ZnO nanorods can be readily produced by hydrothermal methods on glass substrates at low temperature (95°C) in a short period time (4 hours). The initial pH value of the aqueous solution makes a big difference on the morphology of ZnO nanorod arrays. Under acid condition (pH=5), ZnO nanorods are much bigger and sparser than the final products under neutral condition (pH=7). Another significant feature is that the nanorods from pH=5 randomly tilt from the substrate to a certain angle, whereas, the nanorods from pH=7 are standing vertically.
In order to explain how the direction of ZnO crystal growth was influenced under distinct condition, the growing process of the nanorods was monitored by SEM. The initial pH value is believed to have a great effort on the appearance of the ZnO crystal nucleation in the early stage, and continuously affects the nanorod development. The crystalline structure and optical properties of ZnO nanorods were also studied by using XRD, TEM and Photoluminescence techniques.

Designing, fabricating and integrating arrays of nanodevices into a functional system is the key for transferring nano-scale science into applicable nanotechnology. Despite of the numerous efforts devoted to achieve uniformly ordered assembly of various low-dimensional nanomaterials, planar metal-oxide-semiconductor field-effect-transistor (MOSFET) is still the dominant configuration for implementing functional nanodevices. Novel architecture like 3D integrated circuits has also been adopted to facilitate integration of nanostructure-based planar building blocks by sequentially assembling them into vertically stacked layers. Nevertheless, lack of cost-effective technology for aligning and integrating these nanodevices into circuitry with sufficiently high density hinders further practical applications.
For the emerging applications of bio-integrated electronics such as smart skin and human/machine interfacing, schemes for integrating functional nanomaterials with peripheral circuits on deformable/stretchable substrates at low temperature and low cost are highly desirable. To address these application needs, we demonstrate the first and by far the largest 3D array integration of vertical ZnO nanowire (NW) piezotronic transistors circuitry on 4-inch PET flexible substrates, by combining the patterned bottom-up solution synthesis of vertically aligned ZnO NWs at low-temperature (85 oC) with state-of-the-art top-down microfabrication. The as-fabricated array circuit possesses device density of 8464/cm2, which is much larger than the number of mechanoreceptors embedded in the human fingertip skins and enables a 15-to-25-fold increase in number of taxels and 300-to-1000-fold increase in taxel area density compared to recent reports.
The position, dimension, crystal orientation, morphology and material properties of synthesized ZnO NWs can be well controlled by the hydrothermal solution synthesis and optimized via engineering measures. The solution-synthesized ZnO NWs array exhibits good uniformity in electrical characteristics and response to applied pressure among all of the devices. The reliability and stability of device operations have also been probed, which indicates a good stability of the array operation for future applications like in vivo physiological sensing in complex environments. Moreover, the feasibility of the fabricated array for self-powered active and adaptive artificial skin without external bias has been presented as well. The scalability of this demonstrated technology in integrating solution-derived single-crystalline with interfacing circuitry at low temperature and low cost enables future implementation of nanomaterials for bio-integrated applications in human-machine interfacing and biomedical diagnosis/therapy.
Ref: Wu W. Z.*, Wen X. N.*, Wang Z. L. Taxel-addressable matrix of vertical-nanowire piezotronic transistors for active and adaptive tactile imaging. Science 340, 952-957, 2013.
*Authors with equal contributions

ZnO continues to attract considerable attention due to its potential applications in UV detection, LEDs, spintronics, gas sensors, field effect transistors, field emission, photovoltaics and photocatalysis. Many of these applications require epitaxial films or nanostructured morphologies and ZnO is popular for these applications due to the ease of synthesizing a myriad of nano-forms (e.g. rods, rings, particles, belts) by solution methods. Solution methods are of particular interest because of the low temperatures employed (often < 100oC) and the ease of forming single crystal films and nanostructures.
This talk will present our observations concerning the growth of ZnO in water both as nanostructures and in film form. In the film form, epitaxial films have been grown at <100oC and much of the work has looked at reducing the defects in the grown films. Epitaxial films with threading dislocation densities in the low 108 cm-2 values utilizing lateral epitaxial overgrowth with and without photolithographic masking will be discussed. Recent results from initial works on the growth of homoepitaxial ZnO and MgZnO films and also nanostructured polycrystalline films will also be presented. For the latter, functional surface properties such as wetting will also be reported.
In addition, post growth annealing is required to optimize properties of solution grown ZnO and this study shows that such annealing leads to the formation of pores within epitaxial films and also in single crystal rods. It is believed that these pores form upon coalescence of anion and cation vacancies. Pore formation can be detrimental, adversely affecting transparency and mobility and as such, more detailed investigations has been undertaken utilizing a variety of characterization techniques such as scanning transmission electron microscopy (STEM), tomography and absorption spectroscopy.

As the most promising candidates for Diluted magnetic semiconductors (DMSs) with high Curie temperature (Tc), TM-doped ZnO has attracted considerable attention of scientific community due to its attractive advantages such as low cost, abundance, friendly environment and optoelectronic property. Although there are many reports on room-temperature ferromagnetism (RTFM) of ZnO diluted magnetic semiconductors doped with transition-metal (TM), the origin of RTFM is still quite controversial. Recently, some computational results calculated using the first-principles method based on density functional theory (DFT) show that codoping appears to be a potential approach to obtain intrinsic and enhanced ferromagnetism in TM-doped ZnO.[1,2] Stirred from the above mentioned facts, it would be quite interesting to synthesize and investigate the properties of codoping ZnO DMS, such as Cr-Ni codoped ZnO DMS. Meanwhile, magnetic field has been used as an efficient way to modulate the growth, morphology and the properties of the crystalline materials while it is applied in the synthesis process. In this work, Cr-Ni codoped ZnO powders were synthesized by hydrothermal method under the high pulsed magnetic field. The effects of pulsed magnetic field on the morphology, structure and magnetic properties of Cr-Ni codoped ZnO were investigated by X-ray diffraction, scanning electron microscope, high resolution transmission electron microscope, Raman scattering spectra and vibrating sample magnetometer. It was found that high pulsed magnetic field processing not only affects on the morphology of ZnO nanocrystallines, but also improves the Cr-Ni ions doping into the ZnO matrix. The room temperature ferromagnetism observed in the samples demonstrates clearly that codoping is an optional method to fabricate intrinsic ferromagnetism in TM-doped ZnO. According the bound magnetic polaron model (BMPs) proposed by Coey et al,[3] Cr and Ni ions incorporation may prompt the formation of bound polaron (oxygen vacancies, Vo), which may be the reason for the field processing sample with better ferromagnetism.
Acknowledgements
The authors thank the project supported by Shanghai Science and Technology Commission(11nm0501600), and the Analysis and Research Center of Shanghai University for their technical supports.
Reference
[1] B. Lu et al. Appl. Phys. Lett, 101:242401, 2012.
[2] P. Gopal et al. Phys. Rev. B, 74:094418, 2006.
[3] J.M.D. Coey et al. Nat. Mater, 4:173, 2005
*Corresponding author contact: [email protected]

We recently put forward a solution based method of laser induced chemical deposition for nanomaterials. The grow rate of SnO2 nanotube by laser induced chemical deposition can reach a value more than 300 nm/s. The method can be applied to produce various chalcogenide nanomaterials. Nanomaterials synthesized by laser-induced chemical deposition share the characteristic of uniform fine microstructure. In this paper, we demonstrate that this method can be used to coat 3 dimensional porous structure with uniform nanoparticles. Paper fibers coated with iron oxide nanoparticle as an example is studied in this paper. Heavy loading of Iron Oxide nanoparticles can achieved in a short time. The relationship between the laser power and production rate is shown. The size and crystal structure of the coated nanoparticle are investigated by SEM and TEM. The hybrid structure of nanoparticle coated paper fibers is used as an effective sorbent for heavy metal in water treatment.

In this presentation, we discuss our recent results in developing an electrochemical-liquid-liquid-solid (ec-LLS) growth process that relies on an unconventional aqueous electrodeposition strategy to produce crystalline covalent Group IV and III-V semiconductor nanomaterials. This process employs a liquid metal as a traditional cathode substrate and as a recrystallization flux to directly produce crystalline Group IV and III-V semiconductors at or near lab ambient conditions. The first half of the talk will focus on general features of the ec-LLS process used for the direct electrodeposition of crystalline GaAs and InAs thin films from aqueous solutions without any thermal annealing. Here, dissolved As2O3(aq) in water is electrochemically reduced on reactive Ga or In to produce the respective binary crystalline semiconductor. The necessity for clean (i.e. oxide free) group III metal interfaces will be discussed. Spectroelectrochemical data will then be presented that detail the extent of this electrodeposition process at low and elevated temperatures, highlighting a key balance between the rates of several electrochemical, metallurgical, and transport processes.. The second half of the presentation will highlight recent data that extends the ec-LLS strategy to using arrays of liquid gallium (Ga(l)) nanodroplet electrodes supported on Ge or Si wafers for the electrodeposition of epitaxial and single crystal Ge nanowires from dissolved GeO2(aq). High resolution transmission electron microscopy investigations will be presented which verify the epitaxial nature between the nanowire/substrate interface as well confirm the position of the Ga(l) nanodroplet at the tip of the nanowire following growth. The influence of the substrate crystal orientation on the resultant nanowire growth direction will be revealed by scanning electron microscopy. The observed uniformity in as-grown nanowire height will be discussed within the context of the traditional instantaneous electrochemical nucleation model. In the same vein, the propensity for this ec-LLS strategy to be used for wafer-scale preparation of homogenous Ge nanowire arrays will be described.

Titanium dioxide (TiO₂) has found its applications in many important areas including dye-sensitized solar cells, photocatalysis, and lithium-ion batteries (LIBs). It has been demonstrated that some structural features of TiO₂ materials, such as the particle size, geometric shape, and surface property would have tremendous effects on their physicochemical properties, thus influencing their performance. For example, TiO₂ has been studied as a promising anode material for high-performance LIBs. However, the low electrical/ionic conductivity of TiO₂ limits its electrochemical performance. By utilizing nanostructured TiO₂ materials, such as low-dimensional nanowires or nanosheets with reduced Li-ion/electron transport length and increased electrode/electrolyte contact area, lithium storage properties of TiO₂ could be significantly improved.
We have developed several solvothermal systems for the facile preparation of various TiO₂-based nanostructures, namely ultrathin anatase TiO₂ nanowires, asymmetric anatase TiO₂ nanorods with exposed high-index facets, and hierarchical spheres constructed by titanate nanosheets. Mixtures of some common organic solvents were used for these syntheses, including isopropanol, dimethylformamide and acetic acid, without the assistance of other additives (except for the synthesis of nanowires, in which lithium salt was added). It is speculated that the organic solvent molecules not only serve as reaction media, but also play as efficient structure directing agents to facilitate the anisotropic growth of nanocrystals, thus resulting in the various low-dimensional nanostructures. Electrochemical investigation shows that these TiO₂ nanostructures are promising candidates as high rate and long cycle life anode materials for LIBs.
Reference
[1] H. B. Wu, H. H. Hng, X. W. Lou, Direct synthesis of anatase TiO₂ nanowires with enhanced photocatalytic activity, Adv. Mater. 2012, 24, 2567-2571.
[2] H. B. Wu, J. S. Chen, X. W. Lou, H. H. Hng, Asymmetric anatase TiO₂ nanocrystals with exposed high-index facets and their excellent lithium storage properties, Nanoscale 2011, 3, 4082-4084.

Reverse micelle synthesis is a solution-based synthesis technique that takes advantage of confined water nanodomains in a bulk oil phase via self-assembly of surfactant molecules at the water-oil interface. This technique can be used for synthesizing functional nanoparticles for a wide variety of applications. The technique can be used to make unagglomerated nanoparticles with a narrow size distribution or compositionally layered nanoparticles, for example. Although some aspects of this synthesis method are well understood, other aspects are based on trial-and-error modifications. In this study, we describe and analyze the fundamental aspects of electrostatic interactions on reverse micelle synthesis. One of the fundamental aspects to be studied includes how solutes affect the size and stability of reverse micelles that define concentration stability limits. The interaction between a precipitated particle in suspension and the stability of the reverse micelle that contains the precipitate will also be evaluated to define precipitation limits. The effect of surfactant substitution, non-aqueous solvent substitution, and the water to surfactant ratio will also be evaluated for optimizing the combination of solute concentration stability and precipitation limits that can be used for the design of controlled nanoparticle formation.

The advances in synthesis of of high-quality epitaxial thin films and heterostructures of inorganic materials have led to the improved functional and multifunctional behavior. The important role that interfaces play in the behavior of these materials requires a detailed understanding of their structure. Electron microscopy approaches provide powerful information regarding local structure relevant to this challenge. The advent of correctors for spherical and chromatic aberrations (Cs and Cc, respectively) in transmission electron microscopy (TEM) has led to significant improvements in imaging, especially for high-resolution TEM, and some new imaging modes are now possible. One of the primary benefits of chromatic aberration correction is that it significantly reduces the focus blur in images formed from electrons with an energy spread, improving high resolution imaging in energy-filtered TEM (EFTEM) mode. Since EFTEM is formed using inelastically scattered electrons, atomic resolution EFTEM offers another method to determine structural and chemical information at atomic resolution. Although image formation in energy filtered high resolution electron microscopy (EF-HREM) is complex, it provides another approach to obtain “Z”-like contrast in atomic resolution images. Similarly, a new high-resolution TEM imaging technique allows the direct observation of A-site associated oxygen octahedral rotations in perovskite oxide superlattices. In this approach, we exploit the difference in extinction distance for atomic columns that arise due to channeling effects when a high-energy electron beam passes through them. Using this approach, we are able to distinguish between Ba and Ca and resolve oxygen octahedral rotations at the interfaces of a BaTiO3/CaTiO3 superlattice structure, helping to explain the mechanism for enhance ferroelectricity in this tailored structure.
*Research sponsored by the U.S. DOE, Office of Science - Basic Energy Sciences under contract DE-AC02-06CH11357. The Electron Microscopy Center at Argonne is supported by the Office of Science.

Sb2Te3 is a narrow band gap semiconductor with a broad spectrum of applications e.g. in thermoelectric power generation or as a phase change material in nonvolatile data storage. It consists of covalently bonded Te-Sb-Te-Sb-Te layers in ab direction. These quintuple layer stacks are interconnected via v. d. Waals forces resulting in a layered structure in c direction. For enhanced thermoelectric power generation, the thermal and electrical transport properties can be tuned by applying Sb2Te3 in nanosized form. [1] In data storage applications a temperature induced phase change between the amorphous and crystalline state in polycrystalline Sb2Te3 thin films exhibiting low and high electrical conductivity, respectively, is utilized. [2] However, the microstructure of such thin films affects the performance of the devices and the interplay of intrinsic and grain boundary effects is rather unexplored. Therefore it would be highly desirable to study the phase transition in Sb2Te3 on the level of individual micro- or nanocrystals.
In this work we introduce the solution based synthesis of defect free, hexagonally shaped Sb2Te3 single crystals following a modified protocol of Zhang et al. [3]. These hexagonal platelets (HPs) have an average lateral dimension of about 1.5 µm and a few tens to 250 nm in thickness. We will show that the reaction pathway towards this HPs passes via spherical and layered amorphous intermediates, whereas the latter surprisingly already show a hexagonal morphology. The detailed analysis of the reaction pathway is enabled by nanodiffraction analysis of the intermediates in a FEI TITAN 80-300 STEM, which allows to locally probe the crystallinity of a sample with nm resolution.
[1] W. Shi, L. Zhou, S. Song, J. Yang, H. Zhang, Adv. Mater. 2008, 20, 1892
[2] D. Lencer, M. Salinga, B. Grabowski, T. Hickel, J. Neugebauer, M. Wuttig, Nat. Mat., 2007, 7, 972
[3] G. Zhang, W. Wang, X. Lu, X. Li, Cryst. Growth Des. 2009, 9, 145

The multiple properties exhibited by copper and copper oxide nanomaterials, i.e. conduction, plasmonic, surface reactivity, have recently attracted a considerable interest due to their use in many applications (microelectronics, photovoltaics, catalysis or biology). [1, 2, 3, 4, 5] Because the copper oxidation state is a pivotal issue for the targeted applications, the control of the nanomaterial stability against ambient air is of prime importance. For example, attempts were made to block the oxidation process by using alkyl thiol molecules deposited as a monolayer onto a copper film. [6] However, discrepancies still remain concerning the nature of the environment able to efficiently control copper crystals oxidation: long chain carboxylic-acids, -amines, -thiols or pi-donor solvent. [7, 8, 9]. Recently, our group has developed a metallorganic chemical approach which allows to master the surface state of copper nanomaterials. [10] In addition to the usually employed characterization techniques (TEM, IR or UV-Vis spectroscopies) we have tracked the coordination and exchange mechanisms of ligands at/or close to the crystal surface by liquid NMR tools. In the present work, we have studied the role of hexadecylamine (HDA) or tetradecylphosphonic acid (TDPA) on the air stability of ca. 6 nm copper nanoparticles. The tremendous improvement of copper crystals&’ air stability functionalized by HDA compared to TDPA ligands will be presented and detailed. Depending on the choice of the terminal function carried by the ligand, amine or phosphonic acid, the fine tuning between slow oxidation and dissolution of NPs is monitored. This latter effect directly controls the release rate of copper ions potentially useful for bactericide applications. These results have been valuable for the preparation of copper nanoparticles layers stabilized by multivalent ligands (dendrimers bearing phosphonic acid functions) employed in bactericidal/bacteriostatic films.
[1] Hung L.-I., Tsung C.-K., Huang W., Yang, P. Adv. Mater 2010, 22, 1910.
[2]. Wang Z., von dem Bussche A., Kabadi P. K., Kane A. B., Hurt R. H. ACS Nano, 2013, 7, 8715.
[3] Jeong S., Woo K., Kim D., Lim S., Kim J. S., Shin H., Xia Y., Moon J. Adv. Funct. Mater. 2008, 18, 679.
[4] Park J. C., Kim J., Kwon H., Song H. Adv. Mater. 2009, 21, 803.
[5]. Lignier P., Bellabarba R., Tooze R. P. Chem. Soc. Rev. 2012, 41, 1708.
[6] Laibinis P. E., Whiteside G. M. J. Am. Chem. Soc. 1992, 114, 9022.
[7] Kanninen P., Johans C., Merta J., Kontturi K. J. Colloid Interface Sci. 2008, 318 , 88,
[8] Rice K. P., Walker E. J., Stoykovich M. P., Saunders A. E. J. Phys. Chem. C 2011, 115, 1793,
[9] Mott D., Galkowski J., Wang L., Luo J., Zhong C.-J. Langmuir 2007, 23, 5740.
[10] Barriere C., Piettre K., Latour V., Margeat O., Turrin C.-O., Chaudret B., Fau P., J. Mater. Chem. 2012, 22, 2279.

The tunability and performance of magnetic nanoparticles have garnered interest from a diverse set of technologies, ranging from environmental applications, such as groundwater treatment and site remediation, to magnetic resonance imaging (MRI), contrast agents, power electronics, optical isolators, and data storage. In particular, the remarkable properties of metallic iron have sparked significant interest in large-scale synthesis and assembly of zero-valent iron (Fe(0)) nanoparticles. The inherent susceptibility of these materials toward oxidation, however, challenges adoption. Techniques for surface-modification beyond the structure-directing ligands used in the nanoparticle synthesis are key to imparting stability against oxidation, as well as tuning properties and processibility. Here in, we discuss the synthesis, magnetic properties, and stability of Fe(0) nanoparticles with grafted polymer shells. In one approach, iron nanoparticles (e.g. 13 nm) are synthesized in 1-octadencene via microwave irradiation of Fe(CO)₅ in the presence of oleylamine. Thiol-terminated polystyrene is subsequently grafted-to the nanoparticle surface under inert atmosphere via ligand exchange with oleylamine. In a second approach, microwave irradiation of Fe(CO)₅ is conducted directly in a non-oxidizing polymer solution. The synthetic relationship between polymer molecular weight, graft density, and shell size will be discussed. The impact of the structure of the polymer shell on surface oxidation of the nanoparticle, and ultimately, on the magnetic properties of these materials, is also explored. Finally, the optical properties of self-assembled thin films of these hairy magnetic nanoparticles are summarized.

Silica nanoparticles are extensively used in a various areas of science. Their universalism is due to the ease of preparation and possibility of controlling size, a high surface-to-volume ratio, and the biocompatibility of silica.[1] In the last decades different functionalization protocols have been developed depending on the final purpose: sensing,[2] drug delivery [3] or synthesis of smart material [4].
Following this vision we decided to synthetize new silica nanoparticles and to functionalize their surface with bilayers of molecules taking advantage of the principle of Dynamic Combinatorial Chemistry. DCC is defined as combinatorial chemistry under thermodynamic control; that is, in a dynamic combinatorial library (DCL), all constituents are in equilibrium. At equilibrium, the expression of the products in a dynamic combinatorial library (DCL) is governed by thermodynamics and as a consequence, the additional presence of molecular targets can lead to the in situ screening of the ‘best-fitted&’ constituents.
Adapting approaches used in synthetic organic chemistry for applications such as pharmaceutical sciences and chemical discovery, materials scientists have developed a variety of approaches to create libraries in the solid state in order to rapidly examine a broad range of materials characteristics; the ultimate hope is to accelerate the discovery of new materials and/or new materials properties. [5]
Here we present a set of new self-assembled bilayer coated silica nanoparticles synthesized using different dynamic libraries having as common feature the possibility to form a reversible iminic bond. Amino- and Aldehyde-terminated silica nanoparticles were synthesized using a modified Stötber method and the coating analyzed by NMR, IR and TGA. The reaction with different corresponding members (aldehyde or amine respectively) has been tested in order to obtain homo- and mixed-ligand dynamic particles able to assemble/disassemble/exchange depending on the external condition they are exposed to. We investigate the assemble/disassemble of such a bilayer formed on the surface mainly using classical analytical techniques as well as and the arrangement of the molecules on the surface by AFM imaging.
[1] Feifel, S.V.; Lisdat, F. Journal of Nanobiotechnology 2011, 9, 59.
[2]Teolato, P.; Rampazzo, E.; Arduini, M.; Mancin, F.; Tecilla, P.; Tonellato, U. Chem. Eur. J. 2007, 13, 2238.
[3]Mackowiak, S. A.; Schmidt, A.; Weiss, V.; Argyo, C.; von Schirnding, C.; Bein, T.; Braüchle, C. Nano Lett. 2013, 13,
[4]Mori, H.; Müller, A. H. E.; Klee, J. E. JACS 2003, 125, 3712.
[5]Rajan, K. Combinatorial Materials Science and EBSD: A High Throughput Experimentation Tool. Annu. Rev. Mater. Res. 2008, 38, 299.

Metal/intermetallic nanostructures extend the range of bulk metallic properties by virtue of their manifold compositional, structural, phase, and morphological variations. The ability to tune structure-property characteristics of metal/intermetallic nanoparticles (NPs), via controlled synthesis techniques, can enable unique physico-chemical, and optoelectronic properties that find wide-spread scientific applications in new classes of energetic, plasmonic, catalytic and thermoelectric materials. To this end, a novel one-step, one-pot solution-phase experimental route is developed that, for the first time, combines “top-down” laser ablation synthesis in solution (LASIS) with “bottom-up” wet chemical reduction method (CRM). LASIS endows the NPs with metastable crystalline structures and phases due to the extreme liquid-confined plasma conditions, while the simple kinetics of CRM allows for systematic control of their sizes and shapes. We present results from a comprehensive study for the synthesis of Co/Co-oxide and Co/Pt NPs using the tandem LASIS-CRM technique. The effect of laser fluence, ablation time, temperature and solvents condition used were investigated. In most cases of LASIS on pure cobalt, cobalt(II) oxide (CoO) was the main product, except for ablation using a laser fluence of ~20 J/cm2 at high pH conditions (pH = 14), wherein large amount of cobalt(II,III) oxide (Co3O4) nanorods with spinel crystalline structure were formed. Selected area electron diffraction (SAED) and high resolution transmission electron microscopy (HRTEM) data revealed the lattice constant and d-spacing of (111) plane for these structures to be 0.808nm and 0.466nm respectively, which are in good agreement with the standard data for Co3O4 (JCPDS-ICDD No. 42-1467). Added to this, CoO@Pt shell-core NPs and intermetallic Pt-CoO NPs were generated by laser ablation in K2PtCl4 solution, which is demonstrated by the elemental mapping fromenergy dispersive X-ray spectroscopy(EDX). The formation of Co3O4 nanotubes with substantially increased size were found during LASIS in K2PtCl4 solutionsat pH = 14, which is due to the galvanic replacement reactions between Co and K2PtCl4. The present results report the first-ever tandem LASIS-CRM synthesis of controlled nanostructures such as Co3O4 nanorods and CoO@Pt shell-core NPs. Currently, systematic characterizations for magnetic properties and water oxidation catalytic activities of the aforementioned Co3O4 nanorods as well as electrocatalytic activities of the CoO@Pt shell-core nanostructures are in progress.

The use of nanosize silver, and its alloys, represents an interesting alternative to common food preservation methods, which are based on radiation, heat treatment and low temperature storage. These metal nanoparticles, embedded within a polymeric matrix for instance, would extend the shelf life of perishable foods while acting as a bactericidal agent to prevent food-borne illnesses. Common methods used in the synthesis of metal nanoparticles require toxic solvents and reagents that could be harmful to health and the food itself. In addition, several steps are required to obtain aqueous stable, i.e. dispersible, silver nanoparticles. In this work we propose the microwave-assisted aqueous synthesis of silver nanoparticles, (AgNPs) functionalized by gluthatione (GSH) in a single-step using sodium sulfite (Na2SO3), as reducing agent. Different molar ratios of Ag/GSH/Na2SO3 were evaluated. Best results were obtained at molar ratios of 1:3:1 and 1:3:3 at pH 6. UV-Vis measurement clearly showed the plasmon peak attributed to silver nanoparticles, which was confirmed by XRD analyses. The hydrodynamic diameter of AgNPs was <10 nm. FT-IR measurements suggested the actual GSH-Ag surface interaction through -SH and -COOH groups; the functionalization by GSH explained the high stability of the nanoparticles in aqueous suspensions. These Ag-GSH nanoparticles exhibited remarkable antimicrobial activity against E. Coli.

Fluorine doped cesium tungsten bronze (Cs0.33WO3Fx) has been successfully synthesized by hydrothermal method using sodium tungstate and cesium carbonate as raw materials, and hydrofluoric acid as fluorine source. The microstructure and morphology of the as-prepared Cs0.33WO3Fx products were characterized by XRD, SEM, TEM and XPS analyses, and the visible light transparency and near-infrared (NIR) shielding ability were evaluated. The results indicate that hydrofluoric acid plays a role in inducing the formation of rod-like Cs0.33WO3Fx particles, and with the increase of hydrofluoric acid addition amount, the nano-rod like morphology becomes more conspicuous. The XPS analysis results indicate that W atom exists in two forms of W5+ and W6+, and the doped fluorine atoms substituted for oxygen atoms in the lattice. The UV-Vis-NIR transmittance spectra indicate that the as-prepared Cs0.33WO3Fx particles exhibit higher visible light transmittance and near-infrared shielding ability than that of the non-doped Cs0.33WO3 particles, which is considered to be related with the increased band gap and free carrier concentration in the Cs0.33WO3Fx products. Particularly, the as-prepared Cs0.33WO3F0.45 sample shows best visible light transmittance with reaching 48% and near-infrared shielding property with reaching 90%. However, a dramatic decrease on NIR shielding ability has occurred in the sample Cs0.33WO3F0.79, which possibly results from the W-defect generated by the excessive etching of hydrofluoric acid. In addition, the effects of N2 annealing on the microstructure and properties of Cs0.33WO3Fx were also investigated. It is suggested that the hydrothermal synthesized Cs0.33WO3Fx particles with appropriate fluorine doping will have greater potential applications in the field of architectural and automotive window glasses for transparent heat shielding purposes than the non-doped Cs0.33WO3 particles.

Branched metal nanoparticles (NPs) are of current interest due to their unique properties, dependent on their size, shape and composition. However, many syntheses to branched NP yield NPs with inhomogeneous branching patterns from one particle to the next. Seed-mediated co-reduction is a method developed in the Skrabalak Laboratory to synthesize architecturally controlled bimetallic nanocrystals. By manipulating the synthetic parameters, a variety of architecturally complex nanostructures were produced through a general co-reduction approach in which Au and Pd precursors are simultaneously reduced to deposit metal on to shape-controlled metal cores. Previously, we have synthesized symmetrically branched core@shell Au@Au/Pd and Pd@Au/Pd nanocrystals. Here, we explore the roles of the seed symmetry and composition during seed-mediated co-reduction, where it was found that the final symmetry of the branched nanostructure depends on core geometry, shape and crystallinity. By decoupling the parameters that govern branched nanocrystal overgrowth, we can move towards rational design of new branched and bimetallic nanocrystals.

The two most important requirements for the use of nanocrystals in various applications like bio-imaging, solar energy conversion and light emitting devices are accurately defined sizes and narrow particle size distributions. Therefore the synthesis of nanoparticles must fulfill these two points. In the case of sparingly soluble materials, Ostwald Ripening is commonly accepted as the main growth mechanism and is the main reason for the broadening of the particle size distribution. Herein, we investigated the Ostwald ripening of colloids containing nanocrystals of two different crystal phases of the same material. For such polymorphic systems, we can show that in this case Ostwald Ripening leads to a narrowing of the particles size distribution of the thermodynamically more stable phase and the particles of the less stable phase just act as a monomer source. To realize such a system we mixed small NaEuF₄ nanocrystals of the cubic α-phase and hexagonal β-phase having the same mean size and size distribution and followed the temporal evolution of the particle sizes of both phases by XRD and TEM. An explanation of the experimentally observed narrowing of the particle size distribution is found by numerical simulations within the LSW framework. Small changes in the material parameters like bulk solubility or surface energy are sufficient to simulate a narrowing of the particle size distribution. Next to the explanation of the narrowing, we found a method for the preparation of nanoparticles with adequate defined sizes and narrow particle size distributions.

Ceria nanoparticles (NPs) are regarded as high potential materials for three-way catalyst and water-gas-shit catalyst and so on.
In our previous studies, ceria nano-cubes having active {100} facets on their surfaces were successfully synthesized by oleate-modified hydrothermal growth method1,2.
Sodium stearate (SS) is also a kind of surfactant which has a chemical structure similar to sodium oleate (SO). In this study, SS was also used as surfactant in the process and the size and shape control of ceria NPs were investigated.
0.5M Cerium nitride solution was added to 0.5M sodium oleate solution or 0.5M sodium stearate solution. The surfactant metal complexes were hydrothermally treated at 200oC for 6 hours, and the products were collected by centrifugation at 3000 rpm for 5 min.
All products were assigned to CeO2 (JCPDS: 34-0394) in XRD patterns. Ceria NPs synthesized using SO was about 12 nm in size and cubic in shape having {100} facets. On the other hand, ceria NPs synthesized using SS was about 6 nm in size and sphere in shape having many kinds of facets. Both NPs exhibited very high dispersibility in non-polar solvent.
(1) Taniguchi, T. et al., Crystal Growth & Design 2008, 8, 3725-3730.
(2) Taniguchi, T. et al., Crystal Growth & Design 2011, 11, 3754-3760.

Nanozirconia powders have been used for making structural ceramics as well as an electrolyte for solid oxide fuel cells. Forming of dense sintered components from nanopowders requires use of deagglomerated powders. In the present study 3YSZ powders were synthesized through coprecipitation and conditioning of the precipitate was carried out by treatment with different amounts of ethanol. Deagglomeration attained in calcined YSZ nanopowders improved with increase in amount of ethanol used for washing of the yttrium-zirconium hydroxide precipitate. Presence of adsorbed ethanol on the yttrium-zirconium hydroxide precipitate was confirmed through TG-DTA. BET specific surface area measurements, CHN analysis, tap density measurements and pressure-displacement curves for powder compaction revealed that a minimum ethanol amount with respect to water present in the precipitate was required to reduce extent of agglomeration considerably in the calcined powders. Green compacts produced from ethanol washed powders when subjected to nanoindentation were found to be “harder” than compacts produced from water washed powders due to superior particle packing. This was also was also evident from the SEM observations of the green compacts. Ionic strength of the suspending medium and zeta potential of the precipitate suspended in the medium showed no correlation to the obtained powder characteristics.

Nano-size Magnesium Aluminum Titanate dielectrics (eleven samples with different amount of TiO2) have been prepared by a modified Pechini-type soft chemistry technique. Also conventional solid state ceramic sample preparation methods were used to have a reference. Obtained powders were isostatically pressed (200-800 MPa) and heat treated at various temperatures (between 1000-1500°C). As the temperature and pressure were increased an increment in relative density was observed resulting higher dielectric quality factor compared to conventional sample preparation techniques. Dielectric constant was affected not only by sample composition but also by grain size, relative density and oxygen stoichiometry. Thermal conductivity at room temperature was measured by laser flash technique. It was also determined that, by using wet chemical methods, spinodal decomposition reaction hindered which improves dielectric properties of the materials.

Alumina-silicone hybrid nanolaminate films were synthesized by plasma enhanced chemical vapor deposition (PECVD) process. PECVD allows digital control over nanolaminate construction, and may be performed at low temperature for compatibility with flexible substrates. These materials are being considered as dielectrics for application such as capacitors in thin film transistors and memory devices. In this work, we present the temperature dependent electrical and dielectric properties of the nanolaminate dielectric films in the range of 200- 340 K to better asses their potential applications for different devices. It is observed that the frequency dependent dielectric constant (εr) and dielectric loss (tanδ) increase with the temperature. Both quadratic (α) and linear (β) voltage coefficient of capacitance (VCC) increases as the temperature increases. The temperature coefficient of capacitance (TCC) decreases whereas α and β increases as the Al2O3 composition increases in the alumina/silicone nanolaminates. The nanolaminate films show low leakage current density (J) and better dielectric loss tangent compared to that of single layered films.

Rare-earth-doped nanocrystals (NCs) have attracted great research interest in the past decades for their wide application in lighting, displays, lasers, including their emerging potential in biological imaging. Much effort has been devoted to the phase-controlled synthesis of these NCs and studies on their structure-dependent luminescence properties. Our work is focused on two types of rare-earth-doped NCs: ultraviolet-excited phosphor LaVO4:Eu, and near-infrared-excited phosphor NaREF4:Yb,Er/Tm. Phase-controlled synthesis was realized in both systems by rational design, and drastic change in luminescent properties was observed.
LaVO4:Eu NCs. While La is an abundant and cheap RE element, La compounds are less employed as phosphor host material, because of the structural difference between La and other RE compounds induced by the larger radius of La3+. For RE orthovanadates, while other REVO4 NCs tends to crystallized to tetragonal (t) phase, LaVO4 NCs usually crystallize to monoclinic (m) phase, which shows poorer luminescence properties. In our work, pure m-LaVO4:Eu and t-LaVO4:Eu NCs were both obtained by a hydrothermal method, with their phase controlled with additives. We found that chelating ligands, such as ethylenediaminetetraacetic acid (EDTA), favour the formation of t-LaVO4:Eu NCs. The phase transformation from m-LaVO4:Eu to the metastable t-LaVO4:Eu NCs resulted in a remarkable improvement of the luminescent properties.
NaREF4:Yb,Er/Tm NCs. Recently, studies on upconversion (UC) phosphors have grown rapidly, owing to their potential applications in near-infrared-excited bioimaging. NaREF4:Yb,Er/Tm NCs are most important type of UC materials, which exhibit large anti-Stokes shifts, high resistance to photobleaching and low biotoxicity. NaREF4 NCs exist in two phases, cubic phase (α) and hexagonal phase (β). As particle size and UC luminescent properties of the NCs are concerned for biological applications, phase-controlled synthesis are desirable. By tuning Na/RE ratio, solvent composition, reaction temperature and time, this is achieved in the thermal co-decomposition method. Further more, in-situ phase transition (from hexagonal to cubic phase ) of NaREF4 NCs were observed with electron beam irradiation. Spectral studies of NCs before/after phase-transition showed a remained branch ratio and a drop in emission intensity.

The pursuit of complex nanoscale architectures resides in our inspiration from nature, i.e. biomineralization processes, where the diversity and complexity of crystals produced is far from being rivaled by synthetic nanomaterials. Understanding the role of organic molecules in the fundamental crystal nucleation and growth processes that yield such biominerals can also enable precise and efficient crystal morphology engineering of functional nanomaterials. We previously reported the screw dislocation-driven growth of one-dimensional (1D) nanomaterials, such as nanowires and nanotubes, and two-dimensional (2D) nanoplates of various compositions in aqueous solutions. We are now assessing the influence of amino acids, as well as other small molecules, such as citric acid, on the screw dislocation-driven growth to achieve different 2D morphologies, such as hexagonal nanoplates vs. triangular ones. Further, we utilize this mechanism as a controllable “dimension-switch” from 2D to 1D morphologies, and vice versa, to construct homo- or heterostructures. To observe these changes, we are using nanoplates of zinc hydroxyl sulfate that can be easily converted to ZnO as convenient platforms for various imaging techniques. We mainly use in situ fluid atomic force microscopy and fluid optical microscopy to visualize growth spiral evolution under the influence of select molecules, and different growth conditions. These screw dislocation-driven building blocks could be useful for many applications, such as solar energy conversion and electronics.

The I-III-VI₂ ternary nanocrystals (NCs), such as copper indium sulfide (Cu_xIn_yS₂, CIS) or silver indium sulfide, are gaining great interest as a new field of strongly light-emitting semiconductor nanocrystals in visible to near-infrared (NIR) region or solar-harvesting applications due to their markedly low toxicity compared to Cd-based NCs. While developing the new synthetic strategies to utilize relatively nontoxic and chemically well-defined precursors, two metal dialkyldithiocarbamate single-molecular sources, we discovered the characteristic phase transformation of Cu₂S@In₂S₃ heterogeneous alloy structure to homogeneous CIS in the sizes of 2 - 8 nm. Even though the phase transformation of CIS was a well-studied phenomenon, we first observed that it could be related to the optical properties of CIS NCs. Due to the different thermal decomposition temperature and kinetics, Cu precursor decompose earlier than In precursor, resulting the heterogeneous alloy showing PL close to 800 nm NIR region, whereas the band-edge emission of bulk CIS is 827 nm in theory. Upon heating the 2 - 4 nm CIS NCs at relatively low temperature, the red emission in the range of 600 - 700 nm evolves upon reaction time while the NIR emission portion becomes lower and quantum yield in overall increases irrespective to the size and composition change, confirmed by ICP-AES, UV-VIS, and PL analysis. Similar phenomenon could also be observed for the CIS NCs with Cu/In ratio varied. We propose the reason behind this occurrence is the little lattice distortion and the chalcocite Cu₂S in superionic conducting state. This study gives insight to the understanding CIS formation mechanism for various syntheses.

Food packaging is indispensable to preserve the quality and safety of the food from the time of manufacturing to the final use by the consumer. It is indispensable to evaluate new or enhanced antimicrobial materials to be dispersed in biodegradable polymers for food packaging applications. The present work focuses on the synthesis and evaluation of the bactericidal capacity of Zn_xMg_1-xO solid solutions. Zn_xMg_1-xO solid solutions were synthesized through the thermal decomposition of ZnMg- precursor synthesized in aqueous and ethanol solutions via a two-steps process. X-Ray diffraction and FT-IR spectroscopy analyses confirmed the formation of two isolated phases at Zn concentrations of 10 at.% and above; below this Zn concentration, only the signal of MgO phase was detected. The antimicrobial activity of Zn_xMg_1-xO solid solution against E. coli was evaluated using the spread plate method in presence of Zn_xMg_1-xO powders (x= 0.00-0.50) of different composition. The powder concentrations were 500, 1000, and 1500 ppm. Zn_0.05Mg_0.95O powders exhibited a bacterial growth inhibition from 26% up to 100% when the particles&’ concentration increased from 500 up to 1500 ppm, respectively. On the contrary, a decreasing trend was observed for powders containing 30% and up of Zn (Zn_0.30Mg_0.70O); the corresponding bacterial growth inhibition was, respectively, 12%, 6%, and 5% when the particles concentration was 500, 1000, and 1500 ppm. The formation of two-isolated oxide phases at higher Zn concentrations could explain the observed inhibition of the corresponding bactericidal capacity.

Size-dependent melting decouples melting temperature from chemical composition and provides a new design variable for phase change applications. To demonstrate this potential, we embedded monodisperse bismuth colloidal nanoparticles into matrix materials. The melting temperature in these composites can be tuned by more than 20 Celsius by only varying the nanoparticle size. Adjusting the nanoparticle volume fraction also allows control over the composite's thermal energy density. Our further studies have generalized this approach to other nanoparticle compositions (e.g. In and Sn), and thereby provide a much broader temperature range for phase change applications. Additionally, we have developed a solution-phase chemistry approach to embed nanoparticles into inorganic matrices. This composite consists of a nanoparticle ensemble dispersed in a metal matrix, hence we anticipate a much higher thermal conductivity relative to polymer matrices and a corresponding improvement in thermal charging and discharging rate.

Fabrication of mesostructured silica materials has attracted a great deal of attention due to the potential applications of these unique materials in variety of fields including catalysis, energy, optical coatings, nano-medicine and sensors. Various methods have been developed to prepare mesostructured silica materials with different morphology (e. g. sphere, rod, plate, foam, and fiber) and well-defined pore structures (e. g. hexagonal, worm like, helical and lamellar) using different surfactants or surfactant mixtures, co-solvents or organosilane co-monomers. However, new methods, with vast control over the structure, are still needed to produce, especially, nanosized mesostructured silica materials.
In this research, we developed a facile one-pot method to synthesize mesoporous silica nanoparticles exhibiting variety of different structures such as helical structured nanorods, core-shell nano- spheres/rods and their hollow counterparts. In the first step, we condensate the tetraethyl orthosilicate (TEOS) monomer in the presence of cetyltriammonium bromide (CTAB) surfactant and rose Bengal (RB) dye to prepare helical mesoporous silica nanorods. Negatively charged RB molecules interact with the positively charged CTAB micelles to change their shape from spheres to helical mesostructured rods. Note that in the absence of RB common MCM-41 type mesoporous silica nanospheres were obtained. In addition, it is possible to tune the aspect ratio of nanorods by simply changing RB amount in the synthesis solution. In the second step, after the formation of initial particles, we added excess TEOS to form a thin silica layer around the particles. Finally, particles were calcinated at 550 °C to remove surfactant and RB molecules from the structure. Hierarchically porous nanorods or nanospheres were produced after the calcination process with microporous thin silica shells and mesoporous cores. Interestingly, mesoporous cores of the particles can be simply etched by stirring the particles in PBS (pH 7.4) solution for one day which results in hollow nanospheres and nanorods.

Membranes for ultrafiltration were prepared from polysulfone (PSf) composites with poly(1-vinylpyrrolidone) grafted silica nanoparticles (PVP-g-silica). For the synthesis of PVP-g-silica, hydroxyl terminated silica nanoparticles were reacted with (3-methacryloxypropyl)trimethoxysilane (γ-MPS) to form γ-MPS terminated silica nanoparticles (silica-MPS), which were further reacted with VP monomer. Formation of PVP-g-silica was confirmed by FT-IR, XPS, TGA, FE-SEM, and HR-TEM. PSf/PVP-g-silica membranes exhibited higher water flux than PSf membranes without any loss in solute rejection for membranes containing less than or equal to 5 wt% of PVP-g-silica. The water flux of a membrane containing 1 wt% PVP-g-silica was 2.3 times higher than that of PSf membrane. The hydrophilicity of the PSf/PVP-g-silica membrane also increased with increasing PVP-g-silica content. The hydrophilicity of the PSf/PVP membrane decreased with increasing retention time in a water bath, while the hydrophilicity of the PSf/PVP-g-silica membrane did not change with retention time. PSf/PVP-g-silica membranes exhibited enhanced fouling resistance in fouling experiments using nonionic surfactants.

We report the synthesis of compositionally asymmetric, core-Janus shell plasmonic nanostructures comprised of Au and Ag. Kinetic control was employed to achieve asymmetric shell growth on Au nanoparticles acting as cores. Subsequent differential surface functionalization of the nanostructures enabled programmed shell growth resulting in core-Janus shell nanostructures. UV/vis extinction spectra reveal that the localized surface plasmon resonance of the nanostructures depends on composition and distribution of the components, providing additional handles for tuning the optical properties of metal nanostructures. The core-Janus shell nanostructures demonstrated here are highly Raman-active making them attractive candidates for Raman-based biosensing and bioimaging applications.

Transparent amorphous oxide semiconductors (AOSs) are of great interest for low-cost smart windows and thin film transistors (TFTs) used in flat-panel displays. Creating AOSs that use inexpensive, low-temperature solution synthesis routes with the capability of large-area deposition are thus important. However, the formation of dense high-performance thin film semiconductors at low temperatures by conventional solution routes is challenging due to its use of organic ligands and large numbers of non-functional counterions. These organics and counterions often create porous films when combusted during the deposition, reducing device performances. New solution chemistry is essential to develop “ink-precursors” for high-performance films.
Here we report the electrochemical synthesis of InGaZn clusters using an aqueous precursor for solution-processed amorphous transparent IGZO thin films. The starting solution was prepared by dissolving In(NO₃)₃, Ga(NO₃)₃, and Zn(NO₃)₂ salts in nanopure water. A three-electrode electrochemical cell was used to synthesize clusters without utilizing additional chemical reagents. The working and counter electrodes were placed in the same beaker with the counter electrode enclosed in a medium fritted tube. A constant voltage was applied with respect to reference electrode to reduce the nitrate counterions as well as precisely control the solution pH during the cluster synthesis. The size and stability of the resulting cluster precursors were investigated using dynamic light scattering (DLS) in comparison to the starting salt solution. The electrolyzed precursors are stable for less than 2 h, displaying cluster radius of 0.8-1.0 nm. The optical, electrical, structural, and morphological properties of films, deposited from both cluster and salt solution precursors, were explored. These films are amorphous when annealed below 550 ^oC. SEM and XRR investigations indicate that the cluster films are uniform and crack-free with minimal thickness shrinkage due to thermal annealing. Electrical characterizations indicate that films made from cluster precursors have significantly larger mobility values than those from salt solutions. The best electrical properties are observed in a cluster film composed of In:Ga:Zn=0.4:0.4:0.2 annealed at 550 ^oC in air, yielding a Hall mobility of ~ 10 cm²/Vs and a carrier concentration of 10¹⁵ cm^-3. The TFT characterization using the IGZO film as an active channel layer will be performed in order to support the Hall effect results. This new method would allow for developing aqueous solution precursors to enable a variety of functional mixed-metal-oxide conducting/semiconducting films.

Optical micro-resonators composed of are designed, and fabricated on rare-earth doped thin films using sol-gel solution process. We evaluate the photoluminescence when the concentrations of Er dopant are modified from 0.1% to 5 %. We use finite difference time domain (FDTD) method to optimize the structures of our light emitting resonator, where a high Q factor of 105 is observed and used to enhance the photoluminescence efficiency due to the existing of a whispering-gallery mode. Optical emission spectrum between lambda; = 1.45 µm -1.65 µm and its enhancement factors are characterized by confocal microscopy. Our sol-gel synthesized micro-resonator can provide a small footprint light source for optical interconnect and integrated photonic circuits.

Here we present a shape recovery phenomenon of Pt-Ni bimetallic nanocrystals, which is unequivocally attributed to the defect effects. Further experiments and theoretical investigations indicate that the intrinsic defect-dominated growth mechanism allows the site-selective nucleation of the third metal M around the defects to achieve sophisticated designing of trimetallic core-shell structures (Pt₃Ni @ M, M=Au, Ag, Cu, and Rh). Trimetallic atomic steps in Pt₃Ni @ M as reactive sites could significantly improve catalytic performance, which are corroborated by several model reactions. The synthesis strategy based on our works paves the way for the atomic level design of trimetallic catalysts.

Here we developed a novel hydrothermal method by using alkali metallic nitride (LiNO3) as surfactant to synthesize tetragonal PbTiO3 octahedral-shaped nanocrystals (PT OCT). Systemically microstructure characterizations reveal that PT OCT nanocrystals with a size of 50~100 nm adopt a fascinating hybrid configuration, where tetragonal perovskite PTO crystalline core was surrounded by a lithium-concentrated amorphous thin layer of several nanometers in thickness. Under the mediation of the surfactant, the PT OCT nanocrystals were probably formed through an oriented attachment of primary particles [1]. In particular, such as-prepared nanocrystals demonstrate an excellent performance in the degradation of MB solution under visible light irradiation than the perovskite oxide systems in the emerged reports [2, 3], and the first-order kinetic constant for the PT OCT nanocrystals has been determined to be 0.042. On the basis of microstructure analysis and detailed catalysis experiments, it is proposed that the amorphous layer should be the position to generate electron-hole pair under visible light irradiation, while the electric polarization of ferroelectric core could significantly accelerate the carrier separation, leading to the unique catalytic property of PT OCT nanocrystals. The findings present here may offers an opportunity to design and explore novel high efficient visible photocatalyst by using ferroelectric nanomaterials.
Reference
[1] Jillian F. Banfield, Susan A. Welch, Hengzhong Zhang, Tamara Thomsen Ebert, R. Lee Penn, Science, 2000, 4, 289
[2] Feng Gao, Xinyi Chen, Kuibo Yin, Shuai Dong, Zhifeng Ren, Fang Yuan, Tao Yu, Zhigang Zou, Jun-Ming Liu, Adv. Mater. 2007, 19, 2889
[3] Xiaobo Chen, Lei Liu, Peter Y. Yu, Samuel S. Mao, Science, 2011, 331, 746

Much of the current research has been oriented towards lead-free piezoelectric materials, both in bulk, and due to requirements for miniaturization of electronic and micro-electro-mechanical devices, also in thin film form. (K0.5Na0.5)NbO3 (KNN) is one of the widely studied lead-free materials compositions which could replace lead-based piezoelectrics.
Due to the presence of two volatile alkali oxides, the KNN coating solutions should include an excess of alkalis to preserve the perovskite phase upon annealing. The thin films were prepared by spin-coating the acetate-alkoxide derived solutions with 0, 5 or 10 mole% sodium or potassium acetate excess, pyrolysis at 300 oC and rapid thermal annealing at 750 oC for 5 min. The amount of alkali excess in the solutions influenced the degree of {100} perovskite orientation, the monoclinic distortion of the unit cell, and the nucleation and growth processes of the films. The microstructure of about 250 nm thick films, prepared from the 5 mole% alkali excess solutions, consisted of fine equiaxed grains of about 50 nm across, whereas the films, prepared from the 10 mole% alkali excess solutions, were about 200 nm thick and consisted of columnar grains of about 200 nm across. The phase transitional behavior of KNN thin films was investigated by combined X-Ray Diffraction and Raman analyses. In the films with columnar grains, prepared from the 10 mole % alkali excess solutions, the Curie temperature was decreased as compared to the value reported for the powder, which was connected to the presence of tensile stresses arising from the thermal expansion mismatch between the substrate and the film, while the temperature of the monoclinic to tetragonal phase transition in the films closely corresponded to the powder value which was related to the evolution of a pronounced b-axis orientation. Furthermore, the exact values of the Curie point depended on the chemical composition of the films which was also reflected in different sizes of respective unit cells. In the films with fine grains, prepared from the 5 mole % alkali excess solutions, the phase transitions had a diffuse character, but they were nevertheless also evidenced by dielectric spectroscopy. The room temperature values of dielectric permittivity, dielectric losses, remnant polarization, and coercive field of the latter films, measured at 1 kHz, were 610, 0.015, 8 µC/cm2, and 80 kV/cm, respectively. The local leakage measurements by the conductivity-module atomic force microscope revealed that the film with fine grains exhibited a much higher resistance as compared to the film with large columnar grains, which was also confirmed by macroscopic I-V measurements. Furthmore, a local piezoelectric response of the films with a fine grained microstructure was confirmed by piezo-force module microscope.

Ternary system of 0.96((1-x)BiFeO₃-xPbTiO₃)-0.04Pb(Mn_1/3Nb_2/3)O₃ (x=0.3,0.31,0.32,0.33,0.34 and 0.35) were fabricated by conventional solid state reaction. XRD patterns revealed that all compositions possess pure perovskite structure with the coexistence of rhombohedral and tetragonal phases. Study of the dielectric properties indicated that the composition for x=0.33 shows the best performance of the experimental series with the dielectric constant and dielectric loss of 480 and 0.026 at 100 Hz. The dielectric-temperature measurement showed the Curie temperature of about 620 °C, which implied its potential in high temperature application. However, a big problem of pinched -like shape ferroelectric hysteresis loop for the ceramic needed to be solved. So, we also investigated the effect of thermal quenching on the ferroelectric properties. A more opened ferroelectric hysteresis loop could been achieved with remnant polarization as high as 6 mu;C /cm² at 90 kV/cm.

Large area transparent displays have been widely studied as next-generation displays because of its applications such as smart windows, transparent tablets, interactive white boards and so forth. To operate the transparent displays, it should be developed the transparent and high performance thin film transistors (TFTs) as switching or driving components. For this reason, various semiconductors such as indium zinc oxide and zinc tin oxide have been studied and introduced for high performance TFTs, but they require a high-gate bias operating voltage. Accordingly, many research groups have conducted studies using high K binary oxides as a gate insulator such as hafnium (Hf), zirconium (Zr), and yttrium (Y) based oxides to achieve high electrical capacitance and reduce operating voltage. However, binary oxide dielectrics have a tendency to crystallize and produce grain boundaries which can increase leakage currents. Herein, we demonstrated a simple fabrication with a solution-processed amorphous hafnium-lanthanum oxide (HfLaOx) gate insulator which has a dense and smooth layer with low leakage currents and high breakdown strength. The HfLaOx solution was easily prepared by mixing Hf and La precursors. Since Hf4+ has a different ionic radius and crystalline lattice phase with La3+, HfLaOx dielectric layers showed amorphous phase and high breakdown voltage as 5 MVcm-1. Also, HfLaOx dielectric layers showed the high dielectric constant above 22 in frequency range from 20 Hz to 100 kHz. For the electrical performance test of solution-processed HfLaOx dielectric layer, the TFT device with Si / 60 nm HfLaOx / 5 nm ZnO / 100 nm Al was fabricated. In ambient conditions, the solution-processed ZnO/HfLaOx TFTs, showed mobility with 1.6 cm2V-1s-1 under 5 V gate bias and 0.15 cm2V-1s-1 under 1 V gate bias. These results show the advantages and possibility of the solution processed amorphous HfLaOx dielectric layer as gate insulator for oxide TFTs. We believe that amorphous HfLaOx dielectric layer has a potential for next-generation and high performance electronic devices.

Low-dimensional nanomaterials, including nanowires and nanotubes, have received great attention due to their fascinating catalysis, optics and electronics properties. Among these nanomaterials, much attention has been paid to two-dimensional (2D) nanostructure materials because of their unique electronic, magnetic and storage properties.[1-3] Although a variety of simple compounds have been successfully synthesized, 2D free-standing single-crystal multicomponent oxide nanomaterials, such as ferroelectric oxides, have been rarely presented. In this work, free-standing single-crystal and single-domain PbTiO3 (PT) nanoplates have been synthesized by a facile hydrothermal method.[4,5] XRD results suggest that these nanoplates are indexed to a pure tetragonal perovskite PT structure. Microstructures characterization of SEM, TEM, DC-EFM and HRTEM demonstrate that these PT nanoplates have a rectangular outline, side length of 700~1100 nm, height of ~150 nm, grow along ab plane of tetragonal perovskite structure and {001} facets as the top and bottom surfaces are exposed. “Self-templated” crystal growth process is proposed to discuss the formation mechanism for PT nanoplates under hydrothermal conditions. The formation of PT perovskite structure nanoplates is suggested to toughly relate with the lead oxides/titanium dioxide nanoplates. DC-EFM results reveal that the free-standing PT nanoplate has ferroelectric single-domain structure and writing and reading manipulation of polarization area within such nanoplates has been realized. These free-standing single-crystal and single-domain PT nanoplates prepared by a facile hydrothermal method are desired objects for understanding the morphology and size effect on ferroelectricity at nanoscale and offering the opportunity for nanodevice application.
Reference
[1] C. Schliehe, B. H. Juarez, M. Pelletier, S. Jander, D. Greshnykh, M. Nagel, A. Meyer, S. Foerster, A. Kornowski, C. Klinke, H. Weller, Science, 2010, 30, 550-553.
[2] D.Y. Wang, Y. J. Kang, V. D. Nguyen, J. Chen, R. Küngas, N. L. Wieder, K. Bakhmutsky, R. J. Gorte, C. B. Murray, Angew. Chem. Int. Ed., 2011, 50, 4378-4381.
[3] A. Yella, E. Mugnaioli, M. Panthöfer, U. Kolb, W. Tremel, Angew. Chem. Int. Ed., 2010, 49, 3301-3305.
[4] C.Y. Chao, Z.H. Ren, Y.H. Zhu, Z. Xiao, Z.Y. Liu, G. Xu, J.Q. Mai, X. Li, G. Shen, G.R. Han, Angew. Chem. Int. Ed., 2012, 51: 9283-9287.
[5] C.Y. Chao, Z. H. Ren, S. M. Yin, S.Y. Gong, X. Yang, G. Xu, X. Li, G. Shen, G. R. Han, CrystEngComm, 2013, 15, 8036-8040.

BaTiO₃, a ferroelectric at room temperature, has many attractive applications such as a high-k dielectric in microelectronics, as transducers and in multiferroic composites. In thin film geometries of sub-micron thicknesses, it is possible to decrease operation voltages which makes this material especially suitable for memory usage in computer applications[1]. Particle based solution deposition is advantageous for thin film fabrication and allows control over the particle size and crystallinity. In addition, the easy scaling up possibilities, fast and cheap film deposition are attractive. In this study, BaTiO₃ films based on sequential spin coating of nanoparticle dispersions have been manufactured. The BaTiO₃ nanoparticles are produced via efficient microwave assisted non-aqueous sol-gel route followed by spin coating. In between each spin coating step, intermediate drying has been applied to optimize the thickness and the removal of organics. It is of crucial importance to optimize the microstructure of the films in terms of thickness and prevention of macro-crack formation relative to the organics involved and drying procedure. For this, thermogravimetric analysis and confocal Raman microscopy are applied in order to monitor and optimize the drying procedure. After reaching the desired thickness, films are sintered for compaction and adhesion. Microstructural characterization of the films is done via high resolution scanning electron microscopy, X-ray reflectometry and atomic force microscopy. Electrical properties are revealed via conductivity versus temperature and impedance measurements. The films are several hundred nanometer thick, crack-free and with roughness values below 1 nm. UV-vis measurements indicate that they are at least 99% transparent in the visible range. From electrical measurements, it is understood that films possess high dielectric permittivity. In summary, crack-free BaTiO₃ films of high uniformity and low roughness have been produced using nanoparticle dispersions made via non-aqueous sol-gel route. Owing to the advantages of this process such as controlled crystallinity, stoichiometry and dispersions on a nanoscale, sub-micron films of superior properties could be realized. Another highlight of this study is the monitoring and optimization of the drying process, which contributed to the crack-free and highly insulating microstructure of the films.
References
[1] Spaldin N., Introduction to the Theory of Ferroelectrics 2011. p. 195-200.

The highest performing piezoelectric materials include lead as a major constituent. Worldwide, increased restrictions on the use of lead have resulted in a search for candidates to replace these lead-based piezoelectric materials. One promising material is the solid solution of (Bi_0.5Na_0.5)TiO₃ - (Bi_0.5K_0.5)TiO₃ (BNT-BKT). Although promising behavior has been observed in bulk materials, similar results have been elusive for BNT-BKT thin films. In this work, 0.8 BNT - 0.2 BKT thin films (near morphotropic phase boundary composition) were synthe-sized on platinized silicon substrates via chemical solution deposition. Well-crystallized BNT - BKT thin films were grown at varying processing conditions. Phase purity was confirmed by X-ray diffraction. As Bi, Na, and K are volatile elements, overdoping of these cations (addition of excess cation precursors) was introduced to compensate for volatilization during synthesis. Quantitative compositional analysis of films was performed with electron probe microanalysis and compositional depth profiling to confirm atomic ratios via X-ray photoelectron spectroscopy. The composition data from both measurements were consistent and indicated stoichiometric films were achieved. Dependent on the overdoping and annealing conditions, dense, smooth, crack-free films were achieved with relative dielectric constants from 390 to 730 and low dielectric loss of 2 - 5% at 1 kHz. Additionally, maximum and remanent polarizations of 45 and 16 µC/cm², respectively, were recorded at 200 Hz. The addition of Bi(Mg_0.5Ti_0.5)O₃ (BMgT) was also explored, as promising piezoelectric response (high field d₃₃ up to 600 pm/V) in bulk compositions has been observed. BNT-BKT-BMgT thin films were prepared, showing very promising piezoelectric response with d_33,f up to 75 pm/V and strain values up to 0.35%, as measured by double beam interferometry. Finally, Rayleigh analysis was completed on several Bi-based thin film compositions to extract the intrinsic and extrinsic contributions to the dielectric properties.

Solution processing is a promising method for manufacturing large-area low-cost electronic devices. High performance metal oxide semiconductor-based field-effect transistors can be fabricated by solution processing methods. For applications of flexible electronics, a low processing temperature is required to avoid overheating of the substrate material. It is a challenge to fabricate a dense impurity-free oxide semiconductor film at a temperature which is lower than the softening temperature of plastic substrates. To decrease the processing temperature of zinc oxide (ZnO) thin film, a water-based ZnO precursor with ammine-hydroxo complex [Zn(NH3)x](OH)2 was introduced several years ago. However, repeated time-consuming centrifuge and decantation steps are required to remove impurity ions from the precursor.
To simplify the processing steps we discovered a new strategy to prepare aqueous ZnO precursor. Based on this precursor, ZnO field-effect transistors (FETs) with a benchmark dielectric SiO2 have been fabricated at 200 °C. The transistors exhibited promising performance with a saturation field-effect mobility of 0.7 cm2V-1s-1 and a typical on/off current ratio on the order of 1E4. The simple processing route is only composed of two steps: The first step is to dissolve zinc nitrate hexahydrate and acetylacetone in ammonium hydroxide and stir vigorously at room temperature for 20 hours. As-prepared precursor has a zinc molar concentration of 0.6 M. The second step is to filter the as prepared precursor and dilute it with ultra pure DI water.
Thermal properties of the low temperature ZnO precursor were analyzed by differential scanning calorimetry (DSC). In the DSC diagram, a precursor conversion temperature appeared at about 170 °C, and there are no peaks observed in the region between 170 °C and 220 °C. This result suggests a complete conversion from ammine-hydroxo precursor to solid ZnO thin film at a temperature lower than 200 °C. Excellent crystallinity was shown in the 200 °C processed ZnO thin film. A sharp (002) peak is shown in the X-ray diffraction pattern, and this demonstrates a wurtzite crystal structure with a preferred growth along the c-axis.
Various types of solution processed high-k dielectric materials, such as alkali metal ion incorporated aluminas and zirconium oxide, have been used to decrease the ZnO FETs operation voltage to 2 ~ 5 V. The high-k dielectrics exhibited a good compatibility with our low temperature ZnO precursor and excellent transistor performance has been achieved in these devices. With this discovery, we are able to fabricate low temperature low voltage transistors on plastic substrates such as polyimide. This simple low temperature ZnO precursor could also be applied to fabricate flexible inverters with a combination with p-type solution processed polymer semiconductors, such as PBTTT and TIPS-pentacene.

Amorphous oxide semiconductor(AOS) thin film transistor is very attractive in these days for their importance in the field of display application due to their high mobility and stability even in thin film type and amorphous phase. It is reported that indium ion can offer charged free electron to active channel layer of oxide TFTs in order to achieve high field effect mobility, because indium has the route of carrier transport in AOS systems, which provide sufficient electrons to active channel layers. We have investigated and compared silicon-included oxide thin films under various silicon ratios.
In this study, we focused on the effects of the silicon in amorphous oxide TFTs fabricated by a sol-gel method. The solution process is alternative deposition method in thin film transistors. Active channel layer was deposited by the spin coating method. We investigated the role of Si on the mobility and stability of solution processed oxide TFTs.

Nanoporous materials that are also electrically conducting would create exciting new possibilities in sensing, electrocatalysis, photovoltaics, and molecular-scale electronics. We demonstrate this can be achieved using a Metal-Organic Framework (MOF) infiltrated with redox-active TCNQ molecules. MOFs are crystalline supramolecular materials comprised of metal ions linked by rigid organic ligands. As a result, they possess exceptional synthetic versatility and have highly ordered structures compared with amorphous materials such as conducting porous carbon. Guest TCNQ molecules in the copper-containing MOF HKUST-1 produce air-stable Ohmic conductivity, tunable over six orders of magnitude and with values as high as 7 S/m. Periodic calculations using density functional theory demonstrate that a continuous chain of TCNQ molecules bridging MOF coordination sites is feasible, leading to a delocalized system with an extremely low energy barrier to conductivity. These results suggest strategies for creating isoreticular families of porous conducting MOFs.

It is difficult to obtain a transparent medium with a superhydrophobic coating that has high optical quality, mechanical durability, and can be fabricated at large scale with good uniformity. Traditional superhydrophobic coatings are soft in nature, with a Teflon-like surface chemistry, which results in reduced adhesion and durability. By combining vapor phase deposition together with wet chemical processes to produce differentially-etched, nanostructured glass materials, we have overcome many of these common problems. Here we describe the formation of atomically bonded, optical-quality, nano-textured thin glass film coatings on glass plates, utilizing phase-separation by spinodal decomposition in a sodium borosilicate glass system. As formed, these coatings are structurally superhydrophilic (i.e., display anti-fogging functionality) and demonstrate robust mechanical properties. After appropriate chemical surface modification, they exhibit exceptional superhydrophobic performance with water droplet contact angles reaching as high as 172^o. As an added benefit, in both superhydrophobic and superhydrophilic states these nanostructured porous surfaces can block ultraviolet (UV) radiation and can be engineered to be anti-reflective with broadband and omnidirectional transparency. Moreover, by changing the chemical affinity of the surface, omniphobic functionality of these films (i.e., repellency against various liquids) is also demonstrated.

We have recently developed a method for selectively growing silver nanoplates within the confines of hollow nanostructures, utilizing a previously developed seeded synthetic approach to achieve the selective deposition of silver on the edges of nanoplate seeds, leading to exclusively lateral growth. Although previous studies have demonstrated the templated growth of nanomaterials, these nanoparticles typically grow isotropically and their shape conforms exactly to that of their container. In our study, we use the anisotropic growth of silver nanoplates within hollow nanopsheres to observe the effects of physical confinement on an anisotropically grown nanomaterial. By combining an anisotropic synthetic technique with a template, we are able to achieve unique control over the silver plate synthesis.
By coating small silver nanoplates with a sacrificial silica template using a modified Stöber method, followed by a subsequent coating of titanium dioxide and removal of the template via base etching, we can obtain hollow titania spheres containing small nanoplates. In order to stabilize the silver plates against etching by ammonia during the initial silica coating step, a thin layer of gold is deposited on the plate edges prior to coating. Using a controlled seeded growth technique, we can then grow the plates laterally until their edges reach the walls of the template, at which point the plates become circular due to the spherical shape of the titanium dioxide shell. Depending on the strength of the container walls, further plate growth results in silver deposition on the plate face or the “escape” of a small portion of the plate which can break through the wall and seed further plate growth around the hollow container. This work demonstrates the potential of combining anisotropically grown nanoparticles with a template, which opens up a number of interesting possibilities for new nanoscale synthetic techniques.

Ion exchange has emerged as an effective technique to modify as-synthesized colloidal nanoparticles by transforming them into structures that are not easily achieved by conventional synthetic methods. Here, we demonstrate novel pathways to tune the composition of nanoparticles through ion exchange in nanoparticles.
Firstly, we present our recent work on anion exchange from CoO into Co₃S₄ nanoparticles. Anion exchange in nanoparticles is much more rare than for cation exchange. Previous reports show that the reactivity is considerably lower for the few reported anion exchange reactions and temperatures higher than 200 oC or reaction times longer than 6 hours are commonly required. The low reactivity of the anion exchange reactions may be due to the low reactivity of the precursors. In this work we find that ammonium sulfide ((NH₄)₂S) is an effective precursor for low-temperature (70 °C) anion exchange reactions. (NH₄)₂S exhibits high reactivity as a sulfide reagent in the anion exchange reaction transforming hollow CoO into hollow cobalt sulfide nanoparticles. The overall nanoparticle morphology (spherical and hollow) is retained in the transformation. The faster diffusion of Co²⁺ and O^2minus; than the incoming S^2minus; during the anion exchange causes a significant expansion of the nanoparticle voids. This low temperature (70 °C) anion exchange reaction produces amorphous cobalt sulfide nanoparticles with Co:S ratio of ~3:4, which are converted into crystalline nanoparticles with a major phase of cubic Co₃S₄ by annealing at high temperature in an organic solution. The use of this low-temperature precursor to facilitate anion exchange in nanoparticles should enable new avenues for solid-state chemical tailoring of nanoparticles.
Secondly, we demonstrate the chemical transformation from copper sulfide to wurtzite zinc sulfide (ZnS) and cadmium sulfide (CdS) via cation exchange. During this transformation, heterostructures symmetrically form due to their similar sulfur sublattices between {100} planes of the starting copper sulfide and {001} planes of wurtzite ZnS/CdS. By controlling the reaction time, the 2-dimensional copper sulfide layer in the center can be tuned to widths between 1 nm and 10 nm, confined between two regions of ZnS. Upon full conversion the zinc sulfide nanoparticles become single crystalline and preserve the original shape and size of the starting copper sulfide nanoparticles. These heterostructured nanoparticles show surface plasmon resonance due to the intrinsically high carrier concentration of copper sulfide phase. This plasmon resonance can be tuned over a broad range from 1270 to 1800 nm by controlling the thickness of the 2D confined copper sulfide layer.
This work demonstrates novel routes to composition control in nanoparticles through chemical transformation.

Innovative low temperature approaches open access to new compounds and optimize the synthesis of known materials in terms of purity, yield, and efficiency.
Classically - and often used in industrial processes - inorganic solids, such as ceramics and alloys are produced at temperatures up to 2000 °C within hours and days. Looking for new materials this is a significant constraint, since high-temperature processes typically yield thermodynamically stable phases only. Often undesirable secondary phases, which can hardly be separated, emerge during cool down. Nano-structuring or directing of morphology are nearly impossible, although these aspects can be crucial for the chemical and physical properties. Moreover, the energy efficiency of such high temperature methods is low. Several solution-based alternatives at low temperatures have been developed during the last century. Two of the most recent are the use of ionic liquids as a flux and the microwave-assisted polyol process.
Ionic liquids are salts that melt below 100 °C. They combine many useful attributes of classic salt melts and molecular solvents: high polarity, wide liquid range, negligible vapor pressure, large electrochemical window, and thus remarkable redox stability. Various combinations of cations and anions allow modifying their physical (e.g. conductivity, diffusion) and chemical properties (e.g. polarity, acidity). We used Lewis-acidic ionic liquids for the synthesis of low-valent main group and transition metal compounds. These one-pot reactions proceed at or slightly above room temperature and are much faster than the hitherto used high temperature routes. Nonetheless, yields and phase-purity are typically very good. In addition, unusual new compounds became available, such as an unconventional one-dimensional superconductor on the basis of a partially reduced π-stack of aromatic tellurium squares. The excellent solubility of metal-rich species in ionic liquids also allows excision of high-temperature structural fragments of complex solids as a source for new compounds. For example, we were able to mobilize a 23-atomic cluster from a conventionally synthesized metal-rich compound and to recrystallize it in a modified form.
Another low-temperature method is the microwave-assisted polyol process. We adapted it for the synthesis of nanoparticles of intermetallics, which can hardly be accesses by other methods. Surfactant properties of the solvent, homogeneous heating, and the interaction of the metallic seeds with the microwaves result in very high yields, small particle size distributions, and well-shaped isolated crystallites. Remarkable surface-related properties were found: Nano-BiRh proved to be a superior catalyst for the semi hydrogenation of acetylene to ethylene. Nano-Bi₃Ni shows rare coexistence of ferromagnetism and superconductivity. Nano-Bi₃Ir reversibly intercalates oxygen at room temperature, forming the first room temperature fast oxide ion conductor.

The coating of TiO2 shells onto sub-micron sized particles has been widely studied in recent years with much success occurring in the coating of templates with sizes above 50 nm. Direct coating on particles below this size has been difficult to attain especially with good control over properties such as thickness and TiO2 crystallinity. Here we demonstrate a mixed solution of titanium n-butoxide and ethylene glycol to create a titanium-glycolate coating on aqueous nanoparticles. Direct coatings on metal nanoparticles such as gold and silver can be easily achieved with a corresponding shift in the surface plasmon resonance. Additionally, coatings on larger microspheres such as SiO2 and polymer spheres can be done through a simple extension of this method. Further the thickness of these coatings can be tuned from a few nanometers to ~30 nm through subsequent coatings. This coating can subsequently be crystallized into TiO2 through refluxing in water for low crystallinity or calcination to obtain highly crystalline shells that show good activity for the photocatalytic degradation of Rhodamine B. This procedure can be very useful for the production of TiO2 coatings with tunable thickness and crystallinity as well as for further study on the effect of TiO2 coatings on nanoparticles.

Colloidal nanocrystals exhibit exciting physiochemical properties useful for energy storage and conversion. Their practical implementation in devices has been limited by the presence of insulating organic ligands on their surfaces. These ligands can be removed chemically or thermally for nanocrystal films supported on solid substrates. However, this results in films with extensive cracking, gross mesoscale disorder, and generally requires multiple rounds of deposition and stripping due to inefficiencies in mass diffusion through thicker films. As such, it is highly desirable to develop surfactant-free nanocrystal inks for single-step deposition of conductive nanocrystalline films from stable dispersions. To this end, we will report our recent results in ink processing, leveraging our mechanistic understanding of nanocrystal-ligand structure and bonding. This understanding has led to successes in ligand-stripping chemistries that yield dispersible nanocrystal inks for large-area deposition of active layers for energy devices. We highlight important differences in stripping outcomes based on the bonding character of different nanocrystals, and demonstrate the first stable dispersions of cationic lead chalcogenide nanocrystals. This allows for single-step deposition of highly uniform, conductive thin films of nanocrystals, along with solution-phase directed assembly for controlling mesoscale architecturing. The resulting functional materials have applications in energy storage and conversion, and recent work in this area will also be presented.

A significant issue related to Pd-based catalysts is that sulfur containing species, such as alkanethiols can form a PdSx underlayer on nanoparticle surface and subsequently poison the catalysts. Understanding the exact reaction pathway, the degree of sulfidation, the chemical stoichiometry and the temperature dependence of this process is critically important. Combining energy-filtered transmission electron microscopy (EFTEM), X-ray diffraction (XRD), and X-ray Absorption Spectroscopy experiments at the S K-, Pd K- and L2,3- edges, we show the kinetic pathway of palladium nanoparticle sulfidation process with the addition of excess amount of octadecanethiol at different temperatures, up to 250°C. We demonstrate that the initial polycrystalline Pd-oleylamine nanoparticles gradually become amorphous PdSx nanoparticles, with sulfur atomic concentration eventually saturating at Pd/S=66/34 at 200°C. This final chemical stoichiometry of the sulfurized nanoparticles closely matches that of the crystalline P16S7 phase (30.4% S), albeit being structurally amorphous. Sulfur diffusion into the nanoparticle depends strongly on the temperature. At 90°C, sulfidation remains limited at the surface of nanoparticles even with extended heating time; whereas at higher temperatures beyond 125°C, sulfidation occurs rapidly in the interior of the particles, far beyond what can be described as a core-shell model. This indicates sulfur diffusion from the surface to the interior of the particle is subject to a diffusion barrier, and likely first go through the grain boundaries of the nanoparticle.

Metal organic frameworks (MOFs) are hybrid inorganic-organic materials possessing crystalline structure with high porosity. MOFs have attracted significant attention due to their various applications as luminescent materials, advanced gas absorbers, sensors etc. Rare earth based MOFs are best known for their excellent luminescence properties 1
Although reports on mechanochemical synthesis of organometallic compounds dates back to 2002, the synthesis of MOFs using this approach was not reported until 2006. Since then there has been intense research activity on MOFs synthesis using this approach.1 Till 2012, all reported mechanochemical synthesis of MOFs involved liquids which were either added externally to assist grinding or were generated in-situ as by-products.
In present study, we report on the mechanochemical synthesis of rare earth based MOFs using metal hydrides as precursors. By performing the differential scanning calorimetric (DSC) measurements on the precursors (trimesic acid and yttrium hydride) milled for various durations, we unambiguously demonstrate that MOFs can be synthesized through a true solid state process and liquids can be excluded completely. Also, the variations in the latent heat associated with melting of trimesic acid in the reaction mixtures milled for varying durations reveal a linear dependence of the mechanochemical reaction on milling time. The possible mechanism of mechanochemical transformation along with the effect of variations in the milling conditions will be discussed.

The uniform Cu2O nanocubes with a {100} side face and various sizes (30~80 nm) were synthesized by reducing Cu(OH)2 using ascorbic acid via the assistance of sodium citrate. The sodium citrate plays an important role as chelating agent to retard the formation of copper hydroxide (Cu(OH)2), that is, reducing the neucleation rate of Cu2O seeds.1 The edge length of the Cu2O nanocubes is found increasing when more citrate ion in the growth media. The mass of the products formed in each batch reached 250 mg, strongly suggesting this method can be easily scaled up. The Cu2O nanocubes with theoretical capacity (375 mA h g-1) was used as anodes in lithium ion batteries. The one with an edge length of approximately 80 nm exhibit good lithium storage behavior in EC/DEC/DMC electrolyte. It shows a high reversible discharge capacities of 420 and 236 mA h gminus;1 at a rate of 0.2 and 1 C after 50 discharge-charge cycles, respectively. The electrode also shows a high stability when the discharge-charge rate was up to 3 C. This result reveals the great potential of using Cu2O nanocubes as an anode material in Li-ion batteries.
Keywords: Cuprous oxide, Nucleation-controlled, Chelating, Nanocube, Li-ion battery
Reference:
(1) Chang, I.-C.; Chen, P.-C.; Tsai, M.-C.; Chen, T.-T.; Yang, M.-H.; Chiu, H.-T.; Lee, C.-Y. Crystengcomm 2013, 15, 2363.

In this work, tin oxide nanostructures are synthesized by hydrothermal approach using SnCl2 and NaOH in deionized water/alcohol mixtural solution under different time and temperature. The product obtained after 24 h is composed of SnO microcrystal and Sn3O4 nanosheets. Nanosheets consist of SnO and Sn3O4 with thickness in the range of 50~60 nm can be acquired when polyvinylpyrrolidone (PVP) is added as exfoliating agent during the synthesis process. The aggregation of pure phase Sn3O4 nanosheets can be obtained when the deionized water/alcohol ratio is one and the reaction time is extended to 30 h. Since seldom researches apply Sn3O4 on lithium ion battery, we try to use the aggregated Sn3O4 nanosheets as an anode material of lithium ion batteries and have a reversible discharge capacity (228 mAhg-1) at a certain discharge- charge rate (0.3C) after 30 cycles by using EC/EMC/DMC ( volume ratio=1:1:1) as electrolyte.

Here we report a facile, solution-phase route to the synthesis of nickel-manganese nanosheets with a layered double hydroxide (LDH) structure in a high yield based on a reverse micelle method. These nanosheets were synthesized by reacting nickel(II) chloride with manganese(II) acetate in xylene with oleyl amine and oleic acid as surfactants. It was found that the addition of both nickel(II) chloride with manganese(II) acetate is prerequisite for the formation of LDH nanosheets. The resulting Ni-Mn LDH nanosheets exhibited very high specific capacitance (1061 Fg-1 at 5 mVs-1), as well as excellent cycling stability in the application as electrode materials for supercapacitors.

High-energy laser (HEL) systems have unique material requirements for both the exit aperture window and the lasing medium. Recently, we demonstrated a record low absorption loss of 6 ppm/cm and superior ruggedness for transparent magnesium aluminate spinel ceramic which positions it as a prime candidate for an exit window aperture for high energy laser systems. We also reported lasing with an efficiency of about 74% in transparent Yb3+:Lu2O3 ceramic made by hot pressing high purity submicron co-precipitated powder. Here, we present our recent results on the development of Yb3+ and Ho3+ doped Lu2O3 or Y2O3 high purity metal oxide ceramic nano-powders for high power solid state laser gain media and in the evelopment of a MgAl2O4 spinel window as a laser exist aperture. We further report on the synthesis of various doped/undoped, high purity metal oxide nano-powders suitable for ceramics in HEL applications. Details of purification, such as re-crystallization of precursors and post-treatment of the resulting powder, are presented. Effect of the powder quality and fabrication process on optical quality of these ceramics is also discussed.

Platinum (Pt) and palladium (Pd) based nanoparticles (NPs) have been studied extensively as anodic and cathodic catalysts in polymer electrolyte membrane fuel cells (PEMFCs). Incorporating another metal with Pd or Pt enhances both catalytic activity and stability of the materials in fuel cell conditions. There have been numerous reports detailing different synthetic routes for nanomaterials, but there are no reports of a generalized synthesis capable of yielding a series of M-Pd NPs (M = Fe, Co, Ni, Cu). Here, we report our progress on a new approach to synthesize 3.5 nm NPs by inducing nucleation at 100 °C with borane-tert butylamine in the presence of oleylamine. By slightly altering the reaction conditions, we can synthesize monodisperse Pd and M-Pd NPs. The composition of the NPs can be tuned by altering the starting metal precursor ratios. The as-synthesized M-Pd NPs were supported on Ketjen carbon, annealed at 150 °C, and evaluated as catalysts for the formic acid oxidation reaction (FAOR). Among the series of M-Pd catalysts evaluated, all MPd catalysts displayed higher specific and mass activity than the monometallic Pd. The CuPd NPs were the most active, with the Cu30Pd70 composition showing the greatest mass activity of 1192.9A/gPd reported for Pd alloy NPs. Using these NPs as a platform for a Pt coating provides a new series of materials to be studied as potential cathodic catalysts for the oxygen reduction reaction. We also report our recent synthetic methods using a seed mediated route in which the 3.5 nm M-Pd NPs are coated with a FePt coating using platinum (II) acetylacetonate and iron pentacarbonyl as the metallic precursors. We will discuss optimal coating thickness and compositions for the ORR.

The uniform and various-sized BaTiO3 (BTO) nanoparticles were synthesized with controlling concentration of NaOH (1, 3, 5, 7 M) by hydrothermal method. As the concentration of NaOH in the solution are increased from 1 to 7 M, the size of BTO nanoparticles decreases from 150 to 20 nm. Furthermore, the synchrotron radiation X-ray data reveals that tetragonal phase in 7 M (20 nm in size) BTO nanoparticles is 57% higher than 39% in 1M (100 nm) nanoparticles by Rietveld refinement. In addition, the 305 cm-1 and 720 cm-1 peaks in Raman spectra also demonstrate that the synthesized BTO nanoparticles are tetragonal phase with P4mm space group. In this work, these BTO samples obtained in basic (pH11) environment show good photocatalytic activity of methylene blue degradation compared to BTO obtained in acid (pH3) and neutral (pH7) environment.

Using the as-prepared SiO2 aerogels via ambient pressure drying as carriers, silica aerogel/WO3-TiO2 composite photocatalytic materials were synthesized by hydrothermal method. The microstructure, morphology and pore characteristics of the obtained silica aerogel/WO3-TiO2 composite particles were studied by X-ray diffraction, electron microscopy and Brunauer-Emmerr-Teller (BET) N2 adsorption-desorption analysis, and the adsorption/photocatalytic degradation for Rhodamine B of the products was investigated. The results indicate that the specific surface area and pore volume of the obtained silica aerogel/WO3-TiO2 composite particles increased with the increase of silica aerogel content. As for the samples with 4.5~41.5 wt% silica aerogel content, the specific surface area, pore volume and pore diameter of the obtained silica aerogel/WO3-TiO2 composite particles were 85~262 m2/g, 0.43~1.11 cm3/g and 13.62~20.00 nm, respectively. The adsorption/photocatalytic experiment indicates that increasing the content of silica aerogels is favorable for improving the adsorption ability of the product, but slightly to the disadvantage of photocatalytic degradation. However, almost all the products exhibited better integrated adsorption/photocatalytic activity than that of the pure WO3-TiO2 samples. Particularly, the silica aerogel/WO3-TiO2 composite samples exhibit much higher adsorption/photocatalytic degradation velocity than the pure WO3-TiO2 samples. The influences of silica aerogels content on the microstructure, pore characteristics and adsorption/photocatalytic activity of the products were emphatically discussed, and the adsorption/photocatalytic degradation mechanism for Rhodamine B was discussed.

Functional materials with improved properties can be fabricated by the coupling of different materials in one nanostructure. In this presentation, we describe the synthesis of TiO2/carbon and Pt-TiO2/carbon nanocomposites by simple and fast microwave-assisted solution routes, their characterization and performance as acid catalysts [1] or electrochemical sensors [2]. Titanium dioxide nanoparticles were preferentially grown on the surface of reduced graphene oxide (RGO) and carbon black (CB) in a few minutes by combining the use of microwave heating with the “benzyl alcohol route”. Platinum nanoparticles could be further deposited onto the metal oxide/carbon nanostructures. The resulting heterostructures were characterized by a wide variety of techniques, including XRD, HRTEM, Raman and XPS, which revealed that the carbons were coated with 8-9 nm anatase particles and ca. 2 nm platinum (for the ternary structures). The TiO2/RGO and TiO2/CB materials were found to be efficient and stable catalysts for the production of valuable compounds from renewable carbohydrate biomass. These materials catalyze the aqueous-phase dehydration of xylose into furfural with high yields (67-69 %) at high conversions (95-97 %). Furthermore, the catalysts could be recycled several times without loss of activity. A Pt-TiO2/RGO composite was applied for the fabrication of a simple non-enzymatic amperometric sensor for H2O2 detection. The sensor allows the detection of this toxic compound with a linear response from 0 to 20 mM of H2O2 and a sensitivity of 40 µA mM-1 cm-2, and is also suitable for the determination of H2O2 concentration in milk.
References:
[1] P.A. Russo, S. Lima, V. Rebuttini, M. Pillinger, M.G. Willinger, N. Pinna, A.A. Valente, RSC Adv. 2013, 3, 2595.
[2] S. G. Leonardi, D. Aloisio, N. Donato, P. A. Russo, M. C. Ferro, N. Pinna, G. Neri, ChemElectroChem 2014, DOI:10.1002/celc.201300106

Controlling the shape, size and orientation of zinc oxide (ZnO) nanostructures is one of the most interesting topics in modern materials science since the novel properties of ZnO depend on their size, shape, and crystalline structure. A wide variety of ZnO morphologies e.g. nanowires, rods, plates, stars, flowers, rings, and spheres were reported for their precipitates and thin films. ZnO nanostructures are promising candidates for various applications such as in light-emitting devices, dye-sensitized solar cells, and catalysts and more.
In this study, we succeeded in synthesizing ZnO hollow microspheres by solvothermal process without using the template and applied them to the photo-anode in dye sensitized solar cells. ZnO hollow microspheres were synthesized as follows. 3 mmol of zinc acetate dihydrate and 12 mmol of HMT were dissolved in 30 ml of mixed solution of EG (95 vol%) and distilled water (5 vol%). It was transferred into a 35 ml Teflon-lined stainless steel autoclave, followed by heating in an oven at 150°C for 12 h.
The diffraction peaks in XRD patterns had good agreements with those of the hexagonal würtzite structure of ZnO (JCPDS card 36-1451). No other diffraction peaks were detected suggesting the formation of pure ZnO. SEM images revealed that obtained samples were hollow microspheres 2-3 mu;m in size and high-resolution TEM image revealed that c-plane of ZnO crystal was exposed to the surface of ZnO hollow microspheres.
The as-prepared ZnO hollow spheres were used as a photoanode in dye-sensitized solar cells and a power conversion efficiency of 0.86 % was obtained for the electrode heat treated at optimal temperature of 500°C. The conversion efficiency was improved by UV treatment of as-prepared ZnO hollow microspheres, and a power conversion efficiency of 1.05 %, a short-circuit current density of 2.25 mA/cm2, an open-circuit voltage of 703 mV, and a fill factor of 0.67 was attained under AM 1.5 G one sun (100 mW/cm2) illumination.

To overcome the problems related to the continuously rising of oil prices and global warming due to the CO2 induced greenhouse effect, there is a pressing need to develop technologies to produce carbon free renewable fuels. A two-step solar thermochemical H2O and/or CO2 splitting process which utilizes mixed valence metal oxide i.e. ferrite based redox reactions is one of the ways of producing solar fuels such as solar H2 or renewable precursors for fuels such as solar syngas (a mixture of H2 and CO). In this process, the first step consists of the endothermic reduction of ferrite at elevated temperatures by releasing O2. The second step corresponds to the oxidation of the reduced ferrite by H2O, by CO2, or by the mixture of the two producing H2, CO or syngas. As, the current research trends in solar thermochemical community are focused towards high and constant levels of solar fuel production in multiple cycles, it is believed that nanosized ferrites derived via sol-gel method will significantly improve the production of solar fuels. Sol-gel derived ferrite nanoparticles with high specific surface area (SSA) are believed to be potential candidates to overcome the diffusional limitations associated with this process and will provide more active sites for solar thermochemical reactions to occur resulting into elevated production levels of solar fuel. In this study, Ni-ferrite and Co-ferrite with nanoparticle/porous morphology and high specific surface area (SSA) were synthesized using a sol-gel method. The metal precursors were dissolved in ethanol and the mixture was sonicated for 15 to 20 minutes, until a visually clear solution was obtained. To this solution, a predetermined amount of propylene oxide was added and the solution was set aside for the formation of gel. As-synthesized gels were aged for 24 h and heated rapidly in a muffle furnace upto different temperature in air and quenched. The calcined powder was characterized using powder X-ray diffraction, BET surface area analysis, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The synthesized ferrite powders were further tested for their ability to produce solar fuels by performing multiple thermal reduction / oxidation (in presence of CO2) cycles in a high-temperature thermogravimetric analyzer (TGA). The ferrite powder was thermally reduced at 1400 - 1450oC while the oxidation was performed at different temperatures. O2 and CO release was monitored by gas chromatography.

Facet of metal alloy plays an important role in determining the catalytic activity and selectivity. Shape-controlled synthesis of metal alloy nanocrystals in solution phase has attracted increasing attention due to their use as highly active heterogeneous catalysts in fuel cells, batteries, and other alternative energy conversions.1 Recent studies based on the single crystal extended surfaces show that the Pt3Ni (111) facets are the most active sites for electrocatalytic reduction of oxygen. Recently, we developed a Gas Reducing Agent in Liquid Solution (GRAILS) method for making uniform cubic, octahedral and icosahedral Pt alloy nanocrystals in non-aqueous solutions using carbon monoxide (CO) gas along with long carbon chain amines and carboxylic acids.3-5
In this presentation, we show that this GRAILS method can be a powerful platform technique for making a variety of Pt alloy nanostructures that are designed for high activity and durability in electrocatalytic reactions. By using CO gas and different surfactant, we show precise controls over the crystal growth of Pt-based nanocrystals to obtain highly uniform nanocrystals with desired facets. I will discuss the selectivity of CO bonding on between Pt{111} and Pt{100}, which is a driving force in the formation of faceted controlled Pt alloy structures. High catalytic activity in oxygen reduction reaction (ORR) was observed in icosahedral and other (111) dominated Pt alloy catalysts. The correlation between the catalytic performance and crystal morphology and surface strain will be discussed.5-6 The controlling factors on the growth of Pt/Pt-based alloy nanoparticles in solution will also be discussed,5 especially on stabilizing the formation of Pt icosahedron, which has been thought to be a type of unstable shape in thermodynamics.
1. H. J. You, S. C. Yang, B. J. Ding, H. Yang, Chem. Soc. Rev., 2013, 42, 2880-2904.
2. V. R. Stamenkovic, B. Fowler, B. S. Mun, G. F. Wang, P. N. Ross, C. A. Lucas, N. M. Markovic, Science 2007, 315, 493-497.
3. J. B. Wu, A. Gross, H. Yang, Nano Lett., 2011, 11, 798-802.
4. J. B. Wu, L. Qi, H. J. You, A. Gross, J. Li, H. Yang, J. Am. Chem. Soc., 2012, 134, 11880-11883.
5. W. Zhou, J. B. Wu, H. Yang, Nano Lett., 2013, 13, 2870-2874.
6. J. B. Wu, P. P. Li, Y.-T. Pan, S. Warren, X. Yin, H. Yang, Chem. Soc. Rev., 2012, 41, 8066-9074.

We report a simple and versatile method which concurrently achieves structural control and introduces functionality into CaCO3 microparticles. The work investigates the microwave-induced metamorphosis of highly hydrated calcium carbonate hexahydrate (ikaite) crystals incorporating microwave-absorbing superparamagnetic magnetite nanoparticles, and demonstrates that unique porous vaterite/ magnetite composite crystals can be synthesised using this route. That the incorporated nanoparticles are accessible and active for reactive processes is demonstrated through the exploitation of the magnetite nanoparticles / calcium carboante microparticles in photocatalytic water oxidation, where it is shown that they function as an effective, convenient and reusable material.
Carboxymethyl dextran-magnetite (CMD-Mag) was prepared by a combined dextran carboxylation and magnetite precipitation reaction. Then, calcium carbonate was precipitated in a solution cooled to 0-3oC by precipitation of CaCl2 with (NH4)2CO3 in the presence of CMD-Mag nanoparticles. The magnetite cores of these particles were 1-4 nm in diameter and had a hydrodynamic diameter of 23 nm after coating with CMD. Coating with CMD stabilizes the particles in the crystal growth solutions and promotes absorption to the CaCO3 crystals, thereby facilitating encapsulation. Imaging of these vaterite crystals showed that they displayed remarkable, open microstructures comprising 200 nm segregated columns formed from packed nanocrystals of vaterite, where the entire internal surface area of the porous CaCO3 particle is intimately associated with magnetite nanoparticles.
The work additionally demonstrates that the Calcium carbonate/ magnetite particles, due to Fe ion release, are effective in photocatalytic water oxidations that liberate O2. It is envisaged that this methodology is not unique to this CaCO3/magnetite system, but could be applied to the straightforward synthesis of a range of composites containing microwave absorbing nanoparticles.

Synthesis of CuInSe2 (CIS) with Cu2Se and In2Se3 is one of the routes to fabricate the absorber layer of solar cells. In this study, we present the synthesized powder of Cu2Se by using CuCl and Se in the solvent of ethylenediamine (EN). The influence of calcination temperature on phase transformation of Cu2Se powders is also explored. From the result of XRD analysis, it shows that CuSe is the major phase when the calcination temperature is under 300°C. As the calcination temperature is raised to 400°C, Cu2-XSe starts to be formed. A pure Cu2-XSe phase can be obtained while the calcination temperature is higher than 400°C. According to SEM images, the shape of the powders transforms from sliced to oval as the calcination temperature is increased. Finally, Photoluminescence (PL) is also examined to characterize their optical features. This study is expected to find the optimum conditions of precursor and process for objective compounds (Cu2Se) applied in synthesizing CIS-based solar cell absorb layer.

Recently it has was demonstrated that the photocatalytic performance of anatase-TiO2 nanocrystals for water treatment can be greatly enhanced by hybridizing them to a graphene substrate. It is found that on graphene, the nanocrystals adopt a cubic morphology rather than the equilibrium truncated octahedron of unattached anatase. In this talk we use first-principles calculations and a modified Wulff construction to examine the role of graphene as a morphactant for anatase. We then define a set of conditions that any anatase-supporting substrate must satisfy in order to effect a change in morphology that increases the area of the active (001) facets — and thereby increases the overall photocatalytic performance.

We developed a method to deposit nickel oxide (NiOx) thin films by employing the strategy of combustion synthesis. Nickel nitrate was used as the oxidizer, glycine, citric acid and acetylacetone were used as the fuel. A processing temperature as low as 140°C was sufficient to convert the combustion precursors to high quality NiOx thin films based on optimized design of the oxider and fuel. The combustion fabricated NiOx thin films exhibited appealing properties, such as a high work function, optical transparency in the visible and near infrared region and flat surface features. The obtained NiOx thin films were employed as hole extraction/injection interlayers in organic solar cells and polymer light emitting diodes, exhibiting superior electrical properties. The results demonstrate that the combustion synthesized NiOx thin films are promising candidates as hole transport interlayers for solution processed optoelectronic devices.

In recent years, there has been considerable interest in gaining a fundamental understanding of nanoparticle (NP) synthesis and reactivity due to their wide applicability in the fields of biomedicine, optoelectronics and catalysis. Although metal NPs with a small and narrow size distribution tend to have high performance, their inherent heterogeneity generally results in less reactivity compared to their homogeneous counterparts. Hence, it is crucial to develop support systems, which not only permit the synthesis of uniform sized NPs and improve the solubility, but also provide a system suitable for “Green” catalysis.
Towards this effort, we have designed water-soluble, biocompatible rosette nanotube (RNT)-supported palladium (Pd) NP composites. The in-situ formation of the Pd NPs occurs within 1 minute upon mixing the corresponding metal salt with the RNTs at ambient temperature in the absence of a reducing agent. We have successfully employed our catalyst in olefin hydrogenation and Suzuki-Miyaura cross-coupling reactions under environmentally benign conditions. The catalysis has also been extended towards the synthesis of small-molecule solar cell, light emitting diode and sensor materials.
Previously, it was determined that RNTs functionalized with lysine (called G0-RNT) display supramolecular chirality. More recently, it was found that this right-handed helicity of G0-RNT is preserved even after the formation of the Pd NPs on their surface. This result encouraged us to explore the potential of our Pd NP/RNT composite in asymmetric catalysis. In this paper, the synthesis and characterization of the Pd NPs/RNTs is discussed followed by preliminary results on the supramolecular chiral catalysis.

Flexible and foldable electrodes based on metal nanowires have been widely researched for next generation electronics. To fabricate these electrodes for practical applications, the low-cost metal nanowires with high conductivity and flexibility should be required. Accordingly, many researchers have studied the synthesis of copper nanowires (Cu NWs) via various methods because of unique Cu intrinsic properties, such as a low cost, high conductivity and remarkable flexibility. There are several methods to synthesize the Cu NWs. However, the current methods for Cu NWs still have some challenges for flexible and foldable electrodes in flexible substrate, such as rapid oxidation and high sintering temperature in process.
Herein, we introduce the synthesis of the single crystalline Cu NWs with average 93 nm diameter and 30 mu;m length via polyol reduction method, and suggest the possible applications that of flexible and foldable electrodes. More importantly, this synthesis of Cu NWs successfully solved the critical problems of previously reported results, such as rapid oxidation, high sintering temperature process and poor dispersibility, with excellent oxidation stability, well dispersibility, low sintering temperature and high conductivity.
In the synthesis process, the whole reaction depends on reduction potential of ethylene glycol (EG) with surfactant of oleylamine and potassium bromide (KBr). On the basis of analysis of Transmission electron microscope (TEM), Selected area electron diffraction (SAED), X-ray diffraction (XRD), and Scanning electron microscope (SEM), we demonstrated the mechanism of Cu NWs formation and confirmed an optimized synthesis condition. Particularly, we showed that the molar ratio of surfactants and nucleation rate play key roles for synthesis of Cu NWs. To prove the excellent oxidation stability, we used XRD, Ultraviolet-visible spectroscopy (UV-vis), X-ray photoelectron spectroscopy (XPS) and 4 point probe to measure the change of the state and electrical conductivity within 7 days. On the basis of these analysis, we can observe that there is no characteristic change for Cu NWs during 7 days, and these Cu NWs are enough stable for practical applications as the electrodes.
The flexible and foldable electrodes were fabricated by filtration of dispersed Cu NWs and sintering at above 180 °C in the vacuum oven. The conductivity performance of bendable electrodes was measured using a home-made bending machine and 4 point probe. On the basis of these analyses, the Cu NWs possess the remarkable flexibility and high conductivity (0.1~0.6 Omega;/sq) after sintering 180~220 °C in the vacuum oven. Moreover, the flexible and foldable electrodes still have high conductivity even if it bended 1000 times or folded five 90°-cross sections. We believed that the Cu NWs synthesized by our introduced method have a good potential for the flexible and foldable electrodes toward next generation electronics.

Superhydrophobic surface with switchable adhesivity is expected in microfluidics to open up applications, such as microreactors and oil/water separation.Several materials, including polystyrene, organically-modified oxides, carbon nanotubes, have been demonstrated to show superhydrophobic surfaces with controlled adhesion force, however, reversible switching of the adhesion force therein is still challenging; the reversible switching of the surface property is usually achieved by taking advantage of functional stimuli-responsive materials, which limits process feasibility as well as low cost fabrication. There remains considerable requirement on a novel material which shows reversible water adhesion 1) with an external stimuli, 2) fabricated by a simple process, 3) on various types of substrates (including soft substrates).
Herein, we develop a novel multifunctional titanate film which is controllably nanofabricated on soft substrate as well as operated by mild heating. A nanostructured titanate is demonstrated to produces a hydrophobic surface with switchable adhesivity. The functional surface is made up of vertically-oriented titanate nanotubes (TNTs) with a high aspect ratio. After fluoroalkylsilane (FAS) modification, the surface exhibits superhydrophobicity with a high adhesion force. The FAS-modified TNTs film shows sticky superhydrophobic surface upon exposing moisture, whereas it becomes slippy by mild heating. Adhesive force of the film is increased by water molecules adsorbed on TNTs surface; the mild heating dehydrates TNTs surface and the exposure to moisture recovers physically-adsorbed water.
Another important finding in the present work is that TNTs can grow on plastic/soft substrates because the protocol does not require severe condition, such as anode oxidation, template removal at higher temperatures, and lithographic processing. The spontaneous growth of TNTs is induced simply by applying a mild hydrothermal reaction on amorphous TiO2 used as a precursory film. Photopatternability is provided by a photocatalytic nature of TNTs with a band gap of 3.87 eV. Because of the large band gap compared with TiO2, the pattern remains for more than a year under fluorescent tube radiation in a laboratory atmosphere. As a result, TNTs create the patternable and switchable surface through the process applicable to soft substrates. The obtained TNTs film can be potentially used for water manipulation in lab-on-a-chip and microfluid devices and water/oil separation. As a proof of concept, here we show that the TNTs surface can controllably catch and repel a water droplet.

Iron (Fe) doped titanium dioxide materials are of high technological interest for many applications in the fields of catalysis, spintronics, photochemistry, gas detection and biological systems. For this reason, diverse synthesis processes, both chemical and physical, are developed and investigated in materials research laboratories. In particular, great efforts are devoted to prepare films without any impurity phase useful for magneto-electronic and optical devices.
Here, we report on the synthesis of Fe-modified titania films by sol-gel procedures. Fe-titania acid catalysed precursor solutions were prepared by using titanium isoproxide, and iron(III) chloride hexahydrate as precursors in the molar ratio Fe/Ti=1/360, Fe/Ti=1/60, Fe/Ti=1/30 and Fe/Ti=1/2 and coatings were grown by dipping on fused silica and (100)-Si-substrate wafers and are subsequently heat-treated after deposition in air at 500°C. The influence of the Fe concentration on the chemical composition, morphology, microstructure and optical properties of the films was investigated in detail by thermal analysis, Fourier transform infrared spectroscopy, field emission scanning electron microscopy and X-ray diffraction.
Specifically, the optical properties are related to the morphological features and microstructural properties of the synthesized coatings. The results show the formation of pure Fe-titania nanocrystalline films where the Fe-O-Ti hetero-bonds formation induces a red-shift of the band gap. In particular, we find that the titania films doped with low Fe-concentration are constituted of nanocrystallites (diameter range: 6nm - 25nm) made of a solid solution of Fe within the anatase-TiO2 lattice. On the contrary, the coatings with a molar ratio Fe/Ti=1/2 present the formation of well defined nanocrystallites of Fe-pseudobrookite (Fe2TiO5), and, in addition, the presence of rutile-TiO2 phase nanocrystallites are observed. The typical crystallite size (diameter) of the Fe-pseudobrookite and rutile-TiO2 phases are, for the process parameters used here, about 23nm and 17nm, respectively.

Optical response of individual nanoparticles mainly dominated by localized surface plasmon resonance (LSPR) strongly depends on their size, shape, composition and small changes in surrounding environments such as inter-particle distance, surface modification. This structure- and environment-dependent LSPR has been used to enhance optical signals such as Raman scattering or fluorescence in a wide range of fields from optics and spectroscopy to biomedical applications. One of the reasons that enhance such an optical signal is the extraordinarily amplified electromagnetic fields (EM-fields) at the junction area positioned between a pair of nanoparticles or at internal crevice of the single nanoparticle. Among many structures, attached heterodimers with different size of nanoparticles or composition generates diverse plasmon modes and extraordinary enhanced EM-fields between the internal junctions. Despite these interesting properties of attached hetero-dimers, neither theoretical nor experimental studies have been done much. Understanding these plasmonic properties of attached heterodimers could greatly increase our knowledge in plasmonics; give insights in designing and synthesizing the plasmonic nanostructures. Herein we focus in shape control of overlapped area on Au-Ag heterodimers and further investigate the plasmon response dependent on the shape and degree of overlapped region and also size of nanoparticles. We further studied that sharpening the overlapped region of dimers is how important and sensitive not only for tuning the LSPR but also amplifying the optical signals such as surface-enhanced Raman scattering (SERS).

Progress in nanomedicine will be driven by the ability to detect and manipulate the living matter at the molecular scale in order to cure cancers or fix genetic anomalies. One of the most promising way is the use of confined optical source in the ultra-violet wavelengths to image by self fluorescence, to analyse by enhanced Raman spectroscopy and to repair the wrong molecular sequences by inducing local chemical reaction. Metallic nanoparticles are widely recognized as local sources of energy that resolve the above issues thanks to their optical properties based to the plasmon resonance. To achieve UV plasmonics, aluminum appears as the best candidate. This metal has a negative dielectric constant combined with a low loss coefficient at UV wavelengths down to 100 nm, matching all the criteria to obtain high energy Localized Surface Plasmon Resonances (LSPR). UV Localized Surface Plasmon Resonances (LSPRs) are very attracting because their energy matches with most of the electronic transition energies of molecules or solids. In this scope, the development of efficient and low-cost techniques for the synthesis of reproducible Al nano-structures with very good crystalline quality and optical properties has to be investigated [1].
In this presentation, we describe a method for the growth of crystalline Al-NPs. The nanoparticles are made using a very reproducible synthesis route based on the reduction of aluminum ions. Particles as small as 2nm have been synthetized and characterized with a transmission electron microscope, extinction spectroscopy and other methods.
By playing on the medium of synthesis and the temperature of reaction, it appears to be possible to tune under control the size of the nanoparticles. We completed the characterizations by investigating the optical properties of the synthesized Al NPs. Extinction measurements were performed on different solutions containing Al NPs using a UV-visible spectrometer. Sharp extinction peaks appear unveiling LSPR excitations of Al NPs. The relatively low FHWM of the LSPR peak indicates a good homogeneity of the NPs size as it has been verified by the TEM characterizations. Finally, we will present applications of such Al nano particles in metal enhanced fluorescence ans labeling.
To summarize, we described in this presentation a wet chemical method for the growth of aluminum nanoparticle. AL-NPs present a very good homogeneity and reproducibility. They exhibit sharp localized surface plasmon resonances (LSPRs) in the UV region as it has been showed by extinction spectroscopy characterization.
[1] Martin, J.; Proust, J.; Gerard, D.; Plain, J. Localized Surface Plasmon Resonances in the Ultraviolet From Large Scale Nanostructured Aluminum Films. Opt. Mater. Express 2013, 3, 954.

Surface-enhanced Raman scattering (SERS) has been widely used for sensitive, real-time, non-destructive, and multiplexing molecular detection. For a viable application of SERS, however, a reliable formation of Raman hot spots such as the nanogap, where the electromagnetic field enhanced by surface plasmon resonance can reaches its highest value, is essential. In order to develop a usable SERS sensor with evenly distributed hot spots on a wafer scale substrate, we propose a hybrid approach combining a physical process, which defines the array of uniform Au disks by nanoimprint lithography, and a chemical process, which controls the interstitial space between the neighboring Au disks with a solution-based reduction of Au ions. Because the lithographically defined Au nanodisks functioned as preferential sites for reducing Au ions from the HAuCl4 (0.3 mM) and NH2OH (0.4 mM) aqueous solution mixture, the Au nanodisks increased in size during the reduction time, and consequently, the interstitial distance between the nanodisks decreased from 60 nm to sub-5 nm. The resulting patterns of the nanogap-rich Au nanodisks successfully increased the SERS signal about 1000-fold. This experimental result corresponded well to numerical electromagnetic simulation. The highly improved and homogeneous SERS activity was also applied to monitor DNA bases. Considering the present results, we expect that the sub-lithographic feature-enhanced SERS substrate from the combination of top-down templating and bottom-up embellishing can be used as a highly reliable and cost-effective molecular detection platform.

Three dimensional asymmetric plasmonic nanostructures, spiky olive like plasmonic nanoparticle, have attracted considerable interest due to possible application to bio-photonic imaging and single molecule detection within biological window region (lambda; ~ 800 nm). SERS relies on the generation of large localized electric fields near nanoscale sharp noble metal tips or their coupling in narrow gap structure due to optical excitation of their surface plasmon resonances in near field. When the particle could have both narrow gap and sharp multi-tip structure, the intense electric field localization induced high sensitivity of these particles could be expected to detect extremely small molecule in solution within biological window region. However, the synthesis of these interesting structures has proved highly challenging.
Here, we introduce an innovative method to synthesize surfactant free, colloidal plasmonic nanoparticles with broken symmetry and sharp multi-tips by microwave irradiation in solution. Surface-enhanced Raman scattering signal with a 785 nm diode laser for our spiky olive like nanoparticles showed enough sensitivity for extremely small molecule detection at least 1.0 pM and its enhancement factor is up to 107. The outer and inner structures of these particles were analyzed mainly by scanning electron microscope (SEM), focused ion beam (FIB) and high resolution transmission electron microscope (HR-TEM). These nanoparticles could be also used for optical plasmonics, for instance, targeting, sensing, imaging, gene delivery, and optical gene regulations.

During the past ten years, an increasing number of studies have highlighted the remarkable properties of copper nanoparticles in various fields like catalysis, plasmonic, microelectronics, as well as biology as an efficient bactericide and fungicide agent. Copper is one of the few metals -like Au and Ag- that presents a localized surface plasmon resonance (LSPR) in the UV-Vis spectral range. The latter have been by far the most studied because of their chemical stability and resistance to oxidation.1 In fact, copper nanocrystals are a really versatile material and the control of their structural properties are key parameters for the engineering of new classes of functional materials. For the first time, we present here a direct evidence of decahedral shaped copper nanoparticles (mean size ca 7 nm) obtained in very mild conditions2 (hydrogenolysis of a metallorganic precursor) in the presence of an alkylamine as ancillary ligands. These nanocrystals have been characterized by High Resolution Transmission Electron Microscopy (HRTEM), liquid Nuclear Magnetic Resonance (NMR) spectroscopy, and UV-Vis spectroscopy during their oxidation process under air. The surface plasmon resonance (LSPR) of these nanoparticles may result in a highly sensitive chemical or biochemical sensor. By coupling the experimental LSPR results and simulations based on the discrete dipole approximation (DDA) we have been able to probe the very first formation steps of localized Cu2O islands on the nanocrystals surface. Under inert atmosphere, a smooth plasmon peak is evidenced at ca 560 nm. Immediately after air exposure, a spectacular increase of the LPSR intensity is measured (more than 100% absorbance gain) whilst a red shift is observed. During the following hours, the absorption continues to increase up to a maximum of ca 580 nm. According to the simulations, a value of 600 nm corresponds to the presence of a complete layer of copper oxide on the crystal. This dynamic phenomenon is related to the progressive spreading of Cu2O all over the Cu crystal, and the increase of absorbance is due to the higher dielectric constant of copper (1+) oxide material compared with the surrounding organic medium.3 A remarkable core-shell structure Cu@Cu2O with the -decahedral geometry has been characterized by HRTEM several days after air exposure. In addition, we have shown that the oxidation kinetic of the crystal surface can be modulated by the ratio of surfactant introduced with the copper crystals (0.1; 0.5; 1 eq. alkylamine).
The coupled LPSR study and simulation analysis of this colloidal suspension allowed the precise determination of the oxidation rate of copper nano-decahedron and may be useful as a very accurate dissolved oxygen probe.
1 Nano Lett., Vol. 7, No. 7, 1947, 2007
2 J. Mater. Chem., 22, 2279, 2012
3 J. Opt. Soc. Am. B, 28, 11, 2735, 2011

Molecular imprinting is a well-established technique to induce recognition features in both organic and inorganic materials for a variety of target analytes. Ion imprinted polymers are porous materials that has the ability to selectively rebind the desired metal ion. In this study, ion imprinted silanes with varying percentage of coupling agent i.e. 3-chloro propyl trimethoxy silane were synthesized by sol-gel method for imprinting of Cr+3 ion. The imprinting of Cr+3 in cross-linked silane network was investigated by FT-IR which indicates the metal ion is coordinated with oxygen atoms of silanes. SEM images revealed that imprinted silanes possess uniformly porous surface which is suitable for adsorption of target ion. It was experienced that by increasing the concentration of 3-chloro propyl trimethoxy silane up to 10% substantially improves the binding capacity of silanes which allows us to recognized Cr+3 ion down to 50µg/L. Furthermore, the selectivity of Cr+3-imprinted silanes was evaluated by treating them with other metal ions of same concentration that possess similar ionic radii e.g. Cr+6, Pb+2 and Ni+2. In this regard, silanes showed much higher binding for imprint ion i.e. Cr+3 in comparison to above mentioned metal ions. Finally, the regenerated silanes were studied in order to reuse them thus, developing cost effective biomimetic sensor coatings.

Titanium dioxide (TiO2) is a promising electrode material for Li-ion batteries due to its good Li+ storage capacity as well as its chemical and mechanical stability during lithiation/delithiation cycling. However, the storage capacity of TiO2 is limited at high cycling rates due to its low electrical conductivity. To address this performance issue, functionalized graphene sheet (FGS)-TiO2 nanocomposites were synthesized via an aqueous, low-temperature (50 °C), surfactant-mediated process, using sodium dodecyl sulfate (SDS) as the surfactant and titanium trichloride (TiCl3) as the metal-oxide precursor. In the production of FGS-TiO2, the concentration of SDS is a key processing parameter as it determines the extent of SDS adsorption on FGSs, which in turn influences the colloidal stability of FGSs dispersed in the aqueous reaction medium as well as the growth of TiO2 on FGSs. In this study, we seek to understand how varying the SDS concentration during FGS-TiO2 synthesis influences its material properties (e.g., nanocomposite surface area and porosity; TiO2 wt %, crystallite size, and morphology), and in particular how those changes the high-rate Li+ storage capacities. We show that by optimizing the SDS concentration, improved Li+ storage performance can be achieved.

Designing arrayed oxide consisting of nano-/quantum-rods of different orientations enables the experimental studies of the angular dependence influences of the physical/chemical/structural properties, electronic structure and efficiency of materials and devices. The outcome also allows the fabrication of innovative and functional particulate thin films and coatings directly onto various substrates without membrane, template, surfactant, undercoating or applied external fields. Those arrays are prepared at minimum interfacial tension, thus particle nucleation is separated from growth, giving exquisite control of particle size over orders of magnitude. In many cases, the differences between interfacial energies among crystal facets can also be exploited to produce controlled anisotropic shapes. In addition, since the thin films are fabricated at low temperature from aqueous solutions and can be grown on almost any substrate, it is possible to safely grow one phase on another. This opens up the possibility of using the anisotropy and properties of one material to generate a high surface area secondary substrate upon which more active materials are grown. In effect, this produces clean (no organic contamination) and cost-effective advanced nanocomposite arrayed thin films -combining properties and architectures from multiple phases to achieve results not available from any single phase. This approach has been successfully applied to develop a new generation of functional materials, the so-called purpose-built materials. Indeed, when thermodynamic stabilization is applied to heterogeneous nucleation rather than homogeneous nucleation, not only the size of spherical nanoparticles can be controlled but also the shape, the orientation and crystal structure of anisotropic building blocks onto various substrates can be tailored to build smart and cost-effective (hetero)nanostructures. This strategy will be demonstrated on various oxide systems of important technological relevance. In addition, recent development on quantum size effect on interfacial chemistry and electronic structure as well as orbital character and device efficiency will also be presented.

This presentation will introduce a reproducible, one-pot sol-gel coassembly approach that results in large-scale, highly ordered porous silica films with embedded, uniformly distributed, accessible gold nanoparticles. The unique coloration of these inverse opal films combines iridescence with plasmonic effects. The coupled optical properties are easily tunable either by changing the concentration of added nanoparticles to the sol-gel solution before assembly or by localized growth of the embedded Au nanoparticles upon exposure to tetrachloroauric acid solution, after colloidal template removal. The presence of the selectively absorbing particles furthermore enhances the hue and saturation of the inverse opals color by suppressing incoherent diffuse scattering. The composition and optical properties of these films are demonstrated to be locally tunable using selective functionalization of the doped opals.

Self-assembling of functional oxide nanostructures has been envisaged as a need to engineer materials at the nanoscale driven by their implementation in functional devices with reduced dimensionality. In particular, Chemical Solution Deposition (CSD) is an ex-situ growth approach with high throughput nanofabrication at low cost, but it is still in its infancy regarding tight control of self-assembling and self-organization processes. Although, strain engineering has been realized as the strategy to define nanostructures with size, shape and orientation control, it has hardly been applied to CSD processes and rarely in the emergent field of functional complex oxides. In this presentation, we will review our effort to underline the capabilities of CSD to control the growth of self-assembled functional oxide nanostructures by strain engineering. We have explored different materials composition (CeO2, La0.7SrO.3MnO2) on different single crystalline substrates and buffered substrates (SrTiO3, LaAlO3, CeO2/Y:ZrO2, Y:ZrO2), in some cases (100) and (110) substrates orientation have been explored. We have obtained different sorts of nanostructures (nanodots, nanowires) and layer-by-layer ultrathin films. We have identified the different growth modes for the different cases and we have made use of thermodynamic modeling to understand the principles controlling nucleation and growth. On one hand, we evaluate the nucleation energy for the nanostructures and underline the relevance of strained islands in the nucleation process. On the other, we emphasize that in some cases, the interface energy and the strain component on the surface energy may have a relevant role in the determination of the stable island morphology and crystalline orientation in addition to the usually considered strain relaxation and surface energies. The role of kinetics in the evolution of these processes is also to be considered and yet less explored. The use of several heterostructures has been very helpful to underpin the different scenarios. Conventional heating and rapid thermal annealing furnaces have been used in this investigation while XRD, AFM and TEM/STEM analysis have been the techniques used in the experimental evaluation. Overall, we believe that our investigation based on a CSD approach has opened a new strategy towards a general use of self-assembling and self-organization which can now be widely spread to many functional oxide materials.

Electrical energy stored in batteries powers most of the portable electronic devices. Batteries are also being intensively pursued for electric vehicles and grid storage of electricity produced by renewable sources like solar and wind energies. Cost, safety, cycle life, and energy and power densities are the major parameters for these applications, which are in turn controlled by the electrode and electrolyte materials used in the battery. With an aim to develop new materials that can enhance energy, power, safety, and cycle life while lowering the cost, this presentation will focus on the use of novel microwave-assisted solvothermal (MW-ST) and hydrothermal (MW-HT) approaches to obtain high-performance, nanostructured electrode materials for lithium-ion batteries. The advantage of the microwave-assisted MW-ST and MW-HT processes is that they offer well crystalline materials at much lower temperatures of < 300 oC within a short reaction time, often within 30 minutes, compared to the conventional high-temperature synthesis, lowering the manufacturing cost. As a result, it gives access to metastable products that are otherwise inaccessible by conventional high-temperature synthesis processes.
Specifically, this presentation will focus first on the synthesis of nanostructured LiMPO4 (M = Mn, Fe, Co, Ni, and VO) by the MW-ST process within 5 minutes at < 300 oC in a polyol medium. The process will then be extended to substitute the divalent M ions with trivalent vanadium ions, which is accompanied by the formation of M vacancies to maintain charge neutrality as indicated by in-depth characterization. As the doped samples are heated to higher temperatures of > 500 oC, the vanadium ions extrude from the lattice, revealing a temperature-dependent solubility of vanadium in the lattice and demonstrating that these phosphates can be doped aliovalently only by low-temperature synthesis processes. The presentation will then focus on the microwave-assisted synthesis of Li2MSiO4, single-crystalline iron oxide nanowires, and graphene from graphite oxide with polyol. The electrochemical performances of these materials in lithium-ion batteries will be presented. In addition, the formation of highly crystalline anatase titanium oxide thin films on conductive substrates such as indium tin oxide (ITO) at temperatures as low as 150 oC will be presented. The ability to achieve high-quality nanocrystalline titanium oxide thin films at low-temperatures could enable processing with plastics. Also, the extraction of oxygen from binary oxides as well as complex perovskite oxides at lower temperatures to obtain lower-valent oxides will be presented.

As a type of organic-inorganic hybrid materials, sol-gel-derived silsesquioxanes with the empirical formula RSiO1.5 form a unique class of materials because of their facility in preparation and controllability of their structures and functions. Silsesquioxanes from organotrialkoxysilanes (RSi(OR&’)3) such as methyltrimethoxysilane (MTMS) offer attractive features in functionality, surface characters, and mechanical properties. However, silsesquioxane monoliths from organotrialkoxysilanes are not popular because of the high tendency to form polyhedral oligomeric silsesquioxanes (POSS) or hydrophobic precipitates without a defined structure. We have been studying on porous monoliths based on random networks derived from organotrialkoxysilanes through careful controls over fundamental sol-gel chemistry, and recent topics including followings will be presented.
Hydrogen silsesquioxane (HSQ, HSiO1.5) monoliths with hierarchical porosity can be prepared by an acid-catalyzed one-step process under the presence of poly(ethylene oxide). On the surface of the resultant monoliths are there abundant Si-H groups, which can be used for simultaneous reduction and immobilization of metal nanoparticles. For instance, the HSQ monoliths embedded with palladium nanoparticles were prepared and used as a supported catalyst for cross-coupling reactions. Also, the HSQ surface can be modified with various alcohols under the presence of a Lewis acid by dehydrogenative addition, which would lead to a new surface modification technique.
Transparent aerogels with methylsilsesquioxane (MSQ) composition can be obtained from MTMS by an acid-base two-step process. Since these aerogels are mechanically strong and flexible against compression, MSQ xerogel monoliths with aerogel-like properties can be prepared by ambient pressure drying. Practical application to low-cost thermal insulators is presently being explored. Hierarchically porous MSQ monoliths with macro- and mesopores can also be obtained using a similar system.
Co-condensation of MTMS with dimethyldimethoxysilane (DMDMS) leads to a unique marshmallow-like porous material with bendable and extremely soft features, while transparency is lost due to the higher hydrophobicity. The marshmallow-like gels can selectively absorb oil from oil-water mixtures because of the high hydrophobicity, and the absorbed oil can be squeezed out because of the flexibility. The flexibility is maintained even at liquid nitrogen temperature. Since the glass transition temperature can be low (~ minus;130 °C) considering the chemical analogy with poly(dimethylsiloxane) (PDMS), the rubber-like mechanical property is maintained at the low temperature with the aid of high porosity and thin skeletons. By employing organoalkoxysilanes with different functional groups, surface property can be varied (such as superamphiphobic).

The photochemical conversion of polysilazane layers -(SiR2-NH)n- in the presence of oxygen into Si-O-Si networks was studied. Applying quantum chemical calculations, it has been found that, high-energy UV radiation in the wavelength range below 220 nm is able to induce scission of the Si-N bond and thus the oxidative conversion process can be started. As UV sources, commercially available 172 nm Xe2* and 222 nm KrCl* excimer as well as 185 nm low pressure mercury lamps were used. In the course of the investigations, the kinetics of the reaction depending on wavelength and intensity of the UV radiation and on the concentration of an additional catalyst, and essential basics of the reaction mechanism were elucidated. Using the inorganic perhydropolysilazane (R = H) as the silazane precursor, thin (100 nm) dense silica layers could be produced which exhibit formidable barrier properties against gas diffusion, especially of oxygen and water vapor. The described approach allowed for establishing a continuous process for the production of fully transparent, flexible barrier coatings on polymer films at normal pressure and moderate temperature (< 80 °C). Thus, a pilot plant has been constructed for the processing of 250 mm wide polymer films from roll to roll at an effective velocity up to 10 m per minute. Using suchlike fabricated barrier films as basic components, the design of high barrier laminates is a promising prospect.

Since the end of the 1990s, and with the development of nanosciences, nanocatalysis has clearly emerged as a domain at the interface between homogeneous and heterogeneous catalysis, which offer unique solutions to answer the demanding conditions for catalyst improvement.[1,2] A modern approach of colloidal chemistry is presently being developed to increase the reactivity of nanoparticles in a limited size up to 10 nm, using several types of capping agents.[3] The organometallic approach represents an efficient synthetic methodology to get well-controlled metallic nanoparticles in terms of size and composition, two key-parameters for application in nanocatalysis.[4] In our team, metal organic complexes are used as metal source, being decomposed in solution under mild conditions and in the presence of various ligands as stabilizers. The choice of the ligand is of prime importance as it will govern the nanoparticles characteristics as their size, shape or surface chemistry and further, influence their catalytic properties.
In that context, sulfonated diphosphine have been used as protective agents for the synthesis of water-soluble Ru(0) nanoparticles. Our aim was to take advantage of the water-soluble properties of the sulfonated ligands to obtain aqueous suspensions of nanoparticles and to study their influence on their catalytic properties, in terms of reactivity/selectivity and of stability/recyclability. This route led to aqueous colloidal solutions that are stable for several months, containing ruthenium nanoparticles with a low size dispersity and very small mean diameters in the range 1.2-1.5 nm. These systems were tested in the hydrogenation of model unsaturated substrates (arenes and alkenes) in biphasic liquid-liquid conditions.[5] The results show that the reaction selectivity may be tuned in favor of target products depending on the reaction conditions. The addition of cyclodextrins was also performed to study their influence on the catalytic performances, namely shuttle effect.[6] Finally, preliminary results of recycling are promising for the recovery of these novel water-soluble nanocatalysts.
References
[1] Thomas, J.M. , Chem. Cat. Chem., 2 (2010) 127.
[2] D. Astruc, Nanoparticles and Catalysis, (Eds). Wiley-VCH, 2008.
[3] K. Philippot and P. Serp, Nanomaterials in Catalysis (Eds.), Wiley-VCH, Weinheim, 2013, 1.
[4] K. Philippot, B. Chaudret Organometallic Derived -I: Metals, Colloids, and Nanoparticles, Elsevier, 2007, 71.
[5] M. Guerrero, A. Roucoux, A. Denicourt-Nowicki, H. Bricout, E. Monflier, V. Collière, K. Fajerwerg, K. Philippot, Catalysis Today 183 (2012) 34.
[6] M. Guerrero, Y. Coppel, N. T. T. Chau, A. Roucoux, A. Denicourt-Nowicki, E. Monflier, H. Bricout, P. Lecante, K. Philippot, Chem.Cat.Chem., 2013, in press (DOI: 10.1002/cctc.201300467)

Localized surface plasmon resonance (SPR) materials have great potential for use in sensors, photonic devices, and Smart window coatings for cars and buildings. The ability to tune the SPR of materials makes it possible to absorb the most intense radiative heat (ideally 750-1200nm) without compromising visibility. Lanthanum hexaboride (LaB6), with an exceptionally high absorbance at ~1000nm, is the focus of our work. Until now, the synthesis of LaB6 nanocrystals has required extremely high temperatures, elevated pressures, or the ball-milling of bulk material. We have developed a low-temperature, atmospheric pressure synthesis performed in a flask using sodium borohydride as both a boron source and the “solvent.” Our method yields uniform, phase-pure nanocrystals and the addition of a ligand to the reaction medium results in soluble LaB6 nanocrystals that are easily incorporated into sol gel and polymer matrices for use in optical coatings.

There has been significant interest in the past decade in nanoparticle-protein interactions and having a complete understanding of the elements that govern these interactions is critical. It was therefore the primary goal of this research was to investigate the effect of nanoparticle surface energy on protein adsorption behavior. A synthesis method for nanoparticles with a tunable surface energy, based on the Stöber sol-gel process, was developed through the doping of silica nanoparticles with up to 20 at% Ni2+ or Zn2+. By studying the effects of catalyst concentration, solvent type, reactant concentration, and synthesis time on nanoparticle morphology, size, and crystallinity it was found that an increase in catalyst concentration and decreases in synthesis time and reactant concentration correlated to a reduction in the diameter of the nanoparticles with an associated increase in polydispersity. It was determined that using methanol as a solvent, and ammonia hydroxide, 12 mM-73 mM, lead to the formation of 20 nm - 80 nm nanoparticles. These synthesized particles were spherical, amorphous, and monodisperse, (nanoparticle size standard deviation < 10%) with the particles size controllable by the reaction time and ammonia hydroxide concentration. Nanoparticle composition was characterized by EDS, XPS, and UV-vis while size, crystallinity, and morphology was characterized by TEM, SEM, and XRD. The techniques of sessile drop and inverse gas chromatography were used to estimate the solid surface energy of the nanoparticles. The synthesis and characterization of these silica-doped nanoparticles along with discussion of their properties will be presented.

Upconversion, the process of converting multiple lower energy photons to a single photon at higher energies, is a process with potential applications in diverse fields including bioimaging and solar energy conversion. The efficiency of exisiting near infrared to visible upconverters, however, remains low (QY < 1%) and limits the viability of such materials. Our approach to increasing quantum efficiency is to use plasmonic nanostructures to enhance both the absorption and anti-Stokes shifted emission. In this presentation, we focus on a model UC-plasmonic system composed of NaYF4:Yb3+, Er3+ nanoparticles and Au plasmonic nanorods. First, we synthesize upconverting nanoparticles of sizes ranging from 30 to 90 nm in octadecene with oleic acid as a ligand. We also synthesize colloidal Au nanorods (80 nm x 17 nm) with longitudinal and transverse plasmon resonances at 950 nm and 521 nm, respectively - tailored to match the absorption and emission frequencies of the nanoparticle.
To optimize plasmonic interactions in a nanocomposite film, high control of the surface chemistry of the nanostructures is desirable. Ligands affect both the frequency of the plasmonic resonance as well as the deposition techniques accessible. Many metallic nanostructures are synthesized using high concentrations (0.2 M) of surfactant. If left in the colloid, these surfactants can diminish the potential enhancement of nearby emitters when deposited on a substrate. By performing a ligand exchange of the CTAB surfactant for methoxy-PEG derivatives, we create stable gold nanorods with minimal organic contaminants that are then easily deposited on a variety of substrates. The charge on the surface of the particle can be controlled by buffer solutions. We combine drop-casting and rapid drying of the colloids to create uniform films of gold nanorods, then spin-coat oleic-acid-stabilized upconverting nanoparticles. In this way, we achieved a monolayer film of metallic nanostructures and upconverting nanoparticles.
This bottom-up, solution processed film enables enhancements of upconversion emission intensity of up to 4x. Time-dependent emission measurements of films at various densities of Au rods elucidate the mechanism of upconversion emission at different powers and providing design parameters for plasmonic-enhancement of upconversion in different power regimes. We will discuss the potential to create three dimensional structures using the monolayer film as building block, creating an avenue to superlattice-like upconverting materials with emergent optical properties.

Colloidal structures such as particles, rods and wires have attracted a great deal of research interest because of their size and shape dependent properties. By varying the reaction parameters such as reagent concentration, pH, and temperature, structures of variable morphologies have already been synthesized. Despite this considerable progress in synthesis strategies, not many efforts have been devoted for predictable and addressable control of size and shape of colloidal structures. In this talk, by taking silica structures as an example, various parameters that control the final morphology of structures will be discussed. Additionally, strategies for having addressable, predictable, and local control of size and shape of silica structures will be discussed.

Metal-organic coordination can be utilized to direct layer-by-layer (LBL) assembly of thin films. The sequential deposition of the organic and metal component on the surface permits tailoring of film structure and composition. Controlled step-wise assembly defines the resulting film structure and presents an opportunity to design the framework for specific applications. This research focuses on understanding the fundamentals of film formation for two types of metal-organic coordinated thin films, multilayers (MLs) and frameworks (MOFs). The ML system studied was an assembly of α,omega;-mercaptoalkanoic acids and Cu (II) ions and the MOF system was composed of benzene-1,3,4-tricarboxylic acid and Cu (II) ions (HKUST-1, Cu₃(btc)₂). Throughout the alternating solution-phase deposition, films were characterized using ellipsometry to measure film thickness and scanning probe microscopy (SPM) to map topographical morphology of film growth LBL. Using image analysis software, quantitative data regarding the growth of these thin films based on the images was procured (e.g. Particle Analysis and Percent Area Coverage). For both ML and MOF systems, ellipsometry shows that film thicknesses uniformly increase by 2 nm per layer deposited. However, SPM images of the foundational film layers reveal two distinct growth mechanisms, one that forms a semi-continuous conformal film with distinct features (ML) and one that forms a rough surface of nucleating crystallites (MOF). Work is underway to determine how many layers are necessary for the MOFs to form a continuous film and to investigate if the growth mechanism transitions at that point. Further studies will investigate the effect of processing variables such as morphology of underlying substrate, chemical functionality of organic binding layer, and post-deposition annealing. Fundamental knowledge gained through this research will be broadly applicable to other metal-organic systems for the advancement of their industrial applications, allowing for structures with tailored assembly and designed catalytic sites.

Amorphous silica membranes exhibit an excellent hydrogen perm-selectivity, which could be achieved by the molecular sieve-like property derived from the in-situ formed microporous amorphous silica network having a suitable mean pore diameter of approximately 0.3 nm. In this paper, recent progress in the development of the hydrogen-permselective microporous amorphous silica-based membranes will be briefly reviewed. Then, our study of novel multicomponent ceramic-based membranes having hydrogen affinity will be shown and discussed. As a first step, ceramic-based membrane materials with ternary [Si-M1-O], or quaternary [Si-M1-M2-O] (M1, M2= hetero element) systems were synthesized by pyrolysis of metal-organic precursors at 873 K in air followed by heating under hydrogen flow at 673 to 1273 K. The XRD and TEM/EDS analyses revealed that the crystallization and the phase separation from the ternary or quaternary amorphous systems depended on the composition and the hydrogen reduction temperature. Then, the TPR/TPD analysis under the hydrogen/argon atmosphere was performed on the synthesized samples. Some of the transition metal nanoparticle-dispersed ceramics showed typical TPD profile due to the desorption of hydrogen below 573 K and that of spillover hydrogen above 673 K, while some of other Si-M1-M2-O materials showed a unique hydrogen desorption peak at 573 to 773 K, and this hydrogen adsorption/desorption detected in the middle temperature range was found to be reversible by the cyclic TPR/TPD analysis. The Si-M1-M2-O ceramic-based membrane having this hydrogen affinity was successfully fabricated by dip-coating of the metal-organic precursor solution on a fine porous alumina support followed by the two-step heat treatment. According to our primary results, the synthesized membrane exhibited a unique enhanced hydrogen permeance at 573 to 773 K. Further results obtained by the FT-IR measurement using DRIFTS technique, the TPR/TPD analysis coupled with mass spectrometry analysis for the desorbed gas species and TEM/EDS analysis will be shown and discussed for clarifying the dominant mechanism of the observed hydrogen permeation behaviors.

We report on the rapid synthesis of a highly porous silica aerogel powder using industrial grade water-glass solution as the precursor at ambient conditions. The co-precursor method was employed using hexamethyldisilazane (HMDZ) as the silylating agent. The surface modification, solvent exchange and sodium ion removal from hydrogels occurred simultaneously in one step and completed in about 60 minutes. The textural properties and the microstructure of the silica aerogel powders were characterized using the Brunauer-Emmett-Teller (BET) method and field emission scanning electron microscopy (FESEM), and energy dispersive x-ray spectroscopy (EDS). The silica aerogel powders with bulk density of about 0.10 g/cm3 and the specific surface area about 1,240 m2/g can be synthesized using this method within 2 hours.

The accurate engineering of thin films that deterministically roll-up into microtubes allows the development of versatile microtubular architectures for nano-bio-related applications, such as micro-robotics, ultra-compact (bio)sensing devices, optofluidic sensors and biophysics of cells in confined spaces, among others [1]. The self-assembled thin films can contain multiple functionalities leading to either on-chip integrated microdevices or mass produced microtubes suspended in solution.
Artificial micro- nanomotors have attracted a lot of attention over the last few years in areas of chemistry, materials science, physics and nanotechnology aiming to efficiently convert chemistry into motion like nature uses biochemistry to power biological motors [2]. Recent advances on rolled-up self-propelled micromotors demonstrated the transport of microobjects [3] and cells [4]. Moreover, various methods of wireless control the motion and the power of the microjets such as magnetic guidance [3, 4,5], temperature [6], chemical gradients [7] and light [8] as external sources has been reported. Those artificial nanomotors act collectively [9] reacting to external stimuli like chemotactic behaviour [7] and are capable to clean polluted water [10].
Here, we will present micromotors composed of rolled-up functional nanomembranes consisting of Fe/Pt bilayers which contain double functionality, i.e. the inner Pt for the self-propulsion and the outer Fe for the in situ generation of ferrous ions boosting the remediation of contaminated water via Fenton reaction. The degradation of organic pollutants takes place ca. 12 times faster than when the Fenton oxidation process is carried out without catalytically active micromotors. The enhanced reaction-diffusion provided by micromotors has been theoretically modeled. The synergy between the internal and external functionalities of the micromotors results into an enhanced degradation of non-biodegradable and dangerous organic pollutants at small scale environments and holds considerable promise for the remediation of contaminated water in locations difficult to reach [10].
[1] Smith, E. J. et al., Lab Chip 2012, 12,1917
[2] a) Sanchez, S., Pumera, S. Chem. As-J. 2009, 4, 1402. b) Mallouk, T.E. and Sen, A. Sci. Am. 2009, 72
[3] a) Sanchez S. et al., J. Am. Chem. Soc., 2011, 133, 701. b) Solovev A. A. et al, Adv. Funct. Mater. 2010, 20, 2430.
[4] Sanchez, S. et al., Chem. Commun., 2011, 47, 698. b) Solovev A. A. et al., ACS Nano 2012, 6, 1751.
[5] Khalil I. S. M. et al., App. Phys. Lett. 2013, 103, 172404
[6] a) Sanchez, S. et al., J. Am. Chem. Soc. 2011, 133, 4860. b) Soler, Ll. et al., Lab Chip, 2013, 13, 4299.
[7] Baraban, L. et al., Angew. Chem. Int. Ed., 2013, 52, 5552.
[8] Solovev, A.A. et al., Angew. Chem. Int. Ed., 2011, 50, 10875.
[9] Solovev, A. A. et al., Nanoscale 2013, 5, 1284.
[10] Soler, Ll. et al., ACS Nano, 2013. DOI: 10.1021/nn405075d.

This lab has initiated compelling research into silicon quantum dot (Si QD) polymers in order to utilize their synergetic benefits with Si QDs and synthetic polymers. This research has been motivated from our previous investigation on the hybrid molecule-semiconductor architecture and quantum dot (QD) solid concepts. In order to realize the Si QD polymers concept, we have utilized the unique advantages of Si QD, quantum well polymer, and molecular electronics calculations. The Si QD has only size-tunable excitation and luminescence due to its quantum confinement effect, in which, more importantly, the material of silicon element is abundant, cheap, nontoxic, and easily integrated into the conventional silicon process technologies. Universal origin of optical and electrical properties for molecular and QD electronic materials is electron trapping and relaxation over donor, spacer, and acceptor building blocks. The quantum well polymer consists of molecular parts having high and low HOMO-LUMO gaps, which are connected alternatively with covalent bonding. Molecular electronics calculations can be a fundamental and cost-effective way for designing the Si QD polymers. Tuning of optical properties of the Si QD by attaching conjugated capping molecules was confirmed by UV-vis absorption spectra showing an extension into the longer wavelength and by significant carrier relaxation in particle-in-a box calculations. Si QD thin films were realized by using spin-coating process in the case of attaching the organic groups to allow the strong molecular interactions, where electronic coupling and interdot distance dependence have to be investigated. In order to endow the quantum well polymer with thermal and electrical stabilities, we have synthesized the Si QD-polystyrene nanocomposites, where thermally robust positive charge trapping phenomena were observed. After using vinyl-functionalized Si QDs, we have realized the synthesis of the Si QD polymers, where the content of the Si QD can be controlled. To support the Si QD polymers concept, we have pursued the calculation of electron transport in conjugated molecules terminated to silicon electrodes, instead of Au electrodes.

Inorganic nanoparticles doped with lanthanide ions, i.e. nanophosphors, have been largely noticed by many scientists due to their unique optical properties including high photostability, no photoblinking, and size-independent luminescence. In addition, they do not contain toxic elements such as Cd and Pb. In contrast to semiconductor nanocrystals showing size dependent luminescence, luminescence properties of nanophosphors are determined by doped lanthanide ions because each lanthanide ion has its own absorption and emission peaks at different wavelength. On the other hand, due to these characteristic absorption/emission peaks, it is very difficult to achieve multicolor emission from the nanophosphors under the single wavelength excitation.
In this study, multicolor tunable β-Na(Y,Gd)F₄:Ce,Tb,Eu nanophosphors were synthesized via solution chemical route and their luminescence properties were investigated. The size of as-synthesized colloidal nanophosphors was smaller than 20 nm. In this phosphor system, Ce³⁺ plays a role as a sensitizer. Since absorption cross-section of Ce³⁺ is large and 4f¹ → 4f⁰5d¹ transition is spin and parity allowed transition, external ultraviolet (UV) light is efficiently absorbed by Ce³⁺ ions and excited energy is transferred from Ce³⁺ to Tb³⁺. As a result, β-Na(Y,Gd)F₄;Ce,Tb emits intense green light peaking at 545 nm under excitation with 254 nm UV light. When β-Na(Y,Gd)F₄:Ce,Tb nanophosphors were co-doped with Eu³⁺ ions, green and red emission peaks were simultaneously observed due to electronic transitions from ⁵D₄ to ⁷F_J (J = 0, 1, 2, 3, 4, 5, 6) in Tb³⁺ and from ⁵D₀ to ⁷F_J (J = 1, 2, 3, 4) in Eu³⁺ as a result of energy transfer from Ce³⁺ to Tb³⁺ and Eu³⁺. As a consequence, Tb³⁺ and Eu³⁺ showed their characteristic peaks, respectively. The β-Na(Y,Gd)F₄:Ce,Tb,Eu nanophosphors with various ratios of Eu³⁺ to Tb³⁺ showed green, yellow-green, greenish yellow, yellow, orange, and red light under illumination of 254 nm UV lamp. In addition, due to their small size feature they were easily incorporated into polydimethylsiloxane (PDMS) monolith. The nanophosphors-PDMS polymer composites were highly transparent and showed excellent color tunability.
In summary, highly bright β-Na(Y,Gd)F₄:Ce,Tb,Eu colloidal nanophosphors with multicolor tunability were synthesized. Due to Ce³⁺ sensitization, Tb³⁺ and Eu³⁺ emission peaks were simultaneously observed under single wavelength (254 nm) excitation. The β-Na(Y,Gd)F₄:Ce,Tb,Eu nanophosphors showed various emission color from green to red by adjusting ratio of Eu³⁺ to Tb³⁺. Moreover, highly transparent nanophosphors-PDMS composites were prepared and they also displayed excellent color tunability.

Atomically thin Molybdenum Disulphide (MoS2) triangles and hexagrams were prepared by a two-step regrowth ambient pressure chemical vapor deposition (APCVD) process. MoO3 nanobelts, a few microns in length and width, were prepared using a hydrothermal technique and utilized as the starting material. High temperature treatment of the MoO3 nanobelts followed by a rigorous sulfurization via APCVD processing provided different morphologies of MoS2 monolayers and bi-layer morphologies. Triangle and hexagram morphologies were characterized using scanning electron microscopy, Raman spectroscopy, photoluminescence, and atomic force microscopy. MoS2 layers have a hexagonally packed structure and are held together by Van Der Waals forces. Zipping effect of triangular and hexagram domains is a process where large area domains form when nucleation sites are increased. PL, Raman Spectroscopy, and Raman mapping peak shifts confirm the presence of monolayer and bilayer regions in our regrowth process.

We report herein that heterogeneous nanowires (NWs) can grow from a catalyst via the successive solution-liquid-solid (SLS) mechanism. First, highly-crystalline PbSe NWs were successfully synthesized using Bi catalysts via the SLS mechanism. TOPS solution was added into the solution bearing PbSe NWs. S atoms from TOPS and the excess Pb atoms remaining in the solution penetrated into the liquid Bi catalysts attached to the tips of PbSe NWs. The Pb and S atoms induced the local supersaturation in the outer parts of liquid Bi catalysts due to the limited solubility, leading to the second SLS growth of PbS NWs. The PbS NWs grew along the one side or two sides of PbSe NWs as they epitaxially well match to each other. A possible growth mechanism related to the above phenomena was proposed based upon the surface diffusion model of the vapor-liquid-solid (VLS) process and the “geminate” NW nucleation mechanism. This is the first report demonstrating that two or three heterogeneous NWs can grow from the same catalyst through the successive SLS growth and we believe that our results will contribute to the better understanding of the SLS mechanism.

(X,Xprime;)3MgSi2O8:Eu2+ (X, Xprime;: Sr2+, Ba2+) powders are the attractive blue-emitting phosphors for use in white light emitting diodes (WLED) pumped by near ultraviolet (nUV) sources. They have been mostly prepared by the conventional solid-state reaction process, but rarely by solution-processing methods.
We prepared (X,Xprime;)3MgSi2O8:Eu2+ (XMSO:Eu2+) powders by a sol-gel method combined with the combustion process (the hybrid process) using strontium acetate, barium acetate, magnesium nitrate hexahydrate, europium nitrate hydrate, and colloidal silica (c-SiO2) as starting materials. This hybrid process dramatically shortened process time compared with the conventional sol-gel process. The phases of the products closely depended on the composition of the starting materials, and the XMSO:Eu2+ single phases could be obtained by controlling the cation ratios of X2+, Mg2+, and Si4+. The photoluminescence excitation (PLE) spectra, which were assigned to the 4f7 → 4f65d1 transitions of the Eu2+ ions, exhibited broad excitation bands with two strong peaks, covering from 300 to 400 nm. The intensive emissions of Sr3MgSi2O8:Eu2+ (SMSO:Eu2+) and Ba3MgSi2O8:Eu2+ (BMSO:Eu2+) were obtained at around 460 and 435 nm, respectively. These different emission wavelengths were attributed to the change in the crystal field surrounding the Eu2+ ions.

The present work focuses on the development of a reproducible synthesis route for ultrafine powder coatings of Y₂O₃:Eu and the assessment of their photoluminescence as a function of crystal size, crystalline phase, and synthesis conditions. Current techniques of Y₂O₃:Eu synthesis require high temperature annealing before the photoluminescence of Y₂O₃:Eu is achieved. The Microwave Plasma Assisted Spray Deposition (MPASD) technique used in this work uses a water solution precursor to synthesize fully functional ultrafine coatings of Y₂O₃:Eu phosphor without the need for annealing. The coatings particles were verified by X-Ray Diffraction, HR-TEM, and SAED to be single crystals of either cubic or monoclinic phase depending on plasma condition. In addition, the coating&’s particles had narrow size distribution and the average particle size (20nm to 100nm) was controlled by changing the precursor concentration. The photoluminescence (PL) of the coatings was measured and strong change in PL spectrum was observed due to crystal phase change where the most intense peak was observed at 611nm and 624nm for the cubic and monoclinic phase respectfully. The effect of coating crystal phase, doping concentration, and deposition conditions on the photoluminescence will be discussed.

Field emission properties of solution processed few-layer TI Bi2Se3 nanosheets are studied in this work, which exhibits a low turn-on field of 2.3 V/mu;m, a high field enhancement factor up to 6860 and good field emission stability. The efficient field emission behaviors are not only attributed to their topologically protected single Dirac cone surface states and lower work function but also related to their numerous sharp edges. We further proposed a field emission model to investigate the origin of its efficient field emission behaviors, which found that the irregular shapes of exfoliated layered Bi2Se3 nanosheets play a key role in the edge effect that resulting in its efficient field emission. This work suggests that layered Bi2Se3 nanosheets have a great potential as high-performance planar field emitters.

The thermal decomposition of Cd(oleate)₂, metal organocarboxylate complex, in the presence of alkylamine and synthesis of CdSe nanoparticles by hot-injection method was studied in order to understand the formation mechanism of the metal chalcogenide nanocrystals (Quantum Dot). The major intermediates and side products were characterized by NMR spectroscopy, XRD, TEM etc. The analyzed results showed that the nucleophilic attack of the metal-coordinated amine on the most electron-deficient carbonyl carbon of the oleate ligands at high temperature initiated the decomposition to generate CdO moiety (intermediates); which was also confirmed by several metal organocarboxylate complexes such as M(C₁₈H₃₃O₂)_n (M = Zn, Fe, or Mn; n = 2 or 3) to produce corresponding MO_x nanocrystals. Based on the experimental results, it was proposed as a new formation mechanism of metal chalcogenide QDs through the formation of MO_x nanoparticles first and followed with the reaction of chalcogenide sources and it was confirmed the critical role of alkylamines as the nucleophile in the thermolysis process. Moreover, the proposed mechanism of the amine-promoted thermal decomposition of M(oleate)_n precursor complexes could be extended to the synthesis of various metal-chalcogenide nanoparticles from other metal precursor complexes.

Silicon quantum-dots (SiQD) have recently gained significant attention as tunable band gap materials for photovoltaics and light emitting diode technologies.[1,2] One of the major challenges to their application in such settings, though, is charge transport character. Due to the high reorganization energies, insulating organic peripheries, and weak electronic coupling in these nanostructures, the mobility of charge and/or exciton transport from dot to dot is relatively low.[3, 4]
To improve the charge transport of Si QD materials, we have designed Quantum Dot Mesomaterials (QDM) consisting of dots and organic semiconductor bridges/terminations. The organic bridges can organize the QDs, assist in charge/exciton transport and may help to achieve crystallographically-aligned-dots. The termination groups can protect the dots from oxidation, act as dopants, and modify the optical energy gap.
To demonstrate the feasibility of this approach, we use some simple silane molecules such as vinyltriethylsilane, vinyltriphenylsilane, tetravinylsilane, and octavinylsilsesquioxane (SSQ) as model SiQD reactions to form vinyl-Si bonds via a modified Heck reaction with bromo-aromatics. Alternatively, we form the vinyl-Si bonds via the hydrosilylation reaction of alkynes with silyl hydrides. For example, hepta-phenyl or isobutyl SSQ are bridged with dibromo or diethynyl aromatics to form the corresponding SSQ-vinyl-aromatic-vinyl-SSQ linkages. All bridged products show significantly red shifted absorption and photoluminescence over their aromatic analogues. Many semiconductor hybrid silane/SSQ material examples and characterization will be reported in this presentation.
[1] G. Pucker, E. Serra and Y. Jestin (2012). Silicon Quantum Dots for Photovoltaics: A Review, Quantum Dots - A Variety of New Applications, Dr. Ameenah Al-Ahmadi (Ed.), ISBN: 978-953-51-0483-4.
[2] K. Cheng, R. Anthony, U. R. Kortshagen, and R. J. Holmes, Nano Lett. 11, 1952-1956, 2011
[3] D. Yu, B. L. Wehrenberg, P. Jha, J. Ma, and P. Guyot-Sionnest, J. App. Phy. 99, 104315, 2006
[4] M. Soreni-Harari, D. Mocatta, M. Zimin, Y. Gannot, U. Banin, N. Tessler, Adv. Func. Mater. 20, 1005-1010, 2010

Engineering micro- and nano-scale texture of the surfaces has received great interest in recent years due to its importance in both fundamental research and practical applications(1). In particular, a great focus on the effect of surface texture on superhydrophobicity is inspired by the lotus leaf effect. Some of the fabrication techniques presented in the literature for making superhydrophobic surfaces are potentially costly and time-consuming for practical implementation in applications. Moreover, for some of the applications, the effects of the superhydrophobic coating on thermal and electrical conductivity of the substrate should be minimized; therefore, insulating coatings presented in most of the previous works are not applicable. Among the conductive coatings, superhydrophobic copper coating has attracted considerable interest due to its high diathermanous and electric performance in addition to its good thermal and mechanical stability (2).
In this work, template-free chemical-bath deposition is used to produce superhydrophobic copper coatings with the water contact angle of 160° ± 6° and contact angle hysteresis of 5° ± 2°. In this technique, copper deposit with hierarchical structure is formed through a two-step electrodeposition process in a concentrated copper sulfate bath. In the first step, applying a high overpotential results in the formation of structures with hierarchical morphology, which are loosely attached to the surface. In the second step, an additional thin layer of the deposit is formed by applying a low overpotential for a short time, which is used to reinforce the loosely attached branches on the surface (3). The presented technique is a potentially low-cost and simple approach for coating metallic surfaces with an enduring superhydrophobic film totally composed of copper. The work also presents a theoretical analysis of the effects of the fabrication parameters on the surface textures that cause the superhydrophobic characteristic of the deposit. This theoretical explanation provides the foundation for using the fabrication technique, presented in this work, in other electrodeposition systems besides copper.
References:
1. Feng, L.; Li, S.; Li, Y.; Li, H.; Zhang, L.; Zhai, J.; Song, Y.; Liu, B.; Jiang, L.; Zhu, D., Super-Hydrophobic Surfaces: From Natural to Artificial. Adv. Mater. 2002, 14, 1857-1860.
2. Li, Y.; Jia, W. Z.; Song, Y. Y.; Xia, X. H., Superhydrophobicity of 3D Porous Copper Films Prepared Using the Hydrogen Bubble Dynamic Template. Chemistry of Materials 2007, 19, (23), 5758-5764.
3. Haghdoost, A.; Pitchumani, R., Fabricating Superhydrophobic Surfaces via a Two-Step Electrodeposition Technique. Langmuir 2013 (DOI: 10.1021/la403509d).

Molybdenum disulfide (MoS2) thin films have been deposited on glass substrate from non-aqueous solution using microreactor assisted deposition. The film has been characterized by scanning electron microscopy, energy dispersive X-ray analysis, and Raman spectroscopy. This method provides a potential fast and easy way to prepare large area MoS2 thin film for multiple applications.

Iron pyrite (FeS₂) is a promising photovoltaic absorber because of its earth abundance, non-toxic composition element, infrared band gap (Eg = 0.95 eV), and excellent photo absorption characteristic (α>10⁵ cm^-1), which make it possible to allow the use of very thin absorption layers. But its use has been hindered because phase-pure pyrite nanocrystals are difficult to be synthesized.
In this work, we synthesized pyrite nanoparticles (NPs) with an average size about 20 nm using FeCl₂.4H₂0, sulfur powder and Oleylamine (OLA); however, the yield is too little to apply in the large area solar cells. After adjusting the molar ratio of sulfur to FeCl₂.4H₂O with the same amount of the OLA solvent, we obtained more pyrite nanoparticles with a mean size of about 70 nm. As the OLA is much more expensive than sulfur powder and FeCl₂.4H₂O, decreasing the fraction of OLA in this process not only lowers the cost but meets the need for low cost pyrite thin film solar cell.
Since the NPs are big (~70 nm) and tend to agglomerate to a size over 100 nm, they are unable to form smooth, continuous ultrathin films. In this work, bead mill at high milling speed was applied to smash the NPs into smaller pieces and then disperse the agglomerate to yield well-dispersed pyrite NPs inks. Moreover, to enhance dispersion stability of the pyrite NPs Inks, surfactant was added during the centrifugal bead mill process. Afterwards, a stable dispersion of pyrite NPs with a primary size about 20 nm in toluene was successfully prepared. In this study, the influences of surfactant on the morphology and mean particle size distribution at selected milling times was measured by means of Scanning Electronic Microscopy (SEM) and Dynamic Light Scattering (DLS). The peak positions and the dispersion stability of NPs Inks were also investigated via X-ray diffraction patterns (XRD) and zeta potential measurement, respectively.
So far, we successfully prepared well-dispersed high quality pyrite NPs inks by combining a lower-cost solution based synthesis and subsequent milling in the agitator bead mill. The pyrite thin films applying the pyrite NPs inks will be fabricated by spin coating and their photoelectric properties will be investigated and reported as well.

Contamination of water by heavy metal ions (e.g. mercury, silver and lead) can cause serious environment and health problems because of their acute and/or chronic toxicity to the biological organisms. For instance mercury, which is widely released to the environment by industrial activities (e.g. gold mining and combustion of fossil fuels and wastes) shows great toxicity on mainly renal and nervous systems through disrupting the activity of enzymes. The most common and stable form of the mercury in water is its solvated divalent mercuric ion (Hg2+). Therefore, monitoring of Hg2+ levels in water is very important in terms of waste management, environmental analyzing, toxicology, water safety and water quality. Although numerous methods have been reported for the analysis of toxic mercury (Hg2+) ions in drinking water, development of simple, rapid, inexpensive and sensitive sensors still remains a great challenge.
In this research, we develop a simple, yet very sensitive colorimetric assay for rapid detection of Hg2+ from water. The colorimetric assay is based on the aggregation of the as-prepared citrate capped gold nanoparticles (AuNPs) in the presence of Hg2+ ions and the positively charged amino acid, lysine. In the first step, Hg2+ spontaneously reduced on the AuNP surface and formed Hg/Au nanoparticles. Then, lysine addition to this solution induced aggregation of Hg/Au nanoparticles and resulted in a rapid color change from red to purple or gray. Detection limit of this inexpensive colorimetric assay is 2.9 nM, which is below the limit value (10 nM) defined by the U.S. Environmental Protection Agency in drinkable water. Also, the colorimetric response of citrate capped AuNPs in the presence of lysine is very selective to the Hg2+. In addition, the colorimetric assay is very fast and all analysis can be completed within a minute.

Peapod structures have been fabricated by the encapsulation of preformed CeO2 nanocubes. Colloidal CeO2 nanocubes ranging between 4 and 60 nm were first synthesized utilizing oleic acid and oleylamine capping agents. The nanocubes were then captured in nanoscrolls via a solvothermal treatment with protonated potassium niobate nanosheets. The influence of various reaction parameters on the size and morphology of the nanocrystals, such as amount of surfactant, base concentration, and temperature, were studied and transmission electron microscopy (TEM), scanning electron microscopy (SEM), and X-ray diffraction (XRD) were used to determine the particle size, shape, and crystal structure of the free nanocubes, including 2-D and 3-D superlattice structures, as well as those encapsulated in the nanopeapods. Typically peapod structures contain spherical nanoparticles. Here the significance of this synthetic approach for the capture of non-spherical particles will be highlighted and the utility of this approach to other morphologies discussed.

The need for faster and more efficient separations continues to drive research into new chromatographic materials and Liquid Chromatography (LC). To meet these needs, Ultra Performance Liquid Chromatography (UPLC) systems have been introduced that push the traditional boundaries of particle size, column pressures, system volume and detector design. The use of columns containing sub-2 µm silica or hybrid organic/inorganic packing materials on UPLC systems that allow for pressures up to 18,000 psi have been key to achieving this improved performance.
When columns packed with small particles are operated at these ultra high pressures and flowrates, frictional heating is generated by the viscous resistance of the mobile phase. As a result, both axial and radial temperature profiles are formed. The radial temperature profile experienced across the column diameter results in chromatographic band broadening and loss of efficiency.
To control this loss of efficiency it is necessary to minimize these radial temperature profiles. This can be achieved by tuning the material properties (including thermal conductivity) and solvent systems for better thermal conduction. This presentation will explore the current understanding of radial temperature profiles as well as the synthesis, characterization and chromatographic use of composite hybrid materials that have different thermal conductivities.

Pyrolysis of cellulose, xylan, lignin and pine wood followed with catalytic cracking of the pyrolysis vapors was investigated using pyrolysis-molecular beam mass spectrometry (Py-MBMS). Some metal oxide catalysts, such as MgO(111), ZrO, NiO(111) and CaO, were applied in this study. Pyrolytic products from pyrolysis of biomass and catalytic upgrading of pyrolysis vapors were identified.

Reaction pathways have been determined for the formation of two thermoelectric materials, PbTe and Bi₂Te₃, synthesized by a modified polyol process. Thermoelectric materials have excellent alternative energy potential, most notably for the conversion of waste heat into usable electricity. Conversion efficiencies have been shown to be improved by modifying the material to be nanostructured; and synthetic methods are being investigated to reduce production costs for economic viability. Presented here is a modified polyol process for the formation of thermoelectric nanoparticles that reduces production cost and energy consumption by using a solution phase “bottom-up” approach. This method uses sodium borohydride to reduce starting materials from metal ions to atoms while mixing them together in a high boiling point polyol solvent (tetraethylene glycol) to form intermetallic nanoparticles. These thermoelectric nanomaterials were characterized by powder x-ray diffractometry, scanning electron microscopy, and energy dispersive x-ray spectroscopy. By generating a range of samples as a function of time and temperature, reaction pathways were determined mapping out changes in elemental composition, crystal structure, and morphology. Growth mechanisms for both PbTe and Bi₂Te₃ have been compared and contrasted to investigate what growth stages are common to the synthetic method and which are specific to the compound being fabricated. For these two compounds, the reaction begins similarly with lead or bismuth ions, respectively, being reduced as the reaction begins and then incorporated into the tellurium material. This incorporation occurs very differently for these two systems and dramatic morphological transitions are observed as intermediate products are formed and converted. Production of the two target materials occurs at similar temperatures, but as temperature is elevated the effect on morphology differs. Further research is underway to investigate the effect of different tellurium starting materials, to study other telluride containing compounds, and to appreciate nuances in reaction pathways for different polyol solvents.

Water-based gels (hydrogels) have a wide range of biomedical applications such as drug delivery and cell therapy. While numerous organic hydrogels have been developed, only a limited number of inorganic systems exhibit hydrogel-like properties; well-known examples being silica gel, aluminum based gels and the V2O5- based hydro- and aerogels (1, 2). Even though inorganic gels have several advantages over organic gels (i.e. resistant to hydrolysis, surface adsorption capacity, minimal purification required, resistance to sterilization methods), current inorganic hydrogels cannot be used for biomedical applications due to toxicity, impurities, extreme pH levels, instability under physiological conditions, and their lack of bioresorption. Inorganic phosphates are biocompatible compounds with a wide range of applications in the drug industry (3).
We have developed a unique form of inorganic hydrogel based on a novel inorganic phosphate system (IPS) that could be used as an additive in the drug industry. The IPS gel is stable at neutral and alkaline pH. Rheological analysis revealed that the gel is extremely thixotropic, which makes it very useful for applications requiring coating and minimally invasive injection even through insulin needles. Interestingly, the gel-to-liquid and liquid-to-gel transitions occur within less than 6 seconds of the induction and removal of shear stress. This extremely high-speed transition is very uncommon in hydrogels (4), and unheard of in any other biomaterials.
In summary, the IPS gel is a unique inorganic hydrogel that combines key properties such as stability, biocompatibility, bioresorption, bioadhesion, thixotropy and injectability. To the best of our knowledge these properties have never been observed in one single material and they open a wide range of industrial and biomedical applications.
(1) Livage J. Vanadium Pentoxide Gels. Chemistry of Materials 1991;3:578-93.
(2) Davidovits J. Geopolymers - Inorganic Polymeric New Materials. Journal of Thermal Analysis 1991;37:1633-56.
(3) Sangeetha NM, Maitra U. Supramolecular gels: Functions and uses. Chemical Society Reviews 2005;34:821-36.
(4) Pek YS, Wan ACA, Shekaran A, Zhuo L, Ying JY. A thixotropic nanocomposite gel for three-dimensional cell culture. Nature Nanotechnology 2008;3:671-5.

There has been a recent research focusing on developing magnetic nanoparticles for application in hyperthermia therapy to reduce and control cancers. In this study, a polyaniline (PANI), which is a conducting polymer, was introduced to modify the surface of metallic iron (Fe) nanoparticles to form a core-shell Fe/PANI composite for potential use in hyperthermia therapy. The size of magnetic Fe nanoparticles was tailored by utilizing poly(acrylic acid) or polyvinylpyrrolidone so that their magnetization and coercivity can be maximized, leading to desirable hyperthermia effect from high Neel relaxation losses and Brownian friction losses. The Fe nanoparticles were subsequently coated with layers of silica (SiO2) and PANI. The shells prevent the possibility of Fe oxidation and further improve the hyperthermia effect benefiting from the high conductivity of the PANI polymer. The method developed in this study could open a new avenue to design magnetic nanocomposites with enhanced hyperthermia effect to treat cancers.

We demonstrate an RGB (red, green blue) additive-color printing system that produces highly-resolved pre-defined patterns that are invisible under ambient lighting, but which are viewable as luminescent multi-color images under NIR excitation. Patterns are generated by independent deposition of three primary-color (red, green and blue) upconverting luminescent inks using an Optomec Aerosol Jet® printer. The primary-color inks are printed as isolated and overlapping features to produce images that simultaneously emit red, green, blue, cyan, magenta, yellow and white upconversion luminescence when excited using a single NIR source. Because the red and green inks are excited via a two-photon process, whereas blue ink excitation is via a three-photon process, the chromaticity of colors produced via the overlap of blue with red and green print features (white, cyan and magenta) depends on the NIR excitation power density. This chromaticity shift can be exploited as an additional authentication feature in security applications. The development of an RGB upconversion printing system paves the way for an entirely new arena in security printing.

Synthesis of high purity hexagonal NaYF4 nanoparticles is important for obtaining a photoluminescence host useful in optoelectronic and biological applications. However, solvothermal synthesis gives mixed cubic and hexagonal phases of NaYF4 nanoparticles when long-chain unsaturated fatty acids are used as a ligand. Purification of hexagonal phase from mixed phases is difficult and generally done through energy-intensive processes such as applying heat or pressure or both. However, the supplied energy promotes crystal growth and results in relatively large particle, enhanced particle aggregation and hence, a loss of control over morphology. Herein, we demonstrate that the polymorphic mixture of NaYF4 phase selectively transforms into hexagonal phase. This methodology involves the oxidative cleavage of olefinic bonds of unsaturated fatty acid ligand at moderately basic condition and it is observed that the hydrophobic nanoparticles transform into hydrophilic nanoparticles, which is more suitable for applications. We have explored aspects of this methodology via the Density Functional Theory (DFT). The computational results indicate that 1) cleaved fatty acid ligands are bidentately adsorbed on Y-terminated and F-terminated surfaces in both hexagonal and cubic phases 2) surface passivation by both hydrogen atom and hydroxyl-groups, and the hydrophilicity of the particles are attributed to these two factors. The steric interaction of the long-chain ligands on the surface lowers coverage thereby in the process reduce the rate of Ostwald ripening. The oxidative cleaving of long-chain ligands increases both surface-ligand interaction and the rate of Ostwald ripening. The computational studies suggest that both the bare surface and ligand adsorbed surface of these cubic phase is less stable in comparison to the bare surface and ligand adsorbed hexagonal phase. These results seem to be support the suggestion that the lower surface energy decreases the activation energy of cubic to hexagonal phase transformation. This work gives a new insight into obtaining phase pure nanocrystals by modification of ligands.

An electroless, wet-chemical copper deposition process provides access to simple metallization of flexible substrate foils and spherical template particles.^[1] Transformation of metal-coated polyimide substrates into conducting line patterns is highly attractive for flexible electronics applications. Controlled three-dimensional coating of template spheres allows for the creation of porous metal shells as building blocks for macroscopic spongy structures with complex geometries and varying relative densities.^[2] Depending on the relative density the copper sponges exhibit different mechanical deformation behaviors under uniaxial compression testing. During the deposition process benzyl alcohol acts as reducing agent leading to the step-wise reduction of initially present Cu^II to metallic copper Cu⁰ in the end. The tight connection between the copper grains is of critical importance for providing either a dense microstructure in the copper thin films and foils or a percolating mechanically stable porous network around the spherical particles. The process is not a simple electroless deposition, where metal ions are reduced by assistance of catalysts, and therefore the resulting macroscopic metal fabrics are well conducting and of high purity. The high flexibility of the process suggests the coating of even more complex or anisotropic shapes and morphologies provided by the template material.
[1] N. Kränzlin, S. Ellenbroek, D. Duran-Martin, M. Niederberger, Angewandte Chemie-International Edition 2012, 51, 4743.
[2] N. Kränzlin, M. Niederberger, Advanced Materials 2013, 25, 5599.

Highly integrated, nano-sized electronic devices require to be assembled with nano-scale electrode arrays. Until now, there have been diverse approaches such as using synthesized metallic nanowires and printed patterns with metal ink. However, the synthesized metallic nanowires are not suitable for uniformly aligned electrode arrays in large area, and inkjet printing technique has the limitation related to narrowing pattern width as small as sub-micron. Other methods using printing rolls are possible to make a few micron patterns, but they are relatively uneconomic processes due to lots of material loss. Here, we fabricated highly aligned copper nanofiber array with regular line spacing and orientation using our own printing method called Electrohydrodynamic Nanowire Printing (ENP). Printed copper nanofiber had average diameter of 710 nm and resistivity of 14.1 µOmega;cm which is comparable with that of bulk copper (Resistivity of bulk copper = 1.7 µOmega;cm). We also demonstrated the pentacene thin film field-effect transistors with copper nanofibers as source/drain electrodes and achieved field-effect hole mobility of 0.1cm2V-1s-1. These results show that highly aligned copper nanofiber array can be used for the electrodes of various electronic applications, and our approach will be a promising strategy in the field of next generation electronics.

CuO is a versatile p-type transition metal oxide semiconductor with a narrow band gap in the region 1.2 - 1.8 eV. Three dimensional ellipsoidal shaped CuO nanostructures and two dimensional nanosheets have been successfully synthesized using surfactant-free simple solution phase method. Synthesis of CuO nanostructures was followed by structural, morphological characterization using X-Ray diffraction, SEM and TEM. We have demonstrated that morphology and dimensionality of nanostructures can be controlled by changing the initial reaction concentrations. Morphological evolution of these nanostructures occurs through a mechanism called ‘self-oriented attachment&’. Ordered aggregation and growth of smaller CuO subunits generates an ellipsoidal shaped morphology at lower reaction concentration, while at higher reaction concentration, sheet like structures are generated. Self-assembled structures provide an opportunity to investigate the formation mechanism and aggregation based growth of nano subunits as fundamental building blocks. This bottom-up method offers facile synthesis of nanostructures of controlled morphology and functionality. Optical properties are investigated using UV-Vis spectroscopy and Raman spectroscopy. Micro Raman spectroscopic measurements reveal the presence of multi-phonon branch. Optical absorption and Raman modes are found to be influenced by the morphology of nanostructures

The study focused herein on introducing a new platform to synthesize the materials in a fast and low cost process with easy implementation. [1, 2] The vortex fluidic device enables the synthesis to be performed in a continuous mode, at ambient conditions, and reduce the processing time by at least half, compared to the conventional method. [2] Moreover, by fine-tuning the process controls such as rotational speed, tilt angle and flow rate there is the ability to easily control the pore size of the periodic mesostructure. This new technique improves the green chemistry metrics for preparing mesoporous silica.
The calcined material has BET surface area of 510 m^2/g and pore volume of 0.4 cm^3/g. The pore size and pore wall thickness is 2.9 nm and 5.1 nm respectively. The material show type IV adsorption isotherms with a H1 hysteresis loop as defined by IUPAC. [3] The morphology and mesoscopic regularities of the material closely resemblance the material produced using the hydrothermal treatment process. Nevertheless, the pore size can be easily tuned by varying the shear on the preformed micelles. By changing the shear condition on the micelles solution from 3500 RPM to 7000 RPM, the pore size ranges from 2.8 nm to 3.8 nm, with the wall thickness remaining constant at ~ 5 nm. [2] This is destined to revolutionize the synthesis of mesoporous materials in general, where the shear in the dynamic thin films in the VFD [4] can be controlled to change the pore size arising from the stretching of the micelles, and also in controlling the thickness of the walls of the pores.
Reference
1. C. Gerardin, J. Reboul, M. Bonne and B. Lebeau, Chemical Society Reviews, 2013, 42, 4217-4255.
2. C. L. Tong, R. A. Boulos, C. Yu, K. S. Iyer and C. L. Raston, RSC Advances, 2013.
3. Z. Luan, E. M. Maes, P. A. W. van der Heide, D. Zhao, R. S. Czernuszewicz and L. Kevan, Chemistry of Materials, 1999, 11, 3680-3686.
4. L. Yasmin, X. Chen, K. A. Stubbs and C. L. Raston, Sci. Rep., 2013, 3.

In this study, it is suggested that a simple and low-cost chemical solution (CS) process for fabrication of aluminum (Al: the most excellent metal for the value of high electrical conductivity at low cost) coated fibrous materials that are applicable to the creation of electric circuits and electrodes for flexible and wearable electronics. The CS process was experimentally confirmed to be very effective for the direct deposition of densely structured Al features both on and inside the fiber units composing fibrous materials because the decomposition of an Al precursor composite (AlH3{O(C4H9)2}) was induced at room temperature. CS processed Al conductive fibrous materials showed astonishingly excellent electrical conductivity and mechanical endurance against bending and folding deformation such that electric circuits consisting of CS processed Al conductive paper and thread operated well even after large mechanical deformation tests. Accordingly, it is expected that the Al conductive fibrous materials produced by the simple and low-cost CS process proposed in this study will contribute greatly to the development of improved electric circuits and electrodes for flexible and wearable electronics and advanced electromagnetic interference (EMI) shielding materials as well.

In this study, we suggested a simple and novel solution-dipping (SD) process for a low-cost preparation of large-area and patterned aluminum (Al) thin film at room temperature. Although the SD process was performed at room temperature, it was experimentally demonstrated that the SD process was very effective for uniform deposition of large-area and patterned Al thin films on rigid and flexible substrates because the decomposition of Al precursor (AlH3{O(C4H9)2}) ink was induced at room temperature with the help of catalyst. Furthermore, SD processed Al films showed astonishingly excellent electrical conductivity and mechanical endurance against external deformation (scratching, bending, and folding deformation) such that electric circuits consisting of SD-processed Al films on soda lime glass and PET substrates operated well even after intensive mechanical deformation tests. Accordingly, it is expected that the SD process will be easily applicable to the production of large-area and patterned Al film for low-cost rigid/flexible electronics such as electric circuit boards, radio frequency identification (RFID) tags, electromagnetic interference (EMI) shields, and electrodes for energy-conversion and -storage devices.

Designing and synthesizing plasmonic nanostructures allow us to manipulate and mix the optical, magnetic and electrical characteristics of materials. Optical response of individual nanoparticles mainly dominated by LSPR strongly depends on their size, shape, composition. Although monometallic nanoparticles have been demonstrated to control their interesting optical properties by changing the size or shape, combining different materials in a limited domain can be resulted to unusual optical and chemical properties. Here we report a high-yield new synthetic method to prepare Au-Ag head-body bimetallic nanostructures by kinetic control using DNA modification and salt concentration at mild aqueous condition. In this work, we focused on the asymmetric growth mechanism. We found out that gold nanoparticles should be modified with DNA strand for surface passivation and controlling nucleation sites. Furthermore, reaction rate can be controlled by salt concentration and the reduction of silver component was preferentially occurred on the one side of DNA-modified AuNPs. Further, we showed that this can be used as a building block to assemble complex structures with orientation.

We have been investigated macroporous inorganic-organic hybrid monoliths which are synthesized by a one-pot 2-step acid-base sol-gel process using tri- and di-functional organoalkoxysilane co-precursor systems with controlling phase separation by cationic surfactant n-hexadecyltrimethylammonium chloride. The materials obtained by the simple process have many unique properties such as homogeneous macropores, hydrophobic surface and a bendable future, which can be controlled by the kind of organic substituent and precursor ratio. These marshmallow-like gels can be used for many kinds of applications. As oil/water separating media, these materials show high selectivity, oil-absorption ratio and reusability. They can be used to exclusively absorb organic liquids from an oil/water mixture and then be squeezed out by hand for many times. Due to superhydrophobicity of the surface (water contact angle is over 150 °), they can separate organic liquid such as hexane, chloroform and trimethylbenzene from water completely in a short time. For sound insulators, these materials show higher performance compared to conventional polymer foams owing to the soft and homogenous pore structure.
In the case of the methyltrimethoxysilene and dimethyldimethoxysilane co-precursor system, the obtained marshmallow-like gels show flexibility in the wider temperature range compared to other organic polymers. They keep their mechanical properties from minus;130 to 315 °C.
Synthesizing with other organoalkoxysilanes, we could also obtain marshmallow-like gels with different surface properties. In the case of the vinyltrimethoxysillane and vinylmethyldimethoxysilane co-precursor system, marshmallow-like gels can be functionalized by a simple reaction such as the thiol-ene click reaction. By this way, we can control surface properties of these porous materials, which is advantageous for applications such as to separation media and toxicant absorbents.

Silver nanoplates exhibit exquisite features in their localized surface plasmon resonance owing to an extreme degree of anisotropy in their structure. These nanoplates have larger surface areas when compared with other nanostructures such as nanospheres and nanowires with the same volume, and ultimately, they have a strong tendency to form large, ultrathin sheets with potentials as metallic inks for printable electronics. In this talk, we report a citrate-free synthesis of Ag nanoplates with an edge length of 100-450 nm and a yield approaching 100%. The synthesis involved the reduction of AgNO3 by poly(vinyl pyrrolidone) (PVP) in an aqueous solution at 160 oC under a hydrothermal condition. I will demonstrate that both PVP enables the formation of Ag nanoplates with no concomitance of multiple twinned particles in the final products. By examining the reaction, I confirm that etching plays an essential role in promoting the growth of Ag triangular nanoplates with straight edges at the expense of multiple twinned particles via Ostwald ripening. Once all the multiple twinned particles are gone, etching will continue at the corners of nanoplates, leading to the formation of enneahedral nanoplates with curved edges. More interestingly, when the nanoplates with straight edges are transferred into ethanol and subjected to a solvothermal treatment, nanoplates with wavy edges and sharp corners are formed due to etching on the edges. A comparison study indicates that, at the same particle concentration, Ag nanoplates with wavy edges embraces a SERS enhancement factor at least 6 and 13 times stronger than those with straight and curved edges, respectively. The results from finite difference time domain calculations support our experimental observation that the sharp features on nanoplates with wavy edges are the most active sites for SERS.

The ability to produce stable, high-quality nanocrystals (NCs) in solution with high-throughput is a critical issue in the chemical processes. NCs are generally synthesized by thermal decomposion of precursors in a mixture of solvents and coordinating ligands, and generally employ “hot-injection” methods. However, even the most promising materials produced using this method suffer from a number of fundamental limitations; in particular, the nature of this method leads to local fluctuations in temperature and concentration and inhomogeneity in mixing which make precise control of reaction nearly impossible. These problems are magnified as the reaction vessel size is increased and thus the technique has a fundamental limitation in scalability. This creates an opportunity for other synthesis methods to achieve reliable, high throughput synthesis of high quality NCs for commercial applications. In addition to this, synthesizing of NCs via a continuous method may facilitate more precise control of reaction conditions, reduce the required production time, and lower the cost per mass of synthesized NCs.
Herein, we report a continuous micro-reactor assisted synthesis of mono-disperse and solution-stable NCs synthesized via the hot-injection method. The use of this system allows for finely tuned synthesis parameters to achieve a high-quality NCs synthesis. Furthermore, we have been able to demonstrate a gas-liquid segmentation flow provided a recirculation motion in the solvent to enhance the overall uniformity of the reaction.

Liquid-phase deposition has long been carried out from fully homogeneous solutions due to the belief that non-homogeneous solutions can lead to lack of predictability or reproducibility and poor film properties. We show that deposition from a heterogeneous solution presents an innovative strategy to prepare thin films with unique properties that may be unobtainable with classical synthesis routes due to the independent nano-length scale control of both the bulk and the interfacial properties of these materials. Here, we focus on a hybrid organic/inorganic system that serves as an interphase layer between an inorganic substrate and a polymeric material, and can dramatically improve the reliability of multilayer devices in microelectronic, photovoltaic and display technologies.
The two primary precursors used to synthesized the hybrid include epoxy-functionalized silanes and metal-alkoxides which crosslink to form a molecular network consisting of a dense inorganic mixed-metal oxide as well as an organic network of poly(ethylene oxide) oligomers. By unraveling the underlying hydrolysis and condensation reactions that occur in solution, and utilizing optimized solution deposition techniques, we can manipulate the hybrid molecular structure formation and the composition distribution throughout the film. As a result, an outstanding 3-fold improvement in the adhesive/cohesive properties of these hybrid films can be obtained from otherwise identical precursors.

Robust low cost synthesis routes to highly complex nano-materials are required for practical application in many areas of sustainable energy conversion and storage, catalysis and magneto-electric applications. Solution based processing routes allowing for designed multi-phase, multi-elemental nano-materials in one or few steps are probably the best suited for achieving this. Here synthesis routes to complex oxides, nano-composites and metals using homo- or hetero-metallic alkoxides or salt complexes yielding thin and ultra thin films and coatings will be described. Multi component oxides were prepared at very low temperatures in the forms of polycrystalline and epitaxial thin and ultra thin films on flat and nano-structured surfaces such as wires and porous nano-structures. Systems of varying complexities will be discussed such as doped and non-doped Fe2O3, TiO2 and ZnO and CoFe2O4 and perovskites. The influence of the alkoxide precursor and thermal treatment will be discussed in relation to the structure, processing temperature and quality of the target oxides as well as the option to make thermodynamically unstable extended doping-levels when using reactive alkoxides in a controlled way. Further the tailored metal salt complexes developed to yield thin or ultra-thin films and coatings, core-shells, and sponge or foam-like materials of metals and alloys as well as highly homogeneous metal-oxide composites will be discussed. These simple low cost routes allow for nano-crystalline materials to be prepared with crystallite sizes below 10 nm as well as ultra-thin coatings on nano-structured structured oxides including powders, wires and electrodes. Temperatures in the range 150-500oC were used and no reducing gas was necessary. Similarly metal-in-ceramic composite films and thin or ultra-thin coatings on wires and porous oxide electrodes with a wide range of metals (Ni, Co, Cu, Ru, Pthellip;) and oxide matrixes, having particle sizes down a few nm and loadings up to >80% were prepared. The scalability of the processes have been shown by an industrial pilot 50 m roll-to-roll coating of robust, record efficiency spectrally selective solar thermal absorbers consisting of graded Ni-Al2O3 films and large scale production of superior hardness and toughness WC-Co composite mining and excavation tools by metal coating of WC powder for improved sintering properties. The Ni-Al2O3 composites have also been proven for methane activation in the dry-reforming reaction of CO2 + CH4 to CO + 2H2, which requires all sub 6-9 nm sized Ni particles to avoid carbon filament growth deactivating the catalyst.

Crystalline metal oxide thin films on plastics are strongly demanded in flexible electronic device technologies as well as by those who aim at replacing glasses by lightweight plastics. Many of the active functions of oxide thin films emerge in their crystalline states where low porosities are also preferred. Crystallization as well as densification, however, is driven in principle by atomic diffusion at high temperatures where plastics cannot survive. This is why great efforts have been made for over thirty years to develop "low-temperature" deposition techniques, where people have focused on how to crystallize and densify the films "without firing."
Here we propose a totally different route. The technique is significant in that a "firing" step guarantees the crystallization and densification, which are the key factors for superior functionalities of ceramic thin films, and that the principle of the technique is available for any combinations of ceramic thin films and plastic substrates. The technique comprises (i) the deposition of a polymer layer on a silicon substrate, (ii) the deposition of a precursor gel film on the polymer layer by spin- or dip-coating, (iii) the firing of the gel film into a crystalline metal oxide film, and (iv) the transfer of the fired film onto a plastic substrate. The polymer or its decomposition layer allows the ceramic film to be detached from the silicon substrate and transferred onto the plastic substrate. The transfer is conducted by melting or softening the surface of the plastic substrate, which can be realized by heating the plastics/ceramic-film/release-layer/silicon stack from the silicon substrate side under compression.
The ceramic thin films thus transferred onto plastic substrates were crack-free and optically transparent, and had smooth surface both in scanning electron and scanning probe micrographic scales. 60 nm thick anatase thin films with high optical reflectivity, 660 nm thick ITO thin films with electrical conductivity, and 85 nm thick ZnO thin films with (002) orientation could be prepared on plastic substrates including polycarbonate, acrylic resin and PET. Patterned ITO thin films could be prepared on plastics simply by using a mother silicon substrate with periodic grooves. Alternating ITO and ZnO ribbons could also be fabricated on plastic substrates.

The ability to create functional inorganic materials through the combination of individual components with contrasting but complementary properties is currently receiving considerable attention due to its promise of materials with novel, tailored properties. Here, we describe a facile strategy which leads to nanocomposites in which inorganic nanoparticles are uniformly distributed throughout a single crystal matrix with true nano-scale mixing. The method employs functionalised inorganic nanoparticles as simple crystal growth additives, and is based upon prior observations that certain organic additives, including small molecules, micelles and gels can sometimes be occluded within single crystals, depending on the structures of the additives and crystal, and the solution conditions. Using the incorporation of magnetite and gold nanoparticles within calcite nanoparticles as suitable model systems, we show that tailoring of the surfaces of the nanoparticles with appropriate diblock copolymers can lead to their efficient occlusion, thereby endowing the host crystal with new magnetic properties or colour, without perturbing its single crystal structure. Fundamental to this approach is tailoring of the surfaces of the nanoparticles with appropriate diblock copolymers, where one block should adsorb onto the nanoparticles, while the other block both promotes binding of the nanoparticle to the crystal and ensures colloidal stability of the nanoparticles in the crystal growth solution via electrosteric stabilisation. This new experimental method is expected to be quite general, such that a small family of block copolymers could be used to drive the incorporation of a wide range of pre-prepared nanoparticles into partner host crystals, giving intimate mixing of phases with contrasting properties, while limiting nanoparticle aggregation and migration.

In the past years, great efforts have been devoted to combine the functionality of oxides with the performances of semiconductor platforms for the development of novel and more efficient device applications. However, further incorporation of functional oxide nanostructures as active materials in electronics critically depends on the ability to integrate crystalline metal oxides into silicon structures. In this regard, the presented work takes advantage of all the benefits of soft chemistry to overcome the main challenges for the monolithic integration of novel nanostructured functional oxide materials on silicon including (i) epitaxial piezoelectric α-quartz thin films with tunable textures on silicon wafers [1] and (ii) 1D single crystalline phases of manganese oxide based nanostructures with enhanced ferromagnetic properties on silicon wafers that share common growth mechanisms [2].
Importantly, these mechanisms are governed by a thermally activated devitrification of the native amorphous silica surface layer assisted by a heterogeneous catalysis under atmospheric conditions driven by alkaline earth cations present in the precursor solution. Quartz films are made of perfectly oriented individual crystallites epitaxially grown on silicon substrate with a controlled porosity after using templating agents. At the same time, manganese based molecular sieve nanowires growth mechanism, involves the use of track-etched nanoporous polymer templates combined with the controlled growth of quartz thin films at the silicon surface, which allowed OMS nanowires to stabilize and crystallize. All together, the methodology presented here exhibits a great potential and offers a pathway to design novel oxide compounds on silicon substrates by chemical routes with unique optical, electric, or magnetic properties.
[1] A.Carretero-Genevrier et al. Science 340, 827 (2013).
[2] A.Carretero-Genevrier et al. Chem.Soc.Rev. DOI: 10.1039/C3CS60288E, (2013).

Chemical Solution Deposition (CSD) is a relevant low-cost technique to synthetize functional epitaxial oxide thin-films with good chemical purity. The combination of CSD and an energy source with high spatial resolution and fast pulsed structure such as lasers opens a range of new opportunities for the development of functionalized oxides such as Ce_1-xZr_xO_2-y (CZO), LaNiO₃ (LNO), La_1-xSr_xMnO₃ (LSMO) and Ba_1-xSr_xTiO₃ (BST). The main advantage of laser annealing over conventional heating techniques is that the local heating achieved with lasers may allow the integration of complex oxides, such as those mentioned previously, on application-oriented substrate architectures, which are sometimes limited by temperature.
In this work, Nd:YAG (lambda;=266 nm, 10 Hz) and KrF excimer (lambda;=248 nm, 20 Hz) lasers were used to study the crystallization of functional oxides thin-films on different single-crystalline (YSZ, STO, LNO-coated LAO) and application-oriented (YSZ on stainless steel, LNO on Si, platinized Si wafers) substrates. Temperatures achieved in the system were modeled using optical and thermo-physical properties of films and substrates. Those simulations allowed us to select proper irradiation conditions (i.e. fluence and substrate temperature) to achieve the crystallization of the desired oxide material. It has been observed that those parameters are very important to achieve the crystallization of the materials studied. For instance, the use of a substrate base temperature improves the crystallization.
HRTEM and advanced XRD analysis were used to study the growth mechanism of laser-annealed films, as well as, to differentiate between epitaxial and polycrystalline growth. For the case of oxides grown on single-crystalline substrates, an increase of the epitaxial fraction was observed by increasing the number of pulses, and in some cases fully epitaxial films were obtained. Moreover, perovskite oxides, such as LNO, LSMO and BST, display a higher degree of crystallization than fluorite-type oxides such as CZO. This may be attributed to the enhanced kinetics of these oxides since their melting temperatures are about 800 °C smaller than that of CZO.
The physical properties such as electric resistivity or magnetization of laser-grown oxides were analyzed and compared with conventionally annealed ones in order to evaluate their future use for applications. Properties measured were in some cases close to the samples obtained by conventional thermal treatments.

The combination of different nanobuilding blocks in a single heterostructure can lead to materials with improved properties by selecting components with the desired characteristics for a specific application. Carbon-based heterostructures containing metal oxides are particularly promising for energy and environmental applications.
In this presentation, we will discuss new advances in the microwave-assisted non-aqueous sol-gel approach, we recently reported[1,2], for the fabrication of metal oxides supported on reduced graphene oxide and more recently onto carbon nanotubes and carbon black.
In particular, we will focus on the role of the microwave heating, compared to traditional heating, leading an effective and homogeneous coating of the carbon substrate. For example, the use of reaction vials made of materials that are almost transparent or fully absorb microwave radiation allows us to shed some light on the metal oxide nucleation and growth mechanisms, and the final properties (e.g. absence of metal oxide leaching) of the nanostructures.
References:
[1] S. Baek, S.-H. Yu, S.-K. Park, A. Pucci, C. Marichy, D.-C. Lee, Y.-E. Sung, Y. Piao, N. Pinna, RSC Adv. 2011, 1, 1687
[2] P. A. Russo, N. Donato, S. G. Leonardi, S. Baek, D. E. Conte, G. Neri, N. Pinna, Angew. Chem. Int. Ed. 2012, 51, 11053

Laboratorio di Scienza dei Materiali e Nanotecnologie (LMNT), INSTM and CNBS, Universit_a di Sassari, Palazzo Pou Salid, Piazza Duomo 6, 07041 Alghero, SS, Italy. E-mail: [email protected]
Integration of bottom-up and top-down routes is an important trend in current research in materials science, this is also true for developing advanced lithographic techniques that enable the fabrication of advanced functional materials in one or few steps are required.
Interaction of soft-matter, such as sol-gel films before drying, with high energy photons in the 3-20 keV range induces strong chemical and structural changes; several effects can be observed and they can be employed for developing an advanced patterning tool. In general the formation of free radicals promotes the condensation and a significant modification of the physico-chemical properties of sol-gel films. If hard X-rays are used instead of UV to densify the soft materials, the formation of free radicals is much higher and the densification process occurs on a very short time scale. Intense X-ray radiation can be also used to break the organic bonds while inducing at the same time condensation of the inorganic network in controlled areas of the sample. This effect can be applied to different types of sol-gel materials, such as oxides, organic-inorganic hybrids and mesoporous films.
Exposition of fresh mesoporous films to hard X-rays produces several concurrent different effects on the material because just in one step is possible removing the organic template, to condense the oxide structure and patterning the film. If a proper precursor is introduced in starting solution is also possible achieving one-step fabrication of patterned nanocomposite films containing oxide or metallic nanoparticles.
The technique is very versatile and patterns with high aspect ratio, sharp edges, and high homogeneity have been produced in thick hybrid organic-inorganic films. The coating has been doped with a variety of polycyclic aromatic hydrocarbon functional molecules, such as anthracene, pentacene, and fullerene. Such variety of possibilities shows that soft matter can be well combined with "hard" top down interactions and that new frontiers in micro and nanofabrication have still to be explored.

Although rare-earth (RE) iron mixed oxides dominantly exhibit thermodynamically stable orthorhombic phase (o-REFeO3) consisting of FeO6 octahedra, some of them have possibility to form metastable hexagonal REFeO3 (h-REFeO3) phase, in which iron ions are in trigonal bipyramidal coordination surrounded by five oxygen atoms. One can expect high catalytic activity of metastable h-REFeO3 due to the unusual crystal structure, while the preparation of such metastable phase has generally been difficult by use of conventional methods. We have succeeded to synthesize h-REFeO3 having hexagonal plate morphology by solvothermal method at low temperature and recently demonstrated its higher catalytic activity than that of stable o-REFeO3 [1]. In the present study, we will report the improved activity of the h-YbFeO3 catalyst by appropriate modification with Mn species, affording higher activity for propane combustion than well-known Pd/Al2O3 catalyst.
Mn-modified h-YbFeO3 was synthesized by solvothermal reaction (ST) of ytterbium acetate, iron acetylacetonate and manganese acetylacetonate in 1,4-butanediol at 315 degrees C. For comparison, h-YbFeO3 modified by Mn species was also prepared by Pechini (PC) method.
The solid solutions were formed by the PC method in entire composition range from h-YbFeO3 to h-YbMnO3, while the major part of Mn ions in ST sample did not take part in the substitution of the Fe ions in the h-YbFeO3 structure. Although the crystallite sizes of PC sample were not altered by Mn doping, Mn modification in h-YbFeO3 by ST method decreased the crystallite size. For catalytic combustion of propane, ST sample with hexagonal-plate morphology had much higher activity than irregularly-shaped PC sample. Note that Mn-modified h-YbFeO3 synthesized by ST method showed higher catalytic activities than Pd/Al2O3.
[1] S. Hosokawa, H.-J. Joen, M. Inoue, Res. Chem. Intermed., 37 (2011) 291.

In this study we give new insights on the role of self-assembled monolayers (SAMs) as surface treatment of sol-gel metal oxide thin films in opto-electronic devices. In these devices, SAMs have been used for electrodes or metal oxide interlayers surface functionalization, mainly for better energy levels alignment between the treated surface and the active layer. While most attention has been paid on the role of the terminal functional group of the SAM for generating a proper electrical dipole at interfaces, we here show how the anchoring group of the SAM has a preponderant effect on device performance by controlling the surface defects of the solution-processed metal oxide layer. We base our conclusions on the comparison of three different SAMs deposited on a zinc oxide interlayer in a hybrid organic/inorganic solar cell, for cathode surface modification. The three SAMs all contain one common component, an aminesilane, as the base for comparison. The three SAMs, of gradual complexity, are: a single SAM, a mixed SAM composed of two different molecular species and a composite SAM comprising an additional fullerene layer. By following the change of cell performance as a function of the SAMs composition, we were able to link each device efficiency parameter, i.e the open-circuit voltage, the short-circuit current density and the fill factor, to the change of the surface state of the zinc oxide layer, terminated by the molecular SAM. In particular we show that the fill factor considerably improves after SAM treatment, due to the action of the anchoring group, which controls interface defects at the cathode, mainly by saturating hydroxyl groups during the silylation reaction at the zinc oxide surface. The distinction between the different thin film surface defects, for example the oxygen defects, hydroxyl groups or other dangling bonds is highlighted by combined X-ray Photoelectron Spectroscopy and Ultraviolet Photoelectron Spectroscopy experiments. The study gives precious information for the selection of the proper molecular species for interface engineering of metal oxide thin films processed in solution, to increase their functionality in opto-electronic devices.

The development of supramolecular templating method has enabled the formation of various mesostructured materials by solution syntheses. The formed mesostructures reflect the structures of the liquid crystal phases that are revealed in the course of the formation process. This provides various structural features to these materials such as uniformity and crystallographic symmetries. The template can be removed keeping the ordered structure to form mesoporous materials with uniform and regular mesopores.
The sol-gel process allows facile preparation of such mesoporous materials as a film form, which is favorable for device applications. A wide variety of mesoporous films with diverse compositions and structures have been investigated so far. In addition to applications based on general properties of porous materials such as low density and low refractive index, these mesoporous films can be used as a platform of functional composite films through incorporation of various guest species. Furthermore, the crystallographic orientation of the mesoporous films can be controlled over large scales using the substrates with anisotropic surfaces, which opens up further opportunity of applications using the macroscopic structural anisotropy.
Here, I show optical applications of mesoporous films based on their specific aspects. First, I report a novel anti-reflection (AR) coating using a mesoporous silica film. The flat surface of the film is transformed into innumerable nano-pinnacles by a reactive ion etching process, which reduces the reflection at the surface by forming a graded refractive index structure. Also, the reflection at the substrate interface is suppressed by matching the index of the film to that of a substrate by a controlled incorporation of titania into the mesopores. The AR coatings thus formed achieve very low reflectance over a wide wavelength range on various substrates with different refractive indices. Next, I show the application of the mesoporous films with aligned cylindrical mesopores, which are prepared using rubbing-treated polyimide on a substrate. The incorporation of appropriate guest species such as semiconducting polymers or metal nanowires into the aligned mesopores allows the formation of the composite films with optical anisotropies. I also report on the intrinsic optical anisotropy, birefringence, of the aligned mesoporous films. The pore-walls need to be made of materials with large refractive indices because birefringence largely depends on the index of the wall material. At present, a large Δn value of ~0.08 is achieved using aligned mesoporous titania-silica composite film.
Mesoporous films prepared by simple solution syntheses have large potential of applications other than optics. It is expected that the improvement of the controllability of the structures and expansion of the available materials will create new functionalities and explore novel applications.

Nonaqueous synthesis routes provide a broad and powerful platform for directly obtaining diverse metal oxide nanoparticles with high crystallinity and tunable compositions. The benzyl alcohol (BA) route, for example, has been applied toward numerous oxides including binary, ternary, and even more complex multimetal systems. Though there are many examples of materials prepared with these routes, there are few studies yet that establish relationships between these novel synthesis routes, the resulting defect states, and the final material performance in an optoelectronic device. Here we prepare anatase TiO2 nanoparticles made from the BA route and compare the resulting optoelectronic properties to traditional nanoparticles derived from a hydrothermal route. Both types of nanoparticles were applied as the photoanode of dye sensitized solar cells (DSC) where significantly modified trap states, recombination rates, and transport rates were found. Consistent with XPS measurements, we propose that the BA route leads to additional oxygen vacancies. We next show the tunability of the defect states by incorporating Nb into the nanoparticles, intended to eliminate the oxygen vacancies. These modifications bring the DSC performance of BA derived nanoparticles to be competitive with the state-of-the-art hydrothermal anatase that was optimized for more than 20 years.

The oxidation of graphite enables the access to soluble graphene materials for thin film deposition, and the functional groups introduced by oxidation to graphene oxide (GO), provide a chemical driving force for region-selective self-assembled deposition. The self-assembly of GO has been realized on different surfaces, providing a difference in surface energy due to self-assembled monolayer (SAM) of molecules with functional head groups.[1,2] However, the selective deposition should not be limited only to the difference in surface energy but also could be driven by a stronger interaction such as the electrostatic force, resulting in a higher degree of selectivity.
The routine consists of selective deposition of GO on dedicated SAMs and the subsequent reduction of GO to reduced graphene oxide (rGO) flakes. The driving force for the selective deposition of GO is the strong electrostatic attraction between the negatively charged GO and the positively charged 1-Methyl-3-(dodecylphosphonic acid)imidazolium bromide (IMI-C₁₂-PA) SAM head group. The resulting selective deposition of GO on the substrate showed a high coverage up to 86 %. After reduction, scanning Raman microscopy was used to differentiate the coverage into monolayer (74%), bilayers (14%) and few layers (12%), indicating a highly efficient self-assembly. Besides, due to the difference in the strength of the driving force for the self-assembly process on different SAM head groups, we are able to control the density and hence the surface coverage of GO flakes. Therefore, a site-selective and density-controllable deposition of GO can be realized by using different SAM molecules.
The selective deposition can be applied to the concept of thin film transistors (TFT) based on rGO. The device preparation is based on standard photolithography processes, with all devices in bottom-gate bottom-contact configuration. The devices exhibit a variable Dirac voltage, depending on the dipole moment of the SAM molecule. The electron- and hole-conductions are considerably symmetric, especially in the sense of the transconductance of the transistor. The extracted linear mobility of the TFT for electrons and holes are 3.20 cm² V^-1 s^-1 and 1.75 cm² V^-1 s^-1, respectively. These values, which is based on self-assembly driven by an internal field are much higher than those from a self-assembly driven by an external electrostatic force.[3]
References:
[1] Cho, H. Y.; Han, C. J.; In, I. Site-Selective Deposition of Graphene Oxide Layer on Patterned Self-Assembled Monolayer. Chem. Lett. 2012, 41, 290-291.
[2] Wu, C.; Cheng, Q.; Sun, S.; Han, B. Templated Patterning of Graphene Oxide Using Self-Assembled Monolayers. Carbon 2012, 50, 1083-1089.
[3] Kobayashi, T.; Kimura, N.; Chi, J.; Hirata, S.; Hobara, D. Channel-Length-Dependent Field-Effect Mobility and Carrier Concentration of Reduced Graphene Oxide Thin-Film Transistors. Small 2010, 6, 1210-1215.

Nanoparticulate oxides are used in many catalytic applications, as support to keep highly dispersed the catalytically active phase and/or contributing to the catalytic action with their own reactivity. These oxides are frequently made in solution, so that both their bulk structure and their surface reactivity may be influenced by controlling the synthesis conditions. A few examples will be presented here.
One issue when making solid solutions of oxides is controlling their homogeneity. For example, three-way catalysts purifying car exhaust gases contain a mixed ceria-zirconia solid solution, in which ceria provides redox capability while zirconia provides both refractory character and higher mobility of the lattice oxide ions. Those solid solutions are metastable, and to avoid undesirable phase segregation during high temperature operation a high homogeneity of composition is required. We have shown [1a] how precipitation inside an inverse microemulsion allows obtaining a very homogeneous material; however, depending on the precursor salts used one may have or not local heterogeneities, revealed by EPR, which lead to incipient phase segregation upon calcination at 1173 K as shown by XPS [1b].
Nanoparticle properties can be tailored also using hydrothermal synthesis. In this way we could make ceria nanoparticles having cubic shape and exposing the (001) surface of the CeO₂ phase, which is less stable (and more reactive) than the more common one, (111). Particularly interesting is the observation that dispersing on them CuO gives a more selective catalyst for the preferential oxidation of CO in presence of hydrogen, a process of interest for fuel cell technology. With in situ DRIFT spectroscopy we could ascribe this to a retardation of the reduction of CuO to the zerovalent state, which is justified by a stronger interfacial interaction between both oxides on that surface, as revealed by DFT calculations [2].
Finally, by choosing between sol-gel, hydrothermal and precipitation methods to produce high surface area titania one can control the type and acidic/basic character of its surface OH groups, as revealed by IR and NMR [3]. This in turn affects differently to the photocatalytic properties of the material in the photo-oxidation of a pollutant, as a function of the type and strength of the adsorption interaction (needed for the progress of the photo-catalytic reaction) between the pollutant (in competition with water) and theTiO₂ surface, while the paramagnetic species formed upon irradiation are also affected as shown by EPR.
[1] a) A. Martínez-Arias et al., Langmuir 1 (1999) 4796; b) ibid. J. Phys. Chem. B 107 (2003) 2667.
[2] a) D. Gamarra et al. Appl. Catal. B: Environmental 130-131 (2013) 224; b) M. Monte et al, Catal. Today in press (doi: 10.1016/j.cattod.2013.10.078)
[3] a) A.J. Maira et al., J. Catal. 202 (2001) 413; b) J. Soria et al., Catal. Today 129 (2007) 240; c) J. Sanz et al. J. Phys. Chem. C 116 (2012) 5110.

Hematite (alpha-phase di-iron trioxide) is of an optical band gap of 2.1 eV. When used for solar water splitting, the maximum power conversion efficiency can be as high as 16%. Combined with its good stability against photocorrosion, these properties make hematite an appealing photoanode choice for future solar fuel production. However, hematite also represents a lousy material choice when it comes to band edge position considerations because its valence and conduction band edges are too positive. The positive position makes it impossible for hematite to reduce water without large external potentials. The reduction of water is required for complete water splitting. The positive position also leads to a large difference between the internal energy of photogenerated holes and what is needed for water oxidation, meaning that a large entropy lost is expected when hematite is used for water splitting. In addition, hole diffusion distance within hematite is notoriously short. Charge transfer kinetics across hematite/water interface is also known to be slow. Taken a whole, hematite is a material of great promise and huge challenges. Using atomic layer deposition-grown thin films as a study platform, we evaluate the issues presented by hematite. We show that many of the challenges, including short charge diffusion distances, positive band edge positions and slow charge transfer kinetics may be addressed by the strategy of forming heterojunctions at the nanoscale. These results show that hematite as a photoanode choice is still very much alive.

Inorganic cadmium telluride nanocrystals (3-5 nm) synthesized with an organic ligand shell are soluble in organic solvents and can be spin coated or sprayed onto substrates. This yields photo-active thin films of CdTe after treatment with CdCl₂ and sintering at 380 ^oC in air. As with commercially produced bulk-CdTe films, substantial grain growth ( > 60x) during annealing is facilitated by the presence of CdCl₂ as either a solid or as a vapor. However, little is known about the mechanism of this reaction or how to optimize conditions for active layer quality, particularly when applied to CdTe nanocrystals. We find that long exposure (1-10 min) of CdTe nanocrystals to CdCl₂/methanol solutions results in ligand removal leading to enhanced grain growth. In addition, we show that other cadmium halides can also function in a similar manner. These experiments point toward possible CdCl₂ alternatives as well as a mechanism for the nanocrystal sintering process. CdTe films were solution processed in air on ITO and capped with evaporated Ca/Al contacts for Schottky junction solar cells (glass/ITO/CdTe/Ca/Al). Following device fabrication, air-annealing was found to improve the open-circuit voltage (V_oc), and this effect was tracked over a three week period. The resulting CdTe nanocrystal films were characterized with SEM, UV/Vis, and XRD. The resulting photovoltaic devices produce a V_oc of 393+34 mV, a short-circuit current (J_sc) of 12.0+3.7 mAcm^-2, and an efficiency (eta;) of 2.20% under simulated one sun conditions.

We present the wet-chemical deposition of antimony-doped tin oxide (ATO) nanocrystals into films and demonstrate that these films have the required high quality to be used as transparent electrodes in thin film optoelectronic devices. 3 nm diameter ATO nanocrystals with narrow size distribution, synthesized by an efficient microwave-assisted nonaqueous sol-gel method, are dispersed in tetrahydrofuran (THF) without any additives and processed into films by spin-coating on glass substrates. After thermal treatment, uniform and crack-free films with a low surface roughness of 1.6 nm and tunable thickness of 30 to 800 nm are obtained. A sheet resistance of 395 Omega;/sq is achieved for a 480 nm thick ATO film with a high transparency of 90 % in the visible light range (380 - 780 nm). To demonstrate that these films are indeed viable as transparent electrodes, we show that an organic light emitting diode (OLED) fabricated on our nanoparticle-based ATO electrode exhibits an electrical and optical performance comparable to an OLED on a commercially available indium tin oxide (ITO) film.