were focused on the synthesis of semi-conducting metal oxides by surfactant-free nonaqueous sol-gel approaches, involving the reaction of metal oxide precursors in organic solvents (e.g. benzyl alcohol) at moderate temperature and pressure [1,2]. Compared to aqueous sol-gel chemistry and surfactants-assisted routes, our non-aqueous sol-gel routes offer advantages such as high crystallinity of the as synthesized oxides, high purity, high reproducibility and the ability to control the crystal/film growth. In fact, nonaqueous sol-gel approaches were found particularly suitable for the preparation of metal oxide nanocrystals, ordered organic-inorganic hybrid materials and low dimensional metal oxide structures, such as nanorods, nanowires, etc. The coating of various substrates, including carbon nanotubes, with metal oxide films by using nonaqueous routes in conjunction with the ALD (Atomic Layer Deposition) technique was also recently reported [3,4,5].The synthesis and characterization of these materials as well as their sensing properties for the detection of important gases such as carbon monoxide, ethanol, ammonia, nitrogen dioxide and oxygen will be presented.References:[1] Pinna, N. & Niederberger, M. Surfactant-free nonaqueous synthesis of metal oxide nanostructures, Angew. Chem. Int. Ed., 2008, 47, 5292-5304 [2] Niederberger, M. & Pinna, N. Metal oxide nanoparticles in organic solvents: Synthesis, formation, assembly and application, Springer, 2009 [3] Rauwel, E.; Clavel, G.; Willinger, M.-G.; Rauwel, P. & Pinna, N. Non-aqueous routes to metal oxide thin films by atomic layer deposition, Angew. Chem., Int. Ed., 2008, 47, 3592-3595 [4] Willinger, M.; Neri, G.; Rauwel, E.; Bonavita, A.; Micali, G. & Pinna, N. Vanadium oxide sensing layer grown on carbon nanotubes by a new atomic layer deposition process, Nano Lett., 2008, 8, 4201-4204 [5] Willinger, M.; Neri, G.; Bonavita, A.; Micali, G.; Rauwel, E.; Herntrich, T. & Pinna, N.The controlled deposition of metal oxides onto carbon nanotubes by atomic layer deposition: Examples and a case study on the application of V2O4 coated nanotubes in gas sensing, Phys. Chem. Chem. Phys., 2009, 11, 3615-3622
3:30 PM - K3.3
Processing-microstructure-properties Correlation of Nanostructured Metal Oxide Gas Sensors Produced by Electrospinning.
Avner Rothschild 1 , Osnat Landau 1 , Itai Kamienchick 1 , Eyal Zussman 2 , Il-Doo Kim 3
1 Materials Engineering, Technion - Israel Institute of Technology, Haifa Israel, 2 Mechanical Engineering, Technion - Israel Institute of Technology, Haifa Israel, 3 Center for Energy Materials Research, KIST - Korea Institute of Science and Technology, Seoul Korea (the Republic of)
Show AbstractIn recent years, significant progress has been achieved in developing highly sensitive metal oxide gas sensors using novel 1D and quasi-1D nanostructured architectures. Among the different strategies for producing such sensors, electrospinning offer several advantages including ease of fabrication and versatility. Our first report on nanocrystalline TiO2 gas sensors produced by electrospinning demonstrated excellent performance in terms of gas sensitivity, reversibility, and response time.1 Sensitivity levels as high as 833% (ΔR/R0) were observed upon exposure to 500 ppb of NO2 in air, indicating ability to detect ultra-low gas traces at the sub-ppb level. These merits were attributed to the unique nanostructured fibrillar morphology of the sensors, and in particular to their bimodal pore size distribution with large voids (on the scale of sub-micron to micron) that facilitate fast gas transport in and out of the sensing layer and small mesopores that contribute to the high surface to volume ratio of this layers (surface area on the order of 100’s of m2/g). This unique combination of large and small pores enables to achieve fast gas distribution in mesoporous thick layers, providing an elegant and effective solution to one of the greatest challenges in metal oxide gas sensors. Our current research in this area focuses on detailed investigation of the correlation between processing, microstructure, and gas sensing properties of electrospun metal oxide sensors with the aim of achieving even higher sensitivity levels.2 In this paper we shall report on our progress in tailoring the morphology and pore size distribution by controlling the sol-gel chemistry, electrospining conditions, and post-deposition thermo-compression and calcination processes.1 I.D. Kim, A. Rothschild, B. H. Lee, D.Y. Kim, S. M. Jo, and H. L. Tuller, Nano Lett. 6 (2006) 2009.2 O. Landau, A. Rothschild, and E. Zussman, Chem. Mater. 21 (2009) 9–11.
3:45 PM - K3: Inorganic
BREAK
K4: Biosensors
Session Chairs
Tuesday PM, April 06, 2010
Room 2007 (Moscone West)
4:15 PM - **K4.1
New Amorphous Oxide-based ISFETs for Biosensor Applications.
Elvira Fortunato 1 , Joana Pinto 1 , Rita Branquinho 1 , Pedro Barquinha 1 , Rodrigo Martins 1
1 Materials Science, FCT-UNL, Caparica, na, Portugal
Show AbstractCost-effective diagnosis in resource-limited settings remains a critical global health challenge. In order to have reliable diagnostic tools for the rapid detection and identification of pathogens, new methods allowing label-free and real time measurement of simultaneous interactions must be developed. Besides that rapid and accurate detection of biomolecules is important for medical diagnosis, pharmaceuticals, homeland security, food quality control, and environmental protection. Ion Sensitive Field Effect Transistors (ISFETs) have proven to be a suitable tool for the detection of pH and biomolecular interactions. The possibility of miniaturization and the specificity of the biolayer are some of the advantages that make them suitable for applications in areas like biomedicine, pharmaceutical or even bioterrorism prevention.The use of amorphous semiconductor oxides in thin film transistors as an alternative to silicon represents a great advantage in the production of solid state devices since they can be produced at low temperatures and have been shown to present high electronic performances [2]. Room temperature deposition by radiofrequency (rf) magnetron sputtering allows the use of low cost and disposable substrates. These transistors can therefore be used as transducers for biorecognition.We present the primary results for a set of Extended Gate ISFETs (EG-FETs) based on amorphous semiconductor oxide (a compound mixture of Ga2O3:In2O3:ZnO), deposited by rf sputtering in a bottom gate configuration. Substrates consisting of Si/SiO2 and ITO/ATO films were used. Tantalum oxide films were deposited also through reactive sputtering on top of the gate dielectric or directly over the gate electrode, resulting in different sensitive layers for the EG-FETs. The electric performance of these devices was studied with a semiconductor analyser, applying the gate voltage through a reference electrode. Several buffer solutions were used in order to evaluate the sensitivity to pH. The stability and reproducibility of the devices to pH changes will also be discussed.
4:45 PM - K4.2
Synthesis and Biological Functionalization of Non-toxic and Emissive Semiconductor Nanocrystals.
Preston Snee 1 , Aashima Ghai 1 , Chiun-Teh Ho 1 , Ali Jawaid 1 , Leah Page 1 , Hongyan Shen 1 , Xi Zhang 1
1 Chemistry, University of Illinois, Chicago, Chicago, Illinois, United States
Show AbstractEmissive semiconductor NCs have a significant potential for use in experiments that answer important questions in biology and for energy production. However, the practical implementation of these materials requires mitigation of the inherent toxicity of the often studied cadmium chalcogenide systems. To this end, our group has made significant efforts to both dope highly non-toxic ZnSe NCs with emissive phosphors and explore other, generally unexamined, material compositions for synthesizing emissive NCs.With these materials in hand, we are presently studying methods for biologically functionalizing water soluble, emissive NCs. Unfortunately, traditional chemical methods to create stable bonds between water soluble NCs and biological vectors either have very poor yields or destroy the NC material for reasons which are not entirely clear. Our group will present three novel strategies that result in the formation of functional material systems in high yield with no loss of NC starting materials. We have also synthesized a variety of chemical and biological sensors using these strategies.
5:00 PM - K4.3
Modification of Nanostructured Thin Films by Ion-milling for Use in Biochemical Sensing Applications in Aqueous Environments.
Jonathan Kwan 1 , Jeremy Sit 1
1 Electrical and Computer Engineering, University of Alberta, Edmonton, Alberta, Canada
Show AbstractNanostructured materials are currently being integrated with many technologies to exploit their high surface area characteristic. They find application in a wide variety of fields such as solar cells, catalysis and sensors. However, in applications involving exposure to aqueous environments, such nanostructures deform due to capillary forces. In the case of vertically oriented nanorods, they tend to form islands of bundled nanorods, drastically reducing the effective surface area. We present the use of modified nanostructured thin films fabricated by the glancing angle deposition (GLAD) technique. GLAD allows direct control over the porosity and surface area of the films and can be used with a wide range of materials. In this work, the initial films were SiO2 vertical post nanostructures fabricated on silicon substrates. Ion-milling at normal incident angles redistributed film material from the top of the nanostructures to the bottom. The vertical post films became shorter, smoother and more uniform in size along their length. This helped reduce or eliminate the capillary bundling of vertical posts. The effect of the film thickness, ion-mill exposure time and viscosity of the aqueous environment on this bundling effect was studied. The films were characterized with image analysis techniques using top-down images taken with a scanning electron microscope. The results demonstrate that GLAD vertical post thin films can be modified to prevent deformation under aqueous environments while maintaining their high surface area and porosity.
5:15 PM - K4.4
Palladium Thin Film and Nanoparticles on Silicon by Galvanic Displacement as a Promising Platform for Electrochemical Biosensing.
Albert Gutes 1 , Ian Laboriante 1 , Carlo Carraro 1 , Roya Maboudian 1
1 Chemical Engineering, UC Berkeley, Berkeley, California, United States
Show AbstractA new approach for the development of reproducible, reliable glucose nanobiosensor with fast response time is presented. The process relies on the use of galvanic displacement on silicon for the selective deposition of palladium nanoparticles of a mean diameter of 80 nm surrounded by a thin Pd nanofilm. The formed nanostructure presents excellent electrical behavior, proving extremely effective in the electrochemical catalysis of hydrogen peroxide reduction at 0.0V. The use of this low applied potential avoids possible current interference signals in presence of ascorbic acid, the typical interference in real samples determinations, such as blood tests or fruit juices. The produced nanoPd-Si substrates were tested as hydrogen peroxide sensors prior to the deposition of a polyvynil alcohol (PVA) membrane with trapped glucose oxidase (GOx) in the polymeric matrix. Good linear response towards H2O2 was achieved in the 1-14 micromolar range. Calibration curves for glucose, as well as interference studies for ascorbic acid at the typical blood concentration levels are presented. The results encourage future use of the developed substrates for other biosensing purposes using palladium or other noble metal nanoparticles as electrocatalytic substrates. Simplicity in the fabrication process, combined with the existing sensor industry using silicon technology opens the possibility to mass production of thus-presented microsensing devices.
5:30 PM - K4.5
Biological Sensing and Interface Design in Gold Island Film Based Localized Plasmon Transducers.
Tatyana Bendikov 1 2 , Aharon Rabinkov 3 , Tanya Karakouz 1 , Tamar Yelin 1 , Alexander Vaskevich 1 , Israel Rubinstein 1
1 Materials and Interfaces, Weizmann Institute of Science, Rehovot Israel, 2 Chemical Research Support, Weizmann Institute of Science, Rehovot Israel, 3 Biological Services, Weizmann Institute of Science, Rehovot Israel
Show AbstractIn recent years we have developed a new kind of optical transducers based on discontinuous, island-type gold films prepared by evaporation on transparent substrates (e.g., glass). The transduction is based on the sensitivity of the localized surface plasmon resonance (LSPR) absorption band to changes in the effective refractive index in the immediate vicinity of the metal islands [1]. Such systems can be used as LSPR biosensors by immobilizing biological receptor layers on the Au island surface. Biorecognition is performed by exposing the transducer to specific analyte biomolecules and monitoring molecular binding to the receptor layer as change in the transducer optical response [2]. In the present work LSPR spectroscopy was applied to monitoring of specific binding in two biological systems: protein-protein interactions and DNA sensing.Protein recognition interfaces were prepared by stepwise functionalization of island-type (5 nm nominal thickness) or continuous (20 nm) Au films to carry carboxylate functionalities that covalently link to the amino groups of the protein. In other experiments proteins were directly adsorbed on the Au surface. Antigen-derivatized (with Rabbit or Mouse IgG) Au island films prepared in this manner were used as recognition surfaces for selective sensing of antibody (Anti-Rabbit or Anti-Mouse IgG) binding, distinguishing between specific and nonspecific interactions [3]. HRSEM and AFM imaging enabled direct visualization of the two protein binding steps, showing the difference between specific and nonspecific binding. In addition, contact mode AFM was used for obtaining biological layer thicknesses.LSPR spectroscopy was also used for monitoring DNA hybridization on the transducer surface, distinguishing between binding of complementary and non-complementary strands, in agreement with HRSEM and AFM imaging results.References1. I. Ruach-Nir, T. A. Bendikov, I. Doron-Mor, Z. Barkay, A. Vaskevich, I. Rubinstein, Silica-Stabilized Gold Island Films for Transmission Localized Surface Plasmon Sensing, Journal of the American Chemical Society, 129, 84-92, 2007 and references therein.2. A. Vaskevich, I. Rubinstein, Localized Surface Plasmon Resonance (LSPR) Spectroscopy in Biosensing, in Handbook of Biosensors and Biochips, R. Marks, D. Cullen, C. Lowe, H.H. Weetall, I. Karube (Editors), Wiley: Chichester, 2007.3. T. A. Bendikov, A. Rabinkov, T. Karakouz, A. Vaskevich, I. Rubinstein, Biological Sensing and Interface Design in Gold Island Film Based Localized Plasmon Transducers, Analytical Chemistry, 80, 7487-7498, 2008.
K5: Poster Session: Functional Materials for Chemical Sensing II
Session Chairs
Tuesday PM, April 06, 2010
Exhibition Hall (Moscone West)
6:00 PM - K5.1
Towards the Artificial Nose for the Detection of Carbonyl Species.
Bhavana Deore 1 , Danial Wayner 1 , Duncan Stewart 1 , Gerardo Diaz-Quijada 1
1 Steacie Institute for Molecular Sciences, National Research Council, Ottawa, Ontario, Canada
Show AbstractDue to electronic charge delocalization, conjugated polymers present a suitable platform for the development of new sensors that rely on changes in electrical conductivity when interacting with analytes. The main advantage of this platform is based on the ability to partially tune the response of the sensor by changing the chemical structure of the polymer. The present work presents proof-of-concept chemical sensors that incorporate a chemical recognition site for the detection of common indoor air polluting carbonyl species such as aldehydes and ketones. Emphasis is placed on the detection of formaldehyde which poses major concerns in Indoor Air Quality (IAQ). By taking advantage of the differential response of various polymers towards analytes in question, sensor elements can be implemented in an array format to give an electronic nose.
6:00 PM - K5.10
Sub-nano-gram Mass Measurements on Plasmonic Nanoparticles for Temperature-programmed Thermal Analysis.
Chaoming Wang 1 , Minghui Zhang 2 , Haining Wang 3 , Shengli Zou 3 , Ming Su 1
1 Department of Mechanical, Materials, and Aerospace Engineering, University of Central Florida, Orlando, Florida, United States, 2 Department of Materials Chemistry, Nankai University, Tianjin China, 3 Department of Chemistry, University of Central Florida, Orlando, Florida, United States
Show AbstractUltrasensitive thermo-gravimetric analysis of adsorbed organic molecules has been achieved on an ordered array of gold nanoparticles used as a novel plasmonic nano-balance. The extinction peaks of the resonating surface plasmon of nanoparticle arrays shift upon loading molecules, and return to original position after a linear temperature rise process. A good correlation exists between the film thickness and magnitude of peak shifts. The detection range of plasmonic nano-balance derived from our results can reach sub-nano-gram level (1.8 pico-gram on an active area of 100 µm2), which is much lower than those of mechanical or electronic mass-measuring devices. Such high mass sensitivity, combined with the remote detection capability and high temperature operation of plasmonic sensors, allows the in-situ detections of the masses of loaded material and thermally desorbed molecules.
6:00 PM - K5.12
Highly Sensitive and Selective Room Temperature Gas Sensors Based on Surface Modified Indium Oxide Nanoparticles.
Kun Yao 1 , Daniela Caruntu 1 , Charles O'Connor 1 , Weilie Zhou 1
1 AMRI/Chemistry, Advanced Materials Research Institute/UNO, New Orleans, Louisiana, United States
Show AbstractHomogenous In2O3 nanoparticles (NPs) with diameters in the range of 6~10 nm were synthesized by a chemical solution method and well assembled into film on Si/SiO2 substrate for gas detection. The sensor prototype was fabricated and demonstrated ultra high sensitivity to H2S and NO2 down to part per billion (ppb) levels at room temperature. Different parameters for gas sensing were then systematically investigated in terms of electrodes gap, In2O3 NP film thickness, and surface modification by noble metals. In addition, multiple sensors fabricated for selective detection will also be discussed in this presentation. The NPs sensors with easier assembly, larger size, more homogeneity and structure stability, and higher surface/volume ratio have great potential for homeland security as well as industrial application.
6:00 PM - K5.14
Computational Screening of Large Molecule Adsorption by Metal-organic Frameworks.
Jeffery Greathouse 1 , Mark Allendorf 2
1 , Sandia National Laboratories, Albuquerque, New Mexico, United States, 2 , Sandia National Laboratories, Livermore, California, United States
Show AbstractGrand canonical Monte Carlo simulations were performed to investigate trends in low-pressure adsorption of a broad range of organic molecules by a set of metal-organic frameworks (MOFs). The organic analytes considered here are relevant to applications in chemical detection: small aromatics (o-, m-, and p-xylene), polycyclic aromatic hydrocarbons (naphthalene, anthracene, phenanthrene), explosives (TNT and RDX), and chemical warfare agents (GA and VM). The framework materials included several Zn-MOFs (IRMOFs 1-3, 7, 8), a Cr-MOF (CrMIL-53lp), and a Cu-MOF (HKUST-1). Many of the larger organics were significantly adsorbed by the target MOFs at low pressure, which is consistent with the exceptionally high isosteric heats of adsorption (25 kcal/mol – 60 kcal/mol) for this range of analyte. At a higher loading pressure of 101 kPa, the Zn-MOFs show a much higher volumetric uptake than either CrMIL-53-lp or HKUST-1 for all types of analyte. Within the Zn-MOF series, analyte loading is proportional to free volume, and loading decreases with increasing analyte size due to molecular packing effects. CrMIL-53lp showed the highest adsorption energy for all analytes, suggesting that this material may be suitable for low-level detection of organics.Sandia is a multiprogram laboratory operated by Sandia Corp., a Lockheed Martin company, for the U.S. Department of Energy under Contract DE-AC04-94AL85000.
6:00 PM - K5.15
NH3 Gas Sensor Based on CuxS Nanostructures.
Yung-Tang Nien 1 , Yu-Hsuan Chang 2 , In-Gann Chen 2
1 Center for Micro/Nano Science and Technology, National Cheng Kung University, Tainan City Taiwan, 2 Department of Materials Science and Engineering, National Cheng Kung University, Tainan Taiwan
Show AbstractCopper sulfide (CuxS) has a number of commercial applications, in pigments, semiconductors, solar cells, fluorescent devices and even superconductors. In addition, it can precipitate in ZnS:Cu,Cl phosphor powders to form heterojunctions, which contribute to electroluminescence (EL) under a high electric field. Unlike metal oxide-based sensors, which have to be heated to high temperatures (500-700K) for the detection of target gases, CuxS film has recently been reported to respond to reducing gases at room temperature as a potential gas sensor. However, CuxS can form five stable phases at room temperature from the ‘copper deficient’ side to the ‘copper rich’ side of the phase diagram of the Cu-S system: covellite CuS, anilite Cu1.75S, digenite Cu1.8S, djurleite Cu1.95S, and chalcocite Cu2S. It is a p-type semiconductor in which copper vacancies act as acceptors, indicating the strong dependence of electrical properties upon the deficit amount of copper atoms in CuxS. Therefore, the phase, as well as the x value, is supposed to affect the sensitivity of CuxS-based gas sensors due to changing surface reactions between CuxS and the target gases. In this study, a simple method of preparing Cu2S nanowalls was presented by dispersing Cu foils in Na2S solution. X-ray diffraction analysis revealed the formation of monoclinic Cu2S sheets on Cu foils, which exhibited a thickness of less than 100nm along with a length of several μm (called nanowalls) from the scanning electron microscopic images. From the transmission electron microscopy and x-ray energy dispersive spectrometry characterizations, it indicated that these Cu2S nanowalls were thinner near the surface of nanowalls and had voids in the Cu2S sheets due to etching reaction. A house-made glass chamber equipped with a parametricanalyzer was employed for gas response measurements. DC-electrical resistance of the films was measured under a flow of compressed air through ammonia water (28%) with a concentration level of ppm.
6:00 PM - K5.16
Gas Sensing Characteristics of SnO2 Nanowires Network: The Effect of Nanowire Density.
In-Sung Hwang 1 , Kang-Min Kim 1 , Sun-Jung Kim 1 , Joong-Ki Choi 1 , Chan-Woong Na 1 , Byeong-Kwon Ju 1 , Jong-Heun Lee 1
1 , Korea University, Seoul Korea (the Republic of)
Show AbstractSemiconductor-type gas sensors can be fabricated using either single nanowires (NWs) or NW networks. The single-NW configuration allows a fundamental understanding of the gas sensing mechanism of NW-based gas sensors. However, the formation of electrodes precisely onto a single NW is a challenge requiring rather expensive e-beam lithography processes. In contrast, the fabrication of NW networks sensor is relatively simple and cost-effective compared with that of a single NW sensor. In addition, the networked structure of NWs establishes a number of resistive contacts at the junctions between NWs. The large variation in resistance at these junctions provides an additional sensing mechanism based on the serial connection between the resistive grain boundary and semiconducting core, which leads to an increase in gas sensitivity. In addition, the configuration of NWs network is less-agglomerated than that of the nano-particles counterpart, which can promote the diffusion of target gas on to the sensing surface. Accordingly, the NW-network gas sensor is of great importance not only for cost-effective fabrication but also for enhancing the gas sensitivity. In this study, the SnO2 NWs network sensors with different NW density were fabricated using polydimethylsiloxane (PDMS) patterning and solution deposition and their gas sensing characteristics were investigated. The gas sensitivity was increased up to ∼13 times by increasing the NW density, while the response and recovery speeds decreased. The enhanced gas sensitivity at the high NWs density was attributed to the increase in the number of NW/NW junctions that vary the resistance significantly upon exposure to gas.
6:00 PM - K5.17
Gas Sensing Properties of Titanate Nanotube Films.
Diego C Alves 1 , Leonardo Campos 1 , Erick Avila 1 , Alem-Mar Goncalves 1 , Rodrigo Lacerda 1 , Andre Ferlauto 1
1 , UFMG, Belo Horizonte, MG, Brazil
Show AbstractHydrogen (or sodium) titanates nanostructures such as tubes, fibers and sheets can be efficiently produced by treating TiO2 powders in alkaline solutions [1]. Although most of the work on these nanomaterials have focused on the their structural identification and control, recently several applications have been proposed, such as pollutant cleaning by ion exchange and nano-composite polymeric electrolytes in fuel cells [2].¶In this work, the application of titanate nanotubes (TNTs) as gas sensors is investigated. TNTs were synthesized by refluxing a TiO2 (anatase) suspension in an aqueous NaOH (10 M) solution for 24 hr, followed by washing the suspensions with water until neutralization.¶Characterization by X-ray diffraction and scanning and transmission electron microscopies revealed that the produced material is the sodium trititanate (Na2Ti3O7) and that its morphology consists of entangled tubular filaments. TNT films were prepared by tape casting by using a mixture of TNT with a polymeric binder and DMF.¶A systematic study of the electrical response of devices made by TNT films deposited over a Si/SiO2 wafer with interdigitated contacts was performed. The devices were measured in atmosphere of H2 diluted in N2, with concentration ranging from 100 to 5000 ppm, and at temperatures ranging from 20 to 250°C.¶The sensors presented a very promising performance, showing good sensibility, stability and reproducibility. A interesting results is that the largest sensitivity was observed at 25°C. For 100 ppm, a value of 20 % for the sensitivity was obtained. The films sensitivity shows a peculiar dependence with temperature, presenting one maximum at 25○C and a second one at 150-180°C. The analysis of the temperature dependence of the sensitivity suggest that two kinds of electrical transport ocurr. For temperatures (T) higher than 100°C a thermically activated electronic transport is dominant (activation energy: 0.56 eV). For T<100°C, the conductivity seems to be influenced by the presence of water moluces physisorbed at the surface, suggesting that protonic transport is dominant at low T. Such change in the conduction mechanism might be associated with the variations on the TNT film sensitivity.¶¶[1] D.V. Bavykin, J.M. Friedrich, and F.C. Walsh, Adv. Mater. 18 (2006) 2807-2824.¶[2] B.R. Matos, E.I. Santiago, F.C. Fonseca, M. Linardi, V. Lavayen, R.G. Lacerda, L.O. Ladeira and A.S. Ferlauto, J. Electrochem. Soc. 154, (2007) B1358-B1361.¶
6:00 PM - K5.18
When Organometallic Chemistry and Metal Oxide Nanoparticles Meet Optimized Silicon-based Gas Sensor.
Pamela Yoboue 1 , Philippe Menini 1 3 , Andre Maisonnat 2 , Myrtil Kahn 2 , Katia Fajerwerg 2 3 , Bruno Chaudret 2 , Pierre Fau 2 3
1 LAAS, CNRS, Toulouse France, 3 , Université de Toulouse, Toulouse France, 2 LCC, CNRS, Toulouse France
Show AbstractAir quality control in confined places (automotive cabin, transportation and offices or working places) is getting more and more pregnant in the actual pollution levels we are facing in our industrial environment. Despite the intense research work in the field of new silicon sensors and sensitive elements, the need for a high accuracy and low cost metal oxide gas sensors remains a challenge. This is due to the generally admitted drawbacks of this kind of silicon device: the resistance drift of the polysilicon heating element, the harsh mechanical stress of the membrane applied to the sensitive layer and the progressive deactivation of the thin oxide sensitive layer which lead to a decrease of sensor performance upon time.We have developed a very new generation of metal oxide gas sensor, based on the combination of optimized micromachined silicon substrates and highly sensitive nanosized metal oxides derived from organometallic synthesis means [1, 2]. For the first time, an integrated approach for a general sensor design has been employed [3, 4]. This new sensor design has been built in accordance with the upstream constraints coming from the deposition method required by the liquid nature of the sensitive material. A key parameter for an improved response of the sensor is the highly porous nature of the sensitive layer and the number of electrical contact between oxide grains. The more the number of possible current pathway during sensor operation and the less the risk of sensitivity decreases due to deactivation of grain boundaries. As a matter of fact, nanopowders offer the best ratio of grains and grain boundaries for a giving volume of sensitive layer. The presented results show the thermomechanical behavior of the silicon substrate, the electrical and thermal stability of the platinum based heater element, and the very low and controlled membrane deformation when operated. Round membrane shape and contact electrodes are build in respect with the drop deposition technique employed for the sensitive layer. This robust silicon design has been successfully employed with various metal oxide nanoparticles synthesized by organometallic means (SnO2, ZnO) and deposited by a generic ink jet method. High quality and micron thick layers can be obtained with a very low defect level (no cracks, no délamination) and gas sensitivity (under CO, C3H8 and NOx) and air stability are presented in comparison with classical thin films sensitive layers. [1] C. Nayral et al., Applied Surface Science, 164 (2000) 219 - 226.[2] Miguel Monge, Myrtil L. Kahn, André Maisonnat and Bruno Chaudret, Angew. Chem. Int. Ed., 2003, 42, 5321-5324. [3] Ph. Ménini et al., Eurosensors XXII proceedings, (2008) 342. [4] P. Fau et al, jnte08 proceedings, (2008) 14-15.
6:00 PM - K5.19
Electronic Detection of Toxic Amides Using the a-Si:H-based EIS Sensor.
Miguel Fernandes 1 , Joao Costa 1 , Yuri Vygranenko 1 , Manuela Vieira 1 , Amin Karmali 2
1 Electronics Telecommunication and Computer Dept., ISEL, Lisbon Portugal, 2 Chemical Engineering and Biotechnology research Center, ISEL, Lisbon Portugal
Show AbstractIon-selective field-effect transistors (ISFETs) are chemically active electronic sensors based on a complex electrochemical mechanism occurring at the gate/electrolyte interface that yields a small variation of the deice threshold voltage. In this work we present an alternative device based on the a-Si:H electrolyte-insulator-semiconductor (EIS) structure with an organic detection layer. The device prototype comprises a glass substrate, a bottom semitransparent metal electrode, an n+-a-Si:H/i-a-Si:H/SiN:H/SiOx semiconductor-insulator stack, and a top membrane. The membrane contains enzyme targeting the detection of toxic amides in food and industrial effluents. The proposed device is simpler in fabrication than that for ISFETs, offers scalability of the active area and encapsulation efficiency. For this type of sensor, the change in the surface potential at the electrolyte-transducer interface can be detected by measuring the structure capacitance. However, this method is problematic because of extremely low free-carrier density in undoped a-Si:H. To resolve this technical issue, we propose to measure a photocurrent, which is also sensitive to the band banding at the insulator-semiconductor interface. The lock-in technique was used to measure an ac signal component when device was illuminated by pulsed light. The sensitivity of the devices was evaluated by changing pH of the solution at different temperatures. In order to obtain further insight into the variables affecting the behavior the device, a set of numerical simulations was performed applying the bottom-up approach proposed by Heitzinger and collaborators.
6:00 PM - K5.2
Characteristics of SAW Humidity Sensor Using Nanocrystalline ZnO Films.
Si-Hong Hoang 1 , Gwiy Chung 1
1 School of Electrical Enginnering, University of Ulsan, Ulsan Korea (the Republic of)
Show AbstractComparison with polymers as humidity sensing, the withstanding in high temperature environment of ZnO is better. Presently, although, many previous works was shown that ZnO films with hexagonal obtained on substrates by deposition methods such as sol-gel, sputtering and chemical vapor deposition for humidity applications but to our knowledge, ZnO sensing layer for SAW humidity sensor has not been investigated clearly. For that reason, we focus nanocrystalline ZnO thin film for SAW humidity sensor. Nanocrystalline ZnO was prepared by sol-gel because simple process, low cost and properties of the film can be controlled easily by coating time and annealing temperature. High-quality poly piezoelectric (002)-oriented AlN thin films with thicknesses (h) of 0.5 µm were deposited on (100)-Si wafers by a pulsed reactive magnetron sputtering system. The next, the ZnO coating solution were prepared from zinc acetate (ZnO(CH3COO)22H2O, methoxy- ethanol and monoethanolamine in a magnetic stirrer for 2 hours at 70¡ÆC. The coating layer was performed in 10 times by spin coating to obtain 300 nm thick of ZnO, the samples (ZnO/AlN/Si) were annealed in air by a furnace at 600 C for 1 hr. The SAW humidity sensor with delay line was fabricated with schematic diagram of an inter-digital transducer (IDT) pattern for the SAW humidity sensor. The transmission characteristics of SAW devices were measured by Agilent 8802A Network Analyzer in the humidity range of 10-95% at room temperature. The morphology of the films was examined by scanning electron microscopy (SEM). The crystalline quality of the films was evaluated by analyzing their X-ray diffraction (XRD) patterns. The frequency shift of the SAW humidity sensor (coated ZnO) and delay line without ZnO sensing layer at room temperature and in range of relative humidity from 10% to 95% were evaluated. According to the increase in RH to 95%, the center frequency (127.70 MHz) of the sensor was reduced by about 210 kHz in comparison with that (127.91 MHz) at RH =10%. For the XRD pattern of the ZnO/AlN/Si sample annealed at 600¡ÆC (the picture not show). The ZnO film had wurtzite structure and the poly AlN films grown on Si substrate had a (0002) preferred orientation. Nanocrysatlline ZnO thin film grown on AlN(002)/ Si substrate for humidity sensor applications was fabricated and analyzed. With the annealing temperature at 600¡ÆC for 1 hour, the particle size of the ZnO film was about 38 nm. Surface of the film exhibit spongy, which is suitable for water vapor absorption. In addition, the obtained film had wurtzite structure. SAW humidity sensor was fabricated by using the ZnO/AlN/Si structure. The center frequency response of the sensor was change by 210 kHz along the change in RH form 10% to 95% at room temperature. This result is the basis for study of fully SAW humidity sensors in harsh environments with low cost.
6:00 PM - K5.20
Fabrication and Performance of Catalyst-based Solid-state Sensors for Room Temperature Hydrogen Leak Detection.
Ryan Givens 1 , Stefon Lewis 1 , Kudus Ogbara 1 , Claudiu Muntele 1 , Daryush Ila 1
1 Physics, Alabama A&M University, Normal, Alabama, United States
Show AbstractSilicon carbide based non-linear electronics devices (MOSFET, metal-semiconductor, or p-n junctions) are promising candidates for hydrogen detection schemes if used in conjunction with a platinum group catalyst. For the past decade, the emphasis was mostly on high temperature applications in the automotive (for hydrogen-fueled engines) and in the aerospace industry (for jet engines), but now the focus is broadening to include auxiliary systems such as storage tanks, fuel lines, fuel production systems, all operating in a wide range of temperatures, all the way down to cryogenic levels. Here we are presenting an innovative approach to designing a capacitive configuration sensor solution to address challenges associated with using catalysts as active agents in ultra-sensitive capacitive hydrogen detection schemes at ambiental temperatures. We used e-beam deposition for preparing our samples, and current vs. voltage electrical measurements to monitor the devices’ response to hydrogen. Raman spectroscopy, scanning electron microscopy, and atomic force microscopy were used for investigating the surface morphology of the device and process metrology. Performance results as a function of hydrogen ppm concentration in air and inert environments will be presented at the meeting.
6:00 PM - K5.22
Photoluminescence Based Sensors on All Organic Platform (organic-light-emitting-diode/dye:analyte/organic-photodetectors).
Kanwar Nalwa 1 , Yuankun Cai 2 , Aaron Thoeming 1 , Joseph Shinar 2 , Ruth Shinar 1 , Sumit Chaudhary 1
1 Electrical and Computer Engineering, Iowa State University, Ames, Iowa, United States, 2 Physics and Astronomy, Iowa State University, Ames, Iowa, United States
Show AbstractA photoluminescence (PL)-based oxygen and glucose sensor utilizing organic light-emitting-diode (OLED) as the light source and a polymer-based organic photodetector (OPD) is demonstrated. The device structure is compact and the sensor integrates the sensing element (dye), light source, and organic PD as thin films that are attached such that the sensing element is sandwiched between the OLED and the OPD. The sensing elements are based on the oxygen-sensitive dyes. Organic OPD base don polythiophene and fullerene blend is optimized for enhanced detection of red PL frrom the sensing element. This is the first report on all-organic chemical sensing in the lifetime mode, which is more preferrable that the intensity mode due to its robustness and insentivity to external changes in the input light.
6:00 PM - K5.25
On-wire Lithography and Nanodisk Codes: A New Platform for Chem/Biosensing.
Matthew Banholzer 1 3 , Kyle Osberg 2 3 , Lidgon Qin 1 3 , Jill Millstone 1 3 , Chad Mirkin 1 2 3
1 Chemistry, Northwestern University, Evanston, Illinois, United States, 3 International Institute for Nanotechnology, Northwestern University, Ev, Illinois, United States, 2 Materials Science & Engineering, Northwestern University, Evanston, Illinois, United States
Show AbstractOn wire lithography (OWL) is a 1-D nanostructure-based technique that can be used to generate novel nanostructures with unique optical, electrical, and magnetic properties. With this technique, multisegmented nanowires are prepared by template-based synthetic methods, a backing layer is deposited on one face of each structure, and the sacrificial metal layers are subsequently etched to generate both gapped nanowires and supported disk arrays. In the context of biosensing, we have used the OWL technique to generate Nanodisk Codes: nanostructured biological labels that are dispersible multiplexing SERS-active substrates that allow detection of biomolecules such as nucleic acids with sub-pM sensitivity. These disk codes store information by their Raman spectra and spatial distribution of disk pairs along the long axis of each structure. Efforts to correlate structure and materials composition with Raman response will be discussed, along with some novel applications involving sensing, tagging, energy conversion, and high resolution imaging.
6:00 PM - K5.26
Characterization of Nanomaterials as Highly Selective and Sensitive Sensors to Detect Energetic Compounds in the Vapor Phase at Trace Levels.
Karine Bonnot 2 , Valerie Keller 1 , Denis Spitzer 2
2 NS3E-Laboratoire des Nanomatériaux pour Systèmes Sous Sollicitations Extremes, ISL-CNRS, Saint-Louis France, 1 Laboratoire des Matériaux, Surfaces et Procédés pour la Catalyse-European Laboratory for Catalysis and Surface Sciences, CNRS-Louis Pasteur University, Strasbourg France
Show AbstractThe detection of explosives energetic compounds in air has become an important challenge for homeland security applications due to the threatened increased of terrorism explosive bombs used against civil population. However there is a crucial need for the detection of explosive vapours traces and sub-traces, i.e. at the ppt level or even lower, leading to an increased active and challenging area of research.In order to develop detection purposes having higher sensitivity and selectivity towards numbers of energetic compounds, it is necessary to develop novel nanomaterials with higher specificity, selectivity and sensitivity for sensing applications. There is also a need in characterisation and calibration of such innovative materials in near real conditions.We present herein a tool we developed to test and compare sensitivity and selectivity of several substrates toward sniffing detection of low partial pressure explosives such as 2,4,6-trinitrotoluene (TNT), pentaerythritoltetranitrate (PETN) and hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) which are mostly used in bombs manufacturing. The system was composed of two parts:i)The generation of explosive vapors was based on the equilibrium existing between a solid and its vapor phase at every temperature. It used the well known Clapeyron equations to determine accurately the concentration of explosive in the vapor phase at the working temperature.ii)The test and characterization of sensitive nanomaterial substrates towards one or more explosive vapors. The measurement of the selectivity and sensitivity of the tested materials toward the molecules of explosive was made using a gas-chromatograph coupled with an electron capture detector and a mass spectrometer detectorPreliminary experiences were conducted on a porous nanometric tungsten trioxide to test its selectivity and sensitivity toward vapor of TNT or RDX at different concentrations in the air stream. The results showed good retention properties of the tungsten oxide toward molecules of RDX and higher detection abilities than for TNT. The detection abilities of one material toward an explosive was described as the mass of explosive adsorbed on one µg of sensitive material or the number of molecules that could react on a square nanometer of sensitive surface. Interestingly the tested tungsten material showed poorest efficiencies and retention capacity toward TNT for every vapor concentration. This result suggested stronger interactions between RDX and the tested tungsten trioxide than for TNT and better detection efficiency of this material toward RDX than TNT.We developed, optimized and validated herein a complete tool to test sensitive and selective substrates to detect explosive vapors at trace levels using the nanomaterials sniffing abilities towards explosives molecules. This constitute a first promising step in developing highly sensitive and selective device to detect low partial pressures explosives in complex environments.
6:00 PM - K5.27
Enhanced Gas Sensing Properties of Nanostructured Metal Oxide Thin Films Fabricated by Controlled Large Area Colloidal Templating.
Ho Won Jang 1 , Hi Gyu Moon 1 , Chong-Yun Kang 1 , Jin-Sang Kim 1 , Seok-Jin Yoon 1
1 Thin Film Materials Research Center, KIST, Seoul Korea (the Republic of)
Show AbstractThe enhanced gas sensitivity of macroporous metal oxide thin film gas sensors obtained using colloidal templating, which is an effective method to fabricate quasi-ordered sub-micron structures of various materials, has been demonstrated recently. However, it is challenging to exploit the method for wafer-scale uniformity and throughput because the wetting of sub-micron polymer spheres from colloidal solution onto a substrate is very sensitive to the chemical homogeneity of the surface of the substrate. Thus the maximum area of close-packed monolayer colloidal templates without voids and sphere-free regions is about 1 cm2. This suggests that offering a reliable method for wafer-scale large area colloidal templating is a critical step in developing nanostructured metal oxide thin film gas sensors for real applications.In this work, we investigate CO and NOx gas sensing properties of nanostructured TiO2 thin film gas sensors fabricated by colloidal templating. Our experimental results show that the formation of sphere-free regions (voids) and multi-stacked regions in colloidal templates is strongly affected by the size of polymer spheres, the type of surface charges in polymer spheres, the surface wettability of the substrate, and the surface morphology of the substrate. With the control of interactions among ploymer spheres and between polymer spheres and and the substrate, close-packed templates with wafer-scale large area uniformity could be achieved. Futhermore, the modification of surface wettability and sphere size by plasma treatments leads to a significant improvement in the reliability of the fabrication process. Compared with plain films, the nanostructured films fabricated by the collodial templating exhibits enhanced gas sensing with higher sensitivity and, more interestingly, faster response. The fabrication process of the nanostructured thin films by the large area colloidal templating and the mechanism of the enhanced gas sensitivity of the films are discussed in details.
6:00 PM - K5.28
Cupreous ZnO Nanoclusters: Synthesis and Gas Sensing Properties.
Bharat Kale 2 , Kaluram Kanade 1 , Dinesh Amalnerkar 2 , Uttamrao Mulik 2
2 Nanocrystalline Materials/glass, Centre for Materials for Electronics Technology (C-MET), Department of Information Technology, Govt. of India, Panchawati, Off Pashan Road, Pune – 411008, India, Pune India, 1 Chemistry Department , Annasaheb Awate College Manchar, Pune India
Show AbstractABSTRACT:Methanol mediated Cu doped ZnO nanoclusters were synthesized by co-precipitation method. Dopant percentage of Cu was optimized from copper chloride to achieve the desired percentage of copper in ZnO and same was confirmed with Inductively coupled Plasma Optical Emission Spectrophotometer (ICP-OES). The XRD study shows hexagonal structure with size in the range of 16 -19nm. From UV-Visible, a single sharp peak corresponding to 362nm, equivalent to a band gap of 3.42 eV confers high monodispersivity. FE-SEM and TEM investigations showed well aligned spherical ZnO nanoparticles. The gas sensing for CO and home cooking gas (LPG) was demonstrated using as synthesized nanopowder in pellet form. These sensors showed lowest optimum operating temperature in the range of 125 - 150 C. The lowest operating temperature for ZnO based sensors in the pellet form was demonstrated for the first time. The ZnO doped with 1.0 % Cu has shown high sensitivity response for CO gas, while with 0.5% Cu showed more sensitivity for LPG gas. The response time of the sensors was observed around 12-15 seconds. In nutshell, we observed the nanoscale ZnO enhances the sensing properties as compared to bulk. Keywords: Nano-clusters, zinc oxide, gas sensors, crystal structure, copper For correspondence: Dr. B. B. Kale*: Email:
[email protected]6:00 PM - K5.29
Sensing Studies of N Doped ZnO Nanorod Arrays.
Boqian Yang 1 2 , Xiaoyan Peng 1 , Edwin Arroyo 1 , Peterxian Feng 1 , Marc Achermann 2
1 Physics Department, University of Puerto Rico Rio Piedras, San Juan, Puerto Rico, United States, 2 Physics, University of Massachusetts Amherst, Amherst, Massachusetts, United States
Show AbstractN doped ZnO nanorod arrays were synthesized on quartz substrates by pulsed laser deposition technique. Prototype sensors were fabricated by sputtering Au electrodes with a shadow mask to form contacts to the multiple nanorods. The sensing of the resulting sensors to N2, H2 and CH4 was studied by measuring current-voltage curve characteristics. Using time - resolved photoluminescence spectroscopy, we investigated the charge carrier dynamics at the interface between the gas molecules and the surface of ZnO nanorods. The difference in the sensing mechanisms with gases of N2, H2 and CH4 will be discussed.
6:00 PM - K5.3
Characteristics of Nanocrystalline ZnO Thin Film Grown on AlN/Poly 3C-SiC Buffer Layer/Si Wafers for Harsh Environment SAW Chemical Sensors.
Gwiy Chung 1 , Kyu-Hyung Yoon 1
1 School of Electrical Enginnering, University of Ulsan, Ulsan Korea (the Republic of)
Show AbstractIn this work, the nanocrystalline ZnO/polycrystalline (poly) AlN/poly 3C-SiC/oxidized Si structure was fabricated for sensor applications based on surface acoustic wave (SAW). In this structure, the ZnO film was used as sensing material layer. These ZnO, AlN(0002) and 3C-SiC(111) films were deposited by so-gel process, a pulse reactive magnetron sputtering and an atmospheric pressure chemical vapor deposition system, respectively. These experimental results showed that temperature coefficient of frequency (TCF) of the AlN/3C-SiC/Si structure was small (-18 ppm/°C) and nearly linear in range from 30 to 150 °C. This allows this structure using for SAW applications with variable temperature. The obtained SAW velocity on AlN film was about 5020 m/s at h/λ = 0.0625 (h and λ is thickness and wavelength, respectively). For ZnO sensing layers coated on AlN, films have hexagonal wurtzite structure and nanometer particle size. The crystalline size of ZnO films annealed at 400, 500, and 600°C is 10.2, 29.1, and 38 nm, respectively. Surface of the film exhibits spongy which can adsorb steam or gas in the air. Sol-gel process was chosen because simple and low cost. The cost for fabrication of AlN/3C-SiC/Si structure also is chipper than that of AlN/bulk substrate such as AlN/4H-SiC and AlN/diamond. Moreover, the both of ZnO/AlN and AlN/3C-SiC structure have small lattice mismatch. This can reduce stress of these films. The structural properties of thin films were investigated by XRD, FTIR, AFM and SEM. Generally, ZnO/AlN/3C-SiC/Si structures have low cost, low TCF and ease to integrate into conventional Si manufacturing technologies. Therefore, the structure can be used for SAW chemical sensor applications in various temperature environments.
6:00 PM - K5.30
Sensory Devices Based on Nanogap Electrode Hybrids With Optoelectronic Polydiacetylene Nanoarchitectures.
C. Kobayashi 1 , Y. Choi 2 , N. Matsuo 1 , N. Kim 2 , Y. Aoyama 1 , C. Cui 2 , D. Yang 2 , G. Lee 2 , Takayuki Homma 1 , Dong June Ahn 2
1 Department of Applied Chemistry, Waseda University, Tokyo Japan, 2 Department of Chemical & Biological Engineering, Korea University, Seoul Korea (the Republic of)
Show AbstractSignal transform of sensing events upon recognition of chemical and biological targets is one of the important key issues in construction of novel sensory devices, most of which deliver optical and/or electrical information to human. The devices transmitting electrical signals are considered to have much impact as compatible and integrative with current information technologies. Previous electrical devices in conjunction with conducting polydiacetylene supramolecules have been reported as in the form of micro-scale FETs. In this study, we report on electrical signaling of nanogap electrode hybrids with optoelectronic polydiacetylene nanoarchitectures such as nanosomes, nanowires, and lamellars. The nanogap electrodes made of gold with gap separation of 100 nm were fabricated by electron beam lithography on silicone substrates, of which dimension is intentionally designed to match the scale of the nanosomes. In-situ and ex-situ I-V characteristics were obtained from the nanogap devices assembled with various nanostructures of polydiacetylene. Signals were found to be dependent upon the nature of each nanostructure, and were well correlated to the recognition of chemical targets. Mechanism of electrical signaling regarding structural derivatives of active polydiacetylene materials will be discussed.
6:00 PM - K5.31
The Detection of Chemical Molecules Using Titania Nanotube Arrays.
Thomas Cottineau 1 , Yeuk Tink Law 1 , Sergey Pronkin 1 , Elena Savinova 1 , Valerie Keller 1 , Nicolas Keller 1
1 , LMSPC CNRS UMR 7515, Strasbourg France
Show AbstractIn recent years, one-dimensional (1D) nanomaterials have shown promising potential in the area of sensors because they have, among others, the advantages of sensitivity, rapid response and corrosion resistance [1]. Generally, solid state semiconductor gas sensors play an important role in environmental, industrial, personal safety but also homeland security. The high surface-to-volume ratio of TiO2 based nanotubes makes them potential competitors, as a new generation of sensors, to usually sensors. However, the major challenges are to produce ordered one-dimensional nanostructures, simple in preparation and handling.Amongst different ways of synthesis of 1D TiO2 nanotubes, anodic formation of ordered TiO2 nanotube arrays has created significant interest, due mainly to controllable synthesis parameters [2]. The use of heat treatments, of surface modifications, of doping or promotion with metals, oxides, semi-conductors, or more generally of functionalization is crucial for selective adsorption and consequently detection. Based on the target analytes interested, the nature of the functionalization strongly depends on the chemical function to be selectively adsorbed on the sensing solid.The detection of organic vapors in the air is very important, because of toxicity of many of them. In this work, detection of different organic vapours is carried out using the above mentioned concept of 1D-functionalized TiO2 nanotube arrays The preparation of TiO2 nanotube arrays by anodic oxidation of Ti foil was performed by anodization of Ti foil in fluoride-containing electrolyte. The formation of TiO2 nanotubes is a competition between the dissolution of the titanium oxide layer and the field assisted growth of the layer [3]. The equilibrium of these two phenomena define the maximum lenght of the TiO2 nanotubes. This equilibrium and thus the stucture and morphology of TiO2 layers were varied by changing the preparation conditions. In particular, anodization time and voltage, composition and viscosity of electrolyte were adjusted. The morphology of formed TiO2 nanotubes (nanotubes inner/external diameter, length) is characterized by scanning and transmission electron microscopy. Electronic structure of nanotubes is studied by electrochemical methods (electron transfer polarization curves, electrochemical impedance spectroscopy), reflection UV-vis spectroscopy and XPS. Dependence of structure, composition and morphology of synthesized TiO2 layers on preparation conditions is explored. Correlation between the characteristic parameters of TiO2 layers and their performance in detecting devices is discussed.[1] S. Banerjee, S. K. Mohapatra, M. Mistra, I. B. Mishra; Nanotechnology; 20 (2009).[2] G.K. Mor, O.K. Varhese, M. Paulose, K. Shankar, C.A. Grimes; Sol. Energy Mater. Sol. Cells; 90 (2006) 2011.[3] C.A. Grimes, O.K. Varghese, S. Ranjan; Light, Water, Hydrogen; Springer Editor (2008).
6:00 PM - K5.32
Formaldehyde Sensors Based on SnO2/NiO Composite Films Prepared by Pulsed Laser Deposition.
Jeffrey Dunford 1 , Jim Tunney 1 , Craig Jeffrey 1 2 , Xiaomei Du 1 , Michael Post 1
1 Institute of Chemical Process and Environmental Technology, National Research Council Canada, Ottawa, Ontario, Canada, 2 Research & Development, Abbott Point of Care, Ottawa, Ontario, Canada
Show AbstractFormaldehyde (HCHO) is a volatile organic compound that out-gases from textiles and composite wood products, with adverse health effects resulting from prolonged exposure to concentrations of ~10 ppb in air. Stannic oxide (SnO2) / nickel oxide (NiO) polycrystalline composite films produced by pulsed laser deposition (PLD) are good candidates for HCHO detection, showing sensitivity to < 100 ppb via resistance measurements. Various SnO2/NiO sensor materials were prepared by varying SnO2:NiO composition ratios in the PLD target, substrate temperatures, and oxygen pressures. These variables are shown to affect both composition and morphology, as characterized by XPS, XRD, SEM, and EDX. We have studied the sensitivity, selectivity, and response time of these sensor materials at various temperatures in nitrogen and air environments. Here we present our latest results.
6:00 PM - K5.33
Gas Transport and Response in Porous Silicon Sensors.
Serdar Ozdemir 1 , James Gole 1 2
1 School of Physics, Georgia Institute of Technology, Atlanta, Georgia, United States, 2 School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, Georgia, United States
Show AbstractNanopore covered microporous silicon conductometric gas sensors have been produced via electrochemical etching and standard microfabrication techniques. Reversible and sensitive gas sensors working at room temperature have been fabricated. Sensing of NH3, NOx and PH3 at or below the ppm level have been observed. The porous surface has been modified using selective coatings including electroless tin, gold, nickel and copper solutions to increase the response to NOx, NH3, PH3 respectively. The diffusion of the analyte species has been investigated in the nanopore and micropore regimes by numerical analysis. Comparing the response time of the hybrid porous sensor surface with numerical diffusion calculations on the pores, it has been observed that Knudsen diffusion time scales dominate the sensor response. A transduction model is proposed based on nanopore limited gas diffusion and the experimental response and recovery data.
6:00 PM - K5.34
Hydration Effect Analysis of Ion-sensitive Field Effect Transistor.
Mykhaylo Rybachek 1 , Lihong (Heidi) Jiao 1
1 School of Engineering, Grand Valley State University, Grand Rapids, Michigan, United States
Show AbstractThe Ion-Sensitive Field Effect Transistor (ISFET) is a device where the gate oxide is in direct contact with an analytic solution. This device is a good option for continuous monitoring applications to determine concentration of various ion species due to its advantages over the conventional electrodes such as high sensitivity, fast response time, micro-size and on-chip circuit integration. However, the technology harbors limitations including threshold voltage time drift, temperature dependence and technological difficulty in packaging of a small reference electrode [1] [2]. Therefore, the commercial viability of the ISFET applications in medical and chemical analyses is limited. The drift is the main constrain. It has been reported that an ISFET sensor with a pH gate had a drift of 0.02-0.06 pH/hour, and the initial drift could be even higher. Most of the proposed methods for time and temperature drift compensation involve in redundant data calculation and additional circuitry.In this work, a method for measuring a drift using a reverse compensation to obtain the accurate output values, and correcting a drift is studied. The device comprises of a differential read-out circuitry with an ISFET transistor as a pH sensor, biased by the AgCl reference electrode and a NMOS transistor whose gate is controlled by a controllable external voltage. The ISFET/MOSFET circuitry is fabricated using the standard NMOS process. The AgCl reference electrode is fabricated on the same substrate by a screen printing method. It is believed that the main cause of the drift is the hydration effect, which is due to the change in dielectric constant of the sensing material and a small number of surface binding sites that react slowly to a change in pH. Static modeling of the ISFET with different sensing materials such as SiO2, Al2O3 and Si3N4 was carried out in MATLAB to study the behavior of these sensors. It showed that the average sensitivity of SiO2 surface is about 30 mV/pH and is about 58 mV/pH for Al2O3. The surface potential depends on the concentration of ions, double layer capacitance and specific material properties. In addition, the surface morphology and dielectric constants of different sensing materials are tested to study the hydration effect in order to eliminate the drift. The variation of dielectric constants is measured in a capacitance bridge over a frequency rage of 0.01-100 KHz. Atomic Force Microscope (AFM) is used to study the surface morphology and absorption of macromolecules on the surface after immersion in water. [1] Shahriar Jamasb, Scott D. Collins, and Rosemary L. Smith, IEEE Transactions on Electron Devices, VOL. 45, NO. 6, JUNE 1998[2] Wei-Yin Liao, Hung-Yin Lin and Tse-Chuan Chou, 0-7803-9105-5/05/©2005 IEEE
6:00 PM - K5.35
Surface Functionalization of Nano-scale Oxide Materials Using Phosphonic Acid Self-assembled Monolayers.
Beibei Zhang 1 , Guosheng Cheng 1
1 Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences, Suzhou Industrial Park, Jiangsu, China
Show AbstractBiosensors have profound applications in the area of disease diagnosis, homeland security, food safety and environmental monitoring. Through decades of extensive research, it is still a major challenge to improve marked performances with high sensitivity, selectivity, stability and compatibility. Nano-scale materials with excellent physical and chemical properties have been successfully applied in the biosensor designs, in which the oxide nanomaterials are extensively studied due to their good biocompatibility. Since the performance of the biosensors much relies on the effective immobilization of biomolecules, surface modification of the nanomaterials for this issue is of great interest. Our research focused on the studying of the self-assembled phosphonic acid layers on oxide surfaces, such as ZnO, TiO2, In2O3 and ITO. Phosphonic acid (X (CH2) 9 P(O)(OH)2, X=NH2, COOH) can self-assembled on nano-scale oxides with OH- terminated surfaces through forming P-O-Metal bonds. The functionalized surfaces were consistently characterized by water contact angles, atomic force microscopy (AFM), Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). Furthermore, selective immobilization of protein and nucleic acids (IgG or DNA) on the functionalized surfaces were achieved by covalent binding. This work provides a broad application of the phosphonic acid surface functionalization on biosensors and optoelectronic devices, especially the nanomaterials-based field emission transistors (FET).
6:00 PM - K5.36
Polyaniline Nanofibers as Chemical Sensors.
Bruce Weiller 1 2 , Christina Baker 2 , Jesse Fowler 1 , Robert Kojima 3 , Henry Tran 2 , Shabnam Virji 1 , Richard Kaner 3 2
1 Space Materials Laboratory, The Aerospace Corporation, Los Angeles, California, United States, 2 , Fibron Technologies, Inc., Inglewood, California, United States, 3 Department of Chemistry & Biochemistry and California NanoSystems Institute, University of California, Los Angeles, Los Angeles, California, United States
Show AbstractConducting polymers have been widely used to develop fast and efficient chemical sensors. Of these conducting polymer sensors, polyaniline appears to be the most widely studied due to its ease of synthesis and stability in air. We have shown that polyaniline nanofibers synthesized using our simple chemical method perform much better than conventional polyaniline and respond well to a number of different gases including hydrochloric acid, ammonia, hydrazine, organic solvents, hydrogen sulfide, arsine, phosgene and hydrogen gas. In some cases the sensor gives a response that is orders of magnitude change in resistance. Through the use of composite materials enabled by our unique water dispersions of polyaniline nanofibers, gases that do not cause a response in unmodified polyaniline can be detected. As a result a wide range of detection capabilities is possible with sensors based on polyaniline nanofibers. An overview of chemical detection capabilities of polyaniline nanofibers will be presented.
6:00 PM - K5.37
A Comparative Study of Chemical Sensing Using Single Metal Nanowires Fabricated by Different Methods.
Ping Shi 1 , Hsin-Yu Lin 1 , Jinying Zhang 1 , Paul Bohn 1
1 Department of Chemical and Biomolecular Engineering, University of Notre Dame, Notre Dame, Indiana, United States
Show AbstractMetal nanowires are one of the most attractive materials for chemical sensing because of their unique properties. For example, the conductance of metal nanowires decreases upon molecular adsorption due to scattering of the conduction electrons by adsorbate-image charge interactions with thinner wires exhibiting larger effects. We have employed a few nanofabrication methods such as electron beam lithography (EBL) and focused ion beam (FIB) etching to fabricate single metal nanowire devices. When used for chemical sensing, the nanowires fabricated by EBL exhibit excellent sensitivity to chemisorption of lewis base molecules such as thiols and amines, while those fabricated by FIB etching hardly show significant change in conductance when exposed to adsorbates. This result is probably related to the dramatic different electrical properties between the nanowires fabricated by these two methods. The theoretical explanation for the difference in their electrical properties will be discussed.
6:00 PM - K5.38
Tin Oxide Nanostructures Electrodeposited With Pd Catalyst Nanoparticles as Hydrogen Gas Sensors.
Jun Min Lee 1 , Seri Kim 2 , Jin Hyoun Joe 1 , Sung-Jin Kim 2 , Wooyoung Lee 1
1 Department of Materials Science and Engineering, Yonsei University, Seoul Korea (the Republic of), 2 Division of Nano Science, Ewha Womans University, Seoul Korea (the Republic of)
Show AbstractWe report a novel fabrication method of hydrogen gas (H2) sensors based on networks of Pd nanoparticles (NPs) deposited on tin dioxide (SnO2) nanowires (NWs) and NPs. Synthesis of SnO2 NWs and NPs was obtained by a simple thermal evaporation of SnO crystalline powders. And then the SnO2 NWs and NPs were effectively decorated with Pd NPs by the reduction process in metal ion solution. These sensors have been optimized with experiments at different conditions. Two proposed mechanisms (the reduction/oxidation of SnO2 by the spill-over effects and hydrogen-induced lattice expansion on Pd) completely agree with the on-off response of the sensors. As a result, the sensors show a ultra high sensitivity (~ 1.2 x 10^5 %) and a fast response time (~ 2 sec.) upon exposure to 1% H2 at room temperature. These sensors are also found to have a significant electrical conductance modulation upon exposure to extremely low concentrations (down to 40 ppm) of H2 in air. This novel method allows the production of high-sensitive H2 sensors that exhibit the broad dynamic detection range, the fast response time, and the ultra-low detection limit.
6:00 PM - K5.4
Characteristics of NO Sensors by Using Nanoparticle ZnO Film Integrated SiC Micro Heater.
Gwiy Chung 1 , Jae-Min Jeoung 1
1 School of Electrical Enginnering, University of Ulsan, Ulsan Korea (the Republic of)
Show AbstractThe necessity of NOx gas sensors is caused environment problems of NOx generated by the combustion of fuel or automobile exhaust. ZnO thin films are sensitive for ambient gases and are considered to be effectively used for metal oxide gas sensors for detection of NOx. The NOx sensing layers consisting of RF sputtered ZnO thin films were deposited on 3C-SiC micro heaters which are deposited by APCVD and built on AlN/3C-SiC suspended membranes by surface micromachining technology. ZnO thin film annealed in Ar at 600C is improved crystallinity. The resistance variation and sensitivity of active material according to temperature and NO gas flow rate were measured. The resistance of the ZnO thin film increases in the presence of 2.3 to 11.5 ppm of NO gas. The gas sensitivity ((Rgas-Rair)/Rair) to 11.3 ppm NO measured at 300C of operating temperature of 3C-SiC micro heater was 3 (highest sensitivity). The response time and resistance increasing with NO gas flow are evaluated. At operating temperature of 300C, a rapid initial increase of resistance was followed by almost saturation 100s after the gas injection, and then the resistance continued rising gradually. When the NO gas was removed, the resistance returned to the initial value. The sensitivity and response time are confirmed through two results.
6:00 PM - K5.40
ZnO Nanorod Sensors.
Bjoern Seipel 1 , Kacie Granico 1 , Jeffrey Jernstrom 1
1 , Portland State University, Portland, Oregon, United States
Show AbstractWe present our work on ZnO nanorod based methane sensors grown via electrodepostion at very low temperatures. We grew these nanostructurs on different substrates, with different shapes and sizes, and exposed the specimens to methan/air mixtures of various concentrations at operation temperatures between 200 and 250 degrees Celsius. We find changes in the resistance, which correlate with substrate type and methane concentration down to 0.1%. We are also reporting about using palladium to enhance the sensitivity of our ZnO-based sensors.We also report on response time and recovery time of all specimens in detail.
6:00 PM - K5.41
Size and Morphology Dependent Study of Single Particle Surface-enhanced Raman Spectroscopy (SERS) by Faceted Silver Nanocrystal.
Xing Yi Ling 1 , Peidong Yang 1
1 Department of Chemistry, University of California, Berkeley, Berkeley, California, United States
Show AbstractPlasmonic (metallic) structures are optimal platforms that enhance the sensitivity of the Raman scattering detection, known as Surface-Enhanced Raman Spectroscopy (SERS). The SERS sensitivity has been reported to reach a signal enhancement factor of 1014, which showed the capability of single-molecule detection. However, the current methods lack a systematic means of reproducing stable and sensitive plasmonic nanostructures, most observation are only limited to a few individual spherical silver nanoparticles over a larger surface or localized SERS substrate. Here, we review a systematic and fundamental study on the effects of size and morphology of faceted silver (Ag) nanoparticles to the optimal localized surface plasmon resonance (LSPR) effect, and thus the plasmonic nanocrystals that give rise to optimal Raman enhancement. Our strategy involves the synthesis of highly uniform and reproducible Ag nanocrystals with well-defined facets by a solution-phase “polyol” process. The fine control of the size distribution and crystallinity of the Ag nanocrystals generates a drastic control over the plasmonic characteristics of these particles, with scattering intensity ranging from visible to near infrared has been observed. These particles were then spatially distributed over the substrate, in which the single particle SERS measurement of Ag nanocrystals with size ranging from 60 nm to 400 nm, and Ag nanocrystals of well-defined crystallinity have been carried out. Our results showed significant plasmonic dependent behavior of the Ag nanocrystals to the SERS sensitivities. Our study presents a fundamental understanding towards the size and morphology effects of nanocrystals to SERS sensitivity, and therefore opens up a new pathway in designing better SERS substrate for single-molecule detection.
6:00 PM - K5.42
Single Particle Surface-enhanced Raman Spectroscopy (SERS) by Faceted Silver Nanocrystal.
Xing Yi Ling 1 , Peidong Yang 1
1 Department of Chemistry, University of California Berkeley, Berkeley, California, United States
Show AbstractMetallic nanostructures, in particular Ag are known plasmonic structures with strong scattering properties that are optimal to enhance the sensitivity of the surface-enhanced Raman scattering (SERS) detection. The SERS sensitivity of Ag nanocrystals has been reported to reach a signal enhancement factor of 1014, i.e., the capability of single-molecule detection. However, most observation are only limited to a few individual spherical silver nanoparticles over a larger surface or localized SERS substrate. Here, we aim to produce a systematic means of reproducing stable and sensitive plasmonic nanostructures and to review a fundamental study on the effects of size and morphology of faceted silver (Ag) nanoparticles to the optimal localized surface plasmon resonance (LSPR) effect, and thus the plasmonic nanocrystals that give rise to optimal Raman enhancement. “Polyol” process has been utilized as the synthesis route to produce of highly uniform and reproducible Ag nanocrystals with well-defined facets over the size range of 60 – 400 nm. The fine control of the size distribution and crystallinity of the Ag nanocrystals by our technique has enabled a precise control over the plasmonic characteristics of these particles. The scattering intensity ranging from visible to near infrared has been observed. When the Ag nanoparticles were spatially assembled on a substrate, the single particle SERS measurements were carried out. Our results showed significant plasmonic dependent behavior of the Ag nanocrystals to the SERS sensitivities. Our study presents a fundamental understanding towards the size and morphology effects of nanocrystals to SERS sensitivity, and therefore opens up a new pathway in designing better SERS substrate for single-molecule detection.
6:00 PM - K5.5
Facile Assembly and Enhanced Electrocatalytic Performance of Hybrid Ni-Al Layered Double Hydroxide/Carbon Nanotubes Nanocomposites.
Hui Wang 1 , Xu Xiang 1 , Feng Li 1
1 , Beijing University of Chemical Technology, Beijing China
Show AbstractNovel Ni-Al layered double hydroxide/carbon nanotubes (LDH/CNT) hybrid nanocomposites have been successfully assembled by a simple coprecipitation method. The materials were characterized by power X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDS), thermogravimetry and differential scanning calorimetry (TG-DSC), transmission electron microscopy (TEM), Raman spectra, UV-visible diffuse adsorption spectra (UV-VIS) and X-ray photoelectron spectra (XPS). The results reveal that LDH nanocrystallites could grow in situ and highly disperse on the surface of CNTs matrix through the interfacial electrostatic interaction between the positively charged LDH layers and the negatively charged functional groups of modified CNTs, which becomes a key factor to impact the physico-chemical properties of such type of hybrid materials, and that the distribution and coverage degree of LDH nanoparticles on the surface of CNTs could be tuned easily by changing composite compositions. Further investigation indicates that the electrode modified by LDH/CNT nanocomposite exhibits eight times higher electrocatalytic activity for glucose electrooxidation than those modified by either pristine LDH or CNTs in the absence of glucose oxidase, which is attributable to a cooperation of the unique hybrid nanostructure and the composition of nanocomposite. The present work are meaningful in understanding the assembly process of CNTs/LDHs hybrid nanocomposites and may provide a feasible approach for the control of the microstructure and property of functional LDH materials.
6:00 PM - K5.6
Middle Infrared Laser Sources Based on Chromium-doped Zinc Selenide Thin Films for Chemical Sensing.
Jonathan Williams 1 , Renato Camata 1 , Vladimir Fedorov 1 , Sergey Mirov 1
1 Physics, University of Alabama at Birmingham, Birmingham , Alabama, United States
Show AbstractMost organic compounds have unique absorption characteristics in the middle infrared (mid-IR) spectral region. These absorption features, corresponding to molecular vibrational-rotational transitions, are promising for highly specific chemical sensing based on spectroscopic approaches. Applications of these spectroscopic “molecular fingerprinting” methods include detection of chemical and biological waste, atmospheric pollutants, toxic agents and explosives, as well as a variety of platforms for medical diagnostics. Many of these spectroscopic sensing methods require tunable mid-IR laser sources. Mid-IR wavelengths are usually generated using relatively complex nonlinear optical conversion techniques or by means of direct generation in heterojunction lead-salt, antimonide, or quantum cascade lasers featuring limited output power and tuning range. In this work we explore an alternative approach for broadly tunable mid-IR laser sources: Chromium (Cr) dopant ions in ZnSe host crystals. Cr dopants substitute for Zn in ZnSe crystals forming stable Cr2+ ions whose crystal-field-split ground and first excited states possess different orbital characteristics leading to a significant Franck-Condon shift between absorption and emission. This effect results in broadband absorption and emission that are excellent for broadly tunable mid-IR lasers. In addition, the “heavy” selenium anion in the ZnSe crystal provides a very low optical phonon cutoff that makes this material transparent in a wide spectral range and decreases the efficiency of non-radiative decay, promising a higher yield of fluorescence at room temperature. We have deposited Cr2+-doped ZnSe thin films by pulsed laser deposition (PLD) for photoluminescence (PL), electroluminescence and stimulated emission studies. A KrF excimer laser (2.5–4.5 J/cm2) was used to ablate a polished, hot-pressed target produced by mixing powders of ZnSe and CrSe at various concentrations. PL measurements for films deposited on GaAs consistently indicate luminescence over the 2–2.6 μm range with a peak emission around 2.1 μm, slightly red shifted from the bulk peak emission (2.2 μm), establishing that Cr can be incorporated into ZnSe as optically active Cr2+ ions. Mid-IR emission under electrical excitation is significantly more challenging requiring two conditions: (i) excitation of the crystal host by electrical current; and (ii) energy transfer from the host to the dopant ion. We have designed multilayer structures to meet both conditions. Samples of Al/ZnSe/ZnSe:Cr2+/ZnSe/GaAs were deposited for carrier impact excitation studies in high-field driven devices. More efficient structures are to achieve electrical excitation by carrier recombination in an optically active ZnSe:Cr2+ thin film within the depletion layer of a p-n junction formed in a separate-confinement heterostructure configuration using cladding and guiding layers based on the ZnMgSSe quarternary alloy system, lattice matched to a GaAs substrate.
6:00 PM - K5.7
Highly Porous Nanocrystalline SnO2 by Combustion Method: Structural and Optical Characterization.
Sanjay Apte 1 , Sunil Garaje 1 , S. Potty 1 , Milind Kulkarni 1 , Sonali Naik 1 , Bharat Kale 1
1 Nanocrystalline Materials / Glass Laboratory , Centre for Materials for Electronics Technology (C-MET), Department of Information Technology, Govt. of India, Panchawati, Off Pashan Road, Pune, India, Pune, Maharashtra, India
Show AbstractSnO2 is a well known n- type semiconductor and widely studied sensor material for the detection of gases. The nano clusters of tin oxide were synthesized successfully by combustion method using the Stannic chloride hydrated as a precursor for the first time. The combustion was performed between the temperatures 500-6000C in well designed combustion reactor. Structural study was performed using XRD and showed the existence of highly crystalline phase pure tetragonal SnO2. The broadness of the XRD peaks also shows the nanocrystalline nature of the SnO2. The same has been confirmed using Transmission Electron Microscopy (TEM). TEM showed spherical nanoparticles of size 7-8nm. The Electron Diffraction (ED) pattern also confirms the existence of tetragonal SnO2. The product obtained was highly porous and free flowing in nature. The band gap was observed to be 3.7eV which is higher than the reported bulk material (3.6eV). The broadness in the UV-DRS peaks also shows the presence of porous SnO2 nano-clusters. Keywords: Nanoclusters, SnO2, optical property, gas sensors, nanocrystalline -----------------------------------------------------------*Corresponding author : e-mail addresses:
[email protected] /
[email protected]: 91-020-25898390, 25899273., Fax: 91-020-25898085, 25898
6:00 PM - K5.8
Hexathiapentacene Nanowires as Chemical Vapor Sensors.
Ting Gao 1 , Alejandro L. Briseno Briseno 2 , Edgardo Garcia-Berrios 3 , Jian Wang 1 , Richard McConville 1 , Mark Ellsworth 1 , Ryan Dupon 1 , Nathan Lewis 3
1 Polymers, Ceramics, and Technical Services Laboratories, Tyco Electronics Corp., Menlo Park, California, United States, 2 Department of Polymer Science and Engineering, University of Massachusetts, Amherst, Massachusetts, United States, 3 Department of Chemistry and Chemical Engineering, California Institute of Technolgy, Pasadena, California, United States
Show AbstractHexathiapentacene (HTP) crystalline nanowire is an organic semiconductor that can be synthesized with a simple solution phase route. HTP nanowires show high electronic mobility and have been successfully incorporated as a semiconducting material in FETs. In our work, we used a single crystalline HTP nanowire as a chemical sensor. Quartz Crystal Microbalance (QCM) and complex impedance measurements were employed to investigate the sensing properties of an HTP nanowire to analytes including acid, amine, water and hydrocarbon vapors. QCM measurements showed the absorption into HTP nanowire to be a factor of 10 greater for amines than for acetic acid, and 10 times greater for acid than for analytes such as hexane and toluene at low concentrations. Single HTP nanowire showed a symmetric I-V characteristic with a barrier for either polarity of biasing. Impedance measurements were performed over a range of chemical vapor concentration levels. Cole-Cole plots (0.01Hz-4 MHz) of measured impedance spectra of the sensor described an arc with a very large radius of curvature at low vapor concentration. At high concentration, the radius was reduced and the complete semicircle came inside the measurable impedance range with a spur at low frequency that distorts the semicircle. The sensor showed much higher impedance sensitivity to acetic acid and amine than to water vapor at low concentration and showed similar sensitivity at high concentrations. It also showed faster response time to acetic acid and water than to amine as shown in the complex resistance response to the chemicals monitored at 10 Hz. An equivalent circuit model with a Warburg impedance in the low frequency range closely fits the experimental data and indicates a diffusion of charges in the nanowire under the exposure to the chemical vapor. Impedance spectroscopy, which represents microscopic physiochemical processes occurring in the material as well as the resonance contributors of HTP structure, are discussed to attempt to explain the underlying physical sensing mechanisms.
6:00 PM - K5.9
Detecting Insect Infestation: A Novel Application of Carbon/Polyethylene-co-vinyl Acetate Sensors.
Kanchana Weerakoon 1 , Bryan Chin 1
1 Materials Engineering Department, Auburn University, Auburn, Alabama, United States
Show AbstractPlants, when attacked by herbivores emit plant volatile compounds as a defensive mechanism to protect themselves from herbivores and parasites. Secreting these volatiles is not only toxic towards these insects but also aids enemies of the herbivores to recognize infested plants to locate their prey. In this study, a low mass fraction carbon black/polyethylene-co-vinylacetate composite sensor was designed and fabricated. This sensor was cost efficient, easy to fabricate and was highly stable in air. When an organic vapor is present, the carbon/polymer active layer swells creating a discontinuity in the conducting pathway between adjacent carbon particles, increasing the resistance of the film. When the analyte is no longer present, the polymer will return to its original state, showing a decrease in resistance. A variety of Carbon/black polymer sensors with varying chemical characteristics could be created by using different polymer matrices. Polyethylene-co-vinyl acetate was chosen as the best polymer for this particular application based on its swelling ability in the presence of plant volatiles compared to other polymers. When the carbon concentration of the active layer was low enough to be near the percolation threshold, the sensor can be used as a “chemical switch”. The resistance of the sensor increased significantly mimicking a “switch off” response when exposed to the analyte vapor. When the analyte vapor was no longer present the sensor returned back to its original condition, showing a “switch on” response. The percolation point was obtained when the carbon concentration of the carbon/polymer composite was kept between 0.5-1 wt%. The sensor was tested and found to be sensitive to a variety of volatile organic compounds emitted during insect infestation including γ-terpinene, α-pinene, p-cymene, farnesene, and limonene and cis-hexenyl acetate.
Symposium Organizers
Elisabetta Comini Brescia University
Perena Gouma State University of New York-Stony Brook
Luisa Torsi Universita di Bari
George Malliaras Ecole Nationale Supérieure des Mines de St. Etienne
K6: Inorganic Materials for Chemical Sensing
Session Chairs
Wednesday AM, April 07, 2010
Room 2007 (Moscone West)
9:00 AM - **K6.1
Gas Sensor Based on Metal-insulator Transition in VO2 Nanowire: Fabrication and Tests.
Andrei Kolmakov 1 , Eugene Strelcov 1
1 Physics, SIUC, Carbondale, Illinois, United States
Show AbstractWe report on the facile method of fabrication of VO2 nanowires and nanoplatelets. The intimate link between the domain structure formed in these nanostructures and external stimuli opens few possibilities to create new sensors and actuators. As an example, using Joule heat driven metal-insulator phase transition in single crystal VO2 nanowires, the realization of the novel gas sensing concept has been tested. Stabilizing the temperature of the nanowire close to transition edge, the conductance of the nanowire becomes extremely responsive to the tiny changes in molecular composition, pressure and temperature of the ambient gas environment.
9:30 AM - K6.2
Detecting Phase Transitions on the Surface of a Single Nanotube.
Zenghui Wang 1 , Jiang Wei 1 , Erik Fredrickson 1 , J. Dash 1 , Oscar Vilches 1 , David Cobden 1
1 , University of Washington, Seattle, Washington, United States
Show AbstractPhase transitions within adsorbed monolayer of gas atoms on the surface of a nanotube were detected, using a single oscillating nanotube as the active sensing element. The density of the adsorbed atomic layer is continuously measured by driving a doubly-clamped nanotube to oscillate, determining its resonance frequency, and monitoring the downshift of the resonance upon mass loading. As pressure and temperature are varied, sharp, dramatic change in the density of the monolayer are observed and identified as transition between different low dimensional phases, with the knowledge obtained from adsorption studies on bulk graphitic materials.With the ability to pass an electric current through the nanotube device, we demonstrate that certain phase transition can also be detected by simply monitoring the conductance of the nanotube device, which illustrate the effect of adsorbed atoms on the substrate electrons. Vice versa, we show that the adsorption can also be tuned by the current passing through the nanotube, offering a new way of surveying the phase diagram of such low-dimensional systems.
9:45 AM - K6.3
Optical and Optoelectronic Gas Sensing Properties of Metal Oxide Nanowires.
Silvia Todros 1 , Camilla Baratto 1 , Elisabetta Comini 1 , Matteo Ferroni 1 , Guido Faglia 1 , Giorgio Sberveglieri 1
1 Sensor Lab, CNR & Univ. of Brescia, Brescia Italy
Show AbstractNanostructures of metal-oxide semiconductors have been extensively investigated for their novel physical properties and have found application in electronics, photonics and gas sensing.Among them, ZnO and SnO2 are n-type semiconductor with a wide band gap, showing a broad visible photoluminescence (PL) emission and are used in many applications such as gas sensors, transparent conducting electrodes, catalysts, solar cells and many other optoelectronic devices.ZnO and SnO2 nanowires irradiated with UV-visible radiation (near their band gap) show a great increase of conductance and photocurrent (PC) is generated, if a constant potential is applied.PC is an extremely important property in semiconductors, providing valuable information about impurity levels, ionisation of donors and deep levels, through the analysis of the PC spectrum.Moreover, metal oxide PL emission and PC generation are strongly dependent on surface states and can thus be tuned depending on the surrounding atmosphere. PC measurements, via a lock-in amplifier, have the potential to develop new gas sensors with improved sensitivity.Furthermore, the study of the influence of the gaseous environment on PC generation can provide fundamentals information on surface recombination in metal oxide semiconductors.In this work, ZnO and SnO2 nanowires with high crystalline structure were prepared by evaporation-condensation in a horizontal tube furnace, starting from the oxide powder, on an alumina substrate in presence of Au catalyst. An experimental set-up was implemented for electronic and optoelectronic characterization of nanowires. Photoluminescence emission and photocurrent flowing through biased ZnO and SnO2 nanowires were studied in various gas atmospheres, targeting NO2 and ethanol sensing applications.PL emission spectrum of SnO2 nanowires in dry air showns a broad visible band centred at about 600 nm. The dynamic response of the peak area toward different NO2 concentrations shows a strong PL intensity quenching, proportional to target gas concentration, both for ZnO and SnO2.Nanowire PC was tested in different gas atmosphere, under continuous excitation by UV-visible lamp. The signal acquisition was carried out both by an electrometer and by chopper/lock-in amplifier. Lock-in amplifier allows measuring the part of the signal which varies at the same frequency of the chopper, getting rid of all the processes which take place at a slower rate. Locked-in signal measures surface processes with low activation energy, which are normally hindered by the much higher low frequency (DC) response. Given that the lock in signal is almost unaffected in the frequency range 10 Hz-200 Hz, these newly observed processes time constants are faster than 0.5 ms. Indeed, further measurements are scheduled in order to fully understand the origin of these processes and the correlation between PL and PC response.
10:00 AM - K6.4
Nanoscale Selective Silicon Nanowires Surface Functionalization for Sensing Applications.
Silvia Armini 1 , Marta Carli 1 2 3 , Johan Snauwaert 2 , Vladimir Cherman 1 , Ingrid De Wolf 1 4 , Veerle Simons 1 , Arantxa Maestre Caro 1 5 , Jos Moonens 1 , Pieter Neutens 1 3 , Kai Arstila 1 , J. Ogi 6 , S. Oda 6 , Yoshishige Tsuchiya 7 , Hiroshi Mizuta 7
1 AMPS, IMEC, Leuven Belgium, 2 Physics, Katholieke Universiteit Leuven, Leuven, Vlaamse Brabant, Belgium, 3 Physics, Padova University, Padova Italy, 4 MTM, Katholieke Universiteit Leuven, Leuven Belgium, 5 Chemistry, Katholieke Universiteit Leuven, Leuven Belgium, 6 , Tokyo Institute of Technology, Tokyo Japan, 7 , University of Southampton, Southampton United Kingdom
Show AbstractToday’s micro and nanoelectronics technology development is characterized by the migration of research from pure down-scaling to adding new functionalities. Especially for the chemical (e.g. gas sensing) and biological (e.g. biosensing) sensing applications, surface functionalization is of paramount importance with respect to selectivity and sensitivity. Self-assembled monolayers (SAMs) are one of the most relevant and reliable functionalization approaches to achieve selectivity in the sensing processes. Although the optimization of these organic films has received considerable attention, most of the functionalization routes have focused on the coating of sensors with relative large areas. The downscaling of the SAMs to small nano-devices, such as Si nanowires (NWs) - based sensors, requires additional tools, both for their selective deposition and characterization. In this work we first assess the stability of NH2-SAMs deposited on blanked SiO2 wafers against harsh environmental conditions by performing storage and thermo-cycling experiments followed by contact angle (CA) and Fourier transform infrared (FTIR) surface analysis. In the second part of the work, two main approaches to selective Si nanowires functionalization are being investigated: i) selective Joule heating ablation of the protective polymer layer on the NW surface, and ii) e-beam lithography to open the resist layer on the NW area. In a following step, a NH2-SAM layer is deposited on the unprotected silicon oxide surface and glutaraldehyde molecules are used as a linker between the SAM amino functionality and biotin. An AFM cantilever functionalized with avidin is used to test specific biotin-avidin interactions on the NWs surface in a buffer solution (pH 7.4) and eventual non-specific bindings. The values of the unbinding forces and corresponding adhesion work at a certain loading rate could be calculated from the analysis of the recorded force curves. In addition, an approach to selectivity which is alternative to polymer layers is depositing SAMs bearing functional groups such as methyl or polyethilenglycol (PEG). The NH2-SAM/biotin system is compared with the CH3-SAM/biotin and PEG6/9-SAM/biotin systems in terms of specificity of the interactions with the avidin molecules.This work is supported by EU FP7 NEMSIC project (Hybrid Nano-Electro-Mechanical/Integrated Circuit Systems for Sensing and Power Management Applications).
10:15 AM - K6.5
2, 4, 6-Trinitrotoluene (TNT) Chemical Sensing Based on Aligned Single-walled Carbon Nanotubes (SWNTs) and ZnO Nanowires.
PoChiang Chen 2 1 , Saowalak Sukcharoenchoke 1 , Koungmin Ryu 2 , Alexander Badmaev 1 , Chuan Wang 1 , Lewis Gomez 3 , Chongwu Zhou 1 2 3
2 Mork Family of Chemical Engineering and Material Science, USC, Los Angeles, California, United States, 1 Ming-Hsieh Department of Electrical Engineering, University of Southern California, Los Angeles, California, United States, 3 Department of Chemistry, University of Southern California, Los Angeles, California, United States
Show AbstractChemical sensors based on one dimensional (1-D) nanostructured materials have attracted a great deal of attention, due to exquisite sensitivity and fast response to surrounding environment. In addition, both carbon nanotubes and metal oxide nanowires are important candidates to build an electronic nose (e-nose) system. Among these materials, semiconductor single-walled carbon nanotubes (SWNTs) are molecular-scale wires composed entirely of surface atoms, which should be ideal for the direct electrical detection and are expected to exhibit excellent sensitivity to surrounding chemical and biological species. In addition, metal oxide nanowires have also been widely studied and demonstrated the great potential in chemical sensing applications.Recently, due to the threat of terrorism and the need of homeland security, significant effort has been made in the detections of both explosives and nerve agents, such as 2, 4, 6- trinitrotoluene (TNT), 2, 4- dinitrotoluene (DNT), hexogen (DRX), and dimethyl methylphosphonate (DMMP). One of the leading candidates is 1-D nanostructured material based chemoresistors or FETs. Snow et al. and Wang et al. have reported the detection of DMMP in ppb level by using SWNT and SnO2 nanowire based chemical sensors, respectively. However, to the best of our knowledge, there were only few reports using 1-D nanostructured materials based chemoresistor and FETs to detect explosives and the detection mechanism us still unclear.In addition, electronic devices fabricated on mechanically flexible substrates have recently attracted enormous attention, due to proliferation of handheld and wide applications in portable electronics, aerospace science and civil engineering. Currently, conventional mircofabrication techniques or printing methods can be applied to SWNTs on plastic substrates to form devices, which provide a solution for inexpensive mass-production and conformable electronics. In this talk, we report the transfer of aligned semiconductor SWNTs onto cloth fabric and successful fabrication of flexible SWNT chemical sensors, which have great potential for wearable electronics. These SWNT chemical sensors exhibited good sensitivity of trace chemical vapors, including 8 ppb TNT and 40 ppb NO2, at room temperature. Besides, to realize the concept of electronic nose (e-nose) system for explosives, we also fabricated ZnO nanowire based chemical sensors, which exhibited the detection limit of 60 ppb for TNT molecules at room temperature. To our best knowledge, this is the first TNT sensor built on metal oxide nanowires. In addition, the detection limit of our chemical sensors is close to the requirement of 1.5 ppb TNT set by U.S. Occupational Safety and Health Administration. The flexible TNT sensors could find immediate applications in systems with the demand of mechanical flexibility, light weight, and high sensitivity.
10:30 AM - K6: Inorganic
BREAK
K7: Chemical Sensors
Session Chairs
Wednesday PM, April 07, 2010
Room 2007 (Moscone West)
11:00 AM - **K7.1
Materials and Device Physics of Organic and Hybrid Organic-Inorganic Field-effect Chemical Sensors.
Ananth Dodabalapur 1 , Shannon Lewis 1 , Soumya Dutta 1 , Yeon Taek Jeong 1 , Deepak Sharma 1
1 , University of Texas-Austin, Austin, Texas, United States
Show AbstractOrganic semiconductor thin-film transistor (TFT) chemical vapor sensors have been investigated by many groups in the past several years. Studies have shown that trapping of charges by polar analytes at grain boundaries and other device interfaces often results in a decrease in drain current in a number of semiconductors responding to a variety of analytes. We describe the mechanisms by which current decrease is observed in organic TFT sensors and the measurement of activation energies at various analyte concentrations. An important limitation of organic TFT chemical sensors is that the ordinary bias stress effect ( which is a decrease in drain current with time due to charge trapping) in the absence of analytes is indistinguishable from drain current decrease due to analytes. Inclusion of receptor chemicals augments the sensitivity and selectivity of organic TFT sensors. This occurs mainly due to the fact that the receptors modify the sticking properties of the various analyte molecules to the semiconductor surface. In prior work, we reported on the four-terminal field-effect sensing device, which is one way to overcome the limitations of organic TFT chemical sensors. In such 4-terminal (4T) sensors, two channels are coupled leading to the exposed channel serving as the sensor interface and the second, buried, channel as the measurement interface. This results in enhanced sensitivities and reduced bias stress effect related limitations. We have recently realized several types of 4T sensor devices including those based on silicon/organic, organic/organic, and inorganic thin-film/organic channels. The gate dielectrics include SiO2, solution deposited dielectrics, and a unique high-k nanoscale multilayer dielectric from Northwestern University. The response characteristics and modes of operation of such 4T sensors will be elucidated. In other recent work, a novel hybrid bi-layer ambipolar transistor structure, using zinc oxide as n-type inorganic semiconductor and pentacene as p-type organic counterpart has been shown to work as a chemical vapor sensor. The device operates in four different modes depending on the combination of gate voltage and drain-source voltage. These are as follows: n-channel accumulation mode, p-channel diode mode, n-channel diode mode and p-channel accumulation mode. The sensing is due to charge trapping in the organic semiconductor layer, although in some modes the read-out is the current flowing through the zinc oxide. The modes of operation of this sensor will also be described.
11:30 AM - K7.2
Plasma Enhanced Chemical Vapor Deposition as a Fabrication Tool for High Sensitivity Chemical Sensors.
Jesse Enlow 1 2 , Hao Jiang 1 3 , Daniel Gallagher 1 , Lawrence Brott 1 , Michael McConney 1 4 , Rachel Jakubiak 1 , Rajesh Naik 1 , Vladimir Tsukruk 4 , Timothy Bunning 1
1 Materials and Manufacturing Directorate, Air Force Research Lab, Wright Patterson AFB, Ohio, United States, 2 , UES, Inc., Dayton, Ohio, United States, 3 , Materials Sci. and Tech Applications, LLC, Dayton, Ohio, United States, 4 School of Polymer, Textile and Fiber Engineering, Georgia Institute of Technology, Atlanta, Georgia, United States
Show Abstract Plasma enhanced chemical vapor deposition (PECVD) has recently been investigated as a fabrication tool for highly sensitive chemical vapor sensors. Since PECVD is a solvent-free, well controlled, room temperature process it is amenable to deposition of films onto materials that cannot withstand wet chemical processing or high temperature environments. Plasma polymerization (pp-) produces highly crosslinked amorphous films with smooth surface morphologies, robust mechanical properties and strong thermal, chemical and environmental resistances. These pp-films can be derived from a variety of monomers including gases, liquids and solids, and can be engineered to retain some of the chemical characteristics of the original monomers as well as creating new features that do not exist in the precursor materials. A modified flowing afterglow plasma reactor is utilized to deposit high density functionalized polymer thin films onto several different sensor motifs including RFIDs and silicon cantilevers to detect several chemical vapors including water, nitrobenzene and half mustard gas. Systematic variation of the pp-film’s thickness and density resulted in measurable changes in sensor response to analyte exposure.
11:45 AM - K7.3
Nanoporous Framework Materials Interfaced With Mechanical Sensors for Highly-sensitive Chemical Sensing.
Ronald Houk 1 , Jin-Hwan Lee 3 , Anandram Venkatasubramanian 3 , Alex Robinson 2 , Jack Skinner 1 , Steven Thornberg 2 , Roland Fischer 4 , Mikhial Meilikhov 4 , Kirill Yusenko 4 , Peter Hesketh 3 , Mark Allendorf 1
1 , Sandia National Laboratories, Livermore, California, United States, 3 School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, Georgia, United States, 2 , Sandia National Laboratories, Albuquerque, New Mexico, United States, 4 Lehrstuhl fuer Anorganische Chemie II, Ruhr-Universitaet Bochum, Bochum Germany
Show AbstractWe will describe how novel nanoporous framework materials (NFM) such as metal-organic frameworks (MOFs) can be interfaced with common mechanical sensors, such as surface acoustic wave (SAW), microcantilever array, and quartz crystal microbalance (QCM) devices, and subsequently be used to provide selectivity and sensitivity to a broad range of analytes including explosives, nerve agents, and volatile organic compounds (VOCs). NFM are highly ordered, crystalline materials with considerable synthetic flexibility resulting from the presence of both organic and inorganic components within their structure. Chemical detection using micro-electro-mechanical-systems (MEMS) devices (i.e. SAWs, microcantilevers) requires the use of recognition layers to impart selectivity. Unlike traditional organic polymers, which are dense, the nanoporosity and ultrahigh surface areas of NFM allow for greater analyte uptake and enhance transport into and out of the sensing layer. This enhancement over traditional coatings leads to improved response times and greater sensitivity, while their ordered structure allows chemical tuning to impart selectivity. We describe here experiments and modeling aimed at creating NFM layers tailored to the detection of water vapor, explosives, CWMD, and volatile organic compound (VOCs), and their integration with the surfaces of MEMS devices. Molecular simulation shows that a high degree of chemical selectivity is feasible. For example, a suite of MOFs can select for strongly interacting organics (explosives, CWMD) vs. lighter volatile organics at trace concentrations. At higher gas pressures, the CWMD are deselected in favor of the volatile organics. We will also demonstrate the integration of various NFM on the surface of microcantiliver arrays, QCM crystals, and SAW devices, and describe new synthetic methods developed to improve the quality of NFM coatings. Finally, MOF-coated MEMS devices show how temperature changes can be tuned to improve response times, selectivity, and sensitivity.
12:00 PM - K7.4
Photocatalytic TiO2 Nanostructures for Self-regenerating Sensors.
Daniel Smetaniuk 1 , Michael Taschuk 1 , Michael Brett 1 2
1 Electrical and Computer Engineering, University of Alberta, Edmonton, Alberta, Canada, 2 , NRC National Institute for Nanotechnology, Edmonton, Alberta, Canada
Show AbstractA critical issue in the design of porous materials for sensing is control over the architecture of the porous network. The Glancing Angle Deposition (GLAD) technique enables fabrication of high-porosity nanostructures, from vertical posts to helices, with very fine control over parameters such as porosity, pitch, and film thickness [1]. GLAD films may be created from virtually any material that may be evaporated on any substrate, including flexible and transparent, with the film geometry specifically tuned for the application. For example, hydrocarbon sensors have used GLAD Pt films [2] and capacitive relative humidity (RH) sensors with response times as fast as 50 ms have been fabricated with TiO2 GLAD sensing layers [3]. The anisotropic porous columnar morphology enables water to easily diffuse into the film and provides a large surface area for water adsorption. Sensor ageing, hysteresis, and non-linearity must be addressed for practical commercial and industrial chemical and biochemical sensing applications. Capacitive RH sensors age over time resulting in decreased performance, however ultraviolet (UV) treatment regenerates and improves sensor performance as well as decreases hysteresis in the response [4]. Superhydrophilicity is photo-induced in anatase TiO2 using wavelengths shorter than 387 nm, which increases surface hydroxylation on the films and is important to the physics of water sensing. TiO2 is also an excellent photocatalyst that is able to break down organic contaminants on surfaces. Thus there is the potential of using self-cleaning TiO2 layers in sensors and photovoltaics to reduce device fouling.We are investigating the photocatalytic properties of GLAD TiO2 films and are characterizing the regenerative and cleaning effects on RH sensors. UV LEDs are used in an integrated, self-regenerating, self-cleaning sensor platform. Photocatalytic activity on the films is quantified with the decomposition rate of methylene blue through a range of UV wavelengths. Hydrophilicity is determined by measuring the contact angle of water on the films. Sensors are treated with different wavelengths, and sensor performance, ageing, and hysteresis are monitored. The results of these experiments will be used to optimize RH sensor design, and will be applied to detection of other organic and inorganic species using nanostructured TiO2. Experimental results and device characterizations will be presented.[1] M.M. Hawkeye, M.J. Brett. J. Vac. Sci. and Tech. A 25 (2007) pp. 1317-1335[2] K.D. Harris et al. Sen. And Materials 13 (2001) pp. 225-234[3] J.J. Steele et al. IEEE Sen J. 7 (2007) pp. 955-956[4] M. T. Taschuk et al. Sen and Actuators B: Chem. 134 (2008) pp. 666-671
12:15 PM - K7.5
Novel Concept for the Formation of Sensitive, Selective, Rapidly Responding Conductometric Sensors.
James Gole 1 2 , Serdar Ozdemir 1
1 School of Physics, Georgia Institute of Technology, Atlanta, Georgia, United States, 2 School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, Georgia, United States
Show AbstractRapidly responding, reversible, sensitive, and selective porous silicon-based gas sensors, operating at low power, are formed with a highly efficient electrical contact to a nanopore covered microporous array. Significant changes in sensor surface sensitivity are facilitated for a variety of gases, based on a complementary concept to that of strong and weak acid-base (HSAB) interactions and commensurate with a basis in physisorption has now been formulated to create a range of highly selective surface coatings. A “Materials Selection Table”, implemented on ‘phase matched’ silicon nanopores positioned on porous silicon micropores facilitates the application of nanostructured metals, metal oxides, and nanoparticle catalytic coatings, and provides for notably higher sensitivities and selectivity. Single nanostructure depositions, which include electroless gold, tin, copper, and nickel, as well as nano-alumina, magnesia, titania, and zirconia provide for the detection of gases including NO, NO2, CO, NH3, PH3, SO2, H2S, HCl, and toluene in an array-based format at the sub-ppm level. The value of this conductometric sensor technology results from a combination of (1) its sensitivity and short recovery time, (2) its operation at room temperature as well as at a single, readily accessible, temperature with an insensitivity to temperature drift, (3) its potential operation in a heat-sunk configuration allowing operation to a surface temperature of 80°C even in highly elevated temperature environments (in sharp contrast to metal oxide sensors), (4) its ease of coating with diversity of clearly mapped gas-selective materials for form sensor arrays, (5) its low cost of fabrication and operation, (6) its low power consumption, (7) its ease of rejuvenation following contamination, and (8) its ability to rapidly assess false positives using FFT techniques, operating the sensor in a pulsed gas mode.
K8: Organic Materials in Biochemical Sensing
Session Chairs
Wednesday PM, April 07, 2010
Room 2007 (Moscone West)
2:30 PM - **K8.1
InAs-based Label-free Electronic Sensors.
April Brown 1 , Maria Losurdo 2 1
1 Electrical and Computer Engineering, Duke University, Durham, North Carolina, United States, 2 , IMIP-CNR, Bari Italy
Show AbstractSemiconductors possessing very low conduction band minima with respect to their branch point energies, such as InAs and InN, have a high concentration of electrons (~1012 cm-2 or greater) at their surfaces that can be modulated by local molecular interactions. The functionalization of these surfaces with a range of molecules enables selective interactions to be sensed via modification of the electron concentration. Using simple planar InAs device structures, we have demonstrated the reversible and differential sensing of NO, NO2 and CO at concentrations below 10 ppb by exploiting different metalloporphyrins attached to InAs surfaces. In addition, we have demonstrated the selective detection of proteins (IL-1, IL-6 and TNF-α) at pM concentrations by exploiting surface-attached monoclonal antibodies.The direct electronic transduction of bio-molecular interactions has been explored for decades and continues to be of great interest. One important barrier to achieving high sensitivity is the low surface area to volume ratio of “traditional” electronic device implementations. The minimization of this constraint underlies the observed performance improvements achieved with nanowire electronics devices. However, the intrinsic electronic properties of the InAs surface enable a solution to this problem with numerous additional advantages over semiconductor nanowire sensors.Understanding the chemical and electronic properties of the molecular layer-semiconductor interface is critical. To this end, a range of functionalization processes, exploiting different molecular terminal groups, has been explored and characterized using x-ray photoelectron spectroscopy, spectroscopic ellipsometry, scanning probe microscopy, Raman spectroscopy and conductivity measurements. Functionalization impacts interfacial properties and, consequently, critical sensor figures of merit, such as the limit of detection and dynamic range. The specific electronic and chemical properties of InAs as well as the other semiconductors in this class are shown to be advantageous for electronic sensors.
3:00 PM - K8.2
Large-scale Production of Selective Gas Sensors Based on Carbon Nanotube Mats Transistors.
Louis Gorintin 1 2 , Paolo Bondavalli 1 , Pierre Legagneux 1
1 LMNP, Thales Research and Technology, Palaiseau France, 2 LPICM, Ecole Polytechnique, Palaiseau France
Show AbstractCarbon NanoTube (CNT) transistors are known for several years to be extremely sensitive to gases. This is the reason why scientist tries to use them as gas sensors. But their production is still a problem. In this article, we present our approach to realize large-scale production of reproducible devices using CNT mats deposited by airbrush technique. This technology enable to mass-product high performance and low cost devices. Indeed, with airbrush technique, the density of the CNT network can be adjusted precisely and so the percolation threshold can be reached only for semi-conducting nanotubes. Obtaining this new semiconducting material, we are able to achieve transistors with on/off ratio of more than 5 orders of magnitude. Thanks to these good transfer characteristics, the detection limit of these devices can be lowered under the ppm for a large range of gases. But the other issue for these sensors is selectivity. To perform it, we have develop a new technology patented based on CNTFET based arrays with different metals as electrodes. We demonstrate that each gas interacts specifically with each metal identifying a sort of electronic fingerprinting. Thus we are able to discriminate each gas of one other.
3:15 PM - K8.3
Real Time Detection of Chemical and Biological Species in Aqueous Media Using Organic Thin Film Transistors(OTFTs).
Olasupo Johnson 1 , Anatoliy Sokolov 1 , Mark Roberts 2 , Yadong Cao 1 , Zhenan Bao 1
1 Chemical Engineering, Stanford University, Stanford, California, United States, 2 Center for Integrated Nanotechnologies, Sandia National Laboratories, Albuquerque, New Mexico, United States
Show AbstractThe use of organic electronics ranges from photonic applications such as photovoltaics and light emitting diodes to displays and electronic applications such as radio frequency identification tags (RFID) and circuits. However, the use of sensors based on organic thin film transistors (OTFTs) has garnered a lot of interest in the healthcare, environmental monitoring and food industries. This interest in OTFT sensors has grown owing to the combination of cheap manufacturing processes (i.e. printing) and a variety of robust materials available through chemical synthesis. Thus, OTFTs are championed as candidates for cheap sensors in aqueous media. For OTFTs sensors to be commercially applicable it is imperative that sensors be stable in the media of interest, highly sensitive and selective to the chemical and biological analyte being monitored while maintaining repeatable and reproducible sensor responses. Thus, the first goal is to establish the stability of OTFT sensors in various aqueous media e.g. buffer solutions, marine environments. Thus far, real time chemical and biological detection in aqueous media have been difficult to achieve with OTFTs due to water mediated material degradation and the typical requirement of high operating voltages. We now report that low voltage OTFTs with water stable organic semiconductors thus exhibit show stable operation in water, seawater and biologically relevant buffer solutions. These devices can be used to detect low concentrations of analytes with repeatable and reproducible sensor responses. In this presentation the effects of media and semiconductor materials on stability and sensitivity will be discussed.
3:30 PM - K8.4
Controlled Fabrication of High Temperature Nanostructure Material Based Chemical Sensors.
Laura Evans 1 , Gary Hunter 1 , Jennifer Xu 1 , Gordon Berger 2 , Randall Vander Wal 3
1 , NASA GRC, Cleveland, Ohio, United States, 2 USRA, NASA GRC, Cleveland, Ohio, United States, 3 , Penn State, University Park, Pennsylvania, United States
Show AbstractThe use of nanotechnology based materials for chemical sensing has been of great interest since nanocrystalline materials have been shown to offer improved sensor sensitivity, stability, and response time. Several groups are successfully integrating nanostructures such as nanowires into operational sensors. The typical procedure may include random placement (e.g., dispersion, with fine-line patterning techniques used to create functional sensors) or time consuming precise fabrication (e.g., mechanical placement using an atomic force microscope or laser tweezer techniques). Dielectrophoresis has also been utilized, however it can be challenging to achieve good electrical contact of the nanostructures to the underlying electrodes. In this paper we report on a sensor platform that incorporates nanorods in a controlled, efficient, and effective manner. Semiconducting SnO2 nanorods are used as the sensing element for detection of hydrogen (H2) and propylene (C3H6) up to 600°C.Using a novel approach of combining dielectrophoresis with standard microfabrication processing techniques, we have achieved reproducible, time-efficient fabrication of gas sensors with reliable contacts to the SnO2 nanorods used for the detection of gases. The sensor layout is designed to assist in the alignment of the nanorods by selectively enhancing the electric field strength and allowing for the quick production of sensor arrays. The SnO2 nanorods are produced using a thermal evaporation-condensation approach. After growth, nanorods are separated from the resulting material using gravimetric separation. The rods vary in length from 3µm to greater than 10µm, with diameters ranging from 50 to 300nm. Dielectrophoresis is used to align multiple nanorods between electrodes. A second layer of metal is incorporated using standard microfabrication methods immediately after alignment to bury the ends of the rods making contact with the underlying electrodes within another layer of metal. Electrical contact was verified during testing by the response to H2 and C3H6 gases at a range of temperatures.Testing was performed on a stage with temperature control and probes were used for electrical contact. Gas flows into the testing chamber at a flow rate of 4000sccm. Sensor response of normalized current shift, |Igas-Iair|/Iair, was measured at a constant voltage bias. Sensors showed response to both H2 and C3H6. Detection of H2 was achieved at 100°C and response levels improved approximately 12000-fold at 600°C. Detection of C3H6 started at 100°C and improved approximately 10000-fold at 600°C. Detection of at least 200ppm for both gases was achieved at 600°C.Using this novel microfabrication approach, semiconducting SnO2 nanorods integrated into a microsensor platform have been demonstrated and sensing response showed dramatic increases at higher temperatures.
3:45 PM - K8.5
Strategies to Enable Micro Chemo Mechanical Systems (MCMS) With Chemically Responsive Hinges.
Jatinder Randhawa 1 , Michael Keung 1 , Timothy Leong 1 , Noy Bassik 1 , David Gracias 1
1 Chemical and Biomolecular Engineering , Johns Hopkins Univeristy, Baltimore, Maryland, United States
Show AbstractIn contrast to microelectromechanical System (MEMS) devices, we describe the concept of enabling microchemomechanical Systems (MCMS) using chemically responsive hinges. Our concept is based on the manipulation of the curvature of multilayer thin film hinges in response to chemicals by mechanisms involving dissolution, delamination and chemical reactions. These hinges could then be patterned within microstructures such as cubic containers or microtools such as grippers to enable a variety of chemically responsive functions such as pick-and-place operations and in vitro surgical procedures.[1-3] The highlight of chemically responsive hinges is that they can enable inexpensive, tetherless, actuation, en masse i.e. large numbers of structures can be actuated at once without the need for any wires or batteries. The concept of the active manipulation of stress within thin film hinges also suggests an attractive strategy for integrating chemical and biochemical sensing with mechanical actuation to enable smart and autonomous micromechanical systems. 1.Randhawa, J. S. et al. Pick-and-Place Using Chemically Actuated Microgrippers. Journal of the American Chemical Society 130, 17238-17239 (2008).2.Leong, T. G. et al. Tetherless thermobiochemically actuated microgrippers. Proceedings of the National Academy of Sciences of the United States of America 106, 703-708 (2009).3.Randhawa, J.S. et al. Reversible Actuation of Microstructures by Surface Chemical Modification of Thin Film Bilayers. Advanced Materials, published online DOI:10.1002/adma.200902337 (2009).
4:00 PM - K8: Organic
BREAK
K9: Organic Materials in Biological Sensing I
Session Chairs
Wednesday PM, April 07, 2010
Room 2007 (Moscone West)
4:30 PM - **K9.1
Organic Electronic Ion Pumps and Transistors to Modulate Signaling in Neurons, In Vitro and In Vivo.
Magnus Berggren 1 , Agneta Richter-Dahlfors 2 , Klas Tybrandt 1 , Karin Larsson 2
1 ITN, Linkoping University, Norrkoping Sweden, 2 Neuroscience, Karolinska Institutet, Stockholm Sweden
Show AbstractOrganic electronic materials can conduct electrons and charged biomolecules, thus making them suitable as the transducer at the biology-technology interface. This principle has been explored in several different kinds of organic electronic sensors and actuators. Here, we report the use of the combined ionic-electronic charge transport features of those materials to develop novel kinds of electronic delivery devices to induce signaling in neuronal cells. In a first device, we translate electronic addressing signals to well-defined transport and delivery of neurotransmitters. This device was explored, both in vitro and in vivo, to regulate neuronal signaling and to modulate senses of a mammalian, respectively. Further, to explore bioelectronics circuits one need to introduce transistor functionality into the delivery device. Such systems will enable complex matrix-addressed delivery and multiplexing systems that can generate very complex gradients and signal patterns to regulate the various signaling pathways of biological systems, which are complex and parallel to their nature.
5:00 PM - K9.2
Multiplexed and Miniaturized DNA-modified Electrodes for DNA and Protein Sensing.
Jason Slinker 1 , Natalie Muren 1 , Alon Gorodetsky 1 , Jacqueline Barton 1
1 Chemistry, California Institute of Technology, Pasadena, California, United States
Show AbstractWe report the use of silicon chips with 16 DNA-modified electrodes (DME chips) for multiplexed analysis of DNA and protein targets. Using highly sensitive, redox-active DNA monolayers, four DNA targets were simultaneously distinguished on a single DME chip with fourfold redundancy, including one incorporating a single-base mismatch. DME chips supported DNA monolayer formation with high fidelity, as confirmed by statistical comparison to commercially-available rod electrodes. The DNA sequence-specific activity of the restriction enzyme Alu1 was investigated, and titrations revealed concentration regions with distinct site-specific or star activity. The working electrode areas on the chips were reduced to 10 μm in diameter, revealing microelectrode behavior that is beneficial for high sensitivity and rapid kinetics. These results suggest that DME chips facilitate sensitive, selective, and label-free detection of DNA and protein targets, beneficial for laboratory assays and clinical diagnostic applications.
5:15 PM - K9.3
Design of Functional Liquid Crystalline Materials for Chemical and Biological Sensing.
Nicholas Abbott 1
1 Chemical and Biological Engineering, University of Wisconsin-Madison, Madison, Wisconsin, United States
Show AbstractThis talk will describe the synthesis and characterization of liquid crystalline materials for chemical and biological sensing. The strategy exploits surface-induced ordering transitions in liquid crystalline materials that are confined by chemically tailored interfaces. In one approach, a surface decorated with metal ion receptors that competitively bind liquid crystal and targeted analytes is employed. Exposure of the supported liquid crystal to different chemical environments leads to easily visualized (or quantified) changes in the optical and dielectric properties of the film of liquid crystal. These advances have led to the capability to report parts-per-billion (by volume) concentrations of organophosphonate and organoamine compounds from a vapor in tens of seconds. In a second example of the approach, the interfaces of liquid crystalline materials have been tailored to detect targeted lipid species from aqueous suspensions containing bacteria, thus demonstrating the applicability of the approach to both chemical and biological targets. Finally, adaptations of the approach to self-supporting, chemically responsive liquid crystalline gels will also be presented and discussed.
5:30 PM - K9.4
Synthesis of Size and Shape Controlled Silver Nanoparticles Coated by a Thin Layer of Gold and Their Use as Ultrasensitive Biomolecular Probes.
Derrick Mott 1 , Nguyen Thuy 1 , Yoshiya Aoki 1 , Shinya Maenosono 1
1 School of Materials Science, Japan Advanced Institute of Science and Technology, Nomi, Ishikawa, Japan
Show AbstractNanoscale probes for a wide range of biomolecules are currently being sought because of the beneficial and novel properties the nanoscale materials offer over not only the bulk material counterparts, but because of their increased sensitivity over traditional biomolecular detection techniques such as ELISA or PCR. Such enhanced properties as optical, magnetic, or electronic are highly useful in the creation of new biological probes with greatly enhanced robustness and sensitivity. In this area, silver nanoparticles coated with a thin layer of gold (Ag@Au) have received much attention because of the beneficial optical properties of silver (high extinction coefficient, well defined surface Plasmon resonance band, etc), and the biomolecular reactivity and biocompatibility properties of gold. Despite the intense work performed on this class of materials, there are still several challenges to be addressed in their optimization as bio-molecular probes. Such parameters as particle composition, size, shape, mondispersity, thickness of gold shell, and surface properties all must be improved upon in order to optimize these materials for biological probes, because these are the parameters that give rise to the enhanced properties of the nanoparticles. To this end we have devised an aqueous wet chemical synthesis technique towards size and shape controllable Ag@Au nanomaterials. The synthetic approach consists of three steps including synthesis of silver seed particles, growth of the seeds to a desired size, and finally deposition of a gold shell of controllable thickness. The initial silver seeds show a size of ~15nm, while final Ag@Au particles can be controlled in the range of ~15-60nm. The control of the particle size is highly important as the enhanced optical properties of silver operate at an optimal particle size. Finally, the resulting particles were used as ultra-sensitive probes to detect complementary stranded DNA molecules. The detection of the bio-molecules was carried out using UV-Vis and RAMAN spectroscopy techniques, which take advantage of the enhanced optical properties of the Ag@Au nanoparticles. This presentation will discuss the synthetic approach used towards these nanoparticle bio-probes, as well as their use to detect the complementary stranded DNA molecules.
K10: Poster Session: Functional Materials for Biosensing
Session Chairs
Thursday AM, April 08, 2010
Salon Level (Marriott)
9:00 PM - K10.1
Thermoresponsive Carbonaceous and Polymeric Nanostructures for Bioapplications.
Jérôme Roeser 1 , Robin White 1 , Markus Antonietti 1 , Magdalena Titirici 1
1 , Max Planck Institute of Colloids and Interfaces, Potsdam Germany
Show AbstractThe development of synthetic receptors capable of recognition or uptake of desired molecular targets with high affinity and selectivity is a persistent goal for researchers in fields of chemistry, biology and pharmaceuticals. Mimicking the remarkable examples of processes found in Nature, where essential biological reactions are governed by selective recognition as well as controlled uptake and release of biologically relevant molecules, still remains a major challenge. The design of synthetic functional materials that combine multiple properties incorporating stimuli-responsive moieties are promising candidates to address intelligent drug release and thus have huge potential in biological applications. Here, we want to present two different approaches for the production of such stimuli responsive systems that can be applied in smart chromatography or controlled drug delivery. In both cases poly(N-isopropyl acrylamide) (PNIPAAM) is used as a thermo-responsive polymer since it has temperature sensitivity close to body temperature (LCST at 32°C) and because it is relatively insensitive to small changes in its environmental conditions.One approach involves a polymer with molecular recognition properties which can be manipulated with temperature. As a proof of concept we firstly produced a molecularly imprinted polymer monolith exhibiting recognition properties for theophylline, followed by grafting of PNIPAAM in a second step. We then studied the dependence of the recognition properties of such a system with temperature using chromatography. The recognition of the target molecule takes place when the PNIPAAM is in its expanded state (below LCST) whereas the memory of the target molecule is lost from the surface as a result of polymer collapse above the LCST. Another approach consists in the production of carbonaceous hollow spheres with surface functionality by hydrothermal treatment of carbohydrates in the presence of sacrificial templates (e.g. latex nanoparticles). The size of the carbon capsules can be tuned according to the latex template. Capsule post-functionalization with PNIPAAM, generates reversible swelling-shrinking transitions with temperature, making such materials promising candidates for drug release and controlled release applications.
9:00 PM - K10.10
Bio-composite Materials for the Detection of Estrogen in Water Using Piezoresistive Microcantilever Sensors.
Tim Porter 1 , Tim Vail 2 , Catherine Propper 2 , Nazmul Islam 3
1 Physics, Northern Arizona University, Flagstaff, Arizona, United States, 2 Chemistry and Biochemistry, Northern Arizona University, Flagstaff, Arizona, United States, 3 Electrical Engineering, University of Texas Brownsville, Brownsville, Texas, United States
Show AbstractEndocrine-disrupting compounds (EDCs) may have harmful effects on environments and human health, including abnormalities in the human reproductive system, wildlife hermaphroditism and feminization. These compounds are found in surface and ground effluent at biologically relevant concentrations. For example, the USGS recently measured pharmaceuticals, hormones and industrial compounds in contaminated streams throughout the US, with similar results having been obtained throughout the industrialized world. Field and laboratory studies with wastewater demonstrate the endocrine disrupting potential of wastewater compounds, in particular chemicals with estrogenic activity that induce feminizination of fish and amphibians. The environmental implications of these findings are only just beginning to be understood. As the world becomes increasingly vigilant about estrogen activity, the demand for rapid, on-site/real-time detection is expanding quickly. In this study, we report on the use of piezoresistive microcantilever sensors in the detection of estrogen in water.Piezoresistive microcantilever sensors may be used in a variety of applications, including medical, chemical or in some cases biological sensing. One type of these sensors, embedded piezoresistive microcantilever (EPM) sensors, operate by embedding or partially embedding a small piezoresistive microcantilever into a custom designed sensing material. The sensing material must be synthesized or fabricated in such a way as to respond volumetrically to the presence of the desired chemical or biological analyte. Sensing materials used in EPM applications may include common organic polymers, composite polymer/biomolecule materials, or polymers functionalized with other active particles or chemicals. Exposure to the desired analyte causes the sensing material volume to change, inducing a bending or strain the cantilever which is measured as a simple resistance change. The volumetric shift in the sensing material may be due to diffusion of the analyte molecules into the sensing material, probe-target binding on the material surface or bulk, or surface or bulk chemical reactions between the analyte and sensing material. Cantilever strains of only a few angstroms are potentially measurable. Here, the sensors consist of a piezoresistive microcantilevers functionalized with a probe layer of estrogen antibodies immobilized within a polymer matrix. These sensors were capable of detecting estrogen in water at moderate to low concentrations of estrogen.
9:00 PM - K10.11
pH-Responsive Hydrogel-LbL Assemblies for Confined Incorporation of Quantum Dots.
Eugenia Kharlampieva 1 , Veronika Kozlovskaya 1 , George Lilly 2 , Nicholas Kotov 2 , Vladimir Tsukruk 1
1 Materials Science & Engineering, Georgia Institute of Technology, Atlanta, Georgia, United States, 2 Chemical Engineering, University of Michigan, Ann Arbor, Michigan, United States
Show AbstractWe report on novel responsive hybrid materials with quantum dots immobilized in polyelectrolyte-hydrogel assemblies fabricated by spin-assisted layer-by-layer method (SA LbL). In contrast to previous studies, which utilized LbL films for reversible pH-triggered loading and release of quantum dots, we demonstrate the application of these pH-responsive hybrid systems for incorporation of quantum dots in a confined environment in a controlled way. A stack of strongly interacting PAH-PSS polyelectrolytes serve for confining CdTe nanoparticles stabilized by thioglycolic acid, while a poly(methacrylic acid) (PMAA) hydrogel matrix presents a one-component network with pH-responsive properties. When quantum dot layers are confined inside the hybrid matrix, the system undergoes reversible changes in photoluminescent intensity in response to pH variations. The pH response can be tuned by varying hydrogel structure and charge balance. Photoluminescent intensity of quantum dots is suppressed in excess negative charge at high pH, but excess positive charge at low pH results in significant photoluminescence increase. The approach presented here allows controlling architecture of the hybrid system by simple manipulation of thickness of both PSS-PAH films and PMAA hydrogels. The main advantage of design suggested here is robust and reversible optical response which offers a possibility for development of the quantum dot –containing organized hydrogels for prospective pH- sensor or pH-monitoring.
9:00 PM - K10.13
Electrical Noise Characterization of Thiolate Functionalized Gold Nanoparticle Chemiresistors: Effects of Measurement Environment and Organic Linker Properties.
Lee Hubble 1 , Lech Wieczorek 1 2 , Karl-Heinz Muller 1 , Edith Chow 1 , James Cooper 2 , Burkhard Raguse 1 2
1 Future Manufacturing Flagship, CSIRO Materials Science and Engineering, Sydney, New South Wales, Australia, 2 Wealth from Oceans Flagship, CSIRO Materials Science and Engineering, Sydney, New South Wales, Australia
Show AbstractIn recent years self-assembled monolayer (SAM) capped gold nanoparticle films have generated significant interest as active sensing materials. These systems offer facile fabrication, scalability and cost effectiveness coupled with versatile SAM chemistries leading to analyte discrimination and low limits of detection. Predominately, these materials have been documented throughout the literature for detection of analytes in the vapor phase. Recently, we reported the novel use of thiolate functionalized gold nanoparticle chemiresistors for the detection of organic molecules in aqueous solution.1 In terms of understanding film transport properties and quantifying the ultimate sensitivities of these developed chemiresistors, it is fundamental that the intrinsic electrical noise of the nanoparticle films be understood. The electrical noise of gold nanoclusters has been previously reported for devices operating in air. 2, 3 Herein we report electrical noise measurements on thiolate functionalized gold nanoparticle films operating directly in aqueous solution for comparison to air measurements. The effects of various thiolate capping agents on the voltage-noise spectral density of the chemiresistors in water will be detailed. Depending on the chemical properties of the linker molecules, hydrophilic or hydrophobic, the nanoparticle film voltage-noise spectrum, and real part of the impedance spectrum, does indeed change based on operation in air or water. In water, at low frequencies, these effects can be attributed to increased thermal noise contributions, when measured at zero dc bias voltage. However, at higher frequencies double layer capacitance effects are introduced and these effects will be assessed in terms of a proposed circuit model. The effects of dc bias voltages has been utilized to determine flicker noise, or 1/f (where f is frequency) behavior in the nanoparticle films and we demonstrate that this intrinsic property is indeed a significant electrical noise source when operating in solution based measurement environments. These systems show no hysteresis effects from applied dc bias voltages, when avoiding voltages which would induce Faradaic processes at the electrode surface. Furthermore, through the introduction of target analytes to the chemiresistors the changes in noise prefactors, incorporating Hooge’s parameter, will be investigated. References: 1.B. Raguse, E. Chow, C. S. Barton and L. Wieczorek, Analytical Chemistry 79 (19), 7333-7339 (2007).2.M. G. Ancona, A. W. Snow, E. E. Foos, W. Kruppa and R. Bass, IEEE Sensors Journal 6 (6), 1403-1414 (2006).3.W. Kruppa, M. G. Ancona, R. W. Rendell, A. W. Snow, E. E. Foos and R. Bass, Applied Physics Letters 88 (5), 053120 (2006).
9:00 PM - K10.14
Applications of Polymer Stabilized Cholesteric Liquid Crystal as Gas Sensor Arrays.
Kun-Lin Yang 1 , Laura Sutarlie 1
1 Chemical and Biomolecular Engineering, National University of Singapore, Singapore Singapore
Show AbstractOrganoamines are volatile organic compounds commonly found in industrial or agricultural areas. They are usually hazardous chemicals which can cause severe health or environment problems. Therefore, detection of vaporous amines in the environments has attracted a lot of attention. In this presentation, we will discuss the utility of polymer stabilized cholesteric liquid crystal (PSCLC) as colorimetric sensor for detecting vaporous amines. The PSCLC with various polymer concentrations (5 - 20% w/w) can be made into an array which shows distinct color changes at different temperatures and upon exposure to 400 parts-per-million (ppm) octylamine vapor. Interestingly, PSCLC shows stronger response to primary amine over secondary amine, tertiary amine, and other volatile organic compounds having similar molecular weights. This is probably caused by the formation of hydrogen bonds between primary amine vapors and CLC molecules. Moreover, detection limits of PSCLC for linear primary amines (C3 – C10) decrease linearly with their molecular weights (on a log scale), and the detection limit for decylamine is as low as 2 ppmv. Hence, PSCLC is suitable as colorimetric sensor for primary amine vapors detection. Because PSCLC is transparent at most temperatures and changes color upon exposure to amine vapors, it can be coated on windows or safety goggles to offer protection against amine vapors.
9:00 PM - K10.15
Photopatterned Smart Hydrogel Actuation via pH / Ionic Strength Swelling Differential.
Noy Bassik 1 4 , Beza Abebe 3 , David Gracias 1 2
1 Chemical & Biomolecular Engineering, Johns Hopkins University, Baltimore, Maryland, United States, 4 School of Medicine, Johns Hopkins University, Baltimore, Maryland, United States, 3 Materials Science, Johns Hopkins University, Baltimore, Maryland, United States, 2 Chemistry, Johns Hopkins University, Baltimore, Maryland, United States
Show AbstractFunctionalized materials allow for design of sensitivity in response to specific environmental changes. We sought to use hydrogel technology and its associated large volume phase changes to turn a change in chemical environment into a large mechanical deformation. To do this in a manner that allows for easy integration with microfluidic environments and standalone tetherless devices, we chose photopatterning as an assembly technique. We developed a copolymer of N-isopropylacrylamide (NIPAm) that featured very different swelling responses to combinations of pH and ionic strength (IS). We achieved this behavior by photopatterning NIPAm-co-Acrylic acid (NIPAm-co-AAc) from an organic solution. We measured a maximum swelling ratio differential of 300% to 1500% in several combinations of pH and ionic strength. We then predicted mechanical actuation from a membrane layered from two polymers, which would enable a bilayer membrane to open and close. The resulting organic networks respond to changes and cycle through these reversible transformations within mild aqueous conditions over time spans of seconds to minutes. This behavior was demonstrated in photopatternable bilayers that exhibited differential swelling in response to different aqueous environments and organic solvents. By photopatterning a poly(ethylene oxide) diacrylate (PEODA) / NIPAm-co-AAc bilayer, folding occurred in response to changes from DI water to ethanol and from ph 7.8 (IS = 0.2M) to pH 2.5 (IS = 1.1 M) solutions. These systems may be constructed in any arbitrary shape, allowing for customized actuators for the desired application. By patterning polymer bilayers with more specific chemical sensitivity a chemical to mechanical sensor may be constructed.
9:00 PM - K10.16
Methylated DNA Detection Based on a Cationic Polythiophene.
Kateri Ouellet 1 , Isabelle Charlebois 2 , Maurice Boissinot 2 , Michel G Bergeron 2 , Mario Leclerc 1
1 Département de chimie, Université Laval, Québec, Quebec, Canada, 2 Centre de recherche en infectiologie, CHUL, Québec, Quebec, Canada
Show AbstractIn recent years, new analytical methods have been proposed for the detection of nucleic acids and proteins. They have to be simple, rapid, specific and sensitive for the diagnosis of infections and identification of genetic mutations. In this regard, a water-soluble cationic polythiophene derivative has been used for DNA hybridization transducers for specific single-stranded DNA using optical properties. This method, using UV-Vis absorption or fluorescence spectroscopy, is based on complementary electrostatic interactions without chemical modifications of the probe or the target. Cationic polythiophene could also be use for the detection of hypermethylation of promoter regions in specific genes for diagnosis of cancers. From UV-Vis absorption spectra, we have observed a clear discrimination between fully methylated (100%) and non-methylated (0%) duplex (Polythiophene/Single Stranded nucleic Acid). Further optimization is needed to get reliable responses for in-between methylated ratio. Moreover, the detection can also be monitored using a more sensitive method; the fluorescence spectroscopy. Indeed, a modification fluorescence signal could come from the cationic polythiophene for duplex with methylated nucleotides. Knowing that the methylation levels has the potential to supply additional information for the detection of cancers, improve follow-up cares for patients and therapy responses, the detection method needs to be improve.We have studied the duplex-formation temperature, the triplex-formation (DNA probe, polymer and DNA target), the influence of solvents, the methylation level and the length of the sequence in order to enhance the discrimination between methylated sequences duplex (100% or less) and non-methylated sequences duplex. We believe that cationic polythiophene polymer is sensitive enough to give strong and clear optical signal to slight conformation modification on methylated DNA, single-strand or not.
9:00 PM - K10.17
Tunable Photoluminescence Properties of Fluorescein in a Layered Double Hydroxide Matrix and Its Application in Sensor.
Min Wei 1 , Wenying Shi 1 , David Evans 1 , Xue Duan 1
1 State Key Laboratory of Chemical Resource Engineering, Beijing University of Chemical Technology, Beijing China
Show AbstractThis work reports the preparation of tunable photoluminescence film through incorporation of fluorescein into a layered double hydroxide matrix as well as its application in electrocatalysis for dopamine. The fluorescein (FLU) and 1-heptanesulfonic acid sodium (HES) with different molar ratios were co-intercalated into the galleries of Zn2Al LDH by the anion exchange method. Thin films of FLU-HES/LDH (x%, x stands for the molar percentage of fluorescein), which posses a well c-orientation of LDH platelets confirmed by XRD and SEM, were obtained by the solvent evaporation method on ITO substrates. It was found that the fluorescence wavelength, emission intensity and lifetime correlate with the orientation and aggregation state of FLU in LDH gallery, and can be finely controlled by varying the fluorophore content through changing the molar ratio of FLU/HES. In addition, the FLU-HES/LDH thin film modified electrode exhibits electrocatalytic performances for dopamine with rather high sensitivity and selectivity. The optimal luminous intensity, the longest fluorescence lifetime and the superior electrocatalytic behavior for dopamine of FLU-HES/LDH (x%) can be obtained with x value ranging in 1.34×10–2%~2.35×10–2%. Therefore, the novel strategy in this work not only provides a method for preparation of tunable luminescence materials through incorporation of an organic dye into a 2D inorganic matrix, but also demonstrates its prospective application in the field of biosensors.
9:00 PM - K10.18
Microfluidic System With PCR Integrated With Cell Lysis for DNA Analysis.
You-Cheol Jang 1 , Gi-sung Joo 1 , Kamrul Islam 1 , Hyun Ho Lee 2 , Yong-Sang Kim 3 1
1 Nano Science & Engineering, Myongji University, Yongin, Gyeonggido, Korea (the Republic of), 2 Chemical Engineering, Myongji University, Yongin, Gyeonggido, Korea (the Republic of), 3 Electrical Engineering, Myongji University, Yongin, Gyeonggido, Korea (the Republic of)
Show AbstractMicrofluidic systems have become widely used for various biochemical applications, which include sample pre-handling, reagent mixing, separation, and detection processes, due to short mass transfer length and transport time, very small volume of analytes, almost isothermal conditions, and easy parallelization.In particular case of cell lysis for extraction of intracellular components such as DNA, RNA, protein and metabolites is regarded as a routine procedure in most of the biological research and diagnostic industries. But, the available methods for this purpose are very time consuming, laborious and require multistep chemical treatments, which are often quite expensive. So we need efficient and advanced device, that are miniaturized and automated. The commonly used methods for lysis such as high voltage electroporation; proteinase-K, detergents and lysozyme treatment; laser induced fluorescence (LIF); bead milling and sonication or freeze–thaw in liquid nitrogen are unsuitable for miniaturization and also require additional separation or neutralization steps. However, this method lacked the aim of miniaturization. For example, a few groups have used extremely high voltage to the order of 1–10 kV or laser induced cell lysis and others needed sample pretreatment with addition of yet expensive reagents.On the contrary, our research’s goal is to develop a relatively inexpensive method for PCR with integrated cell lysis that uses minimal reagents power, and can be fabricated using common photolithographic techniques. A low-cost miniaturized flow-through device was fabricated using conventional photolithographic technique for PCR with integrated cell lysis using electrochemically generated hydroxyl groups. The device used low impedance Au-interdigitated electrode (IDE) fabricated on glass substrate to input DC potential to the overlaid PDMS based microchannel. The lysis of human cell line MCF-10A could be achieved between 2 and 5 V of DC input with optimum release of genomic DNA at 5 V for 5 min, which is the lowest potential range reported in any such study. The lysate was extracted to confirm release of genomic DNA and was successfully tested for PCR grade purity of DNA by amplifying a known tumor suppressor gene SMAD4. The proposed method was non-destructive for biocomponents due to absence of Joule heating and can be used in miniaturized PCR analysis as well as in native protein extraction to be performed under aseptic conditions. This integrated device was helpful in reducing the reaction time for DNA extraction as well as PCR amplification.
9:00 PM - K10.19
An Amorphous Silicon Device With an Immobilized Membrane for Acrylamide Sensing.
Joao Costa 1 3 , Miguel Fernandes 1 3 , Manuela Vieira 1 3 , Alessandro Fantoni 1 3 , Guilherme Lavareda 3 , Amin Karmali 2
1 Electrónica e Telecomunicações e de Computadores, Instituto Superior de Engenharia de Lisboa, Lisbon Portugal, 3 CTS, UNINOVA, Lisbon Portugal, 2 Chemical Engineering and Biotechnology Research Center, Instituto Superior de Engenharia de Lisboa, Lisbon Portugal
Show AbstractToxic amides are potentially hazardous to human health so there is great interest in building sensors to detect their concentration levels in food products. In this article we report on a novel acrylamide sensor based on the integration of an a-Si:H structure with a membrane containing immobilized recombinant amidase from Escherichia coli. The semiconductor devices were fabricated on glass substrates by the PECVD technique in the top gate configuration, where the metallic gate is replaced by an electrolytic solution with an immersed Ag/AgCl reference electrode.The devices are characterized experimentally and through numerical simulations to obtain insight into variables affecting their performance. Results show that the current-voltage curves are sensitive to the concentration of ammonium ions, which in turn depend of the concentration of acrylamide. One of the advantages of amorphous silicon devices, such as the one presented in this work, is their low fabrication cost compared with crystalline devices, which could be of interest in applications where there is a requirement for disposable sensors or there is significant risk of sensor damage.
9:00 PM - K10.20
Biosensors for Liver Function Detection Utilizing Electrical Conductivity.
Ya-Hsuan Chuang 1 , Tri-Rung Yew 1
1 Material Secience and Engineering, National Tsing Hua University, Hsinchu Taiwan
Show AbstractLiver has a wide range of functions, including processing nutrients, metabolizing medication, and detoxification. In this study, biosensors composed of Au-electrode arrays were fabricated for rapid and quantitative detection of human serum albumin (HSA), an important biomarker of liver function. Modification of glass sensing surface with amino group was utilized to improve biocompatibility. The current contributed by HSA at various concentrations was measured between two adjacent Au-electrodes directly and quantified. Metaloxide nanoparticles decorated with HSA were also implemented to enhance signal and increase detection sensitivity. Furthermore, electrical properties of biosensors were measured under DC and AC conditions. The surface morphology of sensing area was observed before and after antibody-modification by scanning electron microscopy, atomic force microscopy and fluorescent microscopy. The functional groups of modified nanoparticles were also characterized by Fourier transform infrared spectroscopy.
9:00 PM - K10.21
Schottky-gated Probe-free ZnO Nanowire Biosensor.
Ping-Hung Yeh 1 2 , Zhong Lin Wang 1
1 Materials Science and Engineering, Gerorgia Institute of Technology, Atlanta, Georgia, United States, 2 Physics, Tamkang University, Taipei County Taiwan
Show AbstractWe have demonstrated probe-free and highly sensitive nanowire-based nanosensors for detecting biologically- and chemically-charged molecules. The core of the device relies on the non-symmetrical Schottky contact under reverse bias. The Schottky–gated device(SGD) has a few merits in comparison to the conventional Ohmic contacted devices(OCD). First, it does not need a bio-probe to detect molecules; rather, it depends on the attraction of the charged molecules to the junction region. Second, as for the same type of nanowires, such as ZnO, the sensitivity of the SGD is much higher than that of OCD because a few molecules at the junction region can change the “gate” that effectively tunes the conductance. Third, owing to the nature of the charge and potential profile at the junction region, the SGD is likely to have some selectivity in detecting the positively-charged molecules versus the negatively-charged molecules. A low detection limit of 2 fg/ml has been demonstrated. The approach demonstrated here can serve as a guideline for designing more practical chemical and biochemical sensors.
9:00 PM - K10.22
Thin Hafnium Oxide Gate Insulator by Atomic Layer Deposition for Charge-based Biosensors.
Yi Wei Chen 1 , Maozi Liu 2 , Tetsuya Kaneko 1 , Paul McIntyre 1
1 Material Science & Engineering, Stanford University, Stanford, California, United States, 2 , Agilent Technologies, Santa Clara, California, United States
Show AbstractHighly sensitive, bio-field-effect-transistor (bioFET) molecular sensors require efficient surface charge modulation of the semiconductor channel for optimized performance and reliability. However, the SiO2 layer used as the gate dielectric in many Si-channel bioFETs is not inert to aqueous electrolytes and can absorb ionic species from solution. Hafnium oxide has a dielectric constant at least four times greater than that of SiO2, increasing bioFET sensitivity and permitting use of thicker gate dielectrics which may better protect the semiconductor surface. Moreover, HfO2 deposited by atomic layer deposition (ALD) is capable of coating complex nanostructured sensor surfaces. In this study, we demonstrate the stability of the capacitance response of ALD-HfO2 dielectrics in aqueous electrolytes. We also verify the possibility of biotin functionalization of HfO2 using photoelectron spectroscopy (XPS), capacitance-voltage (C-V) analysis and molecular AFM imaging methods, and compare results on functionalization effectiveness obtained using the latter two methods.
9:00 PM - K10.23
A Portable Grating-based Photonic Biosensor Reader With a Compact Tunable VCSEL and a Built-in Wavelength Meter.
Hyunsung Ko 1 , Bong Kyu Kim 1 , Kyung Hyun Kim 1 , Chul Huh 1 , Wan-Joong Kim 1 , Jongcheol Hong 1 , Seong-Seok Yang 2 , Ho-Jin Jang 2 , Gun Yong Sung 1 , Sun Hee Park 1
1 , ETRI, Daejeon Korea (the Republic of), 2 , Optowell, Jeonju Korea (the Republic of)
Show AbstractWe report a portable and precision photonic biosensor reader that measures the concentration of the anti-gen of the sample using a grating-based photonic biosensor. Among the various types of biosensors, a grating-based photonic biosensor is a grating on which anti-bodies are immobilized. The photonic biosensor uses a guided mode resonance filter (GMRF) structure with a sub-wavelength grating structure and made using nano-imprint lithography technology. It shows a sharp resonance peak in reflectance spectrum. When anti-gen in the sample combines with anti-body on the grating, it produces anti-gen:anti-body complex on the surface of the grating which changes the optical structures of the grating. It shifts the peak wavelength of the reflectance spectrum of the photonic biosensor. The concentration of the anti-gen can be evaluated by monitoring the shift of the peak wavelength of the reflectance of the grating. For the compactness of biosensor reader, we have manufactured a compact tunable vertical-cavity surface-emitting laser (VCSEL), a GMRF on a biosensor chip, and a compact built-in wavelength meter. The tunable VCSEL uses an internal device heater structure and has a wide tuning range. The VCSEL emission wavelength is measured with a built-in wavelength meter, which consists of a small sized edge filter, a linear sheet polarizer and photodiodes for a portable biosensor reader. We used a ratiometric wavelength measurement scheme. In ratiometric wavelength measurement scheme, the wavelength is determined by the ratio of the signals. The wavelength measurement speed of the ratiometric wavelength measurement technique is very fast and it is suitable for real-time measurement of the accurate emission wavelength of the VCSEL. Since the built-in wavelength meter consists of very few components, the size of the built-in wavelength meter is very small and it is suitable for a portable instrument. The manufactured grating-based photonic biosensor reader is palmtop size. We used the biosensor reader to measure the reflectance spectrum of a photonic biosensor and we report on the results.
9:00 PM - K10.25
DNA Hybridization Sensor Using OTFT.
Dong-Hoon Lee 1 , Jung-Min Kim 1 , Hyun Ho Lee 2 , Yong-Sang Kim 1 3
1 Nano Science & Engineering, Myongji University, Youngin Korea (the Republic of), 2 Chemical Engineering, Myongji University, Youngin Korea (the Republic of), 3 Electrical Engineering, Myongji University, Youngin Korea (the Republic of)
Show AbstractThe detection and quantification of DNA hybridization is of great importance in many applications such as biotechnology, medical diagnostics, genetics and pathogen detection. The “label” method is limited due to complicated sample preparation as well as necessary use of large optical systems and specialized analysis. Compared with these technics, DNA hybridzation using Organic Thin Flim Transistor (OTFT) has a bright future due to its low-cost fabrication method and faster detection. In our present work, we fabricated DNA hybridization sensor using OTFT and observed its electrical characteristics with ss-DNA and ds-DNA in varying time limits. The device was fabricated by using glass and Al gate electrode. Al gate electrode’s thickness was 100nm. The gate insulator, Poly(4-vinylphenol) (PVP), was deposited to a thickness of 480 nm by spin coating followed by baking at 200 °C for 60 min. The pentacene active layer was patterned through the shadow mask by thermal evaporation at a rate of 0.1 Å/s to a thickness of about 70 nm. The source and drain electrodes, a 200 nm thick Au layer were deposited through the second shadow mask by thermal evaporation. The pentacene TFTs obtained thereby had a channel length (L) and width (W) of 100 um and 1000 um respectively. The DNA immobilization was performed by pipetting a 1 uL drop of ss-DNA and ds-DNA containing D.I. water onto pentacene TFTs channel and air-dried. The channel current (Ids) of the pentacene TFT without DNA was measured at 23uA having a gate voltage (Vgs) at -30V. After immobilizing ss-DNA for 30min, the channel current (Ids) of the device was approximately reduced to 33%. But it was dramatically reduced more than 90% after 60min. This current change is due to the phosphate group of the DNA backbone having negative charges. The negative charges on DNA molecules are able to attract hole from the channel region, hence the hole concentration will lower in channel region. As ds-DNA is a hybridization of two ss-DNA, ds-DNA has more negative charge which attracts more holes from the channel region than ss-DNA. Therefore, it is expected that current variation of ds-DNA will be reduced more than that of ss-DNA. For that reason, the Pentacene TFT’s channel current (Ids) of ds-DNA immobilization reduced 95 % after 30 min. and then give to device immobilization time for 60 min. And channel current (Ids) was observed a substantial decreased of 99% in original device (without DNA). We observed decreased mobility as the immobilization time has increased. And channel current (Ids) was more decreased with ds-DNA than ss-DNA. In conclusion, we have shown that a dramatical difference in channel current change upon exposure to ss-DNA and ds-DNA using pentacene TFTs. This enables the direct electrical detection of DNA hybridization through the measurement of pentacene TFTs channel current.
9:00 PM - K10.26
Multispectral Refractive Index Sensing Using Surface Plasmon Resonance on Gold Nanoslits.
Pei-Yu Chung 1 , Kuang-Li Lee 2 , Gregory Schultz 3 , Pei-Kuen Wei 2 , Christopher Batich 1
1 Department of Material Science and Engineering, University of Florida, Gainesville, Florida, United States, 2 Research Center for Applied Sciences, Academia Sinica, Taipei Taiwan, 3 Department of Obstetrics and Gynecology, University of Florida, Gainesville, Florida, United States
Show AbstractSurface plasmon resonance (SPR) biosensors are widely used in sensitive chemical, biological and environmental sensing. The common SPR biosensors utilize the attenuated total internal reflection (ATR) method to excite surface plasmon resonance on a thin gold film coated on a prism, but a complicated system setup also comes with the prism based SPR biosensors. Recently, the studies of nano-plasmonics in metallic structures have shown that surface plasmons can also be excited by the metallic nanostructured films which can be used for high-throughput and chip-based SPR type sensing. For these plasmonic sensors, the common method to determine the refractive index sensitivity is measuring changes in the position or intensity of a single resonance peak. However, recent works have demonstrated that a type of full, multispectral analysis, observing all the peak shifts and intensity changes in the multiple plasmonic resonances in the spectra, can improve the signal-to-noise ratio of the system and enhance the sensing capabilities. In this investigation, we studied the best condition for the gold nanoslit arrays by testing their ability for refractive index sensing. Additionally, the multispectral analysis was employed to increase the refractive index resolution of the nanoslit SPR sensors. In this work, gold nanoslit arrays on a glass substrate were fabricated by using electron beam lithography and a reactive ion etching method. The gold thickness is 120 nm, the gap width is100 nm, and the periods of slits range from 400 nm to 20 μm. The area of each array was 150 µm×150 µm. The results show that a 500 nm period nanoslit array achieved a high sensitivity of approximately 18 Abs/RIU. Moreover, the greater sensitivity of up to 28586 %T●nm/RIU was obtained by multispectral analysis (RIU = refractive index unit, and T= transmission). It was also found that the signal-to-noise ratio of the integrated multispectral response was improved by a factor of 4 times the signal-to-noise ratio observed at the most sensitive single wavelength. Due to the future applications of multiplex SPR microarray CCD imaging platforms, the improved signal-to-noise ratio is highly important for scaling up the sensing capacities. Our work demonstrates a simple and robust sensing setup and real-time refractive index sensing with superior sensitivity.
9:00 PM - K10.27
Nanocomposite Route to Ultra-sensitive Surface Enhanced Raman Scattering Substrates.
Abhijit Biswas 1 , Ilker Bayer 2 , Alexandru Biris 3
1 Center for Nanoscience and Technology, Department of Electrical Engineering, University of Notre Dame, South Bend, Notre Dame, IN 46556, Indiana, United States, 2 Department of Aerospace Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801, Illinois, United States, 3 Nanotechnology Center, University of Arkansas at Little Rock, Little Rock, AR 72204, Arkansas, United States
Show AbstractSurface enhanced Raman spectroscopy (SERS) is a powerful technique for identifying molecules at very low concentrations. This capability is critical for many analytical applications such as forensics, medical diagnostics, drug discovery and chemical development. Extremely large enhancements in the Raman scattering signal can occur when molecules are adsorbed onto suitably rough, noble metal surfaces, which feature appropriate nanostructures and morphologies. An important design approach for sensitive and robust SERS substrates is the use of metal nanoparticle aggregates with nanometer tailored interstitial distances between their surfaces, in order to confine the electromagnetic energy. The nanostructural instability of the aggregates to agglomeration due to their strong van der Waals force poses a challenge for the preparation of large-scale, reliable SERS substrates. We present the fabrication of ultra-sensitive, stable SERS substrates that are promising candidates for the direct detection (label-free) and analysis of various biological and chemical samples. The approach uses a novel route to prepare SERS substrates, which is based on polymer–metal nanocomposites with a specific structure and composition just below the percolation threshold. The neighboring nanoparticles are still quite densely packed, but remain separated by narrow polymer gaps (<1 nm). Such a nanostructure allows the creation of densely packed hot spots where electromagnetic energy can be confined. The polymer–metal nanocomposites are fabricated by a simple and single-step method of electron-beam-assisted vapor-phase co-deposition. The preparation of the SERS substrates is based on a simple plasma-etching process, which removes the polymer structures that allow the formation of metal nanoparticle SERS nano-aggregates with very uniform and controllable inter-particle gaps. The method results in "ideal SERS hot spots" throughout the matrix. These hot spots can be created over very large areas. The developed SERS substrate has a number of major advantages: it is easy to produce, highly reproducible and cheap. The method could be leveraged to develop large-scale spectroscopic-based advanced detector systems for rapid and quantitative detection and analysis of various biological and chemical samples.
9:00 PM - K10.28
Scale-up Synthesis of Silver Nanocubes With High Yield and High Reproducibility.
Qiang Zhang 1 , Jingyi Chen 1 , Younan Xia 1
1 Biomedical engineering, Washington U in St. Louis, St. louis, Missouri, United States
Show AbstractProducing narrow size-distributed silver nanocubes in large quantities, together with high yield and high reproducibility has became an emergent issue. The well-defined Ag nanocubes can be used as the structural templates to fabricate gold nanocages via galvanic reaction, which hold great promises in a range of biomedical applications. Here, we report two new methods have been developed recently to pursue the demands of large quantities, uniform size and high reproducibility. These methods are based upon the modification of NaHS-mediated polyol synthesis, which allows for the production of Ag nanocubes on a scale around 0.1 g per batch. The linear relationship between the surface plasmon resonance (SPR) peak position and the size of Ag nanocubes provides a smart route to precisely control the size of silver nanocubes every bath, as confirmed by using the UV-vis spectroscopy. From the two methods, we could obtain silver nanocubes with the sizes ranging from 25 nm to 45 nm or from 25 nm to 70 nm, respectively.
9:00 PM - K10.29
Island Structured Dielectric Thin Films by Scalable Self-assembly: Potential for SERS Sensing.
Sharath Sriram 1 , Madhu Bhaskaran 1 , Paul Stoddart 2 , Arnan Mitchell 1
1 Microelectronics and Materials Technology Centre, RMIT University, Melbourne, Victoria, Australia, 2 Centre for Atom Optics and Ultrafast Spectroscopy, Swinburne University of Technology, Melbourne, Victoria, Australia
Show AbstractSize-dependent optical properties, such as the localized surface plasmon resonance (LSPR) of metallic nanoparticles, offer useful opportunities for chemical sensing. A number of techniques for producing nanostructured metal particle arrays have been reported [1,2]. Prior to the success achieved with the chemical synthesis of nanostructures, the conventional approach to increasing surface area was to increase the surface roughness of either the film or the substrate [3]. This was achieved by depositing the film onto a pre-patterned substrate or by employing films with crystalline and faceted surfaces [3].Combining these two approaches can be expected to provide significantly increased surface area and hence better sensing performance than either method alone. A chemical reaction could be used first to create micrometer-scale surface texture and then a crystalline film could be grown on top, to add nanoscale roughness. Employing a self-assembly driven chemical approach to texturing will also provide the benefits of scalability, allowing texturing of large areas (for example, mass fabrication on silicon wafers).A self-assembly driven process to synthesize island-structured dielectric films is presented. An intermetallic reaction in platinized silicon substrates provides preferential growth sites for the complex oxide dielectric layer. Microscopy and spectroscopy analyses have been used to propose a mechanism for this structuring process [4]. A mechanism for this structuring process is proposed, combining results from microscopy and spectroscopy analyses. Subsequent deposition of a complex oxide dielectric (PSZT) on these substrates results in preferential growth of the dielectric on the platinum-silicon islands, forming an island-structured coating. The substrates resulting from this synthesis process are suitable for sensing applications due to their increased interaction area. The ability of these textures to serve as SERS-active media is demonstrated, with 100× enhancement of detection sensitivity demonstrated for thiophenol as compared to the planar substrates. Further enhancement of the SERS sensitivity could be expected by optimising the silicide island morphology through control of the annealing conditions and through engineering of the nanoscale column structure of the complex oxide to best accommodate a specific analyte.References:1. A. N. Shipway, E. Katz, and I. Willner, Chemphyschem 1 18 (2000)2. M. E. Stewart, C. R. Anderton, L. B. Thompson, J. Maria, S. K. Gray, J. A. Roger, and R. G. Nuzzo, Chem. Rev. 108 494 (2008)3. G. Korotcenkov, Sens. Act. B 107 209 (2005)4. S. Sriram, M. Bhaskaran, G. Kostovski, D. R. G. Mitchell, P. R. Stoddart, M. W. Austin, and A. Mitchell, J. Phys. Chem. C 113 16610 (2009)
9:00 PM - K10.3
Direct DNA Detection Using a Poly (3-methylthiophene) Single Nanowire.
Dong Hyuk Park 1 2 , Nari Kim 1 , Chunzhi Cui 1 , Young Ki Hong 2 , Dae-Chul Kim 3 , Jeongyong Kim 3 , Jinsoo Joo 2 , Dong June Ahn 1
1 Department of Chemical and Biological Engineering, Korea University, Seoul Korea (the Republic of), 2 Department of Physics, Korea University, Seoul Korea (the Republic of), 3 Department of Physics, University of Incheon, Incheon Korea (the Republic of)
Show AbstractDirect DNA detection is presented using a light-emitting poly (3-methylthiophene) (P3MT) single nanowire (NW). Light-emitting P3MT NWs were electrochemically prepared based on an anodic alumina oxide (Al2O3) nanoporous template. The probe DNA (p-DNA) were easily attached to the P3MT NWs through electrostatic interaction between the negative counter-ions and the terminal amine (NH3+) group attached at the end of the p-DNA. The light emission color and intensity of a single strand of the DNA-functionalized P3MT NWs were monitored using a high resolution laser confocal microscope (LCM) and color charge-coupled device (CCD) images. After the functionalization p-DNA and their label–free recognition of target DNA (t-DNA) onto the surface of P3MT NTs, the light-emitting color and intensity of a single P3MT NW were dramatically changed. We observed color change of a single P3MT NW from green to red after attaching the p-DNA and then luminescence intensity of a single P3MT NW was dramatically enhanced by hybridizing t-DNA. This phenomenon can be explained in terms of the dopant-mediated fluorescence resonance energy transfer effect.
9:00 PM - K10.30
Magnetostriction Gradient and Mechanical Deformation of the Thin Film Composites.
B. Narsu 1 , Guohong Yun 2 1
1 Key Laboratory of Physics and Chemistry of Functional Materials, College of Physics and Electronic Information, Inner Mongolia Normal University, Hohhot, Inner Mongolia, China, 2 College of Physical Science and Technology, Inner Mongolia University, Hohhot, Inner Mongolia, China
Show AbstractMultilayered thin film structures usually exhibit unbalanced residual stress due both to the fabrication process and post fabrication process [1]. This stress affects the magnetostriction of the films and may induce a magnetostriction strain gradient. In this work we report a method to characterize the residual stress modulated magnetostriction induced bending deformation of the thick film cantilever system.Based on the four-parameter model [2], an effective bending theory for the cantilever actuated by magnetostrictive films with initial strain gradient is presented. The polynomial expansion methods that have been developed to depict the residual strain and corresponding gradient in the epitaxial films [1] is employed to describe the magnetostriction strain gradients. The results indicate that the magnetostriction strain gradients are favorable for the thick films in enhancing the bending deflection of the cantilever, namely one can enhance the resolution of the corresponding MEMS devices by tailoring magnetostriction gradients in the film. We furthermore proposed an effective experimental method for measuring the magnetostriction strain and its gradient on the basis of curvature measuring technique of the bent cantilever. By modulating the thickness of the substrate in the cantilever system (for instance, etching), one can measure the magnetostrictive biaxial strain (stress) and its gradient definitely. In order to avoid the unexpected surface effect on the bending of the cantilever, thick substrate should be used. The numerical work shows that relatively thick and soft substrate is favorable for this method. In addition, the advantage of the proposed method over the in situ measurement of the film stress in the growing process is that the inhomogenety and the surface effect can be avoided. References[1] E.H. Yang, S. S. Yang, S. H. Yoo, Appl.Phys.Lett. 67 912 (1995). [2] B.Narsu and Guohong Yun, J. Phys. D: Appl. Phys, 41 095309 (2008)
9:00 PM - K10.31
Shape- and Plasmon Wavelength-dependent Refractive Index Sensitivities of Gold Nanocrystals.
Chen Huanjun 1 , Shao Lei 1 , Ming Tian 1 , Wang Jianfang 1
1 Physics, Physics Department, The Chinese University of Hong Kong, Hong Kong China
Show AbstractHigh-performance optical sensors are nowadays strongly desired for biodiagnostics, environmental monitoring, and counter-terrorism. Such sensors should have favorable characteristics of ultrasensitivity, small sensing volumes, multiplex sensing behaviors, and being workable in harsh environments. Plasmon-based sensors with gold nanostructures are promising because gold nanocrystals are chemically stable, biocompatible, and their localized surface plasmon resonances are tunable over a wide spectral range. The plasmon resonance of gold nanocrystals generally red shifts as the refractive index of the surrounding nanoenvironment is increased, which forms the basis for plasmon sensing. The index sensitivity of gold nanocrystals is therefore a key factor in their practical sensing applications.We have systematically investigated the dependence of the index sensitivity on the shapes and sizes of gold nanocrystals that have varying plasmon resonance wavelengths (Langmuir 24, 5233, 2008), including nanospheres, nanocubes, nanobranches, nanorods (NRs), and nanobipyramids (NBPs). The index sensitivity has been found to generally increase both as the plasmon resonance wavelength for a fixed nanocrystal shape becomes longer and as the curvature of the nanocrystals gets larger. The gold nanospheres with a plasmon wavelength of 530 nm exhibit the smallest index sensitivity around 40 nm/RIU, while the index sensitivity of the gold nanobranches with a plasmon wavelength of 1140 nm reaches 700 nm/RIU. We have further studied the dependence of the index sensitivity on the specific shapes of gold nanocrystals that have the same longitudinal plasmon resonance wavelength (J. Phys. Chem. C 113, 17691, 2009). Seven types of differently shaped gold nanocrystals were considered, including large NRs, NBPs, large NBPs, medium NRs, dogbone-like NRs, peanut-like NRs, and small NRs. Their longitudinal plasmon wavelengths are all around 730 nm The refractive index sensitivities have been found to vary with the nanocrystal shape. They are in the range of 156 and 326 nm/RIU and increase in the order of small NRs, peanut-like NRs, dog-bone-like NRs, medium NRs, large NBPs, NBPs, and large NRs. Finite-difference time-domain calculations have been performed on these nanocrystals to reveal the origin of this dependence. A linear relationship is found between the index sensitivity and the product of the electric polarizability with the curvature. These results are important not only for understanding the fundamental aspects of the index sensitivity of noble metal nanocrystals but also for designing and developing ultrasensitive noble metal nanocrystal-based sensing devices.
9:00 PM - K10.32
Superimposed Photonic and Plasmonic Flow-through Nanostructures for Biodetection.
Sarah Baker 1 , Tiziana Bond 1 , Mike Pocha 1 , Allan Chang 1 , Donald Sirbuly 1 , Scott Dhuey 2 , Stefano Cabrini 2 , Sonia Letant 1
1 , Lawrence Livermore National Laboratory, Livermore, California, United States, 2 , Lawrence Berkeley National Laboratory, Berkeley, California, United States
Show AbstractPhotonic crystals (PCs) are ideally suited for use as filtration membranes because they can be fabricated as periodic arrays of air-holes, or pores, in a dielectric material. Computer simulations indicate that the edge of the PC optical band gap, which is sensitive to local changes in the refractive index in the pores, can be exploited to detect low numbers of bio-organisms captured within the PC filtration membrane. We will demonstrate that the same array of holes in a Si membrane that supports a photonic band gap and enables filtration can also give rise to enhanced Raman signals at the PC surface when coated with metal. The integration of metal structures into the PC filtration membranes that can support surface plasmon resonances at visible wavelengths will potentially enable label-free identification of the bound organisms by Raman spectroscopy, and enable localized surface chemistry for organism capture inside the membrane pores. This new class of compact flow-through sensors may enable real-time detection of bio-organisms in counter-terrorism, environmental, and medical applications. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. LLNL-ABS-416212
9:00 PM - K10.33
Nanopores Fabrication for Biomacromolecules Analysis.
Oukhaled AbdelGhani 1 2 , Bacri Laurent 2 1 , Borhis Eric 1 , Gierak Jacques 1 , Madouri Ali 1 , Patriarche Gilles 1 , Schiedt Birgitta 1 , Mathe Jerome 2 , Pelta Juan 2 , Auvray Loic 2
1 , LPN CNRS-UPR 20, Marcoussis France, 2 , université d'Evry Val d'Essonne, Evry France
Show AbstractNanopores in thin solid-state membranes, individual or as arrays, have found a growinginterest in the past few years. Nowadays, the most important application consists of using themembrane as a dividing wall in an electrolytic cell and drawing charged molecules by an electricfield through the pore. The resulting current blockage reveals informations about the passingmolecule.We will present the possibilities of applying our innovative FIB approach for the directfabrication of high-quality nanopores having sizes below 10 nm. In particular, we willshow that such nanopores can be reproducibly fabricated, with our processing methodology, inquantities compatible with industrial requirements.We will also detail some successful translocation experiments.
9:00 PM - K10.34
Device Overshield for Mass-sensing Enhancement (DOME) Fabrication.
Vincent Sauer 1 , Mark Freeman 2 3 , Wayne Hiebert 3
1 Electrical and Computer Engineering, University of Alberta, Edmonton, Alberta, Canada, 2 Physics, University of Alberta, Edmonton, Alberta, Canada, 3 , National Institute for Nanotechnology, Edmonton, Alberta, Canada
Show AbstractNanoelectromechanical systems (NEMS) have demonstrated the ability to measure particle masses as well as to differentiate between different chemical species based on their mass. This is possible by measuring the frequency change which occurs when a resonating NEMS device has a foreign mass added to it. This frequency change is not only dependent on size of the added mass but also on the location the mass is deposited on the resonator. Device overshield for mass-sensing enhancement (DOME) structures are fabricated which physically limit the positions analyte materials are deposited on a NEMS resonating sensor. This allows for a more accurate analysis of the material by removing the ambiguity of random analyte distribution on the sensor. The device operates by acting like an integrated shadow mask above the sensor. Due to its mechanical, dielectric and optical properties a ~200 nm silicon nitride film deposited by plasma enhanced chemical vapour deposition is used as the mask layer. Silicon dioxide is used as a structural layer to suspend the nitride layer above the NEMS device and was chosen for its selective chemical etch and low dielectric constant. These materials are deposited on unreleased NEMS resonators fabricated from silicon on insulator wafers. Since SiO2 is used to suspend the mask layer, both the NEMS device and the SiNx can be released in the same process step. The dielectric properties of the masking layer and the structural layer allow for electrical actuation and detection of the NEMS device. The optical transparency of the mask layer allows for interferometric detection of the device displacement. The fabricated NEMS sensors are 250 nm wide and resonate in the MHz frequency range. The Q-factors of the devices are ~1000 and limited by the undercut of the resonator.
9:00 PM - K10.35
Interfacial Binding Dynamics of Bee Venom Phospholipase A2 Investigated by Dynamic Light Scattering and Quartz Crystal Microbalance.
Nam-Joon Cho 1 3 , Joshua A. Jackman 2 , Curtis Frank 1
1 Chemical Engineering, Stanford University, Stanford, California, United States, 3 Department of Medicine, Stanford University, Stanford, California, United States, 2 Chemistry, University of Florida, Gainesville, Florida, United States
Show AbstractBee venom phospholipase A2 (bvPLA2) is part of the secretory phospholipase A2 (sPLA2) family whose members are active in biological processes such as signal transduction and lipid metabolism. While controlling sPLA2 activity is of pharmaceutical interest, the relationship between their mechanistic actions and physiological functions is not well understood. Therefore, we investigated the interfacial binding process of bvPLA2 in order to characterize its biophysical properties and gain insight into how membrane binding affects interfacial activation. Attention was focused on the role of membrane electrostatics in the binding process. Although dynamic light scattering (DLS) experiments indicated that bvPLA2 does not lyse lipid vesicles, a novel, nonhydrolytic activity was discovered. We employed a supported lipid bilayer on the quartz crystal microbalance with dissipation (QCM-D) to characterize this bilayer-disrupting behavior and determined that membrane electrostatics influence this activity. The data suggest that: 1) adsorption of bvPLA2 to model membranes is not primarily driven by electrostatic interactions; 2) lipid desorption can proceed bvPLA2 adsorption, resulting in nonhydrolytic bilayer-disruption; and 3) this desorption is driven by electrostatic interactions. Taken together, these findings provide evidence that interfacial binding of bvPLA2 is a dynamic process, shedding light on how membrane electrostatics can modulate interfacial activation.
9:00 PM - K10.36
Inducing Selective and Sensitive Sensory Responses into Organic Transistors via Calixarene Modification.
Anatoliy Sokolov 1 , Zhenan Bao 1
1 , Stanford University, Stanford, California, United States
Show AbstractThe field of organic electronics holds tremendous potential for applications that benefit from the use of organic materials, (e.g. very low cost, flexible and amendable to large-area processing techniques or roll-to-roll printing). Specifically, the design and development of sensors that take advantage of these benefits can lead to manufacturing of cheap electronic units for medicinal, food storage, and environmental monitoring applications. The ability to couple the sensory electrical output with on-chip signal processing can overcome the need for bulky, expensive equipment typically required for most optical detection methods. In order to attain commercial viability, chemical sensors based on organic electronics must continue to address the remaining issues in repeatability, reproducibility, stability, and selectivity. Typically, the sensitivity and selectivity of the organic thin-film transistor (OTFT) devices has been accomplished via covalent modification of the semiconductor backbone. To achieve reproducible function of organic transistors optimization techniques may be applied during commercial manufacturing processes; however, this may be difficult to accomplish for each synthetic semiconductor derivative (to achieve selectivity). We address this significant challenge via post-production modification of the OTFT with a sensory layer based on container-like calixarene molecules. Thus, a single semiconductor material lacking inherent specificity or sensitivity to organic vapors may be converted into an array of sensitive and selective sensors through the evaporation of calixarenes on the semiconductor surface. The modification does not alter the charge carrier transport, yet provides a drastic improvement in sensitivity for selected molecules based on the container shape and functionality. The use of such molecules to achieve increased specificity in small molecule vapor detection will be discussed.
9:00 PM - K10.37
Nanomechanical Resonance Spectroscopy: Exploiting Nanoscale Thermal Transfer for Label-free Chemical Detection.
Peter Greaney 1 , Jeffrey Grossman 1
1 Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States
Show AbstractWe present a new approach to chemical sensing in which the vibrational spectrum of an analyte is interrogated directly with an array on nanomechanical resonators. This approach, that we call ”nanomechanical resonance spectroscopy” (NRS), has the potential to combine the label-free chemical identification of spectroscopic methods with the size-scale enabled sensitivity of other nanomechanical approaches to sensing. Using theory and simulation we demonstrate the feasibility of the NRS method in principle, and then discus limits of sensitivity of the method and some guiding principles for its practical implementation.
9:00 PM - K10.38
Development of New Bio-chip for DNA Detection Using Phase Changing Media.
Sung Q Lee 1 , Hyung-Kun Lee 1 , Kang-Ho Park 1 , Sookyung Kim 2 , Xue Zhe Li 2 , Myung-Ryurl Oh 4 , Su Min Kim 4 , Sung-Mook Kang 3 , No-Cheol Park 3 , Li-Hua Jin 5 , Yong-Hoon Cho 5
1 Nano convergence sensor team, ETRI, Daejon Korea (the Republic of), 2 , Nano Storage Co. Ltd, Seoul Korea (the Republic of), 4 , Goodgene Co. Ltd, Seoul Korea (the Republic of), 3 CISD , Yonsei University, Seoul Korea (the Republic of), 5 Dept. of Physics, KAIST, Daejon Korea (the Republic of)
Show AbstractWe present a novel DNA chip and detection method using AuNPs(Au Nano particles)-labeled probe DNA on the phase-change media and commercial DVD optical pickup. When the optical light is focused on Au NPs on the media, the near-field strong enhancement induced by localized surface plasmon resonance is transmitted into the recording layer and changes the phase from an amorphous state to the crystalline state. This bio-chip is expected to overcome photo-bleaching of dye molecules and to keep the information of bio-chip for relatively longer time compared to conventional DNA-detection bio-chips with low cost of the phase change media such as CD or DVD. We investigated the effective incident electric field of Gaussian beam depending on distance between AuNPs for surface Plasmon resonance through FDTD(Finite Difference Time Domain) simulation to induce maximum phase changing phenomenon. The power densities of transmitted beam into the phase-change media by plasmon resonance were investigated on the wavelength of incident beam and the distance between AuNPs. Based on this simulation, we could find the optimum wavelength of incident beam and distance between AuNPs depending on AuNP sizes. In order to confirm the FDTD simulations, feasibility test of field enhancement due to the variation of AuNPs’ density is performed. AuNPs are immobilized on a phase change substrate with the 0%, 25%, 50%, 75%, 100% concentrations of 0.1M solution, respectively. 635nm wavelength laser with 30mW power is transmitted on a substrate to changes the phase from an amorphous state to the crystalline state. Reflections ratio between before and after phase change is measured to investigate the delivered optical power. We could find the 3.5times higher reflection ratio of 100% concentration case compared to 0% case. We devised a bio-chip for DNA detection on phase-changing media. The probe DNAs were immobilized using imine linkage on the phase-changing media containing aldehyde on SiO2 surface that is the utmost surface of phase-changing media. Labeling of AuNP on target DNA utilized the interaction of streptavidin-biotin interaction. Streptavidin was decorated on AuNP and biotin was tagged on target DNA. We found the effective DNA type on the number of base pairs (BPs) and tagging type of biotin such as end-tagging or incorporated-tagging through the investigation of SEM analysis by counting the number of AuNPs after labeling experiments.Finally, we could get the about 20% of AuNPs density in bio-chip. With this density, the 2.0 times of reflection ratio increase is expected if compared to 0% solution. The bio-chip is devised good enough to detect the DNA conjugate, and we are trying to increase the labeling density with small AuNP diameter and to increase the near-field optical power enhancement through Ag enhancement to get higher accurate bio-chip
9:00 PM - K10.39
Functional Polymer Patterns on Flexible Substrate for Bio-sensors.
Kyung Choi 1
1 , University of California, Irvine, California, United States
Show AbstractThere are growing interests in developing functional polymers/engineering processes to satisfy a set of our increasing demands in nanotechnologies. There are many challenges in nanotechnology for chemists to contribute to develop novel materials for this application since the technology is a part of the chemical domain, which builds up functional materials at the molecular level. In this talk, we will introduce functional polymers, which have molecular recognition capability, and thus can fabricate nano- or micro-patterns on flexible substrates for bio-sensor applications. New advances in nanotechnology such as soft lithography and microfluidic approaches are also introduced to develop smaller and more compact devices in miniaturization. Microfluidic approaches have taken intensive attractions since microfluidic reactors/ mixers allow us to synthesize novel materials. We also demonstrate here microfluidic synthesis of functional materials, which can’t be possible from bulk synthesis to fabricated functional patterns on flexible substrates for developing active devices.
9:00 PM - K10.4
Biomagnetic Glasses: Synthesis, Characterization and Biosensor Applications.
Lia Stanciu 1 , Silvana Andreescu 2 , Yu-Ho Won 1 , Mallikarjunarao Ganesana 2
1 Schoold of Materials Engineering, Purdue University, West Lafayette, Indiana, United States, 2 Department of Chemistry, Clarkson University, Postdam, New York, United States
Show AbstractIn this work, a novel avenue to create a generic approach for the fabrication of biofunctional materials with magnetic capabilities to be used in the design of highly stable, magnetically separable enzyme-based systems was explored. Immobilization of Acetylcholinesterase (AChE)and Horseradish Peroxidase (HRP) were investigated using biomagnetic glasses composed of a magnetic core with a size tunable porous silica shell. The efficiency of different methods of enzyme immobilization for this system (i.e., covalent bonding, entrapment) was determined by analyzing their biosensing capability for the detection of the organophosphorous pesticide paraoxon, as well as for hydrogen peroxide detection. Screen printed electrodes (SPE) with the enzyme-biomagnetic glasses showed higher current response and stability than for the corresponding free enzymes. The detection limit of the paraoxon biosensor was in the nanomolar range. The hydrogen peroxide biosensor showed a detection limit of 0.43 µM of at a signal-to-noise ratio of 3 and a sensitivity of 265 µA/mMxcm2.
9:00 PM - K10.40
Functional Hybrid Glass Generates Huge Acoustic Wave Novel Nanostructure Patterns.
Kyung Choi 1
1 , University of California, Irvine, California, United States
Show AbstractAlkylene-bridged hybrid glass doped with Cr/CrOx was developed by sol-gel polymerization. Usually, when laser beam goes through a solid media, density wave is linear since heat doesn’t decay through the media effectively in solid media. Interestingly, we observed a strong ‘acoustic response’ from alkylene-bridged hybrid glass doped with Cr/CrOx due to high grating effect, high photo acoustic diffraction efficiency. TEM image of the hybrid glass reveals unusual nano-fringe patterns, which are highly organized nano-periodicity. We believe that the nano-periodic patterns are sustained over substantial domains and appears to arise from lattice fringes. Electron diffraction analyses of these dark regions shown in the TEM images were also performed. From the diffraction pattern corresponded to the nano-fringes, a lattice space of the nano-striped patterns observed in TEM images was calculated about 50 Å from a distance between two diffraction spots in two sets of diffraction patterns. The acoustic response generated from the Cr-doped hybrid glass was as compressive as liquid thus the acoustic refractive intensity generated from the hybrid sol-gel glass was as strong as liquid. In our laser experiment, the diffraction efficiency (45 %) of the glass is higher than that of methanol (25 %). The hybrid glass can be used to develop novel diffraction beam modulators.
9:00 PM - K10.41
Microfluidic Chip for Combinatorial Screening and Diagnostics.
Paul Kenis 1 , Benjamin Schudel 1
1 , UIUC, Urbana, Illinois, United States
Show AbstractDrug discovery efforts often rely on the combinatorial synthesis and screening of extensive small-molecule libraries to identify inhibitors of disease-related proteins. Current state-of-the-art screening techniques are performed in macroscale setups that use microliters of reagent per experiment in a microplate. Scaling such synthesis and screening efforts down to the nanoliter scale will speed up throughput, reduce cost, and open up the possibility to screen many more potential molecules when the target protein is available only in limited amounts. Here we report a microfluidic chip capable of combinatorial mixing of different solutions in adjacent 200-pl compartments, followed by on-chip screening of binding events within individual wells. This microfluidic chip utilizes arrays of Actuate-to-Open valves to isolate all compartments, which allows the chip to be decoupled from pneumatic control lines and thus to be transported freely between filling, sensing and characterization platforms. Each compartment contains a photonic crystal biosensor to enable the on-chip, in situ, label-free detection of (bio-) molecular binding events. A proof-of-principle 4x4 protein/antibody binding assay was performed to demonstrate the discrete mixing and on-chip sensing capabilities. In a second application, we have integrated molecular beacon based detection schemes in these microfluidic chips. In a proof-of-principle experiments we have been able to identify viral agents in multiplexed fashion using total internal reflection fluorescence (TIRF). The key advantage of TIRF in combination with molecular beacons is that the presence of very low concentrations of oligomer target can be detected. This microfluidic approach to the detection of multiple viral agents may find application as clinical / diagnostic tests.
9:00 PM - K10.5
Nanospring-based Device for Remote Diagnostics of Diseases.
Vladimir Dobrokhotov 1 , Landon Oakes 1
1 Physics and Astronomy, Western Kentucky University, Bowling Green, Kentucky, United States
Show AbstractAs human breath analysis further develops as a multi-disciplinary field, it is clear that sensor development, instrumentation systems and algorithms play critical roles within this research area. Although much emphasis in the last decade has focused on breath biomarker compound identification and physiological relevance, we increasingly turn our attention towards portable, fieldable sensor platforms for non-invasive breath monitoring. In the human body the lungs have an intimate relationship with the blood: as a result, many volatile compounds from all over the body can be found in the breath. Because of that people with cancer, asthma, and many other diseases carry trace amounts of distinctive biomarkers in their breath. The best evidence of this comes from studies of lung and breast cancer and tuberculosis. Exhaled breath is an ideal non-invasive medium for any diagnostic test. It is more convenient, efficient and cost-effective than blood and urine-based testing systems, allowing real-time or near-instantaneous results delivered at the point of need. The collection of breath samples is straightforward and painless: no specimen has to be sent to a laboratory, no waiting for results, no complicated steps, or mixing or handling of fluids. In addition, there is no risk of tampering or masking the results of a breath sample. In many ways, breath-based testing is superior to conventional blood and urine sampling. Several examples of successfully build breath diagnostics device prototypes have been published recently. Typically, they are based on pre-concentration of breath samples and optical spectrum analysis. Sensors of this kind are suitable for doctor’s office or ER vehicle. But what if you need a quick diagnostics and the nearest hospital is far away? Or, if you have an extreme condition and you need an alarm signal with your condition and location to be sent to the emergency clinic? All these problems can be solved with the recent advancements in nanotechnology when the size of diagnostic tools can be reduced by orders of magnitude and equipped with the transmitter thanks to the wireless internet technology. The goal of this proposal is to develop an instrument that can perform a detailed elemental analysis of a human breath together with the quick diagnostics using light-weight portable equipment that someone could carry in the pocket. The proposed research is devoted to the design of an advanced chemical sensor (electronic nose) based on the novel nanomaterials – nanosprings. The proposed device will be able to determine the concentration of wide variety of chemical species especially volatile organic compounds (VOCs) – biomarkers of diseases, analyze the data using a recognition scheme, make a decision about the diagnosis, and send a corresponding signal with the condition and location of a patient to the doctor’s office.
9:00 PM - K10.6
Time-of-flight Secondary Ion Mass Spectrometry to Characterize Different Steps Involved in Biofunctionalization of Diamond Thin Films.
Hao Zhuang 1 , Vadali. V. S. S. Srikanth 1 , Xin Jiang 1
1 Institute of Materials Engineering, University of Siegen, Siegen Germany
Show AbstractAllylamine, an unsaturated short carbon chain amine was used to mediate ss-DNA attachment to an H-terminated polycrystalline diamond thin film surface. The DNA molecules are then hybridized with the complementary DNA molecules containing fluorescence labels. Time-of-flight secondary ion mass spectrometry (ToF-SIMS) is used to characterize the grafting of the trifluoroacetamide group protected allylamine (TFAAA) onto the diamond thin film, the deprotection of the amine group, and the linkage of SSMCC to amine group. Semi-quantification of the SIMS data is performed to determine the optimized surface reaction time. The intensities of F-, CF3-, CNO-, CN- representative of TFAAA are normalized by dividing the absolute total intensity. According to the semi-quantification data, the optimized illumination and deprotection time is 24 hours. SIMS surface mapping shows homogeneous distribution of allylamine on the diamond film surface. A shadow mask was employed during the photochemical attachment of allylamine to the diamond surface, leaving the masked region unfunctionalized. The SIMS mapping shows high intensities of F-, CF3-, CNO-, CN- in the regions which are UV illuminated. Fluorescence spectroscopy is used to confirm the covalent DNA bonding to the diamond film surface.
9:00 PM - K10.7
Impedance Spectroscopy of Lipid Bilayers Employed in OFET Bio-sensors.
Serafina Cotrone 1 , Marianna Ambrico 2 , Teresa Ligonzo 3 , Gerardo Palazzo 1 , Antonella Mallardi 4 , M. Daniela Angione 1 , Luisa Torsi 1
1 Dipt. di Chimica, University of Bari, Bari Italy, 2 Sezione Territoriale di Bari, CNR-IMIP, Bari Italy, 3 Dipt. Interateneo di Fisica, University di Bari, , Bari Italy, 4 Istituto per i Processi Chimico-Fisici (IPCF), CNR, Bari Italy
Show AbstractBio and chemical sensing represents one of the most attractive application of organic electronics. Organic Thin Film Transistor (OTFT) biosensors are in this respect, very promising and have shown the potential to offer (Someya T., et al. PNAS 101, 2004) very high performance level. Organic electronics allows to fabricate sensing circuits, also in an array configuration (Torsi L., et al. Nat. Mater. 7, 2008), on flexible, plastic or even paper, substrates by low cost printing compatible procedures. This can open interesting perspectives for the development of paper test-strip that combine low cost, reliability with label-free electronic detection and data processing.The use of cell-membrane mimics such as liposome and lipid bilayers has recently attracted great attention as biological recognition layer in the OTFT biosensors and several immobilization methods on a solid support have been reported (Lee H.Y., et al. Biosens and Bioelectron. 21, 2005; Pfeiffer I., et al. J Am Chem Soc. 126, 2004). Supported membranes show an intrinsically low bioactivity making them interesting as an interface between the non-biological material on the surface of OTFT and biologically active fluids. Moreover lipid membranes provide a natural environment which allows the immobilization of bioactive molecules such as enzymes and antibodies and preserves their high sensitivity and selectivity by preventing (Stelzle M., et al. J Phys Chem. 97, 1993). The low bioactivity of the supporting membrane reduces spurious signals, and the localization of the active molecules at a surface aids in signal transduction. To investigate the dielectrical properties of supported lipid bilayer (sBLM) and membrane electrical resistance and capacitance, impedance spectroscopy has been employed. The advantage of this technique, is that the low values of the applied potentials preserve membranes from destruction (Passechnik V.I., et al. Electroanalysis 10, 1998).In particular two class of experiments were performed. In the first one sBLM has been characterized directly on a metal support and in the second an organic semiconductor was used to improve the quality of the supported lipid bilayer. The measurements were performed both on the as prepared structures and after exposing them to an electrolyte. The structure of sBLMs formed on the solid surface of the two systems is explained in terms of equivalent circuits composed of simple electrical elements such as resistances and capacitances. Furthermore, information on the presence of lipid bilayer inhomogeneities are gathered from the electrical parameters determined by fitting the frequency-dependent impedance of the equivalent circuits to the measured data. The dependence of the impedance on the frequency at different electrolyte concentration is studied too.
9:00 PM - K10.8
Biomolecules Integration on Organic Electronic Devices for Biosensing Applications.
Maria Magliulo 1 , Daniela Angione 1 , Serafina Cotrone 1 , Antonia Mallardi 2 , Gerardo Palazzo 1 , Luisa Torsi 1
1 Department of Chemistry , University of Bari, Bari Italy, 2 Istituto per i Processi Chimico-Fisici (IPCF) , CNR, Bari Italy
Show AbstractMost of biological sensing techniques are based on optical detection principles that are highly sensitive and specific but very difficult to miniaturize. These techniques also require multiple reagents, long preparative steps, signal amplification and complex data analysis.Organic electronics and organic thin –film transistors (OTFTs) in particular can offer an alternative to overcome some of the optical biosensors drawbacks. Simple and low-cost fabrication techniques, miniaturization, multi-parametric responses, signal amplification and label-free detection are the main features of OTFT biosensors [Anatoliy N. Sokolov et al, Materialstoday 2009; Torsi L et al, Nat Mater. 2008]. Particularly, OTFT technology can be implemented to develop cost-effective and label-free DNA or bio-affinity sensor chips, having a field-effect transport directly coupled to a bio-sensing process, useful to high-throughput testing and point-of-care applications [Feng Yan et al, Biosens Bioel. 2009].The development of new structures that can provide the full integration in OTFT devices of biological recognition elements such as antibodies or other proteins to confer specificity is the main goal of this study. The coupling of the OTFT device and the biological recognition system is actuated by assembling supramolecular structures that integrate biomolecules deposited directly over the OTFT active layer. Bio-probes are immobilized on the sensors surface using either conventional procedures (i.e, physisorption, chemisorption) and more innovative strategies based on the use of phospholipid bilayers. The efficiency of the immobilization procedures is evaluated by imaging techniques based on fluorescence. The bio-recognition reactions (i.e antibody-antigen interaction) are also monitored by real-time quartz crystal microbalance (QCM) measurements. Preliminary results obtained by using the anti-biotin/biotin/streptavidine reagent systems will be presented. The possibility to develop OTFT biosensors capable of offering enhanced sensing performance, particularly in terms of sensitivity and bias control, will be also discussed. The reported technology hold the potential to display a great versatility allowing for a wide range of applicability to many different assays (DNA, bio-affinity and enzyme) by just binding the right bio-recognition element for the analyte of interest. Besides, the label-free assay format ensures a reduction of assay time and reagents consumption with respect to methods relying on labeled molecules that require several incubations, washing, and separation steps. Multianalyte and disposable analytical formats are also possible.
Symposium Organizers
Elisabetta Comini Brescia University
Perena Gouma State University of New York-Stony Brook
Luisa Torsi Universita di Bari
George Malliaras Ecole Nationale Supérieure des Mines de St. Etienne
K11: Organic Materials in Biological Sensing II
Session Chairs
Thursday AM, April 08, 2010
Room 2007 (Moscone West)
9:00 AM - **K11.1
Photonic Field-effect Transistors for Integration into Bio-sensing Functional Components.
Michele Muccini 1 , Raffaella Capelli 1 , Stefano Toffanin 1 , Gianluca Generali 1 , Antonio Facchetti 2
1 , Istituto di Spettroscopia Molecolare CNR, Bologna Italy, 2 , Polyera Corporation, Skokie, Illinois, United States
Show AbstractThe potential of organic semiconductor-based devices for light generation is demonstrated by the recent commercialization of display technologies based on organic light emitting diodes (OLEDs). Organic light-emitting transistors (OLETs)1 are alternative light sources combining, in the same architecture, the switching mechanism of a thin-film transistor and an electroluminescent device that can be easily integrated into functional chip and bio-sensing components. The development of miniaturized cheap and disposable photonic devices for bio sensing, in which organic photonic field-effect transistors are used for light generation, would constitute a radically new generation of devices with unprecedented sensitivity and superior reliability at a markedly reduced cost. Here, we introduce the concept of using a tri-layer organic heterostructure in OLETs providing a novel approach to dramatically improve OLET performance and match the required parameters for use onto point-of-care diagnostic components. In these devices the semiconductor is composed by a central emitting layer sandwiched between an electron and a hole carrying layer. The device operates as a contactless OLED with lateral ambipolar field effect charge transport. The physical separation between the charge transport and the light emission regions intrinsically eliminates exciton-charge annihilation while the location of the light emission area multi-micron away from the electrodes prevents electrode-induced photon losses. Our devices are 100X more efficient than the equivalent OLED fabricated using the same heterostructure and 10X more efficient than any other reported OLETs.
9:30 AM - K11.2
Phosphatidylserine Lipid-containing Cubosomes: Model Membrane and Cell Interaction Studies.
Hsin Hui Shen 1 , Keith McLean 1 , Jonathan Crowston 2 , Patrick Hartley 1
1 , csiro, Clayton, Victoria, Australia, 2 Centre for Eye Research Australia, University of Melbourne, Melbourne, Victoria, Australia
Show AbstractLyotropic liquid crystalline nanoparticles (cubosomes) have the potential to act as amphiphilic scaffolds for the presentation of lipids and subsequent application in, for example, bioseparations and drug delivery. In this work we have formulated lyotropic liquid crystal systems based on the synthetic amphiphile 1,2,3-Trihydroxy-3,7,11,15-tetramethylhexadecane (phytantriol) and containing phosphatidylserine lipids. In biology, the translocation of phosphatidylserine lipids to the exterior of the cell membrane is a key early indicator cell apoptosis (programmed cell death). Annexin V is a protein that has a high affinity for PS in the presence of Ca2+. It has been shown to an effective diagnostic for apoptosis in vivo using radiological and microscopic fluorescent techniques. Our intention is to use PS containing cubosomes for the delivery of annexin-5 and subsequent detection of apoptotic cells.We have prepared a range of PS-Phytantriol cubosome formulations and characterized them using small angle x-ray scattering and cryo-transmission electron microscopy.These techniques show that phosphatidylserine induces marked changes in lyotropic liquid crystalline phase behaviour, characterised by changes in both crystallographic dimension and space group. Furthermore, in vitro cell culture studies indicate that the changes correlate with cubosome cellular uptake and cytotoxicity. To study this phenomenon further, a surface supported phospholipid bilayer was used to gain insights into cubosome – bilayer interactions using quartz crystal microgravimetry (QCM-D) and neutron reflectometry techniques. Both techniques show that attachment of phytantriol-PS cubosomes is increased relative to phytantriol-only cubosomes. We therefore hypothesise that the cytotoxicity of the phytantriol-PS cubosomes is due to their preferential attachment and cell uptake at the cell membrane. Further, we have demonstrated that phytantriol-PS cubosomes can be employed in the specific uptake and delivery of the apoptosis probing protein, Annexin 5.
9:45 AM - K11.3
Nanoimprint Lithography With UV-curable Hyperbranched Polymer Nanocomposites for Optical Biosensing Applications.
Valerie Geiser 1 , Yves Leterrier 1 , Jan-Anders Manson 1 , Guy Voirin 2 , Max Wiki 3
1 STI-IMX-LTC, EPFL, Lausanne Switzerland, 2 , CSEM, Neuchatel Switzerland, 3 , Dynetix AG, Landquart Switzerland
Show AbstractNano-scale patterns are often used in optical devices such as waveguides in wavelength interrogated optical sensors (WIOS) developed for immunoassays with detection sensitivity in the ppb range [1]. For these applications polymers would represent low-cost alternatives to traditional materials (glass, Si). However, polymers often suffer from their lack of dimensional stability. This work introduces UV-curable hyperbranched polymer (HBP) nanocomposites for rapid and cost-effective fabrication of stable nano-sized structures with high dimensional accuracy. Nanocomposites were prepared from a 3rd generation acrylated hyperbranched polyether polyol mixed with amorphous silica nanoparticles. Photo hyphenated methods (rheology, calorimetry, interferometry) were used for real-time analysis of structure build up under UV exposure. Transmission electron microscopy and atomic force microscopy were used to analyze the composite microstructure and the dimensions of the nanostructures. The polymerization shrinkage and stress of HBP with 20%vol SiO2 were found to be as low as 9%vol and 5 MPa, respectively [2]. Nano-scale patterns designed for WIOS were produced with the HBP nanocomposites using a rapid (< 100 s) and low-pressure (1 bar) nanoimprint lithography process with a glass master. The replication fidelity of nanocomposites with up to 25% vol of SiO2 was better than 98 %, thanks to the formation of a superficial, 20 nm thick HBP-rich layer. Photo-rheology enabled identifying the influence of gelation of the nanocomposite on the stability and the dimensions of the imprinted structure. Dimensional accuracy was correlated to the level of internal stress, which increased with the amount of inorganic filler. WIOS waveguides were produced by coating the nanocomposite gratings with a 210 nm thick high refractive index TiO2 layer. The influence of the nanocomposite microstructure and pattern dimensions on the light guide properties and sensor signal quality are being evaluated. Initial series of results indicate a good coupling efficiency and limited scattering of the polymer-based nanocomposite waveguide. Ongoing work aims at determining the ultimate detection limit of the HBP nanocomposite sensor. [1] Cottier et al, Sensors Actuat. A-Chem., vol. 91, p. 241 (2003)[2] Geiser et al, J. Appl. Polym. Sci., vol. 114, p. 1954 (2009)
10:00 AM - K11.4
Synthesis and Biosensing Applications of Oligonucleotide-templated Silver Nanoclusters.
Jaswinder Sharma 1 , Hsin-Chih Yeh 1 , James Werner 1 , Jennifer Martinez 1
1 Center for Integrated Nanotechnologies, Los Alamos National Laboratory, Los Alamos, New Mexico, United States
Show AbstractIn recent years, oligonucleotide-templated silver nanoclusters, consisting of few atoms, have gained a substantial interest due to their unique fluorescence properties. Furthermore, the potential applications of these nanoclusters for bio-and chemical-sensing, in-vivo imaging, and in-vitro bioassays have attracted researchers from across many disciplines. High stability in physiological conditions, ease of synthesis, and high photostability have made these nanoclusters a fluorescent probe of choice for biological applications. While many reports have been published demonstrating the use of oligonucleotides for synthesis of silver nanoclusters, synthesis of oligonucleotide-templated nanoclusters with tunable fluorescence emission is still in its infancy. In addition, efforts are being made to harness the brightness and photostability of these nanoclusters for biosensing purposes. Herein, we address both of these issues by synthesizing oligonucleotide-templated silver nanoclusters with tunable emission, and using them in detection of specific biomolecules, without using stringent coupling conditions. The effect of DNA sequence and length on the fluorescence emission wavelength, brightness, and stability of nanoclusters was also studied using fluorescence correllation spectroscopy. It was found that certain sequences produce highly fluorescent and stable silver nanoclusters compare to the other sequences.
10:15 AM - K11.5
Influence of Debye Screening on Label-free Detection of Cancer Biomarkers.
Aleksandar Vacic 1 , Jason Criscione 1 , Nitin Rajan 1 , Tarek Fahmy 1 , Mark Reed 1
1 , Yale University, New Haven, Connecticut, United States
Show AbstractIn this work we investigate influence of ionic strength of the sensing buffer on the level of signal obtained from label-free detection of cancer biomarkers. Prostate, PSA, and breast, CA 15-3, cancer biomarkers are detected using multiplexed silicon nanoribbon field effect transistors made from SOI wafers with 20nm of active layer, functionalized with 3-aminopropyltrietoxysilane (3-APTES) and corresponding antibodies. After protein injection and stabilization of sensor current level in 1mM bicarbonate sensing buffer (λD~9nm, partially screened), the solution is exchanged to low ion concentration buffer (0.lmM bicarbonate λD~30nm) during which current increases to the maximum, unscreened level, and then to high ion concentration buffer (1mM bicarbonate with 10mM NaCl λD~3nm), where signal is observed to decrease bellow the absorbed protein level. We determine that approximately 60% and 46% of signal is unscreened for CA15-3 and PSA, respectively, in 1mM sensing buffer. In addition, we consider methods of functionalization to potentially overcome this limit.
10:30 AM - **K11.6
Biosensors for Detection of Pathogenic Organisms.
ChangQing Wang 2 , Juyoung You 3 , Jantorn Jiambutr 3 , Arron Xu 2 , Ravi Marala 2 , Moonsoo Jin 3 , Maria Nikolou 4 , George Malliaras 1 , Roisin Owens 1
2 , Corning Life Sciences, Corning, New York, United States, 3 Biomedical Engineering, Cornell University, Ithaca, New York, United States, 4 Materials Science & Engineering, Cornell University, Ithaca, New York, United States, 1 Department of Bioelectronics, Ecole Nationale Superieure des Mines de St. Etienne, Gardanne France
Show AbstractLife Scientists rely on a range of techniques for their ability to carry out fundamental and applied research. At the molecular level this includes the use of fluorescent tags, tracer molecules or other labelling or staining compounds. However, these techniques are generally static and are poor indicators of the function of live cells. Real-time, label-free detection of pathogenic organisms remains a challenge to researchers. In recent years technologies such as surface plasmon resonance, quartz crystal resonators or evanescent wave fibre-optics have evolved to carry out label free detection of events at the single molecule or cellular level. However, these technologies often require large, expensive equipment with significant operator skill required. The trend of late is towards miniaturization technology with associated lower costs and ease of use (for point of care applications i.e. for diagnostics).The advent of organic electronics has created a unique opportunity to interface the worlds of electronics and biology, and give rise to a new generation of devices that can carry out label-free detection. The “soft” nature of organic materials offers better mechanical compatibility with tissue than traditional electronic materials, while their natural compatibility with mechanically flexible substrates suits the non-planar form factors often required for implanted devices. More importantly, the ability of organics to conduct both electronic and ionic carriers opens up a new communication channel between electronics and biology. An example is the organic electrochemical transistor (OECT), a device that provides a very sensitive way to detect minute ionic currents in an electrolyte, as the transistor amplifies the gate current. Here, data will be shown demonstrating the progression from molecular techniques, through large platform technology such as the Biacore system (GE healthcare) and the Epic system (Corning), to newer miniaturized technology for the integration of cells with electronic materials, all with a common goal of detecting pathogenic organisms.
11:00 AM - K11: Organic
BREAK
11:30 AM - K11.7
Transmembrane Proteic System Employed in OFET Bio-sensors.
Daniela Angione 1 , Dan Fine 2 , Antonia Mallardi 3 , Gerardo Palazzo 1 , Serafina Cotrone 1 , Maria Magliulo 1 , Ananth Dodabalapur 4 , Luisa Torsi 1
1 Department of Chemistry, University of Bari, Bari Italy, 2 The Department of NanoMedicine and BioMedical Engineering, University of Texas Health Science Center at Houston, Houston, Texas, United States, 3 Istituto per i Processi Chimico-Fisici (IPCF) , CNR, Bari Italy, 4 Department of Electrical and Computer Engineering, The University of Texas at Austin, Austin, Texas, United States
Show AbstractBiological assays are nowadays largely performed by high-throughput, reliable methods, such as the polymerase chain reaction (PCR) formats or the enzyme-linked immunosorbent assays(ELISA). However, these methods require, extensive sample treatment involving incubation steps, sample cleanup or amplification. The “labeling” of the bio-analyte, a pathogen such as the HIV virus, is also needed to allow the transduction of the bio-recognition event, eventually adding further sample handling, before the analysis can be performed. This makes such approaches suitable mainly for time and resource consuming laboratory based diagnostic. Electronic transduction can open new perspectives for point-of-care diagnosis and treatment monitoring actuated by fast, sensitive, selective and reliable biosensors. Organic semiconductor devices have recently been identified to meet these requirements. In particular, organic field-effect transistors (OFET) are presently blazing the trail for a low-cost and all printed technology platform for distributed intelligence, such as e-paper, electronic ID-tags, sensor stickers, etc. Such a technology should be robust and easy to manufacture and must operate at a power and voltage compatible with the energy sources available for low cost, portable flexible electronics. The sensing Field Effect Transistor approach (different from the ISFET one) has been so far realized either with silicon nanowires or CNT nanoscopic devices or by using organics as active semiconductors. These approaches will be assessed for potential for interfacing/integration with bio-system supramolecular architectures.Novel bio-FETs will be presented where the immobilization of the biological recognition element is obtained by means of proteins incorporation into liposomes that are artificial lipid bilayers organized in vesicles which can provide nearly native environment for biomolecules. The spreading of small lipid vesicles on solid support allows in fact their self-assembling into fluid planar bilayers hosting the selected protein. The mechanism of electronic transduction will intervene by the exploitation of conformal changes and/or charge generation/re-distribution occurring upon the recognition process. Structural and morphological analysis has been performed to relate the conformational changes to the electronic response of the OTFT bio-sensor.
11:45 AM - K11.8
A Biosensor System for the Detection of Salmonella Typhimurium Using Multiple Phage-based Magnetoelastic Biosensors.
Wen Shen 1 , Bryan Chin 1
1 Materials Engineering, Auburn University, Auburn, Alabama, United States
Show AbstractMagnetoelastic (ME) sensors provide a fast, sensitive method to detect bacteria with smaller sensors have higher mass sensitivity for detecting lower concentrations of bacteria. However, signals from smaller sensors are weaker and have more noise due to manufacturing defects. In this paper, we present a biosensor system for the detection of Salmonella typhimurium using multiple magnetoelastic sensors, each with the size of 2000 × 400 × 30 microns. The sensors are immobilized with E2 phage, which specifically binds with Salmonella typhimurium. Unlike traditional methods, our system uses a step pulse to “strike” the sensor, causing it to vibrate at its natural resonance frequency and produce a signal in the pickup coil due to reverse magnetostriction. A Fast Fourier Transform (FFT) was used to determine the resonance frequency. As the biosensor captures Salmonella cells, is mass increases with a corresponding decrease of its resonance frequency. The detection system was composed of one coil with a reference sensor to monitor stability, and another coil with three measurement sensors separated in three tubes for simultaneous detection of bacteria. With multi-sensors the effect of a manufacturing defect is decreased and we get the benefit of averaging for more accurate and reliable results. Stability tests show that the variance of frequency detection is less than 20 ppm of its resonance frequency using several different concentrations of Salmonella suspension. SEM pictures of the sensor surface show a uniform binding of Salmonella cells. Cells were counted and the mass change calculated. The measured frequency change corresponds well to the theoretical change. The results show that the multiple phage based ME biosensors are able to detect one pathogen simultaneously and offer good sensitivity and reliability.
12:00 PM - K11.9
Label Free Detection of DNA Sequence and Mercury Ions With High Sensitivity and Selectivity Using Cationic Conjugated Polymers and DNA Intercalators.
Xinsheng Ren 1 , Qing-Hua Xu 1
1 Department of Chemistry, National University of Singapore, Singapore Singapore
Show AbstractConjugated polymers are known to display interesting optical properties such as optical amplification via fluorescence resonance energy transfer (FRET). They can be used as light harvesting complex to develop biological and chemical sensors with enhanced detection efficiency. In combination of conjugated polymers with DNA intercalators, we have developed a label free DNA sensor scheme with enhanced detection efficiency and further improved selectivity. The high selectivity enables detection of single nucleotide mismatch even at room temperature. The detection sensitivity could be improved by a factor of 19 times through resonance energy transfer using conjugated polymers as a light harvesting complex. In addition, we have also demonstrated a practical scheme for detection of mercury ions in aqueous media at room temperature with high sensitivity and selectivity by using a combination of oligonucleotides, DNA intercalators and conjugated polymers. The limit of detection could be improved to 0.27 nM, much lower than the maximum level of mercury permitted by USA EPA in the drinking water. These methods are label free, low cost and simple to use. They can work in a “mix-and-detect” manner.
12:15 PM - K11.10
Polymer Protected Parallel-nanogap Device for Direct Single DNA Molecule Measurement in Aqueous Solution.
Huijuan Zhang 1 3 , Francesco Stellacci 1 2 , John Thong 1 3
1 Advanced Materials for Micro- and Nano-Systems Program, Singapore-MIT-Alliance, Singapore Singapore, 3 Electrical & Computing Engineering, National University of Singapore, Singapore Singapore, 2 Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States
Show AbstractHere we present a simple approach to fabricate in parallel sub-2 nm nanogaps with 150 nm conformal holes in the overlaying polymer layer by electrical stressing. The polymer-protected nanogaps thus realized exhibit substantial reduction in susceptibility to ionic currents in aqueous solutions. In addition, we demonstrate in situ single DNA molecule trapping into the polymer-protected nanogap. The self-complementary poly-GC DNA strand was covalently bond to the nanogap electrode by thiol-gold binding. The conductance of the double-strand DNA was measured to be about 0.1 uS in near physiological conditions. This work provides unambiguous determination of single DNA conductance and a reliable way to study electrical properties of molecules at the nanometer scale.
12:30 PM - K11.11
Foerster Resonance Energy Transfer Between Single Hydrophylic CdSe/CdS/ZnS-Nanoparticles and Organic Dye Molecules.
Klaus Boldt 1 , Anika Juhl 1 , Sebastian Jander 1 , Marc Thiry 1 , Horst Weller 1
1 Department of Chemistry, University of Hamburg, Hamburg, Hamburg, Germany
Show AbstractThe occurrence of Förster resonant energy transfer (FRET) between semiconductor nanoparticles and coupled dye molecules on their surface can be a valuable source of information about the actual thickness of the particles ligand shell. While electron microscopy only shows the inorganic part of the structure and dynamic light scattering yields the Stokes radius FRET gives access to dipole-dipole distances. This is an elegant method to monitor possible backfolding of the ligand chains.For this study measurements were performed on CdSe/CdS/ZnS core-shell-shell quantum dots with a ligand shell of polyethylene oxide with tridentate thiol anchor groups. The ligands were functionalized with carboxylate groups and coupled to Texas Red-cadaverine dye molecules via EDC/Sulfo-NHS activation following ligand exchange.The samples were studied both as an ensemble and on the single particle level. Due to the occurrence of several distributions in the sample (ligand chain length, number of dye molecules per particle, particle size and intrinsic properties of the quantum dots like fluorescence intermittency and spectral wandering) the single particle fluorescence holds vital information for the interpretation of ensemble spectra and sample preparation.Several curve fitting routines were performed with the data. The best and physically most meaningful results were gained when employing the stretched exponential or Kohlrausch-Williams-Watts function which takes into account the previously mentioned distributions within the sample.It could be shown that the fluorescence lifetime of single quantum dot-dye conjugates were generally shorter than those of uncoupled quantum dots. Both were in good agreement with the ensemble data.
K12: Biosensors
Session Chairs
Thursday PM, April 08, 2010
Room 2007 (Moscone West)
3:00 PM - **K12.1
Building Micro-nanostructured Interfaces Using Functional Inherently Conducting Polymers.
Gordon Wallace 1
1 Intelligent Polymer Research Institute, University of Wollongong, Wollongong, New South Wales, Australia
Show AbstractGiven the unique (and sometimes even useful) functional properties of inherently conducting polymers (ICPs) they have attracted much attention from those interested in developing new chemical and biosensing technologies. ICPs provide the ability to use electrical stimuli to control molecular interactions on the sensing surface and to derive analytical signals based on electronic changes that are caused by these interactions. This phenomena has now been applied in the development of sensors for simple ions, organic ions and even more complex immuno sensors.It has also been established that building micro or nano structured conducting polymers provides improved electrochemical properties – enhancing both the control over molecular interactions and the ability to produce signals from them. It is no surprise therefore that in recent times investigations into the fabrication of such structures have been investigated. Here we will report on latest findings in the use of(i) wet spinning(ii) electrospinning, and(iii) printing technologies to achieve such structures.The use of these structures in controlling and maintaining biological events will also be discussed.
3:30 PM - K12.2
New Nanoparticle Based Methods for Protein Sensing.
Jane Gallagher 1 , Karen Faulds 1 , Duncan Graham 1
1 Pure and Applied Chemistry , University of Strathclyde, Glasgow United Kingdom
Show AbstractSince the advent of nanotechnology, one of its main aims is to gain insight at the cellular level in order to develop a greater understanding of biological processes, since biology has already mastered the art of science on a nanoscale. Disease research is an area of critical importance and currently nanotechnology has provided one route of research.We first must understand the interactions and events which take place to cause the disease before we can begin to treat it. Previously, it was thought that identifying the genome would provide the answers. However it has become apparent that more information is required and as such the total protein complement of the genome has become the ultimate goal, therefore the proteome has become of great interest. Proteins carry out multiple roles within the cell; they are involved in cell pathways and influence the action of each other and it is these interactions that we wish to study. The most common method for detecting proteins is fluorescence, a technique chosen as it allows for selective and specific detection of molecules at low concentrations, fluorescent proteins, such as Green Fluorescent Protein (GFP), have been widely employed in this methodology. Awarded the Nobel Prize in chemistry in 2008, GFP paved the way for a new generation of protein markers. Since the fluorescence generated by these proteins comes from part of the peptide chain, they can form fusions with other targeted proteins and therefore can be easily expressed. Thus the movement of the target protein within a cell can be monitored using fluorescence. However within a cellular pathway multiple proteins can interact at one time and it is difficult to monitor more than one protein in vitro using fluorescence microscopy. Therefore the use of fluorescence has its disadvantages.Surface Enhanced Resonance Raman Scattering (SERRS) can overcome the problem arising from multiple targets. In addition this technique involves the use of metallic nanoparticles, which have great promise within the nanotechnology field due their unique properties and ability to cross the cell membrane. In comparison to fluorescence SERRS has been shown to multiplex efficiently and have greater detection limits, up to 3 orders of magnitude greater than fluorescence. It is proposed that detection of fluorescent proteins through SERRS would be of great advantage. In our group Enhanced GFP has been detected in solution through SERRS. This has been achieved via conjugation to nanoparticles and has been shown to provide much lower detection limits when compared to fluorescence. Various conjugation strategies have been employed with varying results, all of which will be discussed. Other fluorescent proteins have been studied as well as fluorescent protein chimeras. The final aim is to study fluorescent protein chimeras using SERRS within a cellular environment. This work aims to add to the growing research in the cellular nanotechnology field.
3:45 PM - K12.3
A Surface Plasmon Resonance Cellular Antibody Sensor.
Donna Hohertz 1 , Karen Kavanagh 1 , Bonnie Gray 2 , Jamie Scott 3 , Alex Brolo 4 , Reuven Gordon 5 , Naveed Gulzar 3
1 Physics, Simon Fraser University, Burnaby, British Columbia, Canada, 2 Engineering Science, Simon Fraser University, Burnaby , British Columbia, Canada, 3 Molecular Biology and Biochemistry, Simon Fraser University, Burnaby , British Columbia, Canada, 4 Chemistry, University of Victoria, Victoria, British Columbia, Canada, 5 Electrical and Computer Engineering, University of Victoria, Victoria, British Columbia, Canada
Show AbstractFirst reported in 1998, extraordinary optical transmission (EOT) is the transmission of radiation through thin metal films perforated with periodic arrays of sub-wavelength sized holes. EOT is a surface plasmon resonance (SPR) phenomenon. In EOT, periodic modification of the surface causes a resonance coupling between transverse evanescent waves from incident radiation with plasmons at the metal surface. In SPR the surface bound evanescent electric field can only interact with material near the metal surface. Adsorption of a chemical species to the metal surface will therefore influence SPR, making it an extremely sensitive probe to changes in surface chemistry. SPR in the Kretschman reflection configuration is already widely used in biochemical, chemical and biomedical research. EOT’s simpler geometry and tiny sensing elements lends itself to simple miniaturization. The small size of the EOT elements allows us to monitor chemical binding events in a highly localized environment, such as the area surrounding a single cell. EOT nanohole arrays (20 x 20 μm) have been fabricated in thin (100 nm) gold films via focused ion beam milling. The gold surface is functionalized with either antigens or proteins using well established methods for the immobilization of biomolecules. The resulting biomolecular layers are self-assembled monolayers attached to the array surface via Au-S bonds. The arrays are integrated into a microfluidics package in close proximity to cell traps. Living mammalian immune cells are immobilized in the traps and their anti-body production is studied. White light is used to excite EOT while the integrated signal from the area of the array is monitored using a visible light spectrometer. Monitoring shifts in the SPR signal allows us to watch the real time antibody-antigen binding dynamics from each uniquely trapped cell. The sensitivity of the EOT geometry to the measurement of cellular kinetics will be reported.
4:00 PM - K12.4
Lithographically Patterned Gold Nanowires: Spectroscopic/Morphological Characterization and Application to the MS Detection of Peptides.
Lorenzo Colaianni 1 , Scheng Kung 2 , David Taggart 2 , John Greaves 3 , Nicola Cioffi 1 , Reginald Penner 2
1 Dipartimento di Chimica, Università degli Studi di Bari, Bari Italy, 2 Department of Chemistry, University of California Irvine, Irvine, California, United States, 3 Mass Spectrometry Facility, University of California Irvine, Irvine, California, United States
Show AbstractIn the present study, gold nanowires (Au-NWs) have been electrodeposited using lithographically patterned nanowire electrodeposition (LPNE) technique [1,2].Nanomaterials have been subjected to a detailed spectroscopic and morphological characterization by means of analytical techniques like X-ray Photoelectron Spectroscopy, X-ray Diffraction, Scanning and Transmission Electron Microscopies and Atomic Force Microscopy, to fully assess the surface chemical composition, the crystalline structure and the nanomaterial size and shape. Finally, Laser Desorption Ionization-Mass Spectrometry (LDI-MS) results have been obtained by applying the Au nanostructures as desorption/ionization promoters for the selective detection of low-molecular weight analytes, such as amino acids and peptides.In both cases, LDI-MS responses showed that Au-NWs lead to a highly efficient and preferential analyte desorption/ionization, as a limited number of low intensity interferent peaks could be detected. Noteworthy, MS spectra were dominated by analyte signals, always showing a relative intensity of 100%.REFERENCES1. Menke, E.J.; Thompson, M.A.; Xiang, C.; Yang, L.C.; Penner, R.M. Nature Materials, 2006, 5, 914-918. 2. Xiang, C.; Kung, S.C.; Taggart, D.K.; Yang, F.; Thompson, M.A.; Guell, A.G.; Yang, Y.; Penner, R.M. ACS Nano, 2008, 2, 1939-1949.
4:15 PM - K12: Biosensors
BREAK
K13: Functional Materials for Bio-chemical Sensing
Session Chairs
Thursday PM, April 08, 2010
Room 2007 (Moscone West)
4:30 PM - **K13.1
Integrated Sensors for Point of Care Detection.
John de Mello 1
1 Chemistry, Imperial College London, London United Kingdom
Show AbstractMicrofluidic devices have shown themselves to be highly effective for laboratory-based research, where their superior analytical performance has established them as efficient tools for genetic sequencing, proteomics, and drug discovery. However to date they have not been well suited to point-of-care diagnostic applications, where cost and portability are of primary concern. Although the microfluidic chips themselves are cheap and small, they must generally be used in conjunction with bulky optical detectors, which are needed to identify or quantify the analytes or reagents present. Here we report the use of miniature on-chip light sources and photodetectors based on light-emitting polymers (LEPs). LEP devices have simple multilayered structures and may be fabricated directly on the microfluidic chips by sequential deposition of appropriate polymers or electrodes. The LEPs add minimal size and weight to the microfluidic chips, allowing for the creation of low cost, quantitative, integrated diagnostic devices.
5:00 PM - K13.2
Nanoporous Carbon-coated SAW Device System for PPB Detection of Trihalomethanes in Water.
Michael Siegal 1 , Curtis Mowry 1 , Kent Pfeifer 1 , Alex Robinson 1 , Kazi Z. Hassan 2
1 , Sandia National Laboratories, Albuquerque, New Mexico, United States, 2 , Parker-Hannifin Corporation, Huntsville, Alabama, United States
Show AbstractThe treatment of water results in many disinfection byproducts; trihalomethanes (THMs) are among the most common and of greatest concern to regulatory bodies and the public due to their known adverse health effects, which include cancer and miscarriage. The Environmental Protection Agency (EPA) regulatory limit for THMs is 80 ppb (parts-per-billion). The THMs are chloroform, bromodichloromethane, dibromochloromethane, and bromoform. Current detection methods involve retrieving water samples from reservoirs, wells, etc. and sending them to a chemical laboratory for analysis. We have developed a portable system for THM detection in water using purge and trap, followed by isothermal gas chromatography and surface acoustic wave (SAW) device detection, providing a light-weight, low-cost, highly-sensitive, and easily deployable water sensor that performs THM analysis in just a few minutes.The SAW sensor device is the heart of this detection system. SAWs respond to increased surface mass as a function of analyte concentration, which changes the acoustic propagation speed and can be measured as a phase shift in the wave over a fixed length. Sorbent coatings on a SAW surface greatly increase the response. We find that nanoporous-carbon (NPC) is highly sensitive, reproducible and stable for long-term use, significantly improving signal responses for chemical detection. Results demonstrate limits of detection (LOD) of many volatile chemicals below ppb levels, several orders of magnitude better than the use of other common SAW coating materials (polymers, sol-gels, etc.). To be useful for SAWs the coatings must have both high surface area and rigidity. NPC uniquely combines these critical properties. Purely graphitic and nanocrystalline, NPC is chemically robust and stable to temperatures well above any thermal cycling that would be used for the devices. NPC grows via pulsed laser deposition from a pyrolytic graphite target with an energy density just above the ablation limit. The ablated species’ kinetic energy is further attenuated via a controlled argon pressure during deposition. Transmission electron microscopy finds nm-sized domains with increased interplanar spacings between graphene sheet fragments compared to graphite. Essentially, NPC is an all grain boundary material, for easy diffusion of chemicals both in and out of the coating, of which nearly every graphene sheet is available for surface sorption.We demonstrate that using NPC as the SAW coating results in LODs < 1 ppb for chloroform and < 1 part per trillion for bromoform! This enables the development of a portable chemical analysis system for THM detection in the water supply, as well as other chemical detections required by the EPA to protect our clean (and safe) water supply.Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy under contract DE-AC04-94AL85000.
5:15 PM - K13.3
Discovering New Surfaces for Optimal SERRS Detection of Protein Immunoassay Arrays Printed by Dip-Pen Nanolithography.
Eleanore Irvine 1 , Aaron Hernandez-Santana 1 , Jane Gallagher 1 , Duncan Graham 1 , Karen Faulds 1
1 Pure and Applied Chemistry, University of Strathclyde, Glasgow United Kingdom
Show AbstractAdvancements in lithography methods for printing biomolecules or molecular patterning to surfaces, is proving to be potentially beneficial for medical diagnostics and biological research. Biosensor arrays are most often used to detect various biomolecules like nucleic acids, proteins and other biologically important molecules like glucose (screening for diabetes). Looking to reduce the size of these arrays to between the micron and nanoscale can be highly valuable as creating more dense arrays can provide more information and result in lower detection limits for more efficient disease screening. Dip-Pen Nanolithography (DPN) is a lithography technique that has the ability to produce functional arrays on this scale, especially when using sensitive biomolecules such as proteins which require mild conditions and deposition in such a way that activity is not compromised. This research aims to create protein arrays using DPN that are detectable by Surface Enhanced Resonance Raman Scattering (SERRS), an optical detection technique that provides detailed spectra with a high multiplexing capability. Two alternative surfaces have been explored, one being a nitrocellulose surface which has the ability to retain the proteins activity and life once printed on the surface and the other, Klarite, a gold surface with roughened nanostructures that provide an enhanced SERRS signal to the arrays when tagged with a SERRS dye. This presentation will show the efficient printing of various proteins such as GFP and RFP onto these surfaces and the ability to do parallel printing of different proteins via DPN. The investigation into the immobilisation of a PSA immunoassay detectable by SERRS will also be discussed with the aim to produce a more sensitive technique for prostate cancer detection in men.
5:30 PM - K13.4
Novel Plasmonic Biosensors for the Detection of Cancer Biomarkers.
Qiuming Yu 1 , Norman Brault 1 , Jiri Homola 2
1 Chemical Engineering, University of Washington, Seattle, Washington, United States, 2 , Institute of Photonics and Electronics, Prague Czech Republic
Show AbstractOver the last two decades there has been a tremendous effort towards the development of biosensor technologies for the detection and identification of chemical and biological species. Label-free optical biosensors represent a unique technology that enables the direct observation of molecular interaction in real-time and offers benefits of rapid, sensitive and label-free detection of chemical and biological species with potential applications in numerous important areas including environmental monitoring, security, food safety, and medical diagnostics. Optical biosensors based on surface plasmon resonance (SPR) represent the most advanced and mature optical label-free biosensor technology. We will present a new SPR sensor platform in which a surface plasmon resonance coupler and disperser (SPRCD) simultaneously excites a surface plasmon via the second order of diffraction and disperses light diffracted into the first diffraction order over a position sensitive detector. The refractive index resolution as low as 3x10-7 was achieved, which indicates that performance of the prototype of SPRCD sensor is comparable with that of the best commercial SPR instruments. Combined with six microfluidic channels, it allows the detection of multiple samples simultaneously. The sensor surface will be functionalized with ultra low zwitterionic polymer and the antibodies will be chemically linked to the sensor surface. The detection of multiple cancer biomarkers, such as prostate specific antigen (PSA), transforming growth factor beta1 (TGF-β1), interleukin-6 (IL-6), and early prostate cancer antigen (EPCA), will be demonstrated in whole blood.