12:00 PM - NT6.8.08
Self-Assembly of String-Like Nanoparticles for Highly Robust, Transparent Superhydrophobic Coatings
Gaoxiang Wu 1,Dengteng Ge 1,Yubo Zhao 1,Shu Yang 1
1 Univ of Pennsylvania Philadelphia United States,
Show AbstractNanoparticle coatings have attracted significant interest in recent years due to their scalability, low-cost, and versatility in terms of coating methods and choice of substrates for a variety of applications, including anti-reflectivity, self-cleaning, and anti-fogging. The formed nanostructures is essentially a film-like assembly of nanoparticles with morphology and properties determined by their nanoparticle building blocks and, more importantly, how these particles are assembled. So far, most nanoparticle coating research has focused on spherical nanoparticles. While self-assembly is suitable for large area fabrication, it is challenging to achieve high nano-asperity required for robust superhydrophobicity within sub-100 nm thickness. Here, we synthesize an ultra-thin coating (10’s or 100’s nanometer thick) of string-like silica nanoparticles (SNPs) via charge induced adsorption on the substrate.
Different from spherical nanoparticle coating, SNPs form unique two-tiered nano-textures with much larger surface roughness. We attribute the enhanced roughness to the distinctive adsorption mechanism associated to the anisotropic nanoparticles, where the particles could interact with the surface upon different orientation (e.g. the sides or at the ends). As a result, upon evaporation of water, the chain-like particles could re-orient and stack against each other to build up surface roughness much more effectively (see Fig. 1). The result coating not only shows extremely high water repellency (WCA ~170o and CAH
12:15 PM - NT6.8.09
Stretchable Electronic and Photonic (meta)Materials from Self-Assembled Nanoparticles
Yoonseob Kim 1,Nicholas Kotov 1
1 Univ of Michigan-Ann Arbor Ann Arbor United States,
Show AbstractNanoscale science and technologies have been developed tremendously during the last two decades, introducing a variety of nanomaterials with unique properties. However, incorporation of the properties into macroscale functional applications has been limited. An essential challenge is the integration of such unique properties into assemblies for macroscale devices. Here we explore self-assembly of nanomaterials in solid-state for discovering fundamental understandings of mechanisms and dynamics for various engineering applications.
An example of excellent stretchable conductors from self-assembly of nanoparticles (NPs) was first demonstrated. Free-standing stretchable conductors were prepared by layer-by-layer (LBL) assembly. High conductivity and stretchability were observed and the properties originated from dynamic self-organization of NPs. Modified percolation theory to incorporate the self-assembly gave excellent match with experimental data.
Another self-assembly of NPs first demonstrated chiroptical nanocomposites for applications of metamaterial devices and optoelectronics. They were also LBL assembled, from NPs and single-walled carbon nanotubes. Chiroptical activities were reversibly tunable by macroscale stresses. S-like 3D nano-assemblies were responsible for the optical activities and this was confirmed by computational simulations.
Solid-state self-assembly at the nexus of mechanics, electronics, and excitonics/plasmonics can be generalized to other nanoscale materials and open new possibilities for composite-based electronic and optic devices.
12:30 PM - NT6.8.10
Shell and Surface Engineering of Indium Phosphide-Based Quantum Dots: Towards White Light-Emitting Device
Dorian Dupont 1,Mickael Tessier 1,Kim De Nolf 1,Zeger Hens 1
1 Department of Inorganic and Physical Chemistry Ghent University Ghent Belgium,
Show AbstractWhite light-emitting devices (LED) light sources can be based on the combination of a blue emitting LED with one or more luminescent materials that convert part of the blue light to green and red, such as to obtain an overall white color spectrum.1 Semiconductor colloidal quantum dots (QDs) are of particular interest here since they can have narrow emission lines with a color tunable by varying their sizes and shapes. These characteristics make QDs emitting in the visible promising remote phosphors for white LED. In the literature, most studied QDs active at visible wavelengths involve cadmium-based materials, which are relatively easy to synthesize. However cadmium is a toxic heavy metal and its incorporation into products applications is restricted in several countries. To make the use of QDs feasible, Cd-free alternatives are investigated such as indium phosphide (InP) QDs.
Recently, we have published an economical synthesis of size-tunable core/shell InP QDs that exhibit excellent emission properties.2 These QDs are ideal candidates as remote phosphors for white LED. Within this context, shell engineering is an important step towards QD applications. For instance, without shelling process InP core QDs produced with this method are not luminescent. If a II-VI shell materials is grown around the InP core, QDs emitting in the visible can be obtained. The emission properties will be dependent on the nature of the shell material. For example, a ZnS shell coating leads to an emission linewidth broader than for a ZnSe shell coating. On the other hand, better quantum yields are obtained with ZnS shell coating (up to 80%) than for ZnSe shell coating (40-50%). Here, we present synthesis protocols that lead to different types of II-VI shell materials, priming InP-based QDs for remote phosphor applications. In addition, QD-based LEDs also require a long-term photo-stability, a property depending critically on the QD surface termination. Within this context, we found that the photo-stability of the InP QDs can be considerably improved by changing the ligands capping InP-based core/shell QDs. We finally embedded such optimized InP QDs into solid polymer-based layers and analyzed the layers emission efficiencies using an integrated sphere. We demonstrate that the efficiency of these remote phosphors layers can be markedly increased by incorporating all adaptations described above. We conclude that our results strongly improve the prospects of using InP-based QDs as a remote phosphor in, for example, display applications.
(1) Smet, P. F., Parmentier, A. B., & Poelman, D. (2011). Selecting Conversion Phosphors for White Light-Emitting Diodes. Journal of The Electrochemical Society, 158(6), R37.
(2) Tessier, M. D., Dupont, D., De Nolf, K., De Roo, J., & Hens, Z. (2015). Economic and Size-tunable Synthesis of InP/ZnE (E = S,Se) Colloidal Quantum Dots. Chemistry of Materials, 27(3), 4893–4898.
12:45 PM - NT6.8.11
Surface Chemistry Modulates the Low-Frequency Vibrations of Semiconductor Nanocrystals
Anna Jolene Mork 1,Elizabeth Lee 1,William Tisdale 1
1 MIT Cambridge United States,
Show AbstractAcoustic phonons impact fundamental photophysical properties of colloidal quantum dots (QDs), such as the homogeneous fluorescence linewidth, as well as the efficiency of QD-based devices. It has been suggested that the vibrational density of states overlap between the QD core with its ligands and environment centrally contribute to heat dissipation in these materials, so engineering the vibrational spectrum may enable improved device efficiency through thermal management. Organic ligands, the molecules attached to the surface of the inorganic core, are known to affect QD electronic transitions via degree of passivation and energy level alignment; however, we demonstrate for the first time that the bound ligands also affect the QD vibrational spectrum. We use low-frequency non-resonant Raman spectroscopy to non-destructively probe the acoustic phonon vibrational structure of CdSe QD cores with a variety of different attached ligands. The frequencies of the confined acoustic modes shift depending on the size and structure of the ligand, with more massive ligands resulting in red-shifted phonon energies. We develop a mathematical model based on vibrations of an elastic sphere to understand the shifts in the QD Raman spectrum upon ligand exchange. This model has also proved accurate for describing changes in phonon energies after the growth of an inorganic epitaxial shell. These data facilitate improved engineering of nanoparticles for incorporation into nanoelectronic, fluorescence downconversion, and other solid-state applications.
NT6.9: Nanoparticle Synthesis, Assembly and Applications IV
Session Chairs
Thursday PM, March 31, 2016
PCC West, 100 Level, Room 104 AB
2:30 PM - *NT6.9.01
Carbon Nanodots: Synthesis and Applications
Yuxin Li 2,Zaicheng Sun 1
2 Third Military Medical University Chongqing China,1 Beijing University of Technology Beijing China
Show Abstract
Carbon dots, as a rising fluorescent materials have attracted continuously attention for potential applications in LED, solar cells, sensor, bioimaging and photocatalyst. However, its photo luminescent quantum yield (PL QY) is still quite low, especially emission in long wavelength region like red light. Herein, we proposed increasing the PL QY by doped carbon dots with N or S, N. The PL QY of carbon dots dramatically rises up after doping with N. It can reach over 90%. The carbon dots prepared via bottom-up route show excitation independent emission. In order to extend the absorption in the visible light region, S element is further introduced into the carbon dots to form S, N co- doped carbon dots. Due to the introduction of S and N, there is another S state was introduced into the band gap. That results in the new emission at red light region. Blue, green and red light emissions were obtained from carbon dots. Due to the excellent biocompatibility and low cytotoxicity, we further conjugated the cisplatin with carbon dots to obtain the theranostic agent. Also carbon dots also can work as a sensitizer to absorb the visible light for water splitting and dye decolorization.
3:00 PM - *NT6.9.02
Noble Metal and Non-Noble Metal Nanoscale Electrocatalysts toward Oxygen Reduction Reaction
Yujiang Song 1
1 Dalian Univ of Technology Dalian China,
Show AbstractProton exchange membrane fuel cell (PEMFC) is a clean and efficient energy-conversion technology, which has been widely expected to replace internal combustion engine to drive future vehicles. A crucial component of PEMFC is Pt/C electrocatalysts, especially for sluggish oxygen reduction reaction at the cathode, that are composed of 2-5 nm quasi-spherical Pt particles supported on carbon. However, conventional Pt/C electrocatalysts confront the high cost, limited supply, low activity, easy poisoning and poor durability, preventing PEMFC from widespread commercialization. To resolve these issues, new generation of electrocatalysts have to be rationally designed and synthesized, including non-noble metal electrocatalysts, high performance noble metal electrocatalysts, and so on. This talk will concentrate on comprehensive control over the size, shape, composition, and metal loading of electrocatalysts as well as their electrochemical performance.
3:30 PM - NT6.9.03
Tuning the Properties of Atomically Precise Silver Nanoparticles
Megalamane Bootharaju 1,Chakra Joshi 1,Lina AbdulHalim 1,T. M. D. Besong 1,Osman Bakr 1
1 KAUST Thuwal Saudi Arabia,
Show AbstractAtomically precise nanoparticles of noble metals have recently gained significant attention due to their unique optical and physicochemical properties. However, tuning the size of these nanoparticles and controllably introducing heteroatom dopants in their core are great challenges. Often times, the synthesized products are a mixture of different sizes along with a large compositional distribution that complicates the separation of the desired nanoparticles. These challenges demand new paths to overcome the existing synthesis difficulties of atomically precise nanoparticles.
In this work, we describe two strategies, ligand exchange and galvanic exchange, to control nanoparticles size and doping level, respectively. Starting from Ag35(SR)18 (SR: thiolate) nanoparticles, we obtain, through ligand exchange, different nanoparticle sizes such as Ag44, Ag~55, Ag~75, and Ag~200 by varying the choice of incoming ligands. In several cases such ligand exchange reaction is reversible and that cluster sizes are interconvertible.
A templated galvanic exchange route to controllably introduce dopants into silver nanoparticles is devised, with which we were able to synthesize compositionally uniform [Ag24Au1(SR)18]- nanoparticles using the pure [Ag25(SR)18]- nanoparticles as molecular templates. In contrast, direct synthesis methods of Ag24Au1 nanoparticles leads to a mixture of [Ag25-xAux(SR)18]-, x=1-8. Mass spectrometry coupled with X-ray crystallography of [Ag24Au1(SR)18]- nanoparticles explicitly reveal the locations of the Au dopants and their perturbative effects on the Ag25 crystal structure, which are further reflected in the absorption, luminescence and ambient stability of the particle. Our work demonstrates a promising path to modulation of nanoparticle properties by either ligand exchange or heteroatom doping.
3:45 PM - NT6.9.04
Synthesis, Functionalization and Assembly of Graphene Quantum Dots
Binsong Li 2,Xin Yan 2,Xiao Cui 2,Irma Hamilton 2,Liangshi Li 2
1 Innothium LLC Albuquerque United States,2 Indiana University Bloomington United States,2 Indiana University Bloomington United States
Show AbstractColloidal graphene quantum dots (GQDs) are a new type of functional nanomaterials that combines the extraordinary electronic and optical properties of graphene and quantum-confined properties of nanoparticles. A series of large soluble atomic-precision graphene quantum dots with various sizes were synthesized via a solution chemistry approach. The graphene quantum dots have large extinction coefficients in a wide spectral range from UV to near infrared, and thus can serve as excellent light harvesting media for photovoltaics. Beyond their unique inherent properties, their properties could also be tuned by many functionalization methods, such as reducing the bandgap of the graphenes by increasing their sizes, tuning their energy levels by chemically bonding organic functional groups, and depositing metal or metal-oxide nanoparticles by solution chemistry or atomic layer deposition. These functionalization endows them good capability to match the work function of electrode in solar cells, self-assembly on a special substrate in optoelectronic devices, or new properties such as catalytic activity. A systematic study of the functionalization of graphene quantum dots and their applications were discussed.
4:30 PM - NT6.9.05
Synergistic Role of Dopants on the Morphology of Alloyed Copper Chalcogenide Nanocrystals
Ajay Singh 2,Delia Milliron 2,Amita Singh 1
1 Lawrence Berkeley National Lab Berkeley United States,2 The McKetta Department of Chemical Engineering University of Texas at Austin Austin United States,2 The McKetta Department of Chemical Engineering University of Texas at Austin Austin United States2 The McKetta Department of Chemical Engineering University of Texas at Austin Austin United States,1 Lawrence Berkeley National Lab Berkeley United States
Show AbstractControl over composition, by doping or alloying, has emerged as a strategy for tuning optoelectronic properties of semiconductor nanocrystals.1 Compared to tuning bandgap by quantum confinement, the synthesis of nanocrystals with complex (ternary, quaternary, etc) compositions allows chemists to decouple optical properties from size and shape, which also impact assembly and electronic transport. The copper chalcogenides related to Copper Indium Sulfide (CIS) are a particularly important example in this regard since they are the active materials for highly efficient photovoltaic devices.2 The best performing thin film solar cells employ multiple dopants in CIS to tune optoelectronic properties, yet the effects of introducing multiple dopants into CIS nanocrystals has been unexplored, despite the promise of low-cost solution processed photovoltaics based on these nanocrystals. Meanwhile, chemical methods to control doping in colloidal nanocrystals are advancing rapidly and dopants have been implicated in inducing shape changes, e.g. formation of anisotropic structures (1D). In this work, we show that when gallium and antimony dopants are introduced together that they induce a surprising shape effect on CIS nanocrystals, namely that co-doped CIS nanorods join head-to-head, forming highly regular dumbbell shaped crystals. Neither dopant on its own has this effect. By analyzing the progression of the reaction, and mapping the dopant distributions in the final nanodumbbells using high resolution EDS, we uncover the mechanism behind this transformation. In effect, the presence of one dopant catalyzes the incorporation of the other, which then induces dumbbell formation.3 This is an example of a network of chemical reactions influencing crystal growth, with implications for the composition of the product and also its morphology. Recognizing and rationalizing the interactions and synergistic effects of multiple dopants during nanocrystal synthesis is essential to advancing the state of the art in doped and alloyed nanocrystals
References: -
Buonsanti, R.; Milliron, D. J. Chem. Mater. 2013, 25, 1305.
2. van Hest, M. F. A. M.; Ginley, D. S. Future Directions for Solution-Based Processing of Inorganic Materials. In Solution Processing of Inorganic Materials; Mitzi, D. B., Ed.; Wiley: Hoboken, NJ, 2008.
3. Singh, A.; Singh, A.; Bustillo, K.; Ciston, J.; Nordlund, D.; Milliron, D. J. J. Am. Chem. Soc. 2015, 137, 6464.
5:00 PM - *NT6.9.07
X-Ray Diffraction for Nanomaterial Studies
Huimeng Wu 1,Hongyou Fan 3,Zaicheng Sun 4,Feng Bai 5,Charles Cao 6,Zhongwu Wang 2
1 Olympus Scientific Solutions Americas Waltham United States,3 Sandia National Laboratories Albuquerque United States4 Beijing University of Technology Beijing China5 Henan University Kaifeng China6 Chemistry University of Florida Gainesville United States2 CHESS Cornell University Ithaca United States
Show AbstractX-ray diffraction (XRD) is a primary characterization tool for nanomaterials studies. It has been widely used for identification of crystalline, semi-crystalline and amorphous materials, quantification of chemical compositions, and analysis of nanostructure dimensions and orientation distribution. In-situ XRD measurements provide the ability to understand and control the process in reactive conditions. In this talk, we will focus on the important applications of X-ray diffraction techniques (wide angle X-ray diffraction and small angle X-ray diffraction, WAXRD and SAXRD) for nanomaterials. One application example is to use XRD, combining with other techniques, for the foundational mechanistic study of the formation of colloidal heterodimer nanocrystals. Another application example is to use in situ XRD measurements to precisely control pressure-induced phase transformations in nanocrystalline assembles.
5:30 PM - *NT6.9.08
Controlled Self-Assembly and Applications of Porphyrin
Yong Zhong 1,Jiefei Wang 1,Feng Bai 1
1 Henan Univ Henan China,
Show AbstractMolecular self-assembly is a powerful method to synthesize nanostructured materials. The unique property of molecular assemblies has been shown to depend not only on the size, shape, and composition of the molecular building blocks but also to a large extent on ordered spatial arrangement within an assembly. The synthesis of hierarchical structures leveraging the structural advantages of individual molecules still remains a significant challenge. We developed interfacially driven microemulsion (μ-emulsion) method and micelle-confined method to initiate self-assembly and formation of hierarchically structured porphyrin nanocrystals. The resulted nanocrystals exhibit uniform shapes and sizes from ten to hundred nanometers. Due to the spatial ordering of Porphyrin, the hierarchical nanocrystals exhibit collective optical properties resulted from coupling of molecular Porphyrin and photocatalytic activities in reduction of platinum nanoparticles and networks and in photo degradation of methyl orange (MO) pollutants.
NT6.10: Poster Session III: Colloidal Nanoparticles III
Session Chairs
Hongyou Fan
Han Htoon
Ying-Bing Jiang
Songtao Wu
Friday AM, April 01, 2016
Sheraton, Third Level, Phoenix Ballroom
9:00 PM - NT6.10.01
Stress-Induced Phase Transformation, Consolidation, and Optical Coupling of Quantum Dots
Kaifu Bian 1,Binsong Li 2,Sheng Liu 1,Ting Luk 1,Igal Brener 1,Michael B. Sinclair 1,Zhongwu Wang 3,Tobias Hanrath 3,Hongyou Fan 4
1 Sandia National Laboratories Albuquerque United States,2 Angstrom Thin Film Technologies LLC Albuquerque United States3 Cornell University Ithaca United States1 Sandia National Laboratories Albuquerque United States,4 Center for Micro-Engineered Materials,Chemical and Biological Engineering University of New Mexico Albuquerque United States
Show AbstractQuantum dots are promising building blocks for important applications including photovoltaic, light emission, transistors and bioimaging due to their unique size- and shape-dependent optical and electronic properties. The ability to tune optical and electronic properties of quantum dots by engineering their size, shape, and composition has proved to be a versatile way to interrogate structure–property relationships in quantum dots. Here we present a new method to engineer quantum dot assemblies and to probe their structure-property relationships through stress-induced phase transformation and their exchange coupling during high-pressure compression. We show that under hydrostatic pressure, the unit cell dimension of a 3-dimensional (D) ordered quantum dot superlattice can be manipulated to shrink and swell reversibly, allowing fine-tuning of interparticle separation to probe optical coupling in the supertlattice. Further, beyond a threshold pressure, quantum dots are forced to connect with neighboring dots to form new classes of chemically and mechanically stable 1-3D nanostructures including nanorods, nanowires, nanosheets, and nanoporous networks which cannot be achieved by traditional top-down or bottom-up methods. Moreover, through in situ high-pressure synchrotron-based x-ray scatterings and optical absorption measurements, we discovered Hall-Petch-like size-dependent elastic stiffness and size-dependent pressure coefficient of energy gap in quantum dots. Stress-induced phase transformation and exchange coupling provides new insights for fundamental understanding of chemical and physical properties of quantum dots.
Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-AC04-94AL85000.
9:00 PM - NT6.10.02
Highly Stretchable Gold Nanosheet Electrodes Patterned by Stamping Process
Jun Hyuk Song 1,Heeseung Yang 1,Sunghwan Cho 1,Unyong Jeong 2
1 Materials Science and Engineering Yonsei University Seoul Korea (the Republic of),2 Materials Science and Engineering POSTECH Pohang Korea (the Republic of)
Show AbstractStretchable and conductive electrodes are highly desirable for future devices such as flexible displays, flexible transistors, and wearable electronics. In order to realize these uses, metallic conductivity and high electrical stability with stretching are critical requirements. Due to the needs of these stretchable electrodes, many researchers focus on designing electrodes which can meet all the prerequisites. Even with the struggling of these researches, to date, Au nanomaterials have not been explored for stretchable conductive circuits and electrodes. Au electrodes are promising candidate for nanomaterial based stretchable electrodes due to its high conductivity and long term stability. It is also compatible with p-type organic semiconductors which makes it highly valuable for stretchable transistors.
Here, we fabricated Au electrodes made of multilayers of Au nanosheets. The electrodes are patterned on a rubber substrates such as PDMS and Ecoflex by floating and stamping method. These electrodes showed high electrical conductivity and stability at high strain levels. The stretchability of patterned rectangular electrodes in the longitudinal direction and the transverse direction was analyzed. To confirm the validity of the Au electrodes for organic semiconductors, we investigated the charge injection from the Au nanosheet electrodes to poly(3-hexylthiophene)(P3HT) nanofibers as a function of tensile strain.
9:00 PM - NT6.10.03
Eco-Friendly Fabrication of Silver Nanoshells Having Enhanced Catalytic Performances
Jaewon Lee 1,Sooho Ham 1,Du-Jeon Jang 1
1 Seoul National University Seoul Korea (the Republic of),
Show AbstractNanoscale noble-metals have attracted significant attention from researchers in diverse fields of study because of their unusual optical properties as well as novel chemical properties. Especially, silver nanoparticles stand out from various types of noble-metal nanostructures due to their superior performance in a range of applications such as surface plasmon resonances, catalysis, SERS, and biosensing. In particular, extensive efforts have been devoted to the investigation of silver-based nanocomposites to achieve high catalytic performances. We will present that Ag@SiO2@Ag sandwich nanostructures with highly enhanced catalytic performances have been fabricated facilely and eco-friendly by just irradiating 355 nm laser pulses only to Ag@SiO2@Ag-seed nanoparticles for 30 min; silver seeds adsorbed on the silica surfaces have grown up to larger silver nanoparticles via the photochemical reduction of dissolved silver ions to form silver shells. The catalytic activity of the laser-fabricated sandwich nanostructures for the degradation reaction of rhodamine B in the presence of KBH4 has been observed to be higher five times than that of the unirradiated nanoparticles. The sandwich nanostructures can be further transformed into hollow SiO2@Ag nanostructures with irradiation of laser pulses for additional 30 min. Thus, our laser-induced fabrication method of silver-based nanocatalysts can be regarded as a new approach of green chemistry because it does not require any reducing agents nor any surface-treatment processes.
9:00 PM - NT6.10.04
Tuning Collective Surface Plasmon Resonance by Assembling Silver Nanoparticles into a Three-Dimensional Nanostructure
Fu-Cheng Tsai 1,Cheng-Hsi Weng 1,Jen Li 1,Wen-Pin Shih 2,Yuh-Chung Hu 3,Pei-Zen Chang 1
1 Institute of Applied Mechanics National Taiwan University Taipei Taiwan,2 Department of Mechanical Engineering National Taiwan University Taipei Taiwan3 Department of Mechanical and Electro-Mechanical Engineering National Ilan University Ilan Taiwan
Show AbstractNoble metal nanoparticles have surface plasmon resonance effects that can be used in biosensors, tumor curing, enhancing Raman spectroscopy, and solar cells. The plasmon resonance makes the spontaneous charge transfer to or from these nanoparticles. In this research, we used (3-Mercaptopropyl)trimethoxysilane as a crosslinker to assemble silver nanoparticles into a three-dimensional network structure to introduce the collective surface plasmon resonance (CPR). This resonance makes another absorption peak at 500 nm in optical spectrum and retains the original peak at 400 nm due to local surface plasmon resonance (LSPR). The ratio of the absorption amplitudes between these two resonances can be tuned by the degree of aggregation. The absorption amplitude due to CPR can be controlled from zero to equal the one owing to LSPR. We have successfully deposited these aggregated silver nanoparticles on substrate and maintained the effect of CPR and LSPR. It makes the width of absorption broader, that is, more light energy is absorbed to be plasmonelectric energy. This effect enables the development of plasmonelectric devices to be a new-generation solar cell.
9:00 PM - NT6.10.05
Floating Gate Memory Operation in Au Nanoparticle Single-Electron Transistor
Yasuo Azuma 1,Naoki Kusunoki 1,Masanori Sakamoto 2,Toshiharu Teranishi 2,Yutaka Majima 1
1 Tokyo Institute of Technology Yokohama Japan,2 Kyoto University Kyoto Japan
Show AbstractThe bottom-up technology for nanoscale electronic devices and their assemblies based on chemical interaction is a promising approach to realizing future electronics. We have demonstrated chemically assembled SETs consisting of self-terminated electroless-gold plated nanogap electrodes, containing self-assembled monolayers (SAMs), with synthesized Au nanoparticles positioned between the electrodes[1]. Chemically assembled SETs exhibit ideal rhombic Coulomb diamonds[2,3]. We have also fabricated chemically assembled SETs with double-gate electrodes and demonstrated all two-input logic operation[4]. Here, we demonstrate memory operations in Au nanoparticle SETs fabricated by chemical assembling using nanogap electrodes and chemisorbed Au nanoparticles.
We used electron beam lithography and a lift-off process to fabricate the Ti (3 nm)/Au (20 nm) electrode patterns of source (S), drain (D), side gate (SG), control gate (CG) and floating gate (FG) electrodes on a SiO2 (50 nm)/Si substrate. Octanethiol and decanedithiol (C10S2) mixed SAMs were formed onto the electrodes, then decanethiol (C10S)-protected Au nanoparticles were introduced between the S and D electrodes. Some of the C10S molecules surrounding the Au cores were expected to be substituted with C10S2 molecules on the Au nanogap electrodes, and C10S-protected Au nanoparticles were expected to be anchored by the C10S2 molecules. All measurements were carried out at 9 K in vacuum condition.
Fabricated SET shows extremely stable Coulomb diamonds. By applying pulse voltage of +20 V onto the CG electrode, phase shift of 0.5e were observed in not only Coulomb oscillations but also Coulomb diamonds. This phase shift was derived from charge storage onto the FG electrode. FG memory operations were reproducibly observed, and charges on the floating gate electrodes were maintained at least 12 h. By considering capacitance of the floating gate electrode calculated from finite element method, the number of electrons on the floating gate electrode was estimated as 100.
[1] V. M. Serdio V., Y. Azuma, S. Takeshita, T. Muraki, T. Teranishi, and Y. Majima, Nanoscale, 4, 7161 (2012).
[2] Y. Azuma, S. Suzuki, K. Maeda, N. Okabayashi, D. Tanaka, M. Sakamoto, T. Teranishi, M. R. Buitelaar, C. G. Smith, and Y. Majima, Appl. Phys. Lett., 99, 073109 (2011).
[3] N. Okabayashi, K. Maeda, T. Muraki, D. Tanaka, M. Sakamoto, T. Teranishi, and Y. Majima, Appl. Phys. Lett., 100, 033101 (2012).
[4] K. Maeda, N. Okabayashi, S. Kano, S. Takeshita, D. Tanaka, M. Sakamoto, T. Teranishi, and Y. Majima, ACS Nano, 5, 2798 (2012).
9:00 PM - NT6.10.06
A Facile Low Temperature Solid-Phase Synthesis of g-c3n4 Quantum Dots and Their Use in Cell Viability
Aiwu Wang 1
1 City Univ of Hong Kong Hong Kong Hong Kong,
Show Abstract
Quantum dots, typically contain a few thousand atoms and have been widely studied since
1990s owing to their unique physical and optical properties. Based on the specific properties, the applications of the nanostructures have ranged from photonics ,electronics, and drug delivery to biological and biomedical imaging in vitro and in vivo. However,heavy metals(for example, CdSe, PbTe, and CdTe) as essential elements in semiconductor quantum dots have risks of long-Term toxicity and potential environmental hazards. Therefore, the needs for more biocompatible nanomaterials with similar properties are urgently required. Carbon nanoparticles or CDs as a class of heavy-metal-free fluorescent nanomaterials possess some advantageous, such as tunable emission, high optical absorptivity, chemical stability, biocompatibility, and low toxicity. un-doped CQDs might have the disadvantage of self-quenching, thereby limit their further applications in bioanalysis. For C-dots, nitrogen doping of carbon dots have been reported to give excellent optical properties.It needs to be emphasized that graphitic carbon nitride quantum dots(GNCQDs) can be regarded as nitrogen rich carbon quantum dots. The g-CNQDs have the advantages of bright fluorescence, good stability, water solubility, biocompatibility, and nontoxicity, making them good candidates in place of traditional QDs.
However, still now there is few reports to preparation of g-c3n4 qds, suffers such as the lack of effective synthetic methods and the low quantum yield. Bottom up method and Top down method were used to prepare g-c3n4 qds, for bottom up synthesis, Xie group and Yu group have investigated the synthesis method with complicated process, which suffers long time, high temperature, strong acid. For top down synthesis, Sun etal.developed a heat-treatment-based
(refluxing,microwave and solvothermal heating) method with nitrogen-containing or ganic molecules including dimethylamine,1,2-ethylenediamineandN,N-dimethylformamideasthepre-
cursors. Barman achieved an improved quantum yield of 29% using the microwave-mediated method with formamide as the precursor, but the obtained g-CNQDs had wide size distributions from 2nm to 15nm. Zhou et al developed a low temperature solid-phase synthesis of g-c3n4 qds, which requires a temperature of 180. Recently Lu et al developed a facile way to synthesize g-c3n4 qds by hydrothermal method (200)with Citric acid and thiourea as precursors.
In our work, a facile solvent-free low-temperature synthesis of SOCNQDs has been developed with a high quantum yield of 18%. In our best knowledge, the temperature we used (120) is lowest during the preparation of gc3n4 qds. Thermal treatment of a common beaker contained mixed citric acid monohydrate and thiourea with 90 minutes is the strategy, which is the most simple method as far as we know. Furthermore, obtained SOCNQDs were explored with cell imaging.
9:00 PM - NT6.10.07
Solution-Processable Indirect Synthesis of Cu-Doped 2D PbS Nanoplates Exhibiting Low Resistivity and High Responsivity
Wen-Ya Wu 1,Asim Guchhait 1,Sabyasachi Chakrabortty 1,Yinthai Chan 1
1 National Univ of Singapore Singapore Singapore,
Show AbstractWe have reported indirect synthesis of copper-doped PbS nanoplates. We approached cationic exchange from Cu2S nanoplates of average thickness of 3 nm and lateral dimension of 150 nm to PbS nanoplates with same dimension and achieved the Cu doping from the residual amount of Cu present within the PbS nanoplates after final exchange. From the structural characterizations, it was found that basal planes of ± {002} facets of Cu2S nanoplates transformed into the basal plan of ± {111} of PbS nanoplates which are of high surface energy and terminated by atomic layer of either Pb or S. We introduced these Cu-doped PbS nanoplates in a planar structured device for NIR active photodetector application. We found after thermal annealing of the active material, the Cu-doping helped to improve the conductivity of the host material and yielded a responsivity of 1738.88 A/W under illumination of 808 nm light.
9:00 PM - NT6.10.08
Carbon Dots: Doping and Applications
Dan Qu 2,Zaicheng Sun 1
2 State Key Laboratory of Luminescence and Applications Changchun Institute of Optics, Fine Mechanics and Physics Changchun China,1 Beijing Univ of Technology Beijing China
Show AbstractCarbon dots (CDs) have been actively explored in recent years due to their unique optical properties and applications related to catalysis and bioimaging.1,2,3 To date, extending the absorption of CDs into visible light as well as obtaining CDs with long-wavelength emissions are still the hotspots that researchers aspired to enhance. Only then can CDs be better applied in more fields. Admittedly, doping is a widely used technological process in materials science that involves incorporating atoms or ions of appropriate elements into host lattices to yield materials with desirable properties and functions. It is particularly noteworthy that we have successfully manipulated the properties of CDs by doping N, S and Se into CDs. Then highly quantum yield (QY) blue light CDs (~ 94 %) can be produced by doping N,4 multicolor emissions CDs can be obtained by doping S and Se3 with higher QY green light (~ 45 %), yellow light (~ 20 %) and red light (~ 8 %). Obviously, the optical properties of CDs have been tuned deserving to be expect after doping, it is thus logical that these doped CDs can been applied to many areas with broad developing prospect, such as bioimaging,2,3 self-targeting,5 theranostic agents6 and photocatalyst especially in visible water splitting.
Reference
Qu D, Zheng M, Du P, et al. Nanoscale, 2013, 5 (24): 12272-12277.
Qu D, Zheng M, Li J, et al. Light: Science& Applications, 2015, 4, e364, doi: 10.1038/lsa.2015.137.
Qu D, Sun Z, Zheng M, et al. Advanced Optical Materials, 2015, 3 (3): 360-367.
Qu D, Zheng M, Zhang L, et al. Scientific Reports, 2014, 4.
Zheng M, Ruan S, Liu S, et al. ACS Nano, 2015, Accepted.
Zheng M, Liu S, Li J, et al. Advanced Materials, 2014, 26 (21): 3554-3560.
9:00 PM - NT6.10.09
Synthesis of Pt-Nanoparticle-Functionalized Co3O4-In2O3 Heterojunction Nanocomposites and Their CO Sensing Properties
Jen-Pu Liu 1,Chao-Heng Liu 1,Ju-Heng Tsai 1,Yi-Hsiang Chang 1,Tsung-Han Chen 1,Chun-Hua Chen 1
1 Department of Materials Science and Engineering National Chiao Tung University Hsinchu City Taiwan,
Show AbstractIn this study, we successfully synthesized a series of Pt-nanoparticles decorated In2O3/Co3O4 nanocomposites for sensing CO gas at relatively low temperatures. The synthesized one-dimensional In2O3 hierarchical nanobundles comprising numerous parallel assembled nanoparticles and short nanorods, which provide not only open channels for gas inward/outward diffusion, but high surface to volume ratios for gas absorption/desorption, were proven as an excellent base matrix for the subsequent improvement. It was found that Pt nanoparticles play specific roles in significantly lowering the operating temperatures and the nanoscaled p-n junctions formed by the co-synthesis of Co3O4 with the In2O3 nanobundles are crucial for further enhancement. As a result, the fabricated Pt-nanoparticles decorated Co3O4-In2O3 nano-composites exhibit excellent CO sensing performance at room temperature to a very low detecting limitation of about 5 ppm CO.
9:00 PM - NT6.10.10
Characterization of Silver Nanoparticles Prepared by Polyol Method with Atmospheric Plasma Treatment
Hsuan-Ying Chen 1,Shun-Kai Hsu 1,Kun-Dar Li 1
1 National University of Tainan Tainan Taiwan,
Show AbstractIn recent years, silver nanoparticles have been extensively studied in many scientific and technological fields from biology to materials science or electronics because of their unique properties, such as surface plasma resonance effect and powerful antibacterial property. In this research, well-dispersed silver nanoparticles with the sizes of 30-80nm were synthesized via a polyol method by adding PVP and PEG as the reducing agent and solvent to silver nitrate solution. In a following step, a centrifugation process was used to deposit silver nanoparticles directly on silicon substrate. By controlling the centrifugal speed and time, various coverage ratios of silver nanoparticles on the substrate were obtained. Afterwards, an atmospheric plasma treatment was further applied for the modification of silver nanoparticles. Owing to the effects of thermal sintering and ion bombardment, modified silver nanoparticles grew along the c-axis and were re-arranged more regularly. In addition, it was also observed that some tiny silver nanodots re-deposited on the arrayed nanoparticles. From Raman spectroscopy analysis, it demonstrated that the SERS effect would be significantly enhanced and the residual dispersant on silver substrates can be removed after plasma treatment. More detailed mechanism of plasma treatment was discussed in this study.
9:00 PM - NT6.10.11
Giant Magnetic Field Fluctuations in Mn-Doped CdSe Quantum Dots with Strong Band-Edge Emission
Wenyong Liu 1,William Rice 1,Thomas Baker 1,Gen Chen 1,Jeffrey Pietryga 1,Scott Crooker 1,Victor Klimov 1
1 Los Alamos National Lab Los Alamos United States,
Show AbstractSemiconductor quantum dots (QDs) based on CdSe represent an interesting host system for incorporation of magnetic ions of manganese (Mn), as by varying the CdSe QD size one can tune the energy of the band-edge exciton from being smaller than the energy of the emitting transition of the Mn2+ to being larger than that. The goal of the present study has been to prepare high quality Mn2+ doped CdSe QDs that meet the following requirements: facile control of the concentration of impurity ions and their location within the QD, high photoluminescence (PL) quantum efficiency for intrinsic band-edge emission, and high sample monodispersity. Controlled doping of colloidal CdSe QDs with Mn has proven to be difficult, which has been attributed to low dopant diffusion rates and small binding energies at crystal facets prevailing in wurtzite QDs. Here, we demonstrate several approaches for overcoming these issues which allowed us to produce a series of size-controlled Mn2+-doped CdSe QDs that show narrow size distribution and high emission efficiencies. The nominal Mn2+ doping concentration can be as high as 4-5%. Although the emission from as-synthesized manganese-doped QDs was totally quenched, the quantum yield could be recovered (to more than 70%), by growing an epitaxial shell of CdS at slightly elevated temperatures. Importantly this procedure did not result in expelling of Mn from the QDs. By using CdSe QDs of different sizes, we were able to observe both the band-edge and Mn d-d emissions and study the interplay between the two bands as a function of the QD band-gap energy and sample temperature. The strong sp-d exchange interaction between Mn2+ ions and QD electronic excitations was unambiguously demonstrated by both magnetic circular dichroism studies and femtosecond time-resolved Faraday rotation measurements. The latter technique allowed us to observe , for the first time, giant internal magnetic field fluctuations (15-30 T) resulting from incomplete cancellation of Mn2+ spins in the case of a small number of impurity ions [1]. We also observe a strong effect of internal magnetic fields generated by Mn ions on the fine structure of exciton band-edge states and their relaxation dynamics.
Reference
Rice W., Liu W., Baker T., Sinitsyn N., Klimov V. I., Crooker S. A. (2015). Nature Nanotechnology in press (2015).
9:00 PM - NT6.10.12
Interchangeable Colloidal Nanocrystals for Tunable Optical Nanoantenna
Tyler Dill 1,Matthew Rozin 1,Stephen Palani 1,Darwin Zwissler 1,Andrea Tao 1
1 Univ of California-San Diego La Jolla United States,
Show AbstractEngineered structures that support localized surface plasmon resonances (LSPRs) enable vibrational spectroscopy with single-molecule sensitivity and nanometer spatial resolution. Colloidal nanoparticles are ideal building blocks because they exhibit LSPRs in the visible spectrum. In addition, the LSPR is highly tunable with nanoparticle size, shape, and assembly. By carefully selecting nanoparticles and self-assembling them onto an AFM tip, we can engineer an optical nanoantenna with a tunable near-field response. We demonstrate this with Ag nanocrystal coated AFM tips coupled to a metal substrate, these nanoantenna generate a strong optical cavity capable of achieving Raman enhancements of 109 and providing chemical spectra with < 50 nm spatial resolution.
9:00 PM - NT6.10.13
Bimetallic Ag-Au Alloy Nanoparticles: Synthesis, Characterization and Catalytic Activity
Charu Dwivedi 2,Abhishek Chaudhary 2,Chayan Nandi 2
1 Department of Chemistry, School of Physical Sciences Doon University, Dehradun Dehradun India,2 School of Basic Sciences Indian Institute of Technology Mandi Mandi India,2 School of Basic Sciences Indian Institute of Technology Mandi Mandi India
Show AbstractBimetallic nanoparticles (BNPs) are emerging as a new class of nanomaterial due to their unique electronic catalytic and optical properties
1, 2. These properties of the BNP can be tailored according to the specific application by controlling the size, shape and metallic composition of the particles. BNP containing gold as one of the elements have begun to show opportunities for developing novel catalytic systems. Among BNP, core shell nanoparticles are extensively studied but these particles have their own challenges such as poor diffusion barrier of gold surface and difficulty in controlling the uniformity and thickness of the metal shell, etc.
3 These shortcomings of the core shell BNP can be minimized by forming alloy nanoparticles. Gold containing alloy nanoparticles are solid solutions where other metal atoms substitute gold sites in the face centre cubic lattice. The incorporation of even a little content of the other metal changes the catalytic activity significantly. Herein, we are reporting a simple, one pot synthesis method for Ag-Au BNP, using a bio-compatible polymer as stabilizing agent. The synthesized alloy BNPs have been analysed by UV−vis spectroscopy, HRTEM, energy dispersive X-ray spectroscopy (EDS) and powder X-ray diffraction to establish the alloy formation and surface morphology. Additionally the effect of variation of the synthesis conditions on nanoparticles morphology is also investigated in detail. It is observed that with the increase in the gold content the surface plasmon resonance of the alloy BNP is red shifted. The catalytic activities of thus-prepared alloy BNPs with various compositions have also been investigated for reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) by NaBH
4 is investigated via UV-vis spectroscopy. A decrease of the band at 400 nm (4-NP) and the appearance of a new band at around 300 nm (4-AP) within minutes revealed a fast reaction, clearly indicating that the particles are well accessible for the reactants. In conclusion, we introduced a facile and versatile method to prepare highly stable bimetallic NP catalysts with high control over structure, size, and composition.
References 1. M. S. Holden, K. E. Nick, M. Hall, J. R. Milligan, Q. Chen and C. C. Perry, RSC Adv., 2014, 4, 52279-52288.
2. X. López Lozano, C. Mottet and H. C. Weissker, J. Phy. Chem. C, 2013, 117,
3062-3068">3062-3068.
3. I. C. Chiang and D. H. Chen, Adv. Funct. Mater., 2007, 17, 1311-1316.
9:00 PM - NT6.10.15
Simple One-Step Oil Encapsulation in Polyethylene Glycol Using Coaxial Electrospray for the Short-Term Drug Delivery System
Tae Hoon Ki 1,Sun Woong Han 1,Keun Ho Lee 1,Hong Koo Baik 1,Jee Hoon Kim 1
1 Yonsei Univ Seoul Korea (the Republic of),
Show AbstractConventional encapsulation methods of essential oil in polymer particle have several problems such as residual toxicity, oil loss in multi-step process, release in fixed condition. Especially they can control the release rate required for the long-term drug delivery system, but can’t make rapid release profile possessing high encapsulation efficiency. In this study, we report the one-step preparation of water-soluble and biocompatible Polyvinyl alcohol(PEG) microcapsules containing essential oil by coaxial electrospray. In the size range of 0.5-3μm, it was shown that PEG microcapsules had the rapid release rate, high encapsulation efficiency. Furthermore we could easily deposit PEG microcapsules at various substrate used for the short-term drug delivery system.
9:00 PM - NT6.10.16
Analyzing the Roles of Additives in the Synthesis of Gold Nanorods
Iris Guo 1,Byron Gates 1
1 Simon Fraser University Burnaby Canada,
Show AbstractGold nanorods have been extensively studied to finely control their shape and tune their aspect ratio with the goal of better understanding their growth mechanism and obtaining products with well-controlled and well-defined optical properties. This understanding and ability to control their properties are also important for the use of gold nanorods in a variety of applications that include plasmonic materials, photothermal therapy, and catalysis. Seed-mediated solution phase synthesis is one of the most widely used methods to prepare gold nanorods, which incorporates gold seeds that serve to nucleate the growth of nanorods from a mixture of gold precursor and a system of surfactants. Recently, the use of additives and/or binary surfactant systems have been reported to be effective in achieving a more precise regulation of aspect ratio, as well as minimizing by-products compared to methods that use a single surfactant to regulate the growth of the nanorods. The study presented here provides a further investigation into the role of additives on the synthesis of gold nanorods. As one example, a systematic investigation is presented that looks into a reaction mixture containing hexadecyltrimethylammonium bromide along with one or multiple types of salicylic acid derivative(s). Gold nanorods were prepared under a variety of synthetic conditions to control and investigate the kinetics of the growth process and the resulting products were characterized through a combination of extinction spectroscopy, particle size analyses, and electron microscopy techniques. The results of this correlative analysis reveals further insights to the roles of surfactants and additives, as well as their interactions with other chemical species in solution and their influence on the formation of gold nanorods. These results also serve to gain a more detailed insight into controlling seed-mediated methods to reproducibly achieve gold nanorods of a desired size and uniformity.
9:00 PM - NT6.10.17
Identification of Defects in Lepidocrocite Nanoparticles and Correlation with Their Magnetic Properties
Yulia Trushkina 1,Cheuk Tai 1,German Salazar-Alvarez 1
1 Materials and Environmental Chemistry Stockholm University Stockholm Sweden,
Show AbstractLepidocrocite (γ-FeOOH) nanoparticles can be used in a variety of industrial applications such as pigment production, catalysts for chemical synthesis, adsorbents for water and gas purification, etc. However, the properties of nanoparticles can be often altered significantly by the presence of defects present on the surface or within the volume or both. In the case of iron oxy-hydroxide nanoparticles it has been found that depending on the synthesis conditions these materials can exhibit so-called anomalous magnetic properties such as ferrimagnetism in nominally antiferromagnetic substances or vice versa, emergence of exchange-coupling effect, etc.; likely due to changes in the cationic order around the defects [1,2].
We have used high-resolution transmission electron microscopy (HRTEM) and powder x-ray diffraction (PXRD) to examine the defects in lepidocrocite nanorods (average dimensions of 250 × 250 × 28 nm3). From HRTEM data we observed clearly the presence of defects in the structure of nanoparticles, e.g. dislocations in (020) plane whereas the strain analysis shows an enhanced strain on (021) and (111) planes. Rotation electron diffraction (RED) was used to investigate the diffuse scattering in 3D. The diffuse intensity was detected in [010] and [110] directions. Moreover, the magnetic characterization indicates the presence of a ferrimagnetic component and exchange bias at low temperatures. In this talk we present these results and an attempt to correlate the role of the defects with their functional properties and the origin.
[1] Hirt et al., J. Geophys. Res. 107 (2002), EPM 5 1-9.
[2] Wetterskog et al., ACS Nano 7 (2013), 7132-7144.
9:00 PM - NT6.10.18
Flexible Synthesis of Novel Superhydrophobic Nanocomposite Polymer Films
Sebastian Dixon 1,Ivan Parkin 1
1 University College London London United Kingdom,
Show AbstractA new synthetic route is presented for creating novel superhydrophobic nanocomposite polymer thin films on glass substrates which both incorporate functional nanoparticles into the polymer matrix, while exhibiting an extreme repulsion of water. The aim of the work has been to create novel materials which can demonstrate new combinations of functional properties, but which have been demonstrably difficult to synthesise by alternative, established means. The synthetic route devised here is shown to overcome the limitations of previous methods, while affording far greater control over the functional, physical and chemical properties of the end product.
The synthetic route utilises an established method for generating a superhydrophobic polymer thin film on a glass substrate by aerosol-assisted chemical vapour deposition (AACVD). Particles of nanometre scale (nanoparticles), which are widely known for their interesting and useful properties, are then thoroughly incorporated within the polymer film by a recently established method which swells the polymer in an organic solvent, enabling diffusion into the polymer matrix of nanoparticles dispersed in the solvent. Once sufficient time has passed, the solvent is then allowed to evaporate, shrinking the polymer to its original dimensions with the nanoparticles trapped within the polymer matrix. This timely joining of two recently reported techniques into a novel tandem procedure has been demonstrated to incorporate both tungsten (VI) oxide and gold nanoparticles thoroughly within superhydrophobic polydimethylsiloxane (PDMS) films, to yield two new functional materials which have been previously difficult to synthesise. The synthesis is highly flexible and has the potential to be extended to any number of nanoparticle combinations, providing access to a range of previously unattainable superhydrophobic composite films.
A thorough characterisation of the films is carried out to demonstrate their properties and the success of the synthesis. An investigation has been made into the wetting behaviour of the superhydrophobic polymer with reference to its advanced microscopic roughness, demonstrating that the nanoparticle incorporation has little negative impact on its desirable wetting properties or on the polymer microstructure. Characterisation of the nanoparticles within the polymer has demonstrated their curious and useful crystallographic and spectroscopic properties. Elemental analysis techniques have been applied to show the thorough incorporation of nanoparticles achieved by the technique both at the surface and deep within the polymer microstructure, whilst supporting the identification of each and demonstrating the nanoparticle surface redox phenomena.
9:00 PM - NT6.10.19
Optimization of Fluid Characteristics of 2D Materials for Inkjet Printing
Monica Michel 1,Jay Desai 1,Alberto Delgado 1,Anupama Kaul 1
1 University of Texas at El Paso El Paso United States,
Show Abstract2D materials have shown to be the next step in semiconductor use and device manufacturing that can allow us to reduce the size of most electronics. One of the novel ways to obtain 2D materials is through liquid exfoliation, in which these materials can be obtained by dispersing the smallest possible particles in different solvents. Once obtained, the solutions can be used to manufacture devices via different processes, one of which is inkjet printing. This process relies in selecting “jettable” fluids, which need to have the necessary combination of viscosity and surface energy or “wettability”. In this work we have modified the viscosities and surface energies of five solvents: IPA (Isopropanol), NMP (N-methyl – 2 pyrrolidone), DMA (Dimethylacetamide), DMF (Dimethylformamide) and a mixture of Cyclohexanone / Terpineol 7:3. We have found an avenue to tailor the viscosity of these solvents though the addition of Ethyl Cellulose (EC), where the viscosity has been increased by up to 15 times at an EC concentration of 6%. For inkjet printing, ideally a viscosity of 4 – 10 cP is recommended, which we have been able to achieve with all of the solvents studied. It has been found that the different solvents present different susceptibilities to the EC addition, with DMA and DMF being the least sensitive to the EC addition. We have also studied the change in the drop dynamics and interactions of the 2D solutions with the substrate. Through this analysis we have found solvents that appear to be attractive for inkjet printing of MoS2 and graphite. We will close by presenting results on the ink-jet printing of 2D Mos@ and graphite solutions that we have formulated on rigid and flexible substrates, and discuss the electrical transport properties of these printed structures.
9:00 PM - NT6.10.20
Se Doping Assisted Morphology Control of Te Nanorods
Junghyeok Kwak 1,Gyeongbae Park 1,Insang You 1,Kunsuk Koh 1,Unyong Jeong 1
1 POSTECH Pohang Korea (the Republic of),
Show AbstractMorphology control of Te nanorods with Se doping is discussed. DFT assisted calculation and solvothermal based experimental procedure revealed that minute amount of Se(~ 0.3 atomic %) mixed with Te precursor drastically reduce the aspect ratio of resulting nanorods. This effect originates from the surface energy change of axial and radial planes of Te with Se doping. Se-doping-induced surface energy decrease of axial plane acts a key role in overall morphology change and growth kinetics. Se doped Te nanorods with controlled axial and radial dimensions can be used as templates for chemical transformation into Bi2Te3 or PbTe, which are promising thermoelectric materials. Chemically transformed compound nanorods develop nanoscale grain boundaries for maximized phonon scattering, but still maintain previously controlled dimensions.
9:00 PM - NT6.10.21
Formation of Nanoparticle Films via Hypersonic Particle Deposition
Peter Firth 1,Zachary Holman 1
1 Arizona State University Peoria United States,
Show AbstractMany applications that utilize nanomaterials in manufactured products require that the particles be deposited as films or coatings. These may be, for example, thermal barrier coatings on high-temperature parts, active layers in electronic devices, optical layers in laser Bragg mirrors, or biocompatible coatings on medical implants. In all cases, the coatings should have a uniform and controllable thickness—even on curved surfaces of any substrate material—and their constituent particles should maintain their unique nano-scale properties.
Present nanomaterial films developed in laboratories are often unable to be reproduced on an industrial scale; the manufacturing methods are inherently nanomaterial and substrate specific. This specificity results in manufacturing equipment that is expensive or offers limited utility. We propose an advanced nanomaterial film manufacturing technology based on hypersonic particle deposition (HPD) that overcomes these deficiencies.
HPD begins by aerosolizing a nanomaterial using any desired technique, from atomizing a nanoparticle-laden solution to feeding nanoparticle-precursor gas into a plasma. The aerosolized material is fed into the HPD system, which consists of two chambers separated by a slit-shaped nozzle, with the bottom chamber held under vacuum. The nanomaterial is accelerated to a velocity of several hundred meters/second as it and the aerosol background gas are forced through the nozzle, resulting in the formation of a curtain of nanoparticles directed into the downstream chamber. A substrate is passed through the curtain, and the nanomaterial collides with and adheres to the substrate, forming a thin coating.
Using Si, TiO2 and Ag nanoparticles ranging in size from 5nm to 200nm, initial experiments demonstrated the ability to deposit films 5nm to 5000nm thick with +-10% uniformity over a 4 by 4 inch area. Substrates included silicon, glass, aluminum and polyester fabrics. By adjusting process conditions we were able to control of the porosity of the deposited film as confirmed by SEM and Rutherford Backscattering.
9:00 PM - NT6.10.22
LED Lighting System Integrated with Cd-Free Quantum Dot Enhanced Panel (QDEP) for High Color Rendering Index
Min-Sang Lee 1,Young-Ki Lee 2,Daeman Han 3,Yeon-Su Kang 4,Jong-Soo Lee 4
1 Ecolumy Daegu Korea (the Republic of),2 Division of Green Energy Engineering Uiduk University Gyeongju Korea (the Republic of)3 Korea Institute of Industrial Technology Cheonan Korea (the Republic of)4 Department of Energy System Engineering DGIST Daegu Korea (the Republic of)
Show AbstractThe Quantum Dots(QDs) are a types of semiconductor nanoparticles changing the color of absorbed light and physical properties according to their size, used for LED lighting applications in this research. The property of LED light source is a crucial factor for improving color rendering index(CRI) in the lamps, however, the development of LED light source has been restricted within the limits of conventional white color technology. Conventional white LED lamp uses inorganic phosphors on the down conversion of blue or ultra violet LED packages, achieving high CRI white color by the combination of cyan, orange, red and deep red phosphors. In case of conventional white color technology, although the CRI value may reach up to ~90 by optimized mixture of four color phosphors, the reduction of luminous flux more than 30% was inevitable. For the application of high CRI LED lighting system, we report on the controlled colloidal synthesis method of Cd-free InP/ZnS and CuZnInS/ZnS core-shell QDs, so that they can cover the full emission range of visible light. In order to improve the CRI, particularly in the R9 component, which refer to the rendering of deep red colors, QDs of 2~4 emission color were controlled and sprayed on the panel.
9:00 PM - NT6.10.23
Chemically Tunable Colloidal Silicon Telluride through Zero Valent Metal Intercalation
Isabel Al-Dhahir 1,Mengjing Wang 1,Kristie Koski 1
1 Brown University Providence United States,
Show AbstractSilicon telluride is a 2D layered material that is a p-type semiconductor that displays a strong red color and photoluminescence peak (~641 nm) that renders it a viable source of interest as potential LED and photodetector material. We report the colloidal synthesis of silicon telluride; nanorod and branched nanoparticles of ~500 nm length are demonstrated. We show that the band structure of Si2Te3 can be chemically tuned from a semiconductor to a semimetal by intercalation of zero valent metals (Cu, Sn, Co) into the van der Waals gaps.
9:00 PM - NT6.10.24
Fabrication and Characterization of Transparent Nanocomposite Films of Red-emitting YVO4:Bi3+,Eu3+ Nanoparticles and Silicone-Modified Acrylic Resin by Electrophoretic Deposition
Yoshiki Iso 1,Tetsuhiko Isobe 1
1 Keio University Yokohama Japan,
Show AbstractYVO4:Bi3+,Eu3+ nanoparticles (NPs), in which Bi3+ and Eu3+ ions substitute for some of the Y3+ ions, emit red light under near-UV light excitation. We synthesized YVO4:Bi3+,Eu3+ NPs by a co-precipitation method via a citrate precursor. YVO4:Bi3+,Eu3+ NPs are a promising candidate for wavelength converters in near-UV white LEDs and spectral down-shifters in solar cells, because YVO4:Bi3+,Eu3+ NPs are more photostable than luminescent materials of organic dyes and metal complexes, and they are highly transparent in the visible region due to no light absorption and low light scattering intensity. In the present study, we fabricated transparent nanocomposite films of citrate-capped YVO4:Bi3+,Eu3+ NPs and silicone-modified acrylic resin NPs. We chose electrophoretic deposition (EPD) for film fabrication, because EPD has some advantages, e.g., coatings with uniform thickness, and easy control of the thickness by changing deposition voltage and time.
A basic aqueous emulsion of silicone-modified acrylic resin NPs was added to the YVO4:Bi3+,Eu3+ NPs colloidal solution under vigorous stirring, followed by ultrasonication. The pH value was 9.4. The negatively-charged NPs of YVO4:Bi3+,Eu3+ and resin were well-dispersed in a basic aqueous suspension through electrostatic repulsion. The volume ratio of YVO4:Bi3+,Eu3+ : resin was estimated to be 40:60. An ITO-coated glass substrate and a stainless steel plate were used as the anode and cathode, respectively. The distance between both electrodes was kept at 10 mm using an insulating spacer. A nanocomposite film was deposited on the anode by application of a constant voltage of 3.0 V for 1–180 min. After deposition, the as-prepared film samples were dried at 120 °C for 15 min.
Film thickness increased with increasing deposition time. Uniform deposition on a substrate was confirmed by scanning electron microscopy. Good dispersion of the YVO4:Bi3+,Eu3+ NPs around the resin NPs in a fabricated film was confirmed by transmission electron microscopy. The fabricated nanocomposite films were transparent to the naked eye under white light because the constituent NPs show no absorption and low light scattering in the visible region. An emission peak of Eu3+ at 619.5 nm was observed in the photoluminescence (PL) spectra of the nanocomposite films under 365.0 nm near-UV light excitation. This peak is caused by the interband transition of YVO4:Bi3+,Eu3+, followed by energy transfer to Eu3+ and the f–f transition of Eu3+. The PL intensity increased with increasing film thickness.
Since various conducting substrates can be used for EPD, we demonstrated good flexibility of a nanocomposite film coated onto an ITO-coated polyethylene terephthalate (PET) flexible sheet. Such a flexible wavelength-conversion film could be applied in flexible optical devices, e.g., it could be used as a spectral down-shifter in flexible thin film solar cells.
9:00 PM - NT6.10.25
Study on Thermal Insulation and Mechanical Properties of Polyurethane Composites with Hollow Particles
Lei Wang 1,Younghwan Kwon 1
1 Chemical Engineering Daegu Univ Gyeongsan Korea (the Republic of),
Show AbstractThermal insulating polymeric composites have been paid much attention on building materials, aerospace and aviation industry, and oil and gas industry. The heat transfer process in polymeric composites filled with porous material is very complicated, and includes gas conduction, solid conduction and radiation. Convection can be neglected when the pores in composites are smaller than 4 mm in diameter. At low application temperature which is general condition for polymeric composites, the radiation can also be considered to be negligible.
This paper presents a comparative study on thermal conductivity of PU composites containing open-cell nano-porous silica aerogel and closed-cell hollow silica microsphere, respectively. The thermal conductivity of PU composites is measured at 30 oC with transient hot bridge method. The insertion of polymer in pores of silica aerogel creates mixed interfaces, increasing the thermal conductivity of resulting composites. The measured thermal conductivity of PU composites filled with hollow silica microspheres is estimated using theoretical models, and is in good agreement with Felske model. It appears that the thermal conductivity of composites decreases with increasing the volume fraction (Φ) when hollow silica microsphere (η = 0.916) is used.
9:00 PM - NT6.10.26
Rare Pt Nanostructures for Efficient Electrocatalysis
Moumita Rana 1,Ujjal Gautam 1
1 Indian Institute of Science Education and Research-Mohali Chandigarh India,
Show AbstractAmong the noble metals, Platinum is probably the most important one to act as heterogeneous catalyst for energy harvesting. However obtaining the most efficient nanocrystals having appropriate shapes and sizes is sometimes challenging. We have synthesized two of such rare Pt morphology: tetrahedral nanocrystals with bare catalytic surfaces (which were reported twice earlier, albeit with low yields and surface coating); and for the first time, free-standing Pt nanosheets. Electron transfer reactions on Pt <111> is learnt to be more efficient and lasting in comparison to the other surfaces. However obtaining tetrahedral nanocrystals (NTd) of pure Pt containing all Pt <111> surfaces, particularly sub-10 nm sized has widely been considered a synthetic challenge due to their thermodynamic instability.[1] Using a facile surfactant-free strategy, we obtained carbon supported Pt NTds with tunable sizes of 5.2-9.7 nm and 75% yields.[2] Therein, an in-situ generation of a secondary amine is crucial for stabilization of Pt-NTds, which can later be washed away to expose the Pt <111> facets. The bare nanocrystals exhibit one of the best electrocatalytic activity as well as stability towards oxygen reduction reaction ever reported for pure Pt, in addition to facile methanol and formic acid oxidation reactions. For example, ∼90% of their activity was retained after 5000 potential cycles, while the ORR onset potential was 1.01 V vs. reversible hydrogen electrode. If the nanocrystals can be assembled into a larger structure such as nanowire or nanosheet (NS) without agglomeration, one may avoid using a catalyst support for electrochemical reactions. The synthesis of Pt NS is however challenging due to their isotropic growth and has not been reported. We employed a mechanochemical synthetic strategy to obtain robust, free-standing Pt NS.[3] The 26 nm thick NS were obtained by employing galvanic displacement of Te in a nanorod by Pt and fluid induced shearing force of ~2 N and differential shear-stress of 0.5 kPa across the nanorod diameter. This synthesis is also one of the few examples of a purposeful transformation of 1D nanostructure to 2D one. We found that corrugation leads to substantially enhanced surface area of the nanosheets and much improved electrocatalytic properties when compared with conventional carbon-supported Pt catalysts.
References:
1. M. Shao, A. Peles, K. Shoemaker, Nano Lett. 2011, 11, 3714; H. M. Lu, X. K. Meng, J. Phys. Chem. B 2009, 114, 1534
2. M. Rana, M. Chhetri, B. Loukya, P. K. Patil, R. Datta, and U. K. Gautam, ACS Appl. Mater. Interfaces 2015, 7, 4998
3. M. Chhetri, M. Rana (joint first authors), B. Loukya, P. K. Patil, R. Datta, and U. K. Gautam, Adv. Mater. 2015, 27, 4430
9:00 PM - NT6.10.27
Preparation of Few-Layer-Graphene via Surface-Only-Oxidation and Shear Exfoliation for Composites Applications
Tae-Ho Yoon 1,Jae-Young Lee 1,Hyoung-Ju Yoon 1
1 Gwangju Inst of Samp;T Gwangju Korea (the Republic of),
Show AbstractFew-layer-graphene (FLG) was prepared via surface-only-oxidation of natural graphite, followed by shear exfoliation with a commercial blender for composites applications. First, natural graphite was oxidized via a modified Hummers method at 20 °C with time variation to afford surface-only-oxidation. Then, aqueous solution of surface-oxidized graphite (1g/L) was washed twice with DIW to remove salts from oxidation reaction. Third, the surface-oxidized graphite was subjected to grafting of aryl diazonium salts via 2-step process to enhance the water dispersion of FLG after exfoliation. Next, the aqueous solution of surface-only-oxidized graphite was subjected to shear exfoliation with a commercial blender, followed by removal of unexfoliated graphite via centrifugation. Finally, the solution was filtered and characterized by TGA, XPS, SEM, and TEM, and sheet resistance was also measured. For comparison, sonication exfoliation was also attempted with the same solution.
9:00 PM - NT6.10.28
A New View of the Low-Temperature Sintering Phenomenon of Particle of Scores of Nanometers Based on the Molecular Dynamics Study
Norie Matsubara 1,Shinji Munetoh 1,Osamu Furukimi 1
1 Kyushu University Fukuoka Japan,
Show AbstractA metal particle of scores of nanometers is being used as a jointing material between a silicon carbide semiconductor element and a circuit electrode. The low-temperature sintering phenomenon of such particle has been explained by melting-point depression of nanoparticle. It has been reported that this phenomenon occurred when the particle size was less than 10 nm. However, the diameter of metal particle used as a jointing material is usually larger than 20 nm. The difference between the former and the latter is too large and, therefore, it seems to be insufficient to understand the low-temperature sintering phenomenon only in terms of the reduction of the melting-point of nanoparticle.
In this study, we have investigated the heating behavior of metal particle with a diameter ranging from 1 to 24 nm on an atomic scale by numerical analysis using the molecular dynamics (MD) simulation. On solving the equation of motion, the Langevin equation was adopted. The Finnis-Sinclair potential, which can well reproduce the mechanical properties of a body-centered cubic structure, was used as the interatomic force.
We obtained the relationship between the melting point (Tm) of nanoparticle and its diameter by MD simulations. We have also investigated a diffusion coefficient of each atom-forming particle at a temperature above/below Tm of particle. As a result, even in case of heating at a temperature below Tm of particle, the average diffusion coefficient at the central region of the particle was 10-9 to 10-8 cm2/sec, while that at a very thin layer near the surface of the particle was 10-6 cm2/sec. The diffusion coefficient of the outer layer became two to three orders in magnitude larger than that of the inner layer. It is conceivable that these atoms having high diffusion coefficient affect the low-temperature sintering phenomenon of particle of scores of nanometers.
9:00 PM - NT6.10.29
Bimetallic Au/Pd Nanostructures for Ultrasensitive Plasmonic Hydrogen Sensing
Hang Kuen Yip 2,Ruibin Jiang 1,Jianfang Wang 2
2 Department of Physics The Chinese University of Hong Kong Hong Kong Hong Kong,1 School of Material Science and Engineering Shanxi Normal University Xian China
Show AbstractThe Development of alternative clean energy carriers to replace fossil fuels is important due to the limited and decreasing fossil fuel reserves and negative impacts to the environment. Hydrogen is one of the most promising clean and sustainable energy carriers for replacing the current carbon-based energy source and widely used. However, the use of hydrogen is dangerous due to its ease of explosion. According to previous studies, hydrogen can easily explode in air at the volume concentration from 4% to 75% with low ignition energy of 0.02 J. Therefore it is vital to develop safe hydrogen sensors with low detection limits, fast response time and high sensitivities. Palladium is the major material for hydrogen sensing due to its reversible hydride formation properties with hydrogen. Electrical hydrogen sensors that are realized by detecting the change in the electrical conductivity of palladium have been mainly focused before, but the risk of explosion caused by electric sparks is a major disadvantage. On the other hand, optical hydrogen sensors based on the localized surface plasmon resonance (LSPR) of noble metal nanostructures can effectively avoid this problem. Optical sensors utilize the property that the LSPR wavelength is sensitive to the change in the dielectric environment in the vicinity of the nanostructures. Several types of LSPR sensors based on Au/Pd coupled dimers and core/shell nanostructures have been demonstrated to exhibit maximal plasmon shifts up to ~25 nm in gas environments at 4% hydrogen concentration.
Our group has developed plasmonic hydrogen sensors utilizing bimetallic (Au nanorod)/(Pd shell) nanostructures with high sensing performance. Au nanorods are used as the cores due to their large refractive index sensitivities. Maximal plasmon shifts have been improved to ~60 nm at 4% hydrogen concentration. On the basis of this work, we have recently further improved the sensitivity by replacing Au nanorods wih Au nanobipyrimids (Au NBPs), because Au NBPs possess even higher refractive index sensitivities. With Au NBPs, the maximal plasmon shifts are further improved to ~120 nm at 4% hydrogen concentration. Moreover, we have also investigated systematically different factors on the hydrogen sensing performance, including the shell thickness of (Au NBP)/(Pd shell) nanostructures, the size and position of the Pd component on Au NBPs that are either tip- or side-coated with Pd.
Our studies on the plasmonic hydrogen sensors with Au nanorods and Au NBPs, have not only achieved an unprecedented hydrogen sensitivity, but also provided a deep understanding of the refractive index sensing characteristics of Au nanorods and NBPs that are either fully coated or partially adsorbed with molecular species. Such understanding will be very useful for designing ultrasensitive sensors based on Au nanorods and NBPs for detecting other molecular or biological species.
9:00 PM - NT6.10.30
Circular Gold Nanodisks with Synthetically Tunable Sizes and Plasmon Wavelengths
Ximin Cui 1,Feng Qin 1,Jianfang Wang 1
1 Department of Physics The Chinese University of Hong Kong Hong Kong China,
Show AbstractGold nanocrystals have attracted much attention due to their wide potential applications in many fields. Three-dimensional plasmonic nanospheres have been utilized in plasmon-coupled systems to realize plasmonic Fano resonances, new plasmon modes and dramatic electric field enhancements, due to their perfect geometrical symmetry and exact analytic solutions to Maxwell's equations. However, the plasmon resonance wavelength of nanospheres can only be varied in a narrow range from 520 nm to 806 nm. By comparison, one-dimensional plasmonic nanocrystals, for example, nanorods, nanobipyramids, have tunable longitudinal plasmon wavelengths over a wide range from ~600 nm to ~1500 nm. As a result, they have been found wide applications ranging from biotechnology, spectroscopy and optics. However, their anisotropic geometries make the fabrication of uniform plasmon-coupled systems and the understanding of coupled plasmon modes difficult. Nanodisks, as a novel type of two-dimensional plasmonic nanocrystals, combine the advantages of both one-dimensional and three-dimensional nanocrystals. They exhibit a single plasmon resonance mode; they have two large atomically flat surfaces; and their plasmon wavelengths can be varied from the visible to near-infrared range.
We have developed a method for producing monodisperse circular Au nanodisks with broadly tunable plasmon resonance wavelengths from 550 nm to 1000 nm. Our method relies on a stepwise combination of the seed-mediated growth of nanoplates, depletion force-induced self-separation, anisotropic overgrowth and final oxidation. Due to the high stability of low-index {111} facets, the oxidation only occurs at the lateral side of the nanoplates instead of the top and bottom flat {111} surfaces. Thus the thickness remains unchanged during the oxidation process from the nanoplates to circular nanodisks. In our experiments, the thickness of the circular nanodisks can be tailored from ~8 nm to ~50 nm by simply controlling the thickness of the nanoplates at the overgrowth stage. Furthermore, we have demonstrated that the Au nanoplates are plasmonically transparent when their thickness is less than 15 nm. When such thin Au naniplates are deposited on Si substrates, the scattering spectra of Au nanospheres positioned on the nanoplates are identical to those of the corresponding Au nanospheres deposited directly on the Si substrates. Taken together, our circular Au nanodisks with synthetically controllable lateral size, thickness and therefore plasmon resonance wavelength provide a new type of two-dimensional plasmonic nanocrystals. They will greatly facilitate the fabrication of plasmonic 'molecules' with highly desired plasmonic properties out of plasmonic 'atoms' as well as find many applications in surface-enhanced spectroscopies, control of light reflection and transmission, and solar energy harvesting.
9:00 PM - NT6.10.31
Polyaniline-Coated Gold Nanorods and Nanobipyramids with Tunable Plasmon for Plasmonic Switching
Wenzheng Lu 1,Nina Jiang 1,Jianfang Wang 1
1 The Chinese University of Hong Kong HongKong Hong Kong,
Show AbstractGold nanocrystals have attracted growing attention due to their extraordinary optical properties. They possess absorption and scattering cross-sections in the visible and near-infrared spectral ranges due to the excitation of their localized surface plasmon, whose frequency depends mainly on the size and shape of the nanocrystals, the dielectric functions of the surrounding medium, and the gap distance between the closely-positioned particles. Actively controlling the localized surface plasmon resonance without changing the size, shape or composition of metal nanocrystals is essential in many plasmon-based applications, such as optical nanoantennas, chemical and biological sensing, transparent smart windows and displays, and other plasmonic devices. Investigations have therefore been made on the design and fabrication of nanostructures to achieve active and reversible switching of localized surface plasmon resonance. However, so far, most of the developed nanostructures are narrow in the switching spectral range, unstable in the switching process and of high fabrication cost. Up to date, it has still remained challenging to develop nanostructures with widely tunable plasmon energies for active plasmonic switching.
We have developed a method for coating polyaniline (PANI) onto gold nanocrystals for active plasmonic switching. The PANI shell is a conductive polymer, whose conductivity can be varied enormously by controlling its proton-doping state or oxidation state. The switching between different states gives rise to prominent changes in the dielectric function of PANI, resulting in reversible plasmon shifts on the embedded gold nanocrystal. We have already investigated the switching performance of PANI-coated gold nanorods, gold nanobipyramids and gold nanosphere dimers. Reversible plasmon shifts up to 100 nm and with a modulation depth of 10 dB in the scattering intensity of Au nanorods have been achieved by changing the pH value in solutions. In addition, we have for the first time succeeded in switching the plasmon coupling in Au nanophere homodimers with gap distances on the sub-nanometer scale, giving rise to a giant scattering peak shift of 231 nm. Apart from switching by pH, we have also investigated electrochemical switching, which enables much faster switching with the switching process finished in less than 10 ms, smaller than the response time of our electrochemical system. Moreover, the electrochemical switching performance remains almost unchanged even after 200 switching cycles. The large plasmonic shift, ultrafast switching and extraordinary stability make our PANI-coated gold nanocrystals be able to serve as an excellent material for active plasmonic switching, and as a promising building block for developing smart windows and displays.
9:00 PM - NT6.10.32
Synthesis and Characterization of Colloidal Cu Nanocubes
Mun Lahpai 1,Jingyue Liu 1
1 Department of Physics Arizona State University Tempe United States,
Show AbstractThe properties of a metal nanocrystal depend on its size, shape and structure. For example, for structure sensitive catalytic reactions both the activity and selectivity of a supported metal catalyst can vary drastically with the shape or size of the metal nanoparticles. Therefore, it is critical to develop robust synthesis protocols to fabricate metal nanoparticles with desired shapes and sizes. We have developed a one-step hydrothermal method to synthesize colloidal copper nanocubes and nanowires. By controlling the amount of capping and reducing agents, the synthesis temperature, and the synthesis time we have been able to synthesize colloidal copper nanostructures with shapes varying from nanowires to nanocubes. A key challenge is to find the appropriate synthesis conditions to produce specific desirable nanostructure with the uniform shape and size. Aberration-corrected scanning transmission electron microscopy techniques are used to characterize the atomic structures of the synthesized copper nanocubes and nanowires. The nucleation and growth processes of the copper nanostructures are investigated by examining samples taken at various synthesis stages. The electrochemical and catalytic properties of the synthesized copper nanostructures will be discussed as well.
Acknowledgement
This work was supported by the start-up fund of the College of Liberal Arts and Sciences of Arizona State University. The authors acknowledge the use of facilities in the John M. Cowley Center for High Resolution Electron Microscopy at Arizona State University.
References
[1] M. Mohl, P. Pusztai, A. Kukovecz, Z. Konya, J. Kukkola, K. Kordas, R. Vajtai and P. M. Ajayan, Langmuir, 2010, 26, 16496–16502.
9:00 PM - NT6.10.34
Photonic Sintering of Solution Processed Bi2Te3 Thermoelectrics
Stanley Chou 1,Bryan Kaehr 1,Brian Swartzentruber 1,Adam Cook 1,Matthew Janish 2,Thomas Beechem 1,C. Barry Carter 1,C. Jeffrey Brinker 1,David Ingersoll 1
1 Sandia National Labs Albuquerque United States,2 University of Connecticut Storrs United States2 University of Connecticut Storrs United States,1 Sandia National Labs Albuquerque United States
Show AbstractThe renewed interest in thermoelectric power generation has largely focused on solid-state engineering of increasingly exotic materials. However, developing scalable syntheses while simplifying material processing has the potential to broaden the impact of wide-spread dissemination for waste/heat conversion. Herein, we describe printable Bi2Te3 nanoplatelet and the structure-property evolution of its thin films upon sintering with flash lamp. For this, the physical attributes of Bi2Te3, including robust optical absorbance, low thermal diffusivity and low melting point lends itself particularly well for photonic sintering. Upon flash exposure, we observe evolution from a thin film of discrete nanoplatelet subcomponents to a mesoscale mesh-like network with distinct crystalline regimes. The resultant film, with nanostructures consistent with pronounced melt-and-recrystallization within plane, also exhibit electrical connectivity and Seebeck response comparable to undoped Bi2Te3 derived from conventional means. Penultimately, in contrast to previous thermoelectrics assembled from Bi2Te3 nanoplatelets and particles, the photonic sintering method obviates the need for bulk-reformation from nanoplatelets via high-pressure arc/plasma-sintering to yield thermoelectric response. Ultimately, the photonic sintering method may provide a scalable solution method (“ink”) for conformal thin thermoelectric coatings on a variety of substrates with arbitrary geometry.
9:00 PM - NT6.10.35
Ligand Engineering of BiI3 Nanostructures for Hybrid Solar Cells Active Layers
Ivana Aguiar 1,Maia Mombru 1,Maria Perez Barthaburu 2,Heinkel Bentos Pereira 2,Laura Fornaro 2
1 Grupo de Desarrollo de Materiales y Estudios Ambientales (GDMEA), Catedra de Radioquimica, Facultad de Quimica Universidad de la Republica Montevideo Uruguay,2 Grupo de Desarrollo de Materiales y Estudios Ambientales (GDMEA), Departamento de Desarrollo Tecnologico, Centro Universitario de la Regional Este Universidad de la Republica Rocha Uruguay
Show AbstractIn recent years the use of semiconductor nanoparticles in nanostructured and hybrid organic-inorganic solar cell has increased. The incorporation of inorganic nanostructures as electron acceptors provides advantages to the solar cells performance, for example, by altering the cells absorption profile. For this reason, we synthesized BiI3 nanostructures by the hydrothermal method in order to test them as possible electron acceptors in hybrid organic-inorganic solar cells. We employed a home-made Teflon lined stainless steel autoclave, at a temperature of 180οC during 12 h, using BiCl3 and NaI as source materials, in a soft acid medium. We obtained nanostructures performing two sequential precipitations assisted by water. With the aim of achieving a homogeneous distribution of nanostructures within the electron donor polymer, they were functionalized with pyridine or aniline. For this purpose we kept the products under vigorous stirring in the corresponding solvent for 1-3 h at 50-80οC. We characterized the synthesized compounds by XRD, TEM, and UV-Vis and FTIR spectrometry. In the second precipitation we obtained nanostructures of about 5 nm in size, oriented along the [0 0 l] direction, in addition to a better size dispersion if compared to the nanostructures obtained in the first precipitation. Moreover, we achieved stable suspensions in chloroform for both ligands, which allows these nanostructures to be used with P3HT polymer in hybrid solar cells. Future efforts will be focused on constructing homogeneous polymer-nanostructure active layers and on determining how aniline and pyridine affect the charge carrier transport.
9:00 PM - NT6.10.36
N-Doped Mesoporous Inverse Opal Structures for Visible-Light Photocatalysts
Su-Jin Ha 1,Jun Hyuk Moon 1
1 Sogang Univ Seoul Korea (the Republic of),
Show AbstractWe introduce a new type of N-doped mesoporous inverse opal (N-mIO) TiO2 structure as a high-performance visible-light photocatalyst. The mIO TiO2 structure with a 60 nm pore diameter, which possesses a much higher specific area compared with conventional macroporous IO structures, is prepared via a templating approach. We characterize that the N atom is incorporated in an oxygen-substitution configuration, which effectively narrowed the bandgap of TiO2 from 3.2 eV to 2.4 eV, which corresponds to light absorption at wavelengths as long as 520 nm. In the photocatalytic decomposition of MB, the highly N-doped mIO TiO2 exhibits a decomposition rate under visible light exposure that is 4.9 times greater than that of bare IO TiO2. Moreover, compared with the conventional macroporous IO structure, the N-doped mIO exhibits 1.7 times greater activity as a result of its high specific area. We believe this mIO structure can provide a new platform for various electrode applications.
9:00 PM - NT6.10.37
Silica-Silver Nanoparticles as a New Tool for the Molecular Characterization of Tumor Cells by Raman Spectroscopy
Jorge Jimenez-Canale 1,Amed Gallegos-Tabanico 1,Jose Andre-i Sarabia-Sainz 1,Monica Acosta-Elias 1,Erika Silva-Campa 1,Aracely Angulo-Molina 1,Alexel Burgara-Estrella 1,Diego Soto-Puebla 1,Susana Alvarez-Garcia 1,Martin Pedroza-Montero 1
1 Universidad de Sonora Hermosillo Mexico,
Show AbstractCancer may be defined as the mix of diseases that are caused by a failure in the genetic sequence of cells, which usually leads to neoformations, or abnormal cellular growth, also known as tumors. In the past few decades, cancer research has seen an exponential increase in understanding the biological, biochemical and molecular mechanisms that rules the cancer biology. These advances have produced new techniques for diagnostic and treatment, which help survival of patients. Nanotechnology at the same time has taken a really important on today world's scientific role, especially in biomedical applications. The manipulation, design and control of new materials with specific action mechanisms it is very promising for the diagnosis and treatment of diseases such as cancer. For other hand, Raman spectroscopy is a branch of vibration spectroscopy which is capable of probing the chemical composition of materials. Recent advances in Raman microscopy and nanotechnology have added significantly novel tool to characterize on a molecular level, biological samples. This gives great information regarding the biochemical status of a given sample, since it can be inferred from the molecular information obtained, and of course, since it is a faster way to obtain this kind of information than traditional laboratory methods. Silver and gold nanoparticles have been reported that may potentiate the intensity of the Raman vibrational spectrum and induce a SERS (Surface Enhanced Raman Scaterring) effect on biological samples. On this study we synthetized Silica-Silver nanoparticles (Si-AgNP) to induce a SERS effect on HeLa cells to provide a novel tool for cancer diagnosis. Si-AgNP were characterized using physico-chemical techniques such as scanning electron microscope, fluorescent microscopy, dynamic light scattering, Fourier transform infrared (FTIR), etc. SERS effect of Si-AgNP were analyzed in sanguine serum and HeLa cells. Nanoparticles obtained had around diameter of 150 nm, with a Zeta potential of -37.2 mV. Vibrational analysis by FTIR and Raman spectroscopy showed de principal peak of silica nanoparticles. Efficient SERS effect was observed in biological samples used. Further studies regarding tumorous cells with nanoparticles are necessary, in order to increase the information pool for future studies regarding nanomedicine or nanobiology.
Symposium Organizers
Ying-Bing Jiang, Angstrom Thin Film Technology LLC
Hongyou Fan, Sandia National Laboratories
Han Htoon, Center for Integrated Nanotechnologies
Songtao Wu, Toyota Research Institute of North America
Symposium Support
Dongheng Technology (Hong Kong) Co. Ltd.
Los Alamos National Laboratory
NT6.11: Nanoparticle Synthesis and Applications IV
Session Chairs
Friday AM, April 01, 2016
PCC West, 100 Level, Room 104 AB
9:00 AM - NT6.11.01
Surface Plasmon Strain Sensors
Maryam Zahedian 1,William Schaich 2,Bogdan Dragnea 1
1 Chemistry Indiana University Bloomington United States,2 Physics Indiana University Bloomington United States
Show AbstractA number of previous studies have demonstrated that the optical response of a metallic nanoparticle (NP) depends on size, shape and surroundings. Such sensitivity makes these NPs suitable for sensing purposes. The strong configuration dependence of collective surface plasmon resonances in an array of metal nanoparticles provides an opportunity to develop a nanoscopic sensor of mechanical deformations. We propose a strain sensor based on an icosahedral array of nanoparticles encapsulated by a virus capsid. When the system undergoes deformation, the optical cross-section as well as the induced electric field profile will change. By numerical simulations we examine how these changes depend on the symmetry and extent of the deformation. Our simulations serve as a proof of principle for the use of optical spectra to detect rearrangements of nanoparticle in a multicore shell (MCS). Specifically, the development of an extra, red shifted peak in the scattering cross-section as the MCS deforms from an icosahedral into an oblate, spheroidal structure, is a general feature.
9:30 AM - NT6.11.03
Control of Dynamical Self-Assembly of Strongly Brownian Nanoparticles through Convective Forces Induced by Ultrafast Laser
Serim Ilday 1,Oezguen Yavuz 1,Ghaith Makey 1,Gursoy Akguc 1,Onur Tokel 1,Ihor Pavlov 1,Koray Yavuz 1,Fatih Ilday 1,Oguz Gulseren 1
1 Bilkent University Ankara Turkey,
Show AbstractDynamical self-assembly of colloidal particles rely mostly on chemical, magnetic and/or optical forces acting on or interactions with functionalized particles. This require extensive control over the dynamical details of the system, which renders any implementation strongly material specific and limits potential of creating and controlling complex patterns with preplanned functionalities. Here, we report dynamical self-assembly of polystyrene nanoparticles using only convective forces and strong Brownian motion. By steering the stochastic processes through these physical forces we are able to gain extensive control over the emergent pattern: A pattern can form-deform-reform by turning the laser on and off; a pattern can be transformed to another by changing the laser power; a pattern can be transported spatially by moving the laser beam within a few seconds. We note that the laser (with beam diameter of few 10 µm) is not interacting with the particles (250 nm or 500 nm in diameter) per se (there is no optical trapping or tweezing effect involved), but it is used to create steep thermal gradients through multi-photon absorption, and thereby to guide the colloids through convective forces. This enables us to dynamically initiate and control large patterns comprised of hundreds of colloids. Unlike common practice, we do not suppress Brownian motion for self-assembly, on the contrary, we incorporate its effect into the dynamics; i.e., it is the strong Brownian motion that makes it possible to rapidly disassemble particles before they are reassembled within a few seconds at a different location or with a different pattern at the same location. This also serves as a control tool: The convective forces can be thought as a positive feedback mechanism that helps to form and reinforce the pattern, while stochastic forces act as a competing negative feedback mechanism to limit the growth of the pattern, as well as to increase the possibilities of bifurcation into different patterns, analogous to the competition observed in reaction-diffusion systems.
In conclusion, we report a new dynamic self-assembly mechanism, where judicious use of convective and stochastic forces enables effective patterning of objects that are two orders of magnitude smaller than the steering laser beam. Further, by not relying on any specific chemical, optical or magnetic interaction, this new method is, in principle, completely independent of the material type being assembled.
9:45 AM - NT6.11.04
A Reproducible Au-Ag Core-Shell Nanorods Based 3D SERS Substrate
Shuyu Xu 1,D. Bruce Chase 1,John Rabolt 1
1 University of Delaware Newark United States,
Show AbstractOur research has focused on the fabrication of a 3D surface enhanced Raman scattering (SERS) sensor composed of an electrospun poly(caprolactone) (PCL) fiberous mat with fiber diameters of approximately 2 μm. With electrostatistic interactions as driving force, polyelectrolytes poly(sodium 4-styrene sulfonate) (PSS) and poly(diallyldimethylammonium chloride) (PDADMAC) were layer-by-layer assembled onto the fiber surface followed by the immobilization of a uniform layer of silver (Ag) coated gold (Au) nanorods. The 3D SERS sensors obtained were very reproducible (1) a problem that has plagued SERS substrates in the past.
The conditions used to fabricate this substrate (e.g., the diameter of the fibers, the thickness of the Ag layer, etc.) were studied in detail. The performance as a SERS substrate was also investigated by using Rhodamine 6G (Rh6G) as a probe molecule and the 3D PCL architecture was compared to a 2D PCL film. In addition, the reproducibility of this SERS substrate and its application to detect Cu2+ and Hg2+, using chemically functionalized “capture” molecules, was evaluated as well (2).
(1) Immobilization of Gold Nanorods onto Electrospun Polycaprolactone Fibers Via Polyelectrolyte Decoration – A 3D SERS Substrate, Wenqiong Tang, D. Bruce Chase and J. F. Rabolt, ACS Analytical Chemistry 2013, 85, 10702- 10709
(2) Selective and Quantitative Detection of Trace Amounts of Hg2+ and Cu2+ by Surface Enhanced Raman Scattering (SERS), Wenqiong Tang, D. Bruce Chase, D. L. Sparks and J. F. Rabolt, Applied Spectroscopy 2015, 6, 843-849
10:00 AM - NT6.11.05
Size, Shape and Composition Control of CsPbX3 (X = Cl, Br, I) Nanocrystals: From Cubic NCs to Ultrathin Nanoplatelets and Their Anion Exchange Reactions
Quinten Akkerman 1,Mirko Prato 1,Annamaria Petrozza 3,Liberato Manna 1,Filippo De Angelis 2,Francisco Palazon 1
1 Nanochemistry Istituto Italiano di Tecnologia Genova Italy,3 Center for Nano Science and Technology at Polimi Istituto Italiano di Tecnologia Milano Italy2 CNR-ISTM Computational Laboratory for Hybrid/Organic Photovoltaics Perugia Italy
Show AbstractIn the past decade, lead halide based perovskites have quickly emerged as powerful photovoltaic light harvesters, leading to solar cells with efficiencies up to 20%.1 However, the first lead halide based perovskite nanocrystals (NCs) were reported only last year, and exhibited very narrow size distributions as well as narrow emission linewidths and extremely high photoluminescence quantum yield up to 90%, thus making them very interesting for novel optoelectronic materials.2 As known for semiconductor NCs, the size, shape and composition of the NCs strongly influence the optoelectronic properties. Focusing on inorganic CsPbX3 (X=Cl,Br,I) perovskite NCs, we demonstrate that, via controlled anion exchange reactions, we can finely tune the chemical composition and optical properties of pre-synthesized colloidal CsPbBr3 NCs, both in solution as well as on NCs deposited on substrates.3,4 Starting from a single batch of CsPbBr3 NCs emitting at 515 nm, our approach gives access to perovskite NCs with an emission wavelength ranging from 410 nm to 680 nm, with both structural and optical quality comparable to those of directly synthesized NCs. Size and shape control over CsPbX3 NCs was investigated with the synthesis of highly monodisperse colloidal CsPbBr3 nanoplatelets (NPs).5 These NPs, with a well-defined thickness, controllable from only 3 (1.8 nm) to 5 monolayers (3.0 nm), as well with a high monodispersity in the lateral dimensions (7.9 ± 1.2 nm by 40.9 ± 6.8 nm), exhibited strong quantum confinement effects, as their emission shifts from 525 nm for bulk to 437 nm. Furthermore, the optical properties of the NPs were extensively investigated and compared experimentally, as well as theoretically, with cubic CsPbBr3 NCs and bulk CsPbBr3.
References
[1]Jeon, N. J. et al., Nat Mater, 13, 897-903 (2014)
[2]Protesescu, L. et al., Nano Letters, 15, 3692-3696 (2015)
[3]Akkerman, Q. A. et al., J. Am. Chem. Soc., 137, 10276-10281 (2015)
[4]Palazon, F. Akkerman, Q. A. et al., ACS nano, 10, 1224-1230 (2015)
[5]Akkerman, Q. A. et al., J. Am. Chem. Soc. 138 (3), pp 1010–1016, (2016)
10:15 AM - NT6.11.06
Two-Color Blinking Suppression in CdSe/CdS Tetrapods as a Function of Geometry
Nimai Mishra 1,Feng Wang 1,Han Htoon 1,Jennifer Hollingsworth 1
1 Materials Physics and Applications Division: Center for Integrated Nanotechnologies Los Alamos National Laboratory Los Alamos United States,
Show AbstractRecent studies of CdSe/CdS tetrapods synthesized via seeded-growth techniques have explored their unusual characteristics of ultra-large absorption cross-section, high biexciton lifetimes and strain-dependent emission, as well as their potential as efficient energy-conversion and charge-transport materials for solar cell applications. Here, we extend the investigation of single-tetrapod (single-emitter) level optical properties of CdSe/CdS tetrapods to reveal a strong blinking suppression and, in some structures, a unique two-color emission that can be blinking-free. The two colors – red and green – result from CdSe-core photoluminescence, which is present at all excitation levels, and state-filling at higher excitation powers, respectively. We show that shell-thickness and arm-length engineering in these asymmetric core/shell nanoparticles (spherical CdSe core surrounded by multiple arms of an elongated CdS shell) can be exploited to obtain these unusual behaviors. Specifically, we observe that the seeded-tetrapods are, in general, photostable with respect to long-term photobleaching (>30 min), but blinking behavior is strongly geometry-dependent, with thick-shell tetrapods clearly transitioning to non-blinking emission.
10:30 AM - NT6.11.07
Flexible Nanostructured Thermoelectric Devices Printed Using Colloidal Nanoparticles
Tony Varghese 1,Courtney Hollar 1,Yanliang Zhang 1
1 Boise State Univ Boise United States,
Show AbstractThermoelectric generators (TEGs) produce electrical power using thermal energy from various sources, including the waste heat. Thermoelectric materials have undergone tremendous improvement of the figure of merit ZT in recent two decades largely attributed to nanostructuring. Despite these progresses in materials performances, the high cost of manufacturing the nanostructures into functional materials and devices is still a significant barrier to bring these materials into commercial domain.
This work is based upon our previous successes in producing high ZT bismuth telluride nanoparticles using a wet chemical process. A record high ZT of 1.1 was obtained in the nanobulk pellet using the bismuth telluride nanoparticles.
Here, we demonstrate a new class of flexible thermoelectric materials by scalable bottom-up assembly of high-efficiency bismuth telluride nanocrystals inks. The colloidal nanoinks were synthesized using sulphur-doped bismuth telluride nanoplates sculpted by a scalable microwave-stimulated wet-chemical method. Films of several tens of microns were deposited onto a flexible kapton substrate using a screen printer followed by a cold compaction and sintering in vacuum furnaces. The unoptimized films achieve a room-temperature power factor of 0.25 mW/mK2, comparable with the best report value of flexible thermoelectric materials fabricated by other techniques.
The highly scalable and low cost manufacturing process opens up many opportunities to transform thermoelectric cooling and power harvesting applications.
10:45 AM - NT6.11.08
Multistate Blinking and Scaling of the Recombination Rates in Individual Silica Coated CdSe/CdS Nanocrystals
Anton Malko 1,Sid Sampat 1,Tianle Guo 1,Jennifer Hollingsworth 2,Han Htoon 2
1 Univ of Texas-Dallas Richardson United States,2 Center for Integrated Nanotechnologies Los Alamos National Lab Los Alamos United States
Show AbstractNon-radiative Auger recombination is the primary exciton loss mechanism in colloidal nanocrystals and an impediment for prospective optoelectronic applications. Recent development of new core/shell nanocrystals with suppressed Auger recombination rates has opened the possibility for studying multicarrier states using time-resolved photoluminescence (PL) spectroscopy. An important aspect is the scaling of radiative and non-radiative decay rates with the increasing number and type of excitons in individual nanocrystals. We conduct extensive single-dot PL spectroscopy of emissive states in PL blinking trajectories of giant silica coated CdSe/CdS nanocrystals. At low fluences, we observe the appearance of neutral and charged exciton (trion) states. Both negative and positive trions show strongly suppressed Auger recombination rates resulting in PL quantum yields close to 50%. At higher excitation powers, we observe consecutive emergence of lower efficiency states, indicative of higher order excitons. We employ a scaling model for Auger and radiative decay rates and attribute these states to doubly charged excitons, biexcitons and a triexciton. Simultaneous analysis of the second-order correlation statistics proves that biexciton Auger recombination channel can be represented in terms of the superposition of independent recombination channels of trions. Analysis of the PL emission of the triexciton state suggests nonstatistical scaling, likely due to the involvement of the transitions between different symmetries. Finally, measurements at high excitation fluence of nanocrystals with low trion quantum yields does not reveal any higher order excitonic states, corroborating the validity of the scaling model and confirming Auger-related mechanisms responsible for blinking behavior in such core/shell nanocrystals
11:30 AM - NT6.11.09
Transfer Printing Arrays of Gold Plasmonic Nanoparticles by Thermo-Sensitive pNIPAAm for Integration into Organic Photovoltaics
Sirous Khabbaz 1,Gozde Ince 1,Ali Tufani 1,Hasan Kurt 1,Hasan Emre Baysal 1,Cleva Ow-Yang 1
1 Sabanci University Istanbul Turkey,
Show AbstractThe integration of nanoparticles in electronics is a challenge, as in some processes, the synthesis of colloidal nanoparticles cannot be directly integrated into the device processing. To address this challenge, we have developed a new method for transfer printing an array of nanoparticles from a sacrificial substrate onto a target transfer substrate using a thermally sensitive polymer film, poly-N-isopropylacrylamide (pNIPAAm); we further demonstrated the applicability of this technique to transfer printing an array of gold nanoparticles produced by micelle nanoreactor processing into a bulk heterojunction PCDTBT:PC70BM photovoltaic cell (OPV) with power conversion efficiency (PCE) improved by 32.2%. Reverse diblock polystyrene-block-poly(2-vinylpyridine) (PS-b-P2VP) copolymer micelle reactors were used for the synthesis of gold nanoparticles, as they produce particles of a monodisperse size distribution and allow control over the interparticle spacing during spin coating deposition of a micelle monolayer. To transfer print the nanoparticle array revealed after oxygen plasma etching, a polydimethylsiloxane (PDMS) stamp was coated with a thin film of thermo-responsive pNIPAAm grown by initiated chemical vapor deposition. We took advantage of the structural changes of the pNIPAAm surface, which switches from a hydrophilic state at 5°C to a hydrophobic one at 50°C. This change in surface energy enabled the pNIPAAm coating to pick up the particle array from a single crystal silicon substrate at 5 °C and release them onto a transfer substrate at 50°C. In order to demonstrate the efficacy of transfer printing the particle array, we analyzed the 2-D array characteristics of particles, using spatial point pattern analysis of scanning electron microscope images of the sacrificial and target silicon wafer substrates. Quantitative analysis clearly demonstrated registry of the gold nanoparticle array, which on the target substrate (particle size of 16±3.3 nm and interparticle spacing of 28±2 nm) was consistent with the characteristics on sacrificial substrate (16±3 nm and 28±1, respectively). We present the physical mechanism enabling the pick-up and release behavior of the pNIPAAm film, in addition to an example application, in which the plasmonic particle array was transfer printed onto the organic active layer of an OPV during device fabrication. Analysis of the plasmonic enhanced device characteristics will be presented for the 32.2% improvement in PCE.
11:45 AM - NT6.11.10
Intraband Photoluminescence from HgSe/CdS Core/Shell Quantum Dots
Zhiyou Deng 1,Philippe Guyot-Sionnest 1
1 James Frank Institute Univ of Chicago Chicago United States,
Show AbstractHgSe/CdS core/shell CQD are synthesized, and the dynamic change of the optical properties under different treatment, including annealing and ligand exchange with ethanedithiol treatment are investigated. While HgSe quantum dots are naturally n-doped after synthesis, both as colloidal solutions and as films, they lose their n-doping after the CdS shell growth, as seen from the optical absorption in solution. However, n-doping is regained in films and the intraband luminescence of the films of HgSe/CdS is greater than that of the cores. The shell also vastly improves the stability of the quantum dots films at elevated temperatures. As a result, the HgSe/CdS films retain a narrow intraband emission after annealing at 200°C while they sustain a higher laser power leading to brighter emission at 5 microns.
12:15 PM - NT6.11.12
Cationic Gold Nanoparticles for Electrostatic Self-Assemblies
Jukka Hassinen 1,Ville Liljestrom 1,Mauri Kostiainen 1,Robin Ras 1
1 Aalto University Espoo Finland,
Show AbstractSurface functionalization of gold nanoparticles (AuNPs) plays a crucial role in determining their properties and applications. One of the most central features of water-soluble AuNPs is their charge, which governs their electrostatic interactions with other charged molecules or surfaces. Positively charged, cationic AuNPs are essential building blocks in the toolbox of materials science. Due to their capability of binding negatively charged molecules, high surface-to-volume ratio, low toxicity, and ability to internalize into mammalian cells, they can be utilized, for example, in transfection applications such as gene therapy and drug delivery. In addition, as many biological components, such as proteins and viruses, are negatively charged in neutral pH, their combination with cationic AuNPs allows formation of plasmonic electrostatic self-assemblies.
Despite major progress on AuNP research in general, the synthesis of cationic AuNPs larger than 5 nm has remained a major challenge, although these species would give a significantly larger plasmonic response compared to smaller cationic AuNPs. In this work, we present a synthesis method for cationic AuNPs with tunable sizes between 8–20 nm, prepared by a facile two-step phase transfer protocol starting from simple citrate-capped particles.1 This functionalization method is rapid and straightforward, produces highly stable cationic AuNPs with narrow particle size distribution, and can easily be scaled up. These cationic particles form ordered self-assembled structures with negatively charged biological components through electrostatic interactions.
1. Hassinen, J.; Liljeström, V.; Kostiainen, M. A. and Ras, R. H. A. Angew. Chem., Int. Ed., 2015, 54, 7990–7993.
12:30 PM - NT6.11.13
Plasma-Liquid Interface Reaction Controlled Structural and Morphological Evolution of Zinc Oxide Quantum Dots and Their Self Assembly
Subhash Singh 1
1 Allahabad Univ Allahabad India,
Show AbstractPhysical and chemical properties of nanostructured materials have significant dependence on their size, shape and morphology. Therefore, controllable processing of nanostructured materials has greatly demanded in order to explore desired properties for particular applications in the world of nanomaterials. Tuning concentration of chemicals in the reaction vessel, to drive chemical kinetics or to control rate of reaction for monitoring rate of synthesis of desired atoms/molecules as building blocks for nanostructured materials, is current strategy opted by chemist and nanotechnologist to control size, shape and morphology of nanomaterials.
Liquid phase pulsed laser ablation (LP-PLA) is more facile, one step, quicker and greener approach for the synthesis of nanostructured materials, where a pulsed laser is used to ablate solid target placed in liquid media to generate Laser Produced Plasmas (LPPs) having species from target material under liquid confinement. LPP interacts with the interfacial liquid molecules, evaporate and ionize them to generate Plasma Induced Plasmas (PIPs), having anionic species from liquid media. Rate of reaction between cationic species from LPPs and anionic species from PIPs at interface under highly non-equilibrium condition determine size, shape, and crystallinity of as-produced QDs, while polarity and dielectric constant of the bulk liquid, control particle-particle and particle-liquid interaction, which govern self-assembly of QDs to produce fabulous nano-architectures.
Present work utilizes a pulsed nanosecond laser for the ablation of metal zinc target under the confinement of liquid media having different functional group, reactivity, dielectric constant and dipole moment to drive size, shape, morphology and assembly of zinc oxide quantum dots into various marvellous nanoarchitectures. Size, shape, distribution, crystallinity and assembly of as synthesized QDs depend on the nature of liquid media used for ablation. Methanol, ethanol, 2-Propanol, acetic acid and acetone are used as ablation media for the generation of zinc oxide QDs and their self-assembly.
12:45 PM - NT6.11.14
PbSe/CdSe 'Giant' Infrared Quantum Dots: Stable Single-Dot Emitters
Christina Hanson 2,Nicolai Hartmann 1,William DeBenedetti 3,Xuedan Ma 4,Joanna Casson 1,Anton Malko 5,Han Htoon 1,Jennifer Hollingsworth 1
1 Los Alamos National Laboratory Los Alamos United States,2 University of New Mexico Albuquerque United States,1 Los Alamos National Laboratory Los Alamos United States3 Cornell University Ithaca United States4 Sandia National Laboratory Albuquerque United States5 University of Texas at Dallas Richardson United States
Show AbstractLead selenide quantum dots (PbSe QDs) have been explored for their potential applications in photodetectors, infrared (IR) emitting diodes and IR lasers, as their emission wavelengths are broadly tunable (~900-4000 nm). Although often reported as having high and robust quantum yields in emission in the ensemble solution-phase, investigations of PbSe QDs at the single-dot level have been limited by two factors: (1) rapid photobleaching and (2) long fluorescence lifetimes reducing emitter brightness under continuous excitation (slow emitter “recycling rate”). For other such IR QD materials, specialized detectors have had to be implemented to circumvent these challenges limiting single-photon detection, such as superconducting nanowire single-photon detectors. Here, we show that by overcoating PbSe QDs with a thick CdSe shell it is possible to severely limit photobleaching and render these important IR emitters accessible by conventional single-photon detection schemes. Like their thick-shell CdSe/CdS and InP/CdS counterparts,1-3 we refer to these nanostructures as ‘giant’ PbSe/CdSe QDs (g-QDs), where the thick shells were prepared using a two-step approach. First, a thin CdSe shell is grown using our previously developed partial cation exchange process that replaces a fraction of the original Pb in the PbSe QD with Cd. Subsequently, additional CdSe monolayers are added using the successive ionic layer adsorption and reaction (SILAR) growth method. We further show that choice of anionic precursor can be used to tune the morphology and crystal structure of the resulting PbSe/CdSe heterostructures, where the resulting single-dot optical performance reveals a clear correlation with the nanoscale-engineered structure.
1. Chen et al. J. Am. Chem. Soc. 2008, 130, 5026.
2. Ghosh et al. J. Am. Chem. Soc. 2012, 134, 9634.
3. Dennis et al. Nano Lett. 2012, 12, 5545.
NT6.12: Nanoparticle Synthesis, Assembly and Applications V
Session Chairs
Friday PM, April 01, 2016
PCC West, 100 Level, Room 104 AB
2:45 PM - NT6.12.02
A One-Step Method for Depositing Highly Conductive Lead Chalcogenide Quantum Dot Films
Qianglu Lin 1,Hyeong Jin Yun 1,Wenyong Liu 1,Jeffrey Pietryga 1,Victor Klimov 1
1 C-PCS Los Alamos National Laboratory Los Alamos United States,
Show AbstractLead chalcogenide nanocrystal quantum dots (QDs) are among the most promising materials for a wide range of solution-processed device applications, including field effect transistors (FET), solar cells, and radiation detectors. As synthesized, lead chalcogenide QDs have long carbon chain ligands, which hinder inter-particle electron transfer and thus need to be removed for better charge transport in conductive films. So far, device fabrication mostly relies on traditional layer-by-layer technique to remove bulky pristine ligands in order to increase electronic coupling between QDs. However, this inefficient method may hinder further use in applications where particularly thick films are needed, such as in radiation detectors, where macroscopic thicknesses are needed to stop impingent high energy particles.
Here we developed an efficient protocol to perform ligand exchange on lead chalcogenide QDs in solution with short ligands such as SCN-, SeCN-, Br-, I-, and HCOO-, which render efficient and excellent solubility in polar solvent while maintaining high quantum yield. Ligand exchange process can be done in seconds in both low (20mg/mL) of QDs and short ligand passivated QDs are stable for months without precipitation. With elemental analysis, we observe that ligand exchange preferentially happened to replace part of the lead site on the QD surface, resulting small blue shift in the first excitonic absorption peak, and that through choice of ligand, we can realize post-synthetic control over stoichiometry. Device fabrication based on ligand-exchanged QDs can be done by simple spin-coating, with control over thickness provided by solution concentration. This talk will discuss the new method, and the results of FET measurements of carrier mobilities achieved through use of varied ligand chemistries.
3:00 PM - NT6.12.03
Strategies for Performance Enhancement in Quantum Dot Solar Cells
Chia-Hao Chuang 1,Moungi Bawendi 2
1 Materials Science amp; Engineering MIT Cambridge United States,2 Chemistry MIT Cambridge United States
Show AbstractLow-bandgap quantum dots (QDs) with solution-processibility and a broad range of bandgap tunability are a class of promising materials for harvesting solar energy. Solar cells based on QDs exhibit superior stability among various types of low-temperature solution-processed solar cells. However, while the power conversion efficiency of QD solar cells has shown a continued improvement, it is still well below the theoretical limit. We previously identified the major limitations as the presence of sub-bandgap states and the trade-off between light absorption and carrier collection. These factors are closely related to the high surface area to volume ratio of QDs and consequently their surface stoichiometric composition and ligand passivation. Here, we will discuss strategies for improving the performance of PbS QD-based solar cells including simple post-deposition treatments that lead to planar heterojunction devices with a high fill factor of 0.68, or a high certified short-circuit density of 26.2 mA/cm2.
3:15 PM - NT6.12.04
Synthesis and Modeling of Barium Titanate Nanoparticles in a Composite to Determine Dielectric Constants
Scott Tan 3,Kirklann Lau 1,Natasha Allen 1,Shruti Singapur 1,Kaitlin Hansen 1,Olivia Schneble 1,Richard Haskell 1,Albert Dato 1,Todd Monson 2
3 Pomona College Claremont United States,1 Harvey Mudd College Claremont United States2 Sandia National Laboratories, New Mexico Albuquerque United States
Show AbstractBarium titanate (BTO) is a widely used dielectric material because it has a high dielectric constant, typically ranging from 1500 to 2000 in bulk [1]. However, it is still not entirely clear how varying BTO nanoparticle size affects this dielectric constant, particularly for non-sintered discrete nanoparticles. Other research groups have reported BTO nanoparticle dielectric constants from 135 [2] to as high as 5000 [3] with no mention of uncertainty. We found that when suspending nanoparticles in a colloidal suspension to extract their dielectric constants, 0.01% precision in the colloid dielectric constant was required to achieve an uncertainty under 10% in the particle dielectric constant. Barriers to high volumetric loading in suspension, such as particle settling and constituent movement, make it extremely difficult to achieve this level of precision.
To overcome these difficulties, we are employing a novel technique to measure the dielectric constant of BTO nanoparticles by dispersing surface-functionalized nanoparticles in a polymer composite that is cured to prevent particle settling and constituent movement. The effective dielectric constant of the composite is then measured using electrochemical impedance spectroscopy with finite resistances added in parallel to control Nyquist plot contour sizes. Analytical methods such as Effective Medium Theory, the Boettcher model, and the Bruggeman model, as well as computational modeling via COMSOL are used to extract the dielectric constant of the BTO nanoparticle component.
Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-AC04-94AL85000.
[1] Park et al. Journal of Korean Physical Society, Vol. 49 (2006): S680-S683.
[2] Siddabattuni et al. Journal of the American Ceramic Society 96.5 (2013): 1490-6.
[3] Wada et al. Japanese Journal of Applied Physics 42.Part 1, No. 9B (2003): 6188-195.
3:30 PM - NT6.12.05
Mn2+-doped (CdSe)13 Clusters: The Smallest Doped Semiconductor
Jiwoong Yang 2,Taeghwan Hyeon 2
1 Center for Nanoparticle Research Institute for Basic Science Seoul Korea (the Republic of),2 School of Chemical and Biological Engineering Seoul National University Seoul Korea (the Republic of),
Show AbstractDoped semiconductor nanocrystals have attracted tremendous attention for their potential in a variety of applications. However, doping of extremely small-sized semiconductors turned out to be very challenging. Herein, we present the synthesis and characterization of Mn2+-doped (CdSe)13 clusters.1 Single-sized clusters (Cd13-xMnxSe13, x = 0,1,2) can be obtained in large quantity. Interestingly, these clusters exhibit semiconductor band structure despite of their small size. These doped clusters with only 26 atoms show not only giant magneto-optical responses but also fine structure states with different magneto-optical activity.
Reference
1) J. Am. Chem. Soc. 2015, 137, 12776–12779.
3:45 PM - NT6.12.06
Composition-Matched, All-Scale “Solders” for Semiconductors: From Synthesis to High-Performance Transistors and Moldable Thermoelectrics
Hao Zhang 1,Dmitriy Dolzhnikov 2,Jaeyoung Jang 3,Jae Sung Son 4,Alexander Filatov 1,Dmitri Talapin 5
1 Department of Chemistry University of Chicago Chicago United States,2 Department of Chemistry Northwestern University Evanston United States3 Hanyang University Seoul Korea (the Republic of)4 Ulsan National Institute of Science and Technology Ulsan Korea (the Republic of)1 Department of Chemistry University of Chicago Chicago United States,5 Center for Nanoscale Materials Argonne National Laboratory Argonne United States
Show AbstractWe propose a general strategy to synthesize largely unexplored soluble chalcogenidometallates of cadmium, lead, and bismuth. Coordinating solvent molecules (N2H4) lead to unique structures of chalcogenidometallates, including chains of edge-sharing [CdTe4] tetrahedra and distorted [Pb3Te6] octahedra. Cation exchange allows these compounds to be soluble in benign solvents such as dimethylformamide and helps with the removal of foreign elements. Moreover, reactions between chalcogenidometallates and corresponding metal salts result in the formation of stoichiometric metal chalcogenides as mesoscale gel-like species or nanoscale polycrystalline particles. These molecular-, nano-, and mesoscale compounds can be employed as “solders” for semiconductors, from single crystals to nano- and microparticles, widely used in electronics, photovoltaics, and thermoelectrics. For example, CdSe nanocrystals with Na2Cd2Se3 “solder” can be used as soluble precursors for CdSe films with electron mobilities over 300 cm2/Vs, approaching single-crystal mobility. Micro-sized PbTe and Bi2Te3 powders can be molded into thin films or various shapes in the presence of a small additive of solders. Importantly, the chemical design of the solders, i.e., tuning of compositions and scales, allows the selective enhancement or decrease of the majority-carrier concentration at the grain boundaries of the semiconductors. These doping or de-doping effects can be used to optimize the efficiency of moldable thermoelectric devices.
4:30 PM - NT6.12.07
Synthesis of High-Aspect-Ratio Twin Gold Nanorods
Yoshiko Takenaka 2
1 AIST Tsukuba Japan,2 PRESTO JST Kawaguchi Japan,
Show AbstractLarge varieties of sizes in gold nanorods are developed. The long nanorods, especially those longer than 1 μm, are well-suited for use as electrodes, nanogap electrodes, nanorod arrays, and new photonic devices. It is well known that there are two kinds of crystal structures in gold nanorods, namely, single crystal and twin. Twin gold nanorods have different crystal planes at the sides and edges of the nanorods. Thus the twin gold nanorods are modified the surfaces in anisotropic way, whereby the side and edge are modified with different molecules. Moreover nanorods, especially those longer than 1 μm, are also easily manipulated. Therefore, for further application, high-aspect-ratio twin gold nanorods will be arranged or moving on a specially-patterned surface by means of the anisotropic interaction between the two surfaces.
Here we present a new synthesis of high-aspect-ratio twin gold nanorods by using gelled surfactant solution. Generally, twin gold nanorods are synthesized using a stepwise additive method. In this method, citrate-stabilized seeds are added to the growth solution that contains the surfactant, Au ions, and the reducing agents. Some part of the mixture is then added to another growth solution, which is composed of the same constituents and the process is repeated. In these cases, the length of gold nanorods is limited to 500 nm and extra processes will be necessary to elongate nanorods longer than 1 μm. In our method, however, the nanorods with the length of ca. 1.7 μm grow with only one step and no extra processes are necessary. The yield is relatively high: ca. 60 %. In this study, we examined in detail the effects of NO3 concentrations or number of seeds on the length of nanorods. As a result, NO3 has an influence on the length of the gold nanorods and the longest ones were obtained at an optimal concentration of NO3, even for growth in the gelled surfactant solution as well as the growth in aqueous surfactant solution. On the contrary, the number of seeds in the growth solution has no effect on the lengths of the nanorods.
4:45 PM - NT6.12.08
Near-Infrared-Emitting Quantum Dots Nanotracers for Bimodal Imaging
Celine Rosticher 1,Nicolas Lequeux 1,Thomas Pons 1
1 Laboratoire de Physique et d'Etude des Materiaux LPEM - Ecole Superieure de Physique et de Chimie Industrielles de la ville de Paris (ESPCI) Paris France,
Show AbstractThe demand for new imaging tools and new ways to obtain more diagnostic information is constantly increasing. Multimodal imaging agents provide a great opportunity to obtain many informations for diagnostic or therapeutic purposes using images with high resolution and sensitivity. The development of nanoparticles like agents that combine the high resolution abilities of Magnetic Resonance Imaging (MRI) with another more sensitive technique, like optical imaging, leads to significant possibilities for increasing diagnostic quality and clinicians’ understanding of pathologies. We present here a new generation of nanotracers that can be used for near-infrared fluorescence imaging and magnetic resonance imaging (MRI). I–III–VI ZnCuInSe-ZnS core-shell quantum dots coated with silica and iron oxide ultrasmall nanoparticles were developed in this aim with focus on biocompatibility and low toxicity. ZnCuInSe-ZnS quantum dots synthetized by colloidal method were the starting material for this study and have shown an intense emission in the near infrared range at 800nm. Ultrasmall magnetic nanoparticles were then used to ensure magnetic properties to these nanotracers and render them suitable for bimodal imaging.
5:00 PM - NT6.12.09
One Strategy Many Shapes: Morphology Controlled Synthesis of Colloidal Oxide Structures
Jaswinder Sharma 1
1 Energy and Transportation Science Division Oak Ridge National Laboratory Oak Ridge United States,
Show AbstractMorphology controlled synthesis of colloidal structures is an intriguing research area because of its importance in understanding the growth mechanisms that dictate the final shape and due to importance of these structures in a wide range of applications ranging from surface structuring to interface engineering. Though, many strategies have been explored to synthesize such structures, however, control of morphology still remains a challenging task. This talk will focus on synthesis of morphology controlled silica structures, hierarchical structures, and silica-titania hybrid structures. Various parameters that play role in controlling the morphology will also be discussed.
5:15 PM - NT6.12.10
Chemical Crosslinking inside an Organic/Inorganic Nano-Supercrystal: On a New Nanocomposite with Excellent Mechanical Hardness and Strength
Axel Dreyer 1,Artur Feld 2,Andreas Kornowski 2,Ezgi Yilmaz 1,Heshmat Noei 3,Andreas Meyer 2,Andreas Stierle 3,Horst Weller 2,Gerold Schneider 1
1 Institute of Advanced Ceramics Hamburg University of Technology Hamburg Germany,2 Institute of Physical Chemistry Hamburg University Hamburg Germany3 DESY NanoLab Deutsches Elektronensynchrotron DESY Hamburg Germany
Show AbstractNatural hard tissues like nacre or enamel are characterized by outstanding mechanical properties in relation to their rather weak mechanical constituents. The key of their mechanical behavior is the combination of hard inorganic and soft organic constituents in a hierarchical structure which starts on the nanoscale.
Our approach is to synthesize the first hierarchical level by self-organization of organic-coated spherical iron oxide nanoparticles into a well-ordered superstructure. To obtain nanoparticle supercrystals, the standard deviation of the nanoparticle size distribution has to be low. Additionally, the nanoparticle size has to match the surfactant length so that the surfactant can fill the tetrahedral and octahedral sites of the supercrystal completely. Suitable nanoparticles could be synthesized by thermal decomposition of FeO(OH) in the presence of oleic acid at 320 °C in 1-octadecen.
In a sequence of sedimentation, drying, heating, and pressing, the iron oxide particles were arranged in supercrystals and compacted to a solid nanocomposite. Inside this nanocomposite, the inorganic nanoparticles are separated by a layer of surfactants that is a nanometer thick. Therefore, the organic molecules play a prominent role by providing cohesion in the material via strong coordinative bonding of functional groups to the inorganic nanoparticles surface as well as weak van der Waals bonding between adjacent molecules.
To improve the mechanical properties of the nanocomposite, we substitute the weak van der Waals interaction by strong covalent carbon-carbon bonds through chemical crosslinking reactions realized in the solid nanocomposite.
For example, we performed a controlled thermal treatment of the nanocomposite which yields on microscale hardness, modulus, and strength of 3.4 GPa, 60 GPa, and 630 MPa, respectively. To our knowledge, these are the highest combined values of hardness, elastic modulus and strength ever reported for a synthetic organic/inorganic nanocomposite.
We will discuss in detail which chemical changes within the organic phase are responsible for the improvement of the mechanical properties of these nanocomposites. This knowledge enables a tailor-made synthesis of surfactants for the optimization of the mechanical properties.
5:30 PM - NT6.12.11
Nano Materials Based Interfacial Materials for High Efficiency Organic Solar Cells
Jian Zhang 1
1 Guilin Univ of Electronic Tech Guilin China,
Show AbstractOrganic solar cells (OSCs) are intensively investigated in both academic institutions and industrial companies because they could be mass produced by cost-effective roll-to-roll techniques on flexible substrates. The proper selection of interfacial materials plays a central role in the charge collection and extraction, which is a base requirement for high efficiency OSCs.
Due to their solution processability, many nanomaterials of metal oxides, including NiOx and MoO3, and graphene derivatives were shown to be feasible for OSCs. The work function of graphene and graphene oxide (GO) is only ~ 4.7 eV that is much lower than the highest occupied molecule orbital of the organic semiconductors (typically >5.1 eV), which induces interface barriers in OSCs. We demonstrated that the work function of GO can be improved by O2 plasma treatment or photochemical chlorination. Due to high transparence and high work function of GO derivatives, the power conversion efficiency of OSCs was improved significantly when the GO derivatives with higher work function was used as anode interfacial materials. Furthermore, the first high PCE inverted OSC with a room-temperature processed TiOx layer was demonstrated by employing room-temperature processed TiOx/PEI as cathode interfacial materials. The power conversion efficiency of PTB7:PC71BM OSCs with TiOx/PEI layer is improved up to 8.72% from 7.38% of OSCs using only TiOx. The TiOx/ PEI layer fabricated at room temperature is compatible with the roll-to-roll process and can meet the needs of manufacturing on a range of substrates in large scale and has potential for use in other emerging technologies, including perovskite solar cells and dye sensitized solar cells.
Acknowledgement: This research was financially supported by the National Natural Science Foundation of China (21374120, 61564003), and the Guangxi Natural Science Foundation (2015GXNSFGA139002), the Guangxi Key Laboratory of Information Materials (Guilin University of Electronic Technology).
References (12 pt)
D. Yang, L. Zhou, L. Chen, B. Zhao, J. Zhang,* C. Li,* Chem. Comm., 2012, 48, 8078.
D. Yang, W. Yu, L. Zhou, J. Zhang,* C. Li,* Adv. Energy Mater. 2014, 4, 1400591.
D. Yang, P. Fu, F. Zhang, N. Wang, J. Zhang,* C Li,* J. Mater. Chem. A 2014, 2, 17281.