Intrinsic ability of nanoparticles (NPs) to self-organize can be seen virtually everywhere around us. Although omnipresent, the mechanisms of these processes are not well understood and include many surprises. One of the enigmatic aspects of these processes is the ability of large number of NPs to form mesoscale superstructures with high complexity. Two general classes of assemblies will be considered in this talk. Self-organized structures known as “terminal” cannot grow beyond a certain size. The second class of assemblies known as “extended” may continuously grow along specific directions. The distinction between these two cases will be made based on the balance of attractive and repulsive interactions between NPs and their spatial anisotropy. The fundamental problems associated with quantitative description of forces between NPs will be elaborated. It will be demonstrated that even small differences in directionality of NP interactions can lead to large structural effects in mesoscale. Vivid representation of such effects will be the formation of twisted chiral assemblies of NPs.
Practical relevance of terminal assemblies is based on their simplicity, versatility, and multifunctionality. Self-limited supraparticles are made from a variety of charged NPs as well as from their combinations with biomolecules. Chiral assemblies from gold NPs demonstrated exceptionally low detection limits for detection (LOD) of DNA and proteins. The practical relevance of extended assembles is enabled by their ability to produce electrically conductive submicro-, micro-, and macroscale structures. Oriented attachment processes typical for water-soluble NP makes possible epitaxial lattice-to-lattice connectivity for solution processable electronic devices.

Here we investigate ultrasmall nanoparticles (UNPs, < 3 nm) formed in the gas phase by pulsed laser vaporization as reactive “building blocks” in the catalyst-free growth of hyperbranched mesoporous nanoparticle architectures, crystalline nanorods, 2D nanosheets, and thin films by pulsed laser deposition (PLD). Nanoparticles synthesized during typical PLD conditions in background gases (typically >30 mTorr) preserve target stoichiometry, but their integration in films or nanostructures remains poorly understood due to the lack of in situ diagnostics. Here, temporally- and spatially-resolved gated-ICCD imaging, spectroscopy, particle sizing, and ion probes are employed as in situ diagnostics to understand and control the plume expansion conditions in order to synthesize UNPs of primarily oxides, although similar strategies are employed with metal chalcogenides for 2D materials. We first focus on the synthesis conditions, size and optical properties, and atomic structure of loose UNPs of TiO₂, a workhorse wide-bandgap semiconductor, during PLV and PLD in background gas pressures. These UNPs serve as “building blocks” for the assembly of hyperbranched 3D mesoporous architectures at room temperature, but with increasing substrate temperature they become integrated into vertically-oriented crystalline nanorods, sometimes with unusual phases (e.g., TiO₂(B)). Similar results will be shown for other oxides (e.g., SnO₂, MgO, PbZr_(x)Ti_(1-x)O₃). Atomic-resolution Z-contrast scanning TEM and EELS are described to characterize the stoichiometry, atomic structure, and electronic structure (band gap) of individual UNPs. Under typical conditions for the spatial confinement of the plume, ‘amorphous&’ TiO₂ UNPs are formed which do not conform to a known TiO₂ bulk phase. Crystal field splitting measured by EELS and XPS are used to assess the evolution of recognizable phases vs. size and evidence for doping. Computational modeling approaches (both force field and DFT) are described to understand the structure and stability of the observed UNPs, and to understand the size emergence of a stable bulk phase. Ex situ annealing experiments, carried out within HRTEM on heated grids, are used to understand the mechanisms by which gas-phase deposited UNPs become integrated into larger nanostructures and thin films. Methods are described to integrate UNPs during synthesis at lower substrate temperatures. These findings are crucial to understand stoichiometry transfer and film growth modes in PLD, catalyst-assisted nanotube and nanowire growth in PLV, and catalyst-free nanorod synthesis in NA-PLD.
Research sponsored by the U.S. Dept. of Energy, Basic Energy Sciences, Materials Science and Engineering Div. (synthesis science) and Scientific User Facilities Div. (characterization science).

Nanoporous (also called mesoporous) silica material can be synthesized as particles of various morphologies. Specifically, co-assembly of organic liquid crystals with sol-gel silica precursor brings micron-size nanoporous particles of 3D complexity which is typically found only in the biological world. The particles possess well-defined uniform cylindrical pores which diameter can be chosen in the range between 2 and 10nm. The mechanics of self-assembly of those 3D shapes is not well understood as of yet.
Here we present the results of our studies to reveal this mechanism. We demonstrate that the process of self-assembly occurs in three steps: 1) the assembly of 20-50nm silica “seeds”, primordial silica nanoparticles which already have nanoporous structure, 2) aggregation of the seed particles into micron size particulates of undefined shape, 3) minimization and thermalization of the free energy of the particles assembled in step 2.

Over the past decade, an impressive progress has been made in using the molecular recognition properties of DNA to control self-assembly of nanoparticles and colloids. Such particles when functionalized with DNA, represent a novel type of building blocks, and also open a new class of theoretical problems in statistical mechanics and soft condensed matter physics. In my talk I will discuss various aspects of this broad field that range from quantitative understanding of the interactions on the level of few particles, to properties of the resulting multiparticle structures.
The natural next frontier would be the control of the overall morphology of self-assembled mesoscopic objects, i.e. programmable architecture. I will review a number of possible strategies in attacking this problem, and present their theoretical analysis, numerical simulations and some early experiments. I will also make parallels between principles of programmable architecture with the examples of morphological control in biology
Research is supported by the U.S. DOE Office of Science and Office of Basic Energy Sciences under contract No. DE-AC-02-98CH10886

Development of synthetic methods for well-defined nanostructures has introduced new approaches for engineering functional materials. Single- and multicomponent nanocrystal arrays provide a powerful platform for designing “programmable” solids with tailored electronic, magnetic, optical and catalytic properties. We develop approaches to improve control over structure and composition of individual nano-building blocks, particularly focusing on the understanding of collective properties of nano- and mesoscale assemblies. Efficient charge, energy and heat transport are critical for many nano- and mesostructured electronic and optoelectronic devices. By designing surface chemistry which removes transport bottlenecks at interfaces and grain boundaries, we demonstrated solution-processed semiconducting materials with impressive performance. The examples include solution processed field-effect transistors with electron mobility over 300 cm²/Vs, thermoelectric materials with ZT>1.2 and solar cells with the power conversion efficiency above 12%, all achieved through rational assembly of surface-engineered nanoscale building blocks. These examples demonstrate utility of engineered nanomaterials for real-world technologies and applications.

Colloidal “molecules” comprised of hierarchically organized nanoparticles may become building blocks of new functional materials. Directed particle-particle bonding in a specific and reproducible manner is highly desirable but often challenging. Here we report a strategy toward that goal by directed-assembly of nanoparticles into well-defined “molecular” architectures via “click” reactions. Bonding structures were created on nanoparticles at controlled positions by modifying their surfaces with heterogeneously functionalized polymers bearing reactive “click” moieties. Highly selective and efficient “click” reactions are then conducted to covalently organize nanoparticles into colloidal “molecules”. We expect that these “molecular” architectures can be tuned via reaction stoichiometry and particle geometry. We will show our preliminary data on the successful assembly of gold nanorods into structurally defined heterogeneous architectures. We will also discuss the broad utility of this method to organize nanoparticles of different size and shape.

The 3D nanoporous structures of inverse opals (IO), synthesized from a sacrificial colloidal crystal template, are potential candidates for applications in photonics, sensing, and catalysis.¹ In order to utilize these structures as functional materials, tuning the IO composition is extremely important. The incorporation of metal nanoparticles into IO results in coupling of photonic and plasmonic properties, as well as the additional introduction of catalytic properties, thus greatly expands the possible applications of these composite materials.^2,3 Moreover, the precise control over metal nanoparticles distribution into inverse opals structures, in particular the controlled placement of such particles at the air/solid interface of the individual pores, results in a higher accessibility of nanoparticles. In this work we synthesized composite polystyrene (PS) colloids by covalent attachment of gold nanoparticles (AuNPs) to the chemically modified PS surface. These composite PS-AuNP colloids were subsequently used as colloidal templates for IO formation. The accessibility of AuNPs at the air/solid interface allowed further growth of nanoparticles at defined positions of the inverse opal structure. SEM and TEM measurements reveal the formation of ordered 3D porous structures with well controlled gold distribution. The use of these composite IO systems for catalytic applications will be demonstrated.
1. a) Freymann, G.; Kitaev, V.; Lotschzc, B. V.; Ozin, G. A. Chem. Soc. Rev., 2013, 42, 2528. b) Hatton, B.; Mishchenko, L.; Davis, S.; Sandhage, K. H.; Aizenberg, J. Proc. Nat. Acad. Sci., 2010, 107, 10354.
2. a) Tan, Y.; Qian, W.; Ding, S.; Wang, Y. Chem. Mater. 2006, 18, 3385. b) Yu, A.; Meiser, F.; Cassagneau, T.; Caruso, F. Nano Lett. 2003, 4, 177.
3. Y. Vasquez, M. Kolle, L. Mishchenko, B. D. Hatton, J. Aizenberg, ACS Photonics, 2014, 1, 53minus;60

All basic electronic devices are assemblies of several materials with different electronic properties. The challenge of large scale production is the correct assembly of those materials with precise control over layer thickness, interfaces and region-selectivity. The concept of self-assembly promises a highly reproducible and selective approach for the fabrication of functional and ordered nano-structures by cost-effective wet-chemical methods.[1] The Huisgen-1,3-dipolar cycloaddition is known as a powerful tool for the immobilization of materials on functionalized substrates.[2,3] Additionally, the copper-catalyzed alkyne-azide cycloaddition (CuACC) delivers high yields at moderate reaction conditions and can therefore be used for various kinds of materials.[4] In order to achieve region-selective deposition by this reaction, the surface needs to be pre-functionalized with attractive and repulsive domains. We demonstrate a general approach for hierarchical region-selective assembly of functionalized nanoparticles by using patterns of complementary self-assembled monolayers (SAMs) and a fluorinated alkyl-phosphonic acid. Our previous work has shown that AlO_x nanoparticles can be functionalized with mixed monolayers of phosphonic acids, in order to fine-tune its chemical and physical properties.[5] Deposition of the alkyne, respectively azide functionalized nanoparticles on the orthogonally azide, respectively alkyne terminated SAM patterns on the substrate by CuACC was achieved exclusively at the reactive centers. The first selectively immobilized layer of nanoparticles can then be further used for the deposition of orthogonally functionalized nanoparticles by a second CuACC reaction resulting in hierarchical 3D nanoparticle assemblies. The approach is expanded to various types of NP-cores (e.g. ITO, TiO₂, or FeO_x), which enables in principle the formation of electronic devices.
[1] J. C. Love, L. A. Estroff, J. K. Kriebel, R. G. Nuzzo, G. M. Whitesides, Chem. Rev. 2005, 105, 1103-1170.
[2] T. Lummerstorfer, H. Hoffmann, J. Phys. Chem. B, 2004, 108, 3963-3966.
[3] J. P. Collman, N. K. Devaraj, C. E. D. Chidsey, Langmuir, 2004, 20, 1051-1053.
[4] A. P. Upadhyay, D. K. Behara, G. P. Sharma, A. Bajpai, N. Sharac, R. Ragan, R. G. S. Pala, S. Sivakumar, ACS Appl. Mater. Interfaces,2013, 5, 9554-9562.
[5] L. Portilla, M. Halik, ACS Appl. Mater. Interfaces, 2014, 6, 5977-5982.

Discovering new approaches to self assemble nanoparticles (NPs) into mesoscopically-ordered structures can lead to novel materials with new functionality. A particularly fascinating tactic to control NP arrangements is to disperse them in a phase-separating fluid medium. This talk will present recent computational modeling results that explore and characterize the mutual evolution of dispersed NPs in binary and ternary polymer blends following a quench below the critical temperature inducing phase separation. The computational method used is a hybrid Brownian Dynamics-Cahn Hilliard model. The massive three-dimensional simulations specifically focus on chemically neutral NPs that segregate to polymer-polymer interfaces ultimately leading to stabilized mesoscale domains. The morphologies of both bulk and thin film samples will be presented. For thin film samples, the effect of an applied electric field in aligning the domains in the out-of-plane direction is also studied. Relationships between the average channel diameter, the channel density, and the interfacial NP packing fraction with varying NP volume fractions and polymer compositions will be presented. Extending these concepts to ternary polymer blends leads to expanded possibilities for unique composite structures, including various ‘trijel&’ morphologies. From a practical standpoint, these composites have applications as catalytic membranes upon selectively etching one of the polymer domains, thereby leaving mesoscopic pore channels with nanoparticle-coated surfaces.

We discovered a highly anomalous light-induced phenomenon of light-absorbing materials on a substrate under an optical microscope. When liquids containing light-absorbing materials were irradiated with a visible laser light at high power (> 1 mW), a doughnut-shaped microstructure of a highly fluorescent character was formed on the surface of cover glass. In order to elucidate the origin of this novel phenomenon, we analyzed this structure by microscopic and spectroscopic techniques. We expect this result will find many applications including construction of a rigid, fluorescent marker on the glass coverslip.

We report a novel concept for the generation of mesoporous TiO₂ and carbon-TiO₂ nanostructures with highly roughened surfaces at the nanoscale and application for critical elements in high-efficiency photovoltaic devices or visible light active photocatalysis. Those structures were prepared using triblock copolymer P123 simultaneously as template and carbon source combined with colloid self-assembly. A commercially available P123 played key role in the generation of nanovoids within the hierarchical mesoporous TiO₂ bead and also as a carbon source. Firstly, the photovoltaic device with optimized amount of mesoporous carbon-TiO₂ beads, enhanced conductivity due to carbon moieties which contributed to the fast electron transfer and low recombination. Moreover, highly ordered hierarchical mesoporous TiO₂ networks can provide fast electron transport paths, enhance light scattering, facilitate infiltration of the electrolyte, and ultimately increase the power conversion efficiency. It was observed that the incorporation of mesoporous carbon-TiO₂ beads into the conventional photoanode of dye sensitized solar cells led to enhanced photovoltaic performance by ~25.78 %. Secondly, TiO₂ has been recognized as representative metal oxide semiconductor material with excellent photocatalytic activity due to its good stability, nontoxicity, and UV absorbance. However, the lack of visible light activity has been a critical issue due to the relatively large band gap. Highly ordered mesoporous inverse opal nanostructures with nano-textured surface morphology and multiple-length scale nanopores provide increased light-activated surface area and scattering effect, leading to enhanced photoabsorption efficiency and the transport of matters. A significantly enhanced visible light photocatalytic activity was demonstrated for the mesoporous carbon-TiO₂ inverse opals in terms of the degradation of p-nitrophenol and photoelectrochemical water splitting.

Ion beam irradiation is used widely in semiconductor manufacturing process for producing p-type and n-type materials. Generally, ion beam irradiation induces a damaged layer corresponding to the projected ion range on the semiconductor surface. Further irradiation transforms the damaged layer into an amorphous structure. However, porous structures, such as voids, holes, fibers with nano to submicron dimensions, are formed on Ge, GaSb, and InSb surfaces by irradiation. It is clarified that such phenomena occur as a result of migration of collision cascade generated point defects. Porous structures on the semiconductor surface have potential applications for electronic and photonic devices. The problem with those structures is lack of regularity. Therefore the authors proposed a nanofabrication technique, which is combination of top-down and bottom-up approaches utilizing focused ion beam (FIB) on the basis of those phenomena. First, ordered initial structures are formed on the surface by spot irradiation, and then the initial structures are developed by homogeneous irradiation. Formation of periodic nanostructures with 60 nm dot interval was achieved by this method on Ge surface in previous work. In this research, searching for best irradiation condition to fabricate the minimum nanostructures in Ge was performed. Those processes were carried out using 30 keV Ga⁺ in FIB (FEI Quanta 3D 200i) at room temperature and liquid nitrogen temperature. Single crystals of Ge (001) were used in wafer. The chamber vacuum was 5×10^-4 Pa. Structural changes associated with ion beam irradiation were observed by a field emission scanning electron microscope (FE-SEM). The result showed that nanostructures with 30 nm dot interval were formed in low fluence irradiation at room temperature, although some structures were collapsed. Probably nanostructures were coalesced with neighbor structure due to small intervals, and the distance of point defect migration is longer than a wall thickness of nanostructures.

Fresh water is an ever decreasing resource that can be found in small amounts in almost every environment. In nature, there are many organisms, such as the Stenocara beetle which lives in the Namib Desert survives by drinking fog-water that collects on its wing case. The unique design of the Stenocara beetle&’s back involves randomly spaced bumps with hydrophilic peaks surrounded by hydrophobic areas the guide water into its mouth. The Stenocara beetle stands on a sand dune, facing into the morning wind at a forty-five degrees angle. With its head facing downward and its bottom upward, the minute water droplets from the fog collect on the superhydrophilic peak of each bump. When the water droplets grow big enough, they detach from the bump peaks, fall onto the superhydrophobic areas between the bump peaks and are guided downward to the beetle&’s mouth. Additionally, Stipagrostis Sabulicola, and Cotula Fallax, are some other organisms that are able to effectively capture water droplets from the fog of the morning desert by using hydrophilic/hydrophobic combinations. Here we report a new approach for anisotrophically functionalized vertically aligned carbon nanotube forest (NTF) as superhydrophilic/superhydrophobic. Due to combination of hydrophilic and hydrophobic surfaces, we were able to utilize the material for water collection from dry air and high humidity air. By this approach the water microparticles in air can be captured and stored in comparatively large amounts.

Blended organic photovoltaic cells are of scientific and technological interest as they have the potential to become an attractive alternative for low-cost energy generation. However, the present efficiency of organic photovoltaic cells lies around 10%, much below the value for inorganic photovoltaic cells. Energy level, band gap, and mobility of organic materials are crucial factors in achieving high power conversion efficiency. From mesoscopic aspect, controlling the phase morphology of the two components (donor/acceptor) in the photoactive layer is important issue, because the exciton diffusion length in organic materials is of the order of 10 nanometers. The mesoscopic morphology of donor-acceptor organic materials have a huge effect on power conversion efficiency, because of most of the donor or acceptor domains are isolated or far from the electrodes (anode and cathode). This morphology leads to a long conduction path which causes possible recombination of the electron and hole pairs and lowers the efficiency of the cell. In the present study we have evaluated the phase morphology of donor-acceptor organic materials to realize a suitable high efficiency. This research used computational resources of the K computer and other supercomputers of the HPCI system provided by the RIKEN Advanced Institute for Computational Science, Cyberscience Center, Tohoku University, and Information Initiative Center, Hokkaido University through the HPCI System Research Project (Project ID: hp120010, hp140014). The authors would like to express their sincere thanks to the staff of the CCMS, IMR, Tohoku University for their continuous support of the SR16000-M1/320 supercomputing facility.

Mesoporous silica thin films (MSTFs), which were three-dimensional structure, have been prepared by the evaporation-induced self-assembly (EISA) method using a block copolymer F-127. We performed Low angle X-ray diffraction (XRD) on non-treated MSTFs and scanning electron microscope (SEM) on films electro-deposited with Pt to characterize films&’ structure. The non-treated films were equipped on Teflon cell and investigated how mass transport inside three-dimensional MSTFs by using cyclic voltammetry (redox species: Ru(NH₃)₆³⁺Cl₃ and supporting electrolyte: KCl). The results demonstrated that shape of redox curves of probe was influenced by concentration of electroactive species. At low concentration of redox probe, when scan rate was faster, difference between cathodic peak and anodic peak (ΔE_peak) was more reduced, which means adsorption of Ru(NH₃)₆³⁺ on silica was much predominant than diffusion of Ru(NH₃)₆³⁺ inside pore. At high concentration, these results were reversed. In this case, diffusion of Ru(NH₃)₆³⁺ was much predominant that adsorption of Ru(NH₃)₆³⁺ on silica wall. Adsorption of Ru(NH₃)₆³⁺ on silica was caused by attraction between negative-charged silica (in neutral condition) and Ru(NH₃)₆³⁺. To examine interactions between silica wall and Ru(NH₃)₆³⁺, we added HCl and KOH to modulate the surface charge of silica. At acidic condition, the intensity of redox peak was decreased and positive-shifted from original-condition peak, which means repulsion between silica wall and Ru(NH₃)₆³⁺ was occurred. At basic condition, that of redox peak was increased and negative-shifted from original-condition peak, which means Ru(NH₃)₆³⁺ was more strongly attracted to silica wall and became stabilized. Also, we investigated the effect of nonelectroactive species by varying the concentration of supporting electrolyte. When the concentration of electrolyte was higher, the intensity of redox peak was more decreased. The reason was that the amounts of accumulated ions inside pore were larger with increasing the concentration of electrolyte, which hindered the attraction between silica wall and redox probe. Our research data provides a basic information for understanding the mass transport inside few nanometer-sized mesoporous thin films and promotes the application of mesoporous silica for catalysis, sensing, and membrane.

Separation of natural gas from CO₂ requires an increased CO₂ permeation rate as well as improved CO₂/CH₄ permselectivity. Most current materials investigated towards this end have been bound by the “Robeson tradeoff”. In order to exceed this upper boundary, the invention of innovative materials is required. Porous covalent organic frameworks (COFs) are powdered materials which have emerged as potential candidates for future gas storage applications. More recently we have developed chemistry and processing conditions which enable production of these covalently-linked organic materials as thin films (substrate-supported or free-standing) over macroscopic length scales. We refer to the resulting materials as structured organic films (SOFs). Researchers at the Xerox Research Centre of Canada and the Battelle Memorial Institute are currently collaboratively exploring the use of SOFs as permselective membranes for gas separation and / or storage.
This paper will present the chemistry and engineering used to create porous SOFs, which are expected to exhibit unique properties controlled by the specific chemistry and morphology of the building blocks. The physical, electronic, and transport properties were measured for a training set of porous SOF membranes. These results were used to develop models for both the permselectivity and mechanical properties of the membranes. This paper will then discuss synthetic directions to produce SOF membranes with enhanced permselectivity, and the extent to which this class of materials can exceed the limitations of the “Robeson tradeoff”.

Self-assembled monolayers (SAMs) are a widely used platform for studying the physical and electronic properties of organic/organomettalic molecules. The quality, and hence properties, of simple n-alkanethiolate SAMs on Au or Ag have shown a dependency on the overall length of the molecule. The odd-even effect is one such phenomenon that is dictated by whether the n-alkanethiol has an odd or even number of carbons. This effect arises from differences in tilt angle, i.e., the orientation of the terminal -CH₂CH₃ moiety of these alkanethiols. Additionally, the difference in orientation of this terminal moiety is inverted when the underlying substrate is switched from gold to silver. Previously, this odd-even effect was reported to have no impact on the wetting properties of these SAMs. Laibinis and co-workers proposed that there was insufficient interaction between the water molecule and the SAM at the Van der Waals interface. Previous studies of the wetting of water on alkanethiol SAMs, however, were performed using as deposited metal (M^AS) substrates which are known to be rougher than template stripped (M^TS) ones. Interestingly, we observed that asperities on Au^AS and Ag^AS are too large to produce a reliable monolayer, which is why the previous studies observed no odd-even effects. Investigation of the wetting properties of n-alkanethiolate SAM's on Au^TS, however, revealed an odd-even effect. When the study was repeated with Ag^TS the inverse odd-even effect was observed albeit with a smaller variation in theta;_s between the odds and the neighboring evens. We therefore infer that realization of subtle effects on the surface of the SAM is highly dependent on the quality of the underlying surface.

This presentation focuses on preparing clusters of gold nanoparticles with defined stoichiometry and symmetry. In our work, gold nanoparticles with sizes between 5 - 50 nm are assembled via DNA mediated interactions. The self-assembly kinetics are altered by manipulating interparticle energetics by changing DNA coverage, length, rigidity, and sequence, as well as and nanoparticle size. The self-assembled clusters are assembled at different stoichiometries and size ratios, collecting after appropriate reaction times, and purified via ultracentrifugation. The conditions for such assembly and purification will be discussed. The assembled clusters were characterized via dynamic light scattering (DLS), UV-visible spectrophotometry (UV-vis) and fluorescence spectroscopy. The morphology of the clusters were characterized by transmission electron microscopy (TEM) and in-situ cryo-TEM.

In this presentation we describe the preparation and purification of multi-color quantum dot clusters. Using purpose-built CdSe/ZnS quantum dots and rods modified with single stranded oligonucleotides (ssDNA), clusters with defined stoichiometry and emission wavelengths were constructed by DNA mediated interactions using a solid phase assembly approach. To control stoichiometry and to improve assembly yields, the clusters were assembled and released in a step-wise manner at a colloidal solid support. The quantum dots were phase transferred using a polymer wrapping approach, and conjugated with ssDNA via EDC/NHS and click chemistries. Importantly, the DNA modified conjugates, and the assembled clusters were purified via ultracentrifugation that resulted in a more reactive and colloidially pure system. The clusters optical characteristics were characterized by fluorescence spectroscopy and microscopy, and FRET analysis was utilized to probe energy transfer within the clusters. The cluster morphology and hydrodynamic properties were characterized by TEM and DLS, respectively. The use of these clusters for sensing and multi-color multiplexing will also be discussed.

Cadmium telluride (CdTe) nanoparticles (NPs) are a promising type of nanomaterial with convenient properties for solution in processing of electrical devices. They are typically used as thin polyelectrolyte films where CdTe nanoparticles present advantages for advanced electronics. Layer-by-layer (LBL) assembly is one of the most versatile methods for preparation of organic-inorganic nanocompoistes and is based on sequential layering of inorganic nanoparticles and polymers. However, it is difficult to achieve highly conductive LBL films of nanoparticles. Here, we show oriented attachment of CdTe nanocrystals in LBL films. CdTe nanochains serve as charge-transport elements in the electronics. Oriented assembly of CdTe can not only increase conductivity, but also contributes to their mechanical properties.

Crystalline porous materials can be engineered for drug delivery, sensing, and catalysis by the incorporation of functional guest molecules into their pore interiors. Metal-organic frameworks (MOFs) offer many opportunities for host-guest composites due to their well-defined and chemically tunable pore surfaces and unique properties such as framework flexibility and exchangeable ligands. Most of current MOF-guest composites are formed by diffusing guest molecules smaller than MOF aperture size and the small guests stay in MOF through electrostatic interactions. However, approaches for incorporating large and more diverse guests are still limited. Here, we introduce a new concept for incorporating large guests into MOF under linker exchange conditions. Expanded apertures created by the ligand exchange process allow large guest molecules to diffuse into the MOF pore. After guest loading, association of the ligand closes the large aperture, trapping the guest molecule in the MOF pore. This new approach to guest incorporation is expected to be general because framework linker exchange has been carried out under various conditions and exists in a large number of MOFs.

In the recent years, the new materials can be combined to fabrication of fiber carbon composite with specific properties as electrical, thermal and mechanical to development of alternative devices, such as photocatalyst system, energy storage material and piezoelectric material. The TiO₂ and LiNbO₃ nanoparticles have been attachment on carbon fiber, respectively, by previously surface modified, under self-assemble which were prepared by growing oxide particles on textured carbon assisted by hydrothermal synthesis in microwave furnace, the particles-fiber interactions are analyst by comparative study with sputtering deposition and conventional particles impregnation process, respectively. Hence this work, a carbon fiber roughness was modified by a chemical method using HNO3 97% at 103 °C, with exposure time 10, 20 and 30 minutes without degrade the fiber, additional the effect of various parameters such as concentration, pH, pressure (or temperature), time was investigated on hydrothermal synthesis. These sample were characterized by FE-SEM, showing to higher exposure times a densely packet of TiO₂ and LiNbO₃ nanoparticles monolayer, individual, are obtained. The photocatalytic activities were evaluated with dye (Rhodamine B) under visible-light irradiation, the kinetics study was monitored, the results showed that carbon fiber doped with ceramic oxide under visible light display efficient removal of hazardous materials. Additionally, X-ray diffraction (XRD), Raman, surface properties and conductivity studies were performed to investigate the morphology of flexible composite based on fiber carbon revealed the promising properties to fabrication of catalyst or device.

Enhancement of catalytic activity and control of the reaction pathway to produce a high yield of desired product with 100% selectivity are of paramount interest for the development of energy-saving and eco-friendly catalytic reactions. In order to simultaneously achieve high catalytic activity with 100% product selectivity, catalytic systems should be tailored delicately. Synthetic development of metal nanoparticles (NPs) with various sizes and shapes can be one of the great contributions towards realization of this goal. Along with this, the development of various porous inorganic supports like mesoporous (2

Hierarachical structure have attracted great interest in recent years because of their large surface area, high porosity. In addition, their enhanced accessibility to the internal surface, originating from the hierarchical pores and small particle size in the nanometer range, is expected to be highly beneficial for reactions involving bulky guest molecules. Unfortunately, many hierarchically materials consist of a simple and catalytically inactive component, as exemplified by silica. For the practical application, such as catalysis, adsorption, etc., functionalization of hierarchical materials are required.
Among numerous method of functionalization, a direct synthesis and post-grafting method has been widely used. Although these conventional methods for functionalizing inert materials have been somewhat successful, they suffer from some important limitations. For instance, a direct sysnthesis route generally results in the collapse of structural uniformity when a large amount of heteroatoms are introduced. On the other hand, the post-grafting method can introduce a large amount of heteroatoms, but can lead to an inhomogeneous surface dispersion of functionalities. Accordingly, the alterantive functionalizing method should be developed.
Herein we developed an efficient method for functionalzing hierarchically mesopous nanospheres with controllable active sites. The nanosphere exhibits uniform shape, 3D wide-open pore (> 10 nm), and high surface area (ca. 500 m²/g) in a wide range of compositions. The incorporated functionality (acid properties; acid type, strength and amount) of the nanospheres are easily controllable with varying the Si/Al ratio in prepration procedure. The catalytic activity of the developed nanospheres was tested by reaction with bulky molecules (cracking of 1,3,5 triisopropylbenzene, hydrolysis of sucrose). The nanospheres showed the higher activity and stabililty compared to microporous HZSM-5 and mesoporous AlMCM-41 catalysts due to its high accessibility derived from their unique structure. The performance of the nanospheres in hydrolysis of sucrose was more than doubled than the reference catalysts.

Titania is an attractive semiconducting materials due to its efficient charge separation and high carrier mobility. In addition, photocatalysis based on titania has attracted much attention for effective utilization of solar energy in environmental purification and water splitting for hydrogen generation. The incorporation of plasmonic nanoparticles onto wide-bandgap titania enables photocatalysis in the visible region as the strong surface plasmon resonance excitation of nanoparticles. When the 3D structure is applicable to the titania, the light-harvesting efficiency can be enhanced due to the plasmonic coupling.
Previously, the synthesis of submicro-3D flower-like titania needs the inert conditions due to the hygroscopic properties of titanium precursor. Here in, we developed the facile method for the 3D flower-like titania with rutile phase where average size is 600-700 nm. As the thermal treatment time increases, rutile nanorods aggregate on the pre-existing crossed titania structure resulting in 3D spherical shape. The gold nanoparticles are deposited on various titania including 3D flower-like rutile titania by simple impregnation method. As compared to the conventional system, the Au/3D flower-like titania was found to enhance the visible-light photocatalytic activity via methylene blue degradation. Furthermore, we proved and quantified the plasmonic coupling effect by photocurrent analysis, FDTD simulation, and photoluminescence spectroscopy.

Electrochemical energy storage in supercapacitor devices is emerging as prominent technology for high power applications in modern portable electronics for which material systems based on conducting polymers such as polypyrrole which exhibits pseudocapacitance due to charge transfer reactions is widely studied. Most studies focus on 2-dimensional (2-D) random microporous structures for high surface area ion accessibility. Our strategy is to develop electrodes in the 3-D nanoscale architecture for accelerate ion kinetics and pervasive ion access. We synthesized vertically aligned TiO₂ nanotube ordered arrays as core and created conjugated polypyrrole conducting polymer nanotube sheaths for improved electrochemical energy storage.
The vertical TiO₂ nanotube arrays as core of 3-D nanoscale electrode architecture were synthesized over Ti sheet by anodization at +30 V dc in ethylene glycol with 0.25 wt % NH₄F. TiO₂ nanotubes are electrically conducting and amorphous as shown by XRD studies. TiO₂ nanotube arrays morphology is modified as close-packed 3-4 mu;m long and 45-50 nm diameter by adding 2% water. The redox active polypyrrole sheath is created by ultra-short pulsed current electropolymerization under the action of surfactant which homogeneously nucleates and uniformly deposits highly conjugated polypyrrole over inner and outer walls of TiO₂ nanotubes. Polypyrrole sheath thickness is controlled through number, typically 10-110k pulse cycles each of 2 mA.cm^-2 amplitude.
Electrochemical properties of the 3-D nanoscaled TiO₂ nanotube core-polypy rrole sheath electrodes relevant to the energy storage were investigated. Zero current axis symmetric and rectangular cyclic voltammetry plots in -0.1 to 0.5 V range at variable 10-100 mV.s^-1 scan rates testify highly pseudocapacitive electrode behavior. The redox processes are fast in such nanostructured electrodes. Detailed electrochemical impedance spectroscopy (EIS) studies at various polyprrole sheath thickness attained through controlled number of polymerization current pulses elucidate the electrochemical processes during the evolution phases of the polypyrrole sheath over TiO₂ nanotube and the electrolyte interface. High areal capacitance density of 48 mF cm^-2 and low charge transfer resistance 12 ohm.cm^-2 with least ion diffusion limitation are realized at optimized polypyrrole sheath thickness. Raman spectra studies reveal anion at specific chain locations involve in the redox process. Energy and power density of the single electrode system was evaluated by systematic charge-discharge plots generated at different 1-3 mA.cm^-2 current densities which show cyclic stability of 3-D core-sheath electrodes. This paper reports pulsed electropolymerization synthesis, structure and electrochemical aspects of the polypyrrole sheath structured over TiO₂ nanotube core and describes the energy storage performance of such structures in the 3-D nanoarchitecture.

Poly(amidoamine)(PAMAM) can bind and separate heavy metal ions in aqueous solution. In this study, we developed a process to fabricate 50~300mu;m porous PAMAM particles by using silica particles. These porous particles were prepared via inverse suspension polymerization with acrylamide monomers and silica particles. The silica particles were then removed by hydrofluoric acid to produce porous particles. SEM images showed many small pores in PAMAM particles. Detailed synthesis and characterization of the particles and their swelling ratio and metal ion absorption behavior will be presented.

We demonstrate a simple technique to prepare uniform C₆₀ nanocrystals ultara thin film. Solution process is a simple and low energy saving process for fabricating organic electronics devices. However, the organic materials should be soluble in a solvent. Usually, π-conjugated materials are used an organic semiconductor. These materials are less soluble because of the strong π-π interaction. Therefore, soluble groups such as alkyl chain are attached on to the π-conjugated molecules.
In this paper, we have successfully fabricated thin film using typical insoluble organic semiconductor materials such as pristine C₆₀. Fullerene C₆₀ is the attractive material for organic devices due to their high carrier mobility. In our method, fullerene C₆₀ nanocrystals were fabricated by reprecipitation method and the nanocrystals are assembled in two- and/ or three-dimension using a liquid-liquid interfacial assembles technique and electrophoretic deposition method. We have reported that monodispersed C₆₀ nanocrystals can be easily prepared prepared using the reprecipitation method. The shapes and innner structures of the resulting C₆₀ nanocrystals were strongly dependent on the combination of good and poor solvents. In addition, we have succeeded in preparing layerd structure of C₆₀ nanocrystals. Mono-nanocrystal layer can obtained by liquid-liquid interfacial assemble technique and multi-nanocrystal layer can obtained by electrophoretic deposition method. Details of the controlling the size, morphology and structures of fullerene nano/microcrystals will be discussed.

Nowadays, continuous scientific endeavors are being directed toward low-cost, mild, scalable and reliable synthesis of graphene-based materials, in order to advance various graphene-related applications. So far, specific surface areas of current bulk graphene powders or graphene-like nanosheets are yet much lower than the theoretical value (2630 m²/g) of individualgraphene, remaining a challenge for carbon chemists. Herein, mesoporousgraphene-like carbon sheetswith high specific surface area (up to 2607 m²/g) and high pore volume (up to 3.12 cm³/g) were synthesized by performing polyimide chemistry in the molten salt “solvent.” In this process, abundant pyromelliticdianhydride and aromatic diamine undergo polycondensation together with further carbonization in molten KCl-ZnCl₂, in which in-situ formed linear aromatic polyimide with a sp² hybridized carbon skeleton could be directly coupled and rearranged into two-dimensional graphene-like nanosheet around the “salt scaffold”. Carbon nanosheets with well-defined mesopores (~3.5 nm) could be easily obtained by washing salt melts in water, while those salts could be recovered and reused for subsequent reaction. The nitrogen atoms in amine also afforded the resulting carbon with uniform foreign atoms (nitrogen content = ~ 6%). Moreover, holey carbon sheets with well-dispersed and through-plane nanoholes (diameter: 5-10 nm) could be constructed by using different monomers. Being a potential electrode material in supercapacitor, the as-made carbon nanosheet possessed a significant specific capacitance (131.4-275.5 F g^-1) even at a scan rate of 2000 mV s^-1. Additionally, powerful nanohybrids of carbon sheet-Co₃O₄ were also prepared with good performance in the aerobic oxidation of alcohols and amines to aldehydes and imines, respectively.
This work was supported as part of the Fluid Interface Reactions, Structures and Transport (FIRST) Center, an Energy Frontier Research Center funded by the US Department of Energy, Office of Science, Office of Basic Energy Sciences under Award Number ERKCC61

#12288;We have successfully fabricated core-shell type hybridized micro particles composed of mesoporous manganese oxide (MPMO) and fullerene C₆₀ nanocrystals (NCs). In the pseudo capacitor faradic and non-faradic charge storage occurred, which resulted in high charge density. Manganese oxide in one of the materials to apply in the pseudocapacitor because of it low material cost. However, manganese oxide has low electric conductivity, which limit their film thickness.
To obtain the psedocapacitor electrode materials with high energy density by low cost materials and energy saving method, core-shell type hybridized micro particles were fabricated. In the micro particles, MPMO acts as pseudocapacitor whereas C₆₀ NCs act as conduction pass to connect each micro particles. The micro particles ware synthesized by reducing KMnO₄ with maleic acid followed by co-reprecipitaion of C₆₀ NCs on the MPMO micro particle. Scanning electron microscopy image showed a core-shell structure, which composed of C₆₀ NCs as a shell and MPMO as a core with an average diameter of 10 mm. The electrochemical property of the core-shell micro particles as well as MPMO micro particles was studied by cyclic voltammetry. The charge amount of micro particles was doubled in MPMO particles, which suggests C₆₀ NCs acts as conduction pass. The effect of size and the core-shell ratio to the charge storage will be discussed.

Multiscale porous architecture that comprises macroscale template containing mesoporous structures has drawn significant attention due to its advantages in highly increased surface area and enhanced mass transport characteristics. Therefore, recent researches have been focused on the applications of catalyst design for highly selective chemical reactions or electrodes for high capacity energy devices. In particular, as for a macroscale template, inverse opal (IO) structures based on colloidal self-assembly have been extensively explored because of their structural regularity and controllability. However, reported approaches of constructing double periodic IO structures have mostly relied on a means of filling ensembles of nanoparticles inside the unit hollow chamber of the IO template, thereby eventually disrupting the intrinsic porosity of the primary IO phase. Moreover, since the solidification process of the precursor is accompanied by inevitable inclusion of a number of defects and cracks as a result of large volumetric shrinkage, it has been inherently restricted to use these multiscale (double periodicity) porous structures for large-scale applications, such as membranes.
To overcome this limitation and realize the multiscale porous nanoarchitectures over a large area, in this study, we present a means of creating hierarchical IO structures using core-shell structured colloidal particles as a material for forming opal-phase self-assembly. By means of selective removal of the colloidal shell, instead of entirely dissolving the internal colloid, we eventually create the colloidal particle nested inverse opal (CPN-IO) structures. The resulting CPN-IO structures hold several structural advantages in that the internal porosity is readily tuned by the control over core-shell ratio of the colloidal particles and uniform-sized nanochannels can be created through the interconnected pores of the primary IO frame. Since the nanochannel size can be controlled in a range between 5 and 50 nm and the membrane structure is demonstrated over a large area (2-inch wafer) in the form of free-standing films, CPN-IO structures can be applied for the separation of nanoparticles with high selectivity. In addition, we present theoretical calculation for estimating the effective nanochannel size inside the CPN-IO by means of constructing a relevant geometric model.

Natural biopolymer like cellulose is a promising alternate to conventional biotemplates like DNA, viruses and some proteins. Here cellulose fibers were used as a template for the synthesis of gold (Au) nanoparticles with the assistance of surfactant CTAB. Nanoporous titania (TiO₂) was then synthesized on Au decorated cellulose via the sol-gel technique to form a hybrid structure. The plasmonic properties of Au nanoparticles were exploited to enhance photocatalytic performance of this biotemplated hybrid structure. The variation in the thickness of the TiO₂ layer was also included in the study to obtain a most favorable hybrid structure for maximum hydrogen generation via water splitting during the photocatalysis experiment. Further the biotemplated hybrid nanostructure was also characterized by transmission electron microscopy to study the composition and structure of each component and interface.

It is well established that confinement induces significant changes in the thermodynamic behaviour, structure and dynamics of the occluded molecular phases. For example a confined molecular fluid has a critical temperature lower than its bulk counterpart and the temperature difference increases with decreasing pore size. Similarly, the melting temperature of a confined solid may be shifted from the bulk value and the sign of the temperature shift will depend on the nature of the interaction between the confined liquid and the walls of the 3D mesoscale structure [1]. As a last example, the dynamics of a liquids confined in mesoporous silica shows a pathological behavior characteristic for the type of matrix (ordered / disordered, connected or not) [2].
Unlike water and organic fluids [3,4], adsorption phenomena in chalcogens has rarely been studied from the viewpoint of thermodynamics, structure and dynamics. In this contribution, we present a study dealing with the 3D mesoscale confinement of sulfur. Sulfur is the most puzzling element in the chalcogen family, in both solid and liquid state. In the solid state it possesses a huge number of alloptropes [5] whilst in the liquid state a polymerization transition is observed. The confinement has been realized in different 3D porous structures which differ by their chemistry (carbon or silica based structure), their structure (crystalline or amorphous), their network type (ordered or disorderd) and their pore sizes. We will show how the nature of the 3D network influences the solid-solid phase transitions and the melting behavior. Finally the persistence or not of the polymerization transition will be discussed.
[1] L. Gelb et al , Rep. Prog. Phys., 62, 1573 (1999)
[2] P. Levitz , Adv. Coll. Int. Sci., 76-77, 71 (1998)
[3] C. Alba-Simionesco et al., J. Phys. : Cond. Matter 18, R15 (2006)
[4] D. Morineau et al., J. Chem. Phys, 117 , 19, 8966 (2002 )
[5] R. Steudel and B. Eckert, Top Cur.Chem. 230,1 (2003).

Solar energy is believed to be the ultimate energy source to meet the global energy demand due to the dramatic world population growth. Photoelectrochemical (PEC) cells harvest solar energy and convert it into hydrogen fuel through water splitting, a very promising sustainable clean and CO₂-free energy solution that combines the energy harvesting and storage processes. Hydrogen fuel has higher energy density and zero carbon emission compared to hydrocarbons. It is broadly recognized that there is no single material that can meet all the requirements for efficient and durable solar hydrogen production. On the other hand, low-cost materials, facile and cost-effective fabrication techniques are necessary for practical solar hydrogen generation in large scales.
In this presentation, we report solution growth of earth-abundant, environmentally-benign metal oxide nanowire heterostructures grown on high-surface-area mesh substrates for cost-effective, high-efficiency, and scalable solar hydrogen production in a neutral solution. In particular, we present core/shell and branched nanowire heterojunctions made from different metal oxides such as Cu₂O, CuO, ZnO, and TiO₂. The integration of small and large bandgap metal oxide nanowires offers a unique combination of desired properties that are crucial to high-efficiency solar energy harvesting and hydrogen generation, including improved light absorption, enhanced charge separation/transportation/collection, increased reaction surface area, and improved gas evolution kinetics. Different characteristics of metal oxide nanowire heterostructure photoelectrodes, including morphology, atomic structure, PEC performances, solar conversion efficiency, and long-term stability are investigated in detail and will be presented.
Our achieved results reveal a promising practical solution for high-efficiency, sustainable, clean solar hydrogen fuel generation using cheap, nontoxic materials synthesized with low-cost, facile and scalable fabrication processes.

Photoactive nanoporous films are assembled by cross-linking M13 bacteriophages using a layer-by-layer process. By genetically engineering the bacteriophage to display peptides with an affinity for noble metals, plasmonic nanoparticles can be dispersed throughout the thin film in a manner that avoids aggregation, enabling them to act as reliable probes for sensing the effective refractive index inside the film. Furthermore, the resulting plasmonic bacteriophage scaffold can act as a template to build crystalline titania nanoporous networks via biomineralization, allowing sensing to proceed in both biomolecular and inorganic films. This is possible because the localized surface plasmon resonance (LSPR) frequency of sub-wavelength gold nanospheres is very sensitive to the complex dielectric function of its surrounding medium. By combining Mie theory with effective medium theory, the absorption peak position of well-dispersed gold nanoparticles in the bacteriophage-film was predicted and found to be in excellent agreement with experimental measurements. Moreover, the analytical model developed herein allows the porosity of both the biological and semiconducting networks to be determined by simply measuring the absorption peak position of the gold nanoparticles with a spectrophotometer. It is expected that both the organic and inorganic nanoporous networks will find further use in biomedical and energy applications as slight changes in the local environment within the pores of the nanoparticle-loaded film can be detected by monitoring the LSPR peak position in the absorption spectrum.

Nanoimprinting lithography (NIL) has attracted a significant attention as a next generation patterning techniques due to its simplicity, versatility, low-cost, high-fidelity, and potential for achieving high throughput. It is developed now in many laboratories and efforts have been considerably increased toward the possible applications in electronics, photonics, and biology. NIL is a process based on mechanical deformation of a material to the shape of a mold. The preferred materials are thermoplastics and UV-curable resists due to their high formability by viscous flow. There are only a few reports on NIL for inorganic materials although there is a growing demand for inorganic materials with designed nanostructure on the surface.
Direct imprinting of porous substrate (DIPS) is a relatively new concept for patterning the surface of inorganics. Reusable stamps with sub-micrometer scale patterns were applied directly to nano-porous materials. This results in compression or crush of the porous network and transfers the stamp pattern onto the surface of the porous materials. The imprinting can be carried out at room temperature even if the material has high deformation point. This technique has been applied to porous TiO₂ and Al₂O₃ prepared by anodic oxidation of Ti and Al substrates, and porous Au fabricated from phase separated Au-Ag alloy. The vertical and lateral resolutions of the imprinting have been reported to be below 5 nm and 100 nm, respectively [1].
In this work, we applied the DIPS techniques to porous glass prepared from conventional phase-separated glass. Rapidly-quenched homogeneous SiO₂-B₂O₃-Na₂O glass was heated at 575 ^oC for 1 hour to cause phase separation into a SiO₂-rich and a B₂O₃-rich phase. The phase separated glass was then immersed in HNO₃ to etch the B₂O₃-rich phase out leaving the SiO₂-rich phase behind. The pore size is about 10 nm. The transmittance is as high as 90 % from the ultraviolet to near infrared region, which is superior to that of polymer materials such as PMMA. The imprinting was carried out at room temperature in air by using commercial quartz mold. The grating structure with the pitch of 100 nm was well transferred onto the surface of the nano-porous glass. The structure has high thermal durability up to 500 ^oC. The DIPS for phase separated glass is a facile and scalable approach for the patterning of inorganic surface, because of their simple fabrication processes, i.e., conventional melt-quenching and room temperature imprinting. It has potential applications in electronics, photonics, and biology.
[1] J. D. Ryckman, M. Liscidini, J. E.Sipe, and S. M. Weiss, Nano Lett, 11, 1857-62 (2011)

Electrospinning can integrate nano/micro-scale structures to build functioning meso-scale devices. Here we illustrate an example that 3D electrospun polystyrene fibers closely mimicking the unique architectures of multi-direction nano-spiderweb are being used to produce immobilizing devices for Cimex lectularius. These insects are very difficult to trap since they do not respond to lures, and are resistant to chemical solutions. Here we show how an electrospun network of surfactant modified polymer fibers can be used to immobilize the insects. The polymer network is carefully designed such that the diameter of the fibers fits exactly between the setae on the legs of the insect. The spacing between fibers is engineered to be on the micro scale such that the leg of the insect can penetrate. When the insect moves, the legs become trapped in a ratchet type of structure. The body of the insect is platelet like in order to distribute its weight over a large area. Hence the insects apply very little traction forces. In order for them to be trapped, the mechanical response of the fibers has to be specifically tailored so that it is elastically deformed, without fracturing or flowing. Hence the modulus has to be tailored within a narrow regime. We show how this can be accomplished using surfactants with optimized processing variables, increasing the surface charge of the fibers. When the stretching and lengthening of the polymer fiber takes place where solvent evaporating and the increased charges due to the surfactant within the polymer repelling each other. Due to the presence of the electrical charges on the fiber and inability of the fiber to discharge quickly, enhanced repulsion between the fibers, as deposited, cause them to be spaced out giving a fluffy 3 Dimension fiber ‘cloud&’ structure. We utilized Scanning Electron Microscope (SEM) and AFM nanoindentation to characterize the dimension and mechanical response of the fiber respectively. And we also characterized the fiber surface charge and electrical conductance by Zeta potential measurement. Carefully controlling and tailoring the electrospinning parameters we can now create a trap where multiple length scales are integrated to produce a meso-scale working device.

The synthetic parameters of cerium oxide supports are investigated though a sol-gel assisted route. The synthesized particles are found to be monomodal with respect to crystallite size, particle size, and pore diameter, and can be decorated easily with low concentrations of co-catalysts. The surface area and crystallite size are found to be linear relations with calcination temeprature. The activies of these systems are quantified by GC-TCD and RGA-MS studies, and qualifed by in-situ spectroscopic and diffraction studies at Brookhaven National Labs. In-Situ Raman, EXAFS, and PXRD studies show the cerium is reduced in operando from an average oxidation state of 4+ to 3+. The particles observed by TEM post reacitons are shown to be rounded, suggesting step defects as the active sites of the reaction.

We introduce a facile method to synthesize nickel hydroxide (Ni(OH)₂) with hierarchical structure, and to improve the pseudocapacitor properties of Ni(OH)₂ by simply depositing conductive materials, gold particles. Pseudocapacitors using porous metal oxides have received great attention as an alternative energy device because of high specific capacitance, low cost, and easy control on the surface morphology, but suffered from poor conductivity and low cycle stability. In this study, we present an easy and cost-effective method to improve capacitance properties via simple deposition of gold nanoparticles on the surface of Ni(OH)₂. By depositing gold particles, the specific capacitance of Ni(OH)₂ was improved by 42% of that of the pristine sample and retained the high capacitance value at a high current density of 20 A/g and 5,000 cycles. This can be attributed to the fact that the deposited gold particles on the surface of semiconductor Ni(OH)₂ create a virtual 3D conducting network via metal/semiconductor contact, which facilitates fast electron and ion transports, which can be confirmed by the EIS and I-V characteristic data. As the method is easy and efficient, this concept can be applied in many fields such as supercapacitors, gas sensors, and secondary batteries.

The controllable synthesis of well-ordered layered materials with speci#64257;c nanoarchitecture poses a grand challenge in materials chemistry. We report the solvothermal synthesis of two structurally analogous 5-coordinate organosilicate complexes via a novel transesterification mechanism. Since the polycrystalline nature of the intrinsic hypervalent Si complex makes it difficult to determine the crystal structure, a novel strategy incorporating the addition of a small fraction of B species as an effective crystal growth mediator and a sacrificial agent is proposed to directly prepare diffraction-quality single crystals without disrupting the intrinsic elemental type. In the determined crystal structure, two monomeric primary building units (PBUs) self-assemble into a dimeric asymmetric secondary BU via strong Na⁺-O^2- ionic bonds. The designed one-pot synthesis is straightforward, robust, and efficient, leading to a well-ordered (10i)-parallel layered Si complex with its principal interlayers intercalated with extensive van der Waals gaps in spite of the presence of substantial Na⁺ counter-ions as a result of unique atomic arrangement in its structure. On the other hand, upon fast pyrolysis, followed by acid leaching, both complexes are converted into two SiO₂ composites with BET surface areas of 163.3 and 254.7 m²/g for the pyrolyzed intrinsic and B-assisted Si complexes, respectively. The transesterification methodology which simply involves alcoholysis but without any hydrolysis side reaction is designed to have generalized applicability for use in synthesizing new layered metal-organic compounds with tailored PBUs and corresponding metal oxide particles with hierarchical porosity.

The ability to pattern functional materials in planar and three-dimensional forms is of critical importance for several emerging applications. We are advancing programmable assembly methods based on microfluidics, 3D printing, and combinations thereof to enable the rapid design and fabrication of functional mesocale materials in arbitrary shapes without the need for expensive tooling, dies, or lithographic masks. In this talk, I will describe how we have created multiple architectures and demonstrated their use as carbon capture media, rechargeable batteries, and beyond.

Key technologies, from energy applications to tissue engineering, demand complex and multifunctional structures with controlled morphological features at multiple scale lengths. Scientists in industry and academia in multidisciplinary fields are working towards developing novel manufacturing techniques to create new complex designs for a better performance. Additive manufacturing (AM) is now considered the next industrial revolution to produce complex 3D objects made of any possible material built up from nanoparticles or 1D and 2D materials. The challenge of making this prediction a reality, requires novel processing and post-processing approaches to broaden the materials palette in AM, and also to optimize their structural and functional properties from the nano to the macro scale.
Overcoming the challenge of processing very different materials, such as inorganic particles or 2D materials, requires the development of novel and flexible processing techniques that can be transferable to such different systems. Here, we propose the use of responsive molecules¹ to functionalize the surface of ceramic particles and 2D materials to create ‘smart&’ building blocks. These ‘smart&’ building blocks can be assembled ‘on demand&’ by an external stimulus to create complex three-dimensional devices and structures. The responsive building blocks provide a wide range of soft-materials that can be used in several processing approaches. From molding, tape casting and emulsion templating (to create dense and porous hierarchical structures²), to the formulation of responsive inks with the right viscoelastic properties for filament 3D printing.
This talk will focus on the application of these ‘smart&’ building blocks in 3D printing of inorganic particles and graphene oxide sheets to produce freestanding 3D objects. We will present the surface functionalization mechanisms, rheological behavior of the responsive inks and the mechanical and functional properties of the 3D structures³.
1. Weaver, J. & Adams, D. J. Synthesis and application of pH-responsive branched copolymer nanoparticles (PRBNs): a comparison with pH-responsive shell cross-linked micelles. Soft Matter (2010).
2. García-Tuñon, D. E. et al. Designing Smart Particles for the Assembly of Complex Macroscopic Structures**. Angew. Chem. Int. Ed.52, 7805-7808 (2013).
3. Garcia-Tunon, E. et al. Printing in three dimensions with graphene. Submitted to Nature Nanotechnology

We have shown earlier how metallo-dielectric Janus/patchy spheres and microcubes, acquire complex polarization pattern in electrical and magnetic fields, leading to multidirectional interactions. We will present a novel approach for assembling metallo-dielectric microcubes into soft robotic components, which may find applications in fields such as microscale manufacturing and active microfluidics. Their potential is illustrated in a preliminary way by making motile, reconfigurable and self-folding chains from patchy microcubes, which possess repeated bending motions when actuated by an external magnetic field. The residual polarization of the metal-coated facets leads to directional forces between the neighboring particles and between the particles and the field. The dipole-dipole and field-dipole interactions lead to dynamic reconfiguration. Depending on the cube-to-cube binding conformations the assembled chains have distinct responses to the external field. In the case of cis-conformation, the junction between two cubes can be actuated reversibly by a pulsating magnetic field, whereas in the trans-conformation cube-to-cube overlap makes the junction rigid and thus restricts the bending of the chain. Consequently, the sequence of cis- and trans-conformations in the chain determines how the chain will respond and fold in a field and after it is turned off. We also seek to establish fundamental understanding and identify means of control of the chain dynamics. On this basis we design and demonstrate prototypes of soft microclamps capable of grabbing and transporting target objects.

With the rapid global emergence and acceptance of additive manufacturing (AM) and 3D-printing (3DP) as a potentially transformational manufacturing method, the need for a broader array of 3D printable materials is becoming increasingly critical. Select AM and 3DP technologies, although effective, are often restricted to single material systems and have limited versatility, especially with respect to the introduction of new materials. We present here a universal 3D-ink formulation comprised of high volume fractions of nano-to-micron scale particles that can be 3D-printed at room temperature into small or large, complex 3D structures. The particle content may be as high as 90 vol.%, and the process can be applied to a wide variety of material systems. We demonstrate that this method can be used to create complex, user defined constructs with unique, functional properties from materials such as biologics (i.e. extra cellular matrix), graphene and carbon nanotubes, ceramics, metals, alloys, and hollow particles. In this manner, we are able to begin bridging the gap between intrinsic nano-to-micron scale material functionality and meso-to-macro scale device development and performance. In some instances, the as-printed object, referred to here as the green body, can be utilized as is. As an example, we demonstrate that hyperelastic mechanical properties can be imparted on high content ceramic composites through the 3DP process, which, when applied to biocompatible hydroxyapatite ceramic, is highly advantageous for biomedical applications. This process can readily be extended to 1D and 2D nanoparticle systems, such as carbon nanotubes and graphene, which we demonstrate to have enormous energy and biomedical potential in the form of 3D-printed constructs. Beyond the applicability of as-printed constructs, the high particle density also permits many of the 3D-printed structures to be effectively post-processed in a variety of ways, such as direct sintering to produce complex, dense ceramic structures or thermochemical reduction followed by sintering to produce complex metallic structures from ceramic precursor green bodies. Even planetary soils such as lunar simulant powders, which are comprised of more than a dozen distinct ceramic compounds, may be 3D-printed and post-processed to create structurally functional objects. This scalable process is also highly amenable to multi-material 3D-printing, which is necessary for producing a variety of new functional devices.

Rapid and reproducible assembly of aligned nanostructures on a wafer-scale is a crucial, yet one of the most challenging tasks in the integration of nanowires into electronic circuits. We present the synthesis of a periodic nanochannel template designed for electrochemical growth of perfectly aligned, rectangular nanowires over large areas. The nanowires can be characterized in-situ using a pre-patterned multi-probe measurement platform. During the measurement the wires remain within a thick oxide matrix providing protection against breaking and oxidation. We use laser interference lithography, reactive ion etching and atomic layer deposition to create cm-long parallel nanochannels with dimensions below 40 nm. In a showcase study, pulsed electrodeposition of iron is carried out creating rectangular iron nanowires within the nanochannels. By design of the device, the grown wires are in contact with an integrated electrode system on both ends directly after the deposition. No further processing steps are required for electrical characterization, minimizing the risk of damage and oxidation. The developed nanowire measurement device allows for multi-probe resistance measurements and transistor applications. The guided, in-plane growth of electrodeposited nanowire arrays which are tunable in size and density paves the way for the incorporation of nanowires into a large variety of multifunctional devices.

#8203;Three-dimensional (3-D) homogenous and hybrid nanostructures have generated significant interest in many fields, including biomedical, optics, energy and electronics because they provide enhanced functionality and improved performance compared to planar nanostructures. Bottom-up directed assembly of nanoparticles have been considered as one of the best approaches to fabricate such functional and novel nanostructures. However, there is a dearth of studies on making crystalline, homogeneous and hybrid nanostructures. This requires a fundamental understanding of the forces driving the assembly of nanoparticles and precise control of these forces to enable the formation of desired nanostructures. Here, we demonstrate that colloidal nanoparticles can be assembled and simultaneously fused into 3-D solid nanostructures in a single step using externally applied electric field. By understanding the influence of various assembly parameters, we showed the fabrication of 3-D metallic, semiconducting and insulating materials with complex geometries such as nanopillars, nanoboxes, and nanorings with feature sizes from several microns down to 25 nm in less than a minute over large area (wafer scale). Using this technique, we have fabricated nanopillars made from Au, W, Cu, PSL, Si, SiO2, and CdSe and their hybrid derivatives. Novel heterojunctions such as metal-insulator, metal-semiconductor and semiconductor-insulator have also been created. The precise control of nanostructure dimensions is investigated via simulation results as well as various experimental parameters such as the voltage, frequency, time and particle concentration. TEM (transmission electron microscopy) and electrical characterizations reveal that manufactured gold nanostructures have polycrystalline nature and very low resistivity (1.96×10^-7 Omega;middot;m). The fabricated novel 3-D nanostructures also demonstrate high optical quality supporting strong plasmonic resonances with line-widths as narrow as 13 nm. This enabled highly sensitive plasmonic based biosensing of A/G and Immunoglobulin G (IgG) proteins. These results indicate that the presented versatile, fast and controlled approach will facilitate the creation of novel 3-D nanomaterials while enabling scalable fabrication of hybrid nanoelectronic, optical metamaterial and biological devices.

Crack-free inverse-opal films exhibit a sharply defined threshold wettability for infiltration. This liquid-specific wetting behavior naturally couples to macroscopic color changes in these films. We are exploiting this effect in the development of simple and low-cost colorimetric indicators for liquid identification. Moreover, by functionalizing the surfaces of this porous structure with an environment-sensitive groups and observing the changes in the wetting behavior, we can follow the history of the exposure of the material to a certain stimulus. For example, crack-free inverse-opal films functionalized with a photoresponsive polyelectrolyte surface layer exhibits a highly selective wetting threshold that can be directly and continuously tuned by exposing the film to light. This approach may find applications in a broad range of technologies, including a convenient and direct method for liquid detection and encryption, or as a tag for low-cost monitoring of tampering or material aging.

The cricket&’s cercal receptors produce excellent performance in acoustic sensing with long and thin filiform hairs, attracting numerous attempts to mimic them. However, their replication requires high aspect-ratio micropillars, which is a great difficulty when attempted with conventional micro-fabrication techniques and PDMS. Here, we present a new technique based on the direct drawing technique incorporated with the in situ heating, which enables the realization of PDMS micropillars with unprecedented aspect-ratios (40 ~112). Our scheme also allows self-aligned capping of the micropillars with multi-functional microspheres. To validate the utility of the microsphere-tipped micropillars (MSMPs), we transform them into all-optically interrogated acoustic sensors inspired by the filiform hairs.
For the PDMS MSMPs fabrication, we first prepared an array of 58 mu;m-diameter Ag-coated glass microspheres on a piece of double-stick tape as the drawing probe. Then we attached the array to a micromanipulator. Also, we pre-baked a spin-coated PDMS thin film on a hot plate at 100 °C. During the pre-bake, we lowered the microsphere array towards the PDMS film until the separation was reduced to 50 mu;m. After the pre-bake, we further lowered the array so that it can physically contact the PDMS film. After 40 sec, we lifted the array, drawing PDMS micropillars. The micropillars were then post-baked at 100 °C for 2 hours and cured at room temperature for 24 hours. Then we detached the microspheres from the tape, realizing the PDMS MSMPs.
To demonstrate acoustic sensing capabilities of the MSMPs, we turn three different MSMPs into acoustic sensors by adding optical read-out interfaces. For the sensor, the micropillar functions as a vertical waveguide which deforms under airflows and the microsphere as a self-aligned reflector. Here, a probe light enters the micropillar from the base and then gets reflected at the Ag-coated microsphere back into the photodetector. Therefore, in the absence of airflow, the MSMP stays straight, producing maximal reflection. Upon contact with a constant airflow, it bends due to the fluidic drag force, which decreases the reflection through spoiled waveguiding and beam deflection. For constant airflows, the reflectance functioned as a good measure of the airflow rate. We also investigated the utility of the MSMPs for sensing sound-waves. Measured reflection waveforms responding to sound-waves with different frequencies provided accurate information on the excitation frequencies. We also showed that MSMPs under test have resonance frequencies close to 100 Hz. Resonance at this low frequency range is difficult to obtain with cantilevers made of hard materials.
In conclusion, we present a new fabrication technique, enabling the realization of high aspect-ratio, microsphere tipped PDMS micropillars. Bio-inspired acoustic sensors we configured based on the micropillars exhibited high sensitivity at resonance frequencies close to 100 Hz.

Hollow silica nanoparticles are structurally simple colloidal building blocks. However, such silica capsules possess a vast range of interesting properties. Here, I will present a comprehensive overview on the optical, mechanical, and thermal properties of monodisperse hollow silica nanoparticles, which feature particle sizes of less 1 µm and shell thicknesses of only a few ten nm.
Individual hollow silica spheres feature an unique coloration effect, which originates from an incoherent scattering mechanism, namely Mie scattering. The low refractive index of hollow capsules suppresses multiple scattering, which is typically observed in solid colloidal particle powders. The large mean free path of light through such a hollow powder material therefore allows the observation of colorful Mie scattering with the naked eye.¹
Arranging hollow spheres in a two-dimensional superstructure allowed us to determine the collective mechanical properties using nanoindentation. We investigated the elastic response as well as the plastic deformation. Such films feature mechanical properties comparable to solid polymer films. Their granular morphology reflects into an peculiar compression behaviour. Furthermore, such hollow particle films exhibit a large capacity to dissipate energy upon compression.^2,3
Three-dimensional superstructures of hollow spheres can be regarded as an analogue to silica aerogels, however, with a much better defined internal structure and symmetry. The massive nanostructuring of the silica network and the interconnectivity at few, defined contact points between the spheres opposes the transport of thermal energy through such a material. The thermal conductivity through such films is therefore almost as low as in the case of silica aerogels. Without the need for supercritical drying, we can employ well established colloidal processing routes to fabricate highly insulating porous silica films. We present in great detail the influence of various structural parameters on the thermal conductivity.
(1) Retsch, M.; Schmelzeisen, M.; Butt, H.-J.; Thomas, E. L. Nano Lett.2011, 11, 1389-1394.
(2) Yin, J.; Retsch, M.; Thomas, E. L.; Boyce, M. C. Langmuir2012, 28, 5580-5588.
(3) Yin, J.; Retsch, M.; Lee, J.-H.; Thomas, E. L.; Boyce, M. C. Langmuir2011, 27, 10492-10500.

Isomers are a class of molecules having the same molecular formula, but with their atoms arranged in different configurations. Due to this spatial difference, the molecules often exhibit distinct physical and chemical properties. The spontaneous formation of isomers presents a classic problem in self-assembly. Since the precursors are identical, it is the intermediates and assembly pathways that direct which isomer is formed.
Using geometric path sampling and experiments, we investigate a mesoscale model for the formation of octahedral isomers. Mesoscale polyhedral models have a rich history in chemistry and were used by Hermann Sachse and Jacobus van&’t Hoff (the first Nobel Prize winner in Chemistry) in the 19th century to depict molecular structures. Sachse used paper models to illustrate the two isomers of cyclohexane, while van&’t Hoff used solid tetrahedra to model sp³ carbon atoms.
We use microfabricated planar nets of the octahedron to self-assemble two different isomers: (a) a regular octahedron and (b) a boat-shaped concave octahedron. Our work reveals that the rigidity or the degrees of freedom of an intermediate within a self-assembly pathway determine the final outcome. These findings are compared with the chair and boat conformations of cyclohexane discovered by Sachse. Additionally, by manipulating the rigidity of the precursor, we show in experiments that we can preferentially encourage the formation of one isomer over another. This study suggests a new approach to model self-assembly using readily computable and purely geometric criteria that can be used to address a wider class of inverse problems in self-assembly.

Advances in nanoscale fabrication and characterization methods have led to fundamental changes in the scientific understanding of many fields, and many prototype designs have been well-established using these nanotechnology toolkits. However, the current generation of nanoscale materials, such as nanowires and nanospheres, are not complex enough to serve as building blocks for the design of well-ordered and multifunctional mesoscale systems analogous to these found in nature. It is therefore necessary to devise engineering techniques by which one can exercise a greater level of control over material properties, shapes, morphologies and assembly mechanisms that may facilitate the design of various devices with novel optical, mechanical, thermal and electrical properties.
We report the presence of a transitory region, where architecturally diverse nanostructures are produced from glass-polymer core-shell nanowires during the progress of combined iterative size reduction (ISR)-thermal instability technique. Indefinitely long, globally-oriented, in-fibre arrays of nanoschemes such as nanosprings, shell-embedded nanorods, nanopeapods and nanochains can be fabricated in succession by halting the thermal degradation process prior to core-shell nanosphere formation. Conceptual underpinnings behind the fabrication of these structures are remarkable and especially nanohelices, represent the first model of nanostructure formation where the resultant structures obey a non-axisymmetric instability condition.
Our present approach enable the production of a great variety of 3D and 2D mesoscale architectures composed of 0D/low aspect ratio, 1D and complex/quasi-1D nano-building blocks, the diversity of which can be further enhanced by mechanical transformation tools. The transition behavior associated with our nanostructures is expected to be applicable to many material systems (e.g. metals, polymers, semiconductors), and nanofabrication techniques. ISR is particularly advantageous for the generation of macro-scale devices by nanomaterial assembly, as this low-cost, high-throughput process is capable of generating globally aligned, arbitrarily long nanostructures within a robust polymer sheath that circumvents handling issues associated with previous nanostructure platforms and allows the simple macroscopic manipulation of the composite fiber. In renewable energy applications, nanostructure-embedded fibres incorporated within large area photovoltaic devices can bridge the advantages of nanotechnology (e.g. high efficiency) with the requirements of large scale production. The basic capacity to produce single and multimaterial nanoarchitectures in flexible fibres is so general and powerful that it can open up whole new fields of basic and applied research and lead to a vast number of novel device designs.
[1] M. Yaman, T. Khudiyev, M. Bayindir, et al., Nature Materials 10, 494 (2011).
[2] T. Khudiyev, O. Tobail, M. Bayindir, Scientific Reports 4, 4864 (2014).

Carbon infused in large concentrations into liquid metals such as silver, aluminum, and copper under electric fields forms covalently bonded carbon to the metal matrix. The form of carbon in some cases are nanostructures such as graphene-like sheets which persist upon solidification and remelting. The solid metal-high carbon alloy, termed ‘covetic&’ provides a new method of introducing carbon in metals. Ag covetic with 3 wt.% C, for example, displays high electrical conductivity, at least 90% of pure silver. In addition, this material features much improved corrosion resistance and enhanced thermal stability and mechanical properties. Here, we report on a detailed investigation of the alloy structure, and an attempt to rationalize these improved properties. The carbon incorporates in the form of graphene-like ribbons and other nanostructures embedded in the crystal lattice of the metal and forming a 3-D epitaxial structure with the host metal. The temperature dependence of the resistivity of silver and copper covetics exhibit stronger electron-phonon interaction compared to the pure metal. Density functional theory calculations estimate a bond energy between the metal host and C in the range 1.1-2.2 eV per atom or vacancy. Raman scattering indicates that carbon is present in graphitic form by the observation of peaks in the Raman spectrum at 1,300 and 1,600 cm^-1. The spectra also show a broad peak from 500 to 1,000 cm^-1 which our first principles calculations of the dynamic matrix and corresponding phonon spectrum for the supercell structures indicate that these vibration modes are related to the Ag-C bonds and which have covalent character. These materials have promising properties in nanoelectronic applications.
* Funded in part by DARPA/ARL under Grant No. W911NF-13-1-0058, and ONR Award No N000141410042.

2D materials are interesting because they can be processed into aerogels to preserve their intrinsic high surface area. Graphene-derived aerogels have demonstrated high conductivity with relatively good and reversible compressibility [1]. Beyond graphene, exfoliated Transition Metal Dichalcogenides (TMDs) have demonstrated promising properties for electronics, optoelectronics, catalysis and energy storage. Our group has demonstrated the successful chemical exfoliation of TMDs, typically MoS₂ and WS₂, and demonstrated that the octahedral phase of the single-layer TMDs is a good catalyst for the Hydrogen Evolution Reaction (HER) [2,3]. Although metal chalcogenide aerogels have been prepared via sol-gel method, we report aerogel-like foams prepared from chemically exfoliated single-layer TMDs. The electronic properties of such foams can be widely tuned using the metallic and semiconducting phases of TMDs. Composite aerogels have been prepared by mixing graphene oxide with different TMDs and used as electrodes for electrocatalytic reactions including HER and Oxygen Reduction Reaction (ORR). Characterizations of the different aerogels as well as their catalytic performances will be presented.
[1] Sun, H. et al. Adv. Mater. 25, 2554 (2013).
[2] Voiry, D. et al. Nature Mater. 12, 850 (2013).
[3] Voiry, D. et al. Nano Lett. 13, 6222 (2013).

The fabrication of 3-D mesoporous materials using building blocks of oxide nanosheets is demonstrated using both planar sheets and a combination of scrolled and planar sheets. Chemistries of interest include niobates and titanates for water splitting catalysts and oxides of Mn and V for electrochemical pseudocapacitive storage. Structure types of interest are the perovskite-like sheets and sheets with edge-shared octahedra like the birnessites. Processing includes exfoliation of micron-size powders to form nanosheet suspensions, followed by control of surface charge to coagulate the sheets in an edge-to-face geometry. Dispersion of the nanosheets is very sensitive to pH and can be adjusted from full dispersion to full agglomeration. The processing parameters can be modified to produce either highly disordered 3-D structures with spherical pores or crumpled layered structures which have 1-D and 2-D pores. Freeze drying is most effective for final processing of the porous solids. Thermal stability is demonstrated for the assemblies to 550C, which demonstrates the ability to sinter the nanoscale assemblies to final forms as if they were bulk oxides. We find very high hydrogen yields without added cocatalysts of up to ~40,000 micromoles of hydrogen per hour per gram for the niobate photocatalysts.

If low dimensional carbon-based nanostructures such as one-dimensional (1D) carbon nanotube (CNT) and two-dimensional (2D) graphene (G) and graphene oxide (GO) could be controllably interconnected, then new types of 3D macroscopic carbon solids could be created with unexpected properties such as high and tunable surface area, porous structure and interesting electron transport and mechanical properties. These nanoengineered 3D architectures have a broad range of application areas such as supercapacitors, catalytic electrodes, dry adhesion, artificial muscles, gas adsorption and environmental applications. However, the creation of such nanoengineered 3D architectures remains one of the fundamental challenges in nanotechnology. The fundamental problem is introducing atomic-scale junctions between individual nanoscale structures so that they can be organized as covalently bonded nanostructured networks with controllable physical characteristics, such as density and porosity. To create atomic-scale junction between carbon-based nanostructures two main approaches, chemical vapor deposition (CVD) and solvent chemistry, are following. The first approach, CVD method, is useful for direct synthesize covalent junctions between CNTs and the second method, solvent chemistry, requires post treatment to create intermolecular covalent junctions between CNTs. Here, we shall discuss the fabrication of highly porous and covalently interconnected 3D-macroporous architectures from covalently interconnected 1D-CNT and 2D-G.

Creating inorganic nanowire hydrogels/aerogels using various materials and inexpensive means remains an outstanding challenge in spite of their importance for many applications. Here, we present a facile methodology to enable highly porous inorganic nanowire hydrogel/aerogel production on a large scale and at low cost. The hydrogels/aerogels are obtained from in-situ hydrothermal synthesis of one-dimensional (1D) nanowires which directly form a cross-linking network during the synthesis process. Such a method not only offers great simplicity, but also allows the interconnecting nanowires to have much longer length. The longer length offers aerogels with remarkable porosity and surface area, extremely low densities (as low as 2.9 mg/cm³) and are mechanically robust, and can have superelasticity by tuning the synthesis conditions. The nanowires in the hydrogels/aerogels serve both as structural support and active sites for, e.g., catalysis or absorption, in this work, we have found that the as-grown hydrogels can be used directly as water filters to remove pollutants such as heavy metal ions and toxic organic contents. Our studies indicate that this method for nanowire hydrogels/aerogels production is not only economical, but greatly augmented their applications in environmental, catalysis, sensing, absorption, energy storage and beyond.

Some years ago, computer simulations by Balazs and coworkers were used to demonstrate that liquid-liquid demixing could be employed to rationally design new materials from one-dimensional colloidal rods [1]. These studies focused on what could be achieved in two-dimensions when the rods were completely wettable by one of the fluids. Here we present experimental results in support of these simulations elucidating more of the details; we go on to extend this work to the third dimension.
First a simple method for preparing micron sized rods consisting of an iron oxide (akaganéite, β-FeOOH) core and a silica shell will be briefly introduced. The composition of these particles allows easy modification of their properties, for example: varying aspect ratio, removal of the iron oxide core, fluorescent labelling, and changing surface chemistry [2].
Second we demonstrate the manipulation of these rods into percolating structures via the rational use of phase-separating liquids. Sample composition is tuned so that, following a temperature quench, the fluid phase that wets the colloidal rods is the minority phase. For high enough concentrations of rods a percolating structure is formed, induced by confinement in the fluid domain. The architecture can be controlled by adjusting the proportions of the constituents and the depth of the quench. For sufficiently low concentrations of colloidal rods, liquid crystalline phases form within the minority phase droplets. For quenches which end prior to complete phase separation, complex wetting behaviour is observed [3].
References:
[1] G. Peng, F. Qiu, V. V. Ginzburg, D. Jasnow and A. C. Balazs, Science, 288, 1802, (2000).
[2] N. Hijnen and P.S. Clegg, Chem. Mater. 24, 3449 (2012).
[3] N. Hijnen and P.S. Clegg, Langmuir, 30, 5763 (2014).

Nanotechnology aims to understand the properties of nanostructures at the smallest length scales. One of the most fundamental properties of any nanomaterial is its three-dimensional structure. Current state-of-the-art methods for such characterization which allow for not only surface topography but also internal structure mapping are TEM tomography and FIB cross-sectional milling. Multi-Energy Deconvolution Scanning Electron Microscopy (MEDSEM) is a novel alternative to these electron microscope tomography techniques. MEDSEM works by obtaining images at many different electron acceleration voltages and subsequently deconvoluting the obtained image stack. Since every electron image contains some mixture of information from the structure&’s interior, and the penetration depth of electrons is larger at increased voltages, depth-information can already be retrieved by only varying the electron energy. Furthermore, combining MEDSEM with imaging in backscatter electron mode provides elemental contrast as a function of depth. This approach allows probing the interior of a variety of nanostructures including Au@Cu₂O core-shell nanowires. These wires are of particular interest for novel solar energy conversion methods due to their optical and electrical properties. Three-dimensional elemental mapping by MEDSEM of such nanostructures aids in a more complete characterization and understanding of those properties. We show that MEDSEM can be used as a characterization method to probe the interior of such core-shell nanowires at nanometer length scales as a simple, non-destructive alternative to conventional electron microscope tomography.

Although electron energy loss (EEL) spectrum volume tomography enables access to 3D chemical information at the nanoscale, it has never been used to elucidate the 3D-distribution of oxidation states. Here we present the first EELS-tomography 3D-reconstruction of oxidation states in a nanoheterostructured system with high spatial resolution. The success of the data analysis relies on the optimized use of multivariate analysis (which is very effective in handling large number of spectra) and the novel use of compressed sensing (which allows reliable 3D-reconstructions even with a limited number of projections) in tomography algorithms. The feasibility to perform complex spectra treatment in spectrum volume tomography opens the door to a wide range of applications in solving complex nanostructures.
In the present case (45-nm FeO/Fe3O4 core/shell cubic nanoparticles) due to the similarities in the composition and effective atomic number of the compounds, high angle annular dark field imaging could not be used to resolve the structure, justifying the need of a more sophisticated approach.
As an alternative, EELS fine structure is used to obtain information on the iron oxidation state, thus making it possible to distinguish between Fe²⁺ and Fe³⁺ ions. However, there is the limitation that EELS projects the information of the 3D nanoparticle into a 2D map.
To overcome this issue, EELS spectrum image data-sets are considered for 3D tomographic reconstruction after data processing. The reconstruction not only contains information on the chemical composition of the sample (as in [1]) but also on the oxidation state of iron in each voxel.
A tilt series of spectrum images was acquired every 4 degrees in the range from -67 to +69 degrees in a probe corrected FEI Titan TEM microscope, equipped with a XFEG source and operated at 80 kV acceleration voltage. Then the images were treated with the "Hyperspy" software to obtain independent spectral components from the iron edge, which could be correlated with the different iron species. In order to improve the quality of the reconstruction, a recently developed reconstruction algorithm based on the mathematical theory of compressed sensing (CS) was used. CS tomography has proven its ability to robustly reconstruct tilt series with as few as 9 projections at adequate angles [2], minimizing the typical artifacts. Remarkably, this is the first time that the CS algorithm has been used to reconstruct an EELS core-loss spectrum image data-sets.
The reconstructions of two EELS datasets corresponding to the Fe²⁺ and Fe³⁺ in the same nanoparticle are consistent and show a shell thickness of 9nm around the core. The 3D reconstructions also prove the presence of defects on the shell and a sharp interface between both oxide phases.
References:
[1] Ll. Yedra et al., Ulramicroscopy, 122 (2012), pages 12-18.
[2] Z. Saghi et al., Nano Letters,11 (2011), pages 4666-4673.

Nanoporous materials play an emerging role in energy storage applications for gas storage and as electrode materials in advanced battery or supercapacitor systems. The presentation will highlight recent advances and strategies in the area of generating highly porous materials with specific surface areas up to 6000 m²/g.
Soft and hard templating strategies using mesoscale oxide assemblies and special precursor polymers lead to nanoporous carbon materials with surface areas up to 3000 m²/g and hierarchical pore systems that are ideal for applications in high power supercapacitors and lithium sulfur batteries. Self assembly of semiconductor and metal nanoparticles and subsequent supercritical drying leads to a new class of semiconductor aerogels with interesting optical functionality. A third strategy to achieve high porosity is to assemble molecular building blocks such as Metal-Organic Polyhedra into highly porous ordered framework materials. The latter have specific surface areas exceeding 6000 m²/g and enormous capacity for gas storage, especially natural gas at room temperature.
S. Kaskel et al. Adv. Energy Mater. (2014), 4(2), 1300645/1, JACS (2014), 136(7), 2727-30, Angew. Chem. Int. Ed. (2013), 52(37), 9849-9852, Chem. Commun. (2012), 48(88), 10841-10843, Angew. Chem. Int. Ed. (2012), 51(30), 7577-7580.

Crystalline nanostructured semiconductors are highly desirable and have been adapted for novel applications such as optoelectronics, sensors, and energy conversion and storage. However, multiple steps are required to synthesize hierarchically structured inorganic nanostructures with multiple length scale features. Recently, block copolymer self-assembly structure formation coupled with pulsed excimer laser irradiation has been demonstrated as a viable route to fabricate high quality porous single-crystal nanostructures. Here, we report the generation of hierarchically structured crystalline silicon nanostructures by two approaches: (1) a sequential block copolymer and colloidal self-assembly, and (2) a direct block copolymer templating approach, via transient laser-melt-crystallization.

We have developed a method of preparing hierarchical porous carbons (HPCs) with tuneable porosity in the micro-, meso-, and macroporous regimes through application of a freeze-casting technique. Briefly, freeze-casting produces a macroporous solid from a colloidal dispersion via phase separation upon the solidification and subsequent removal of the dispersant. Using this method, we are able to synthesize RF-based monolithic carbons having no intrinsic mesoporosity in the absence of a hard template (e.g. colloidal silica) in the precursor dispersion. Through the addition of colloidal silica to the RF suspension prior to freeze-casting, we are able to prepare HPCs with finely controlled mesoporosity by varying the size and concentration of silica used. In the etched carbon, we see high fidelity between template size and mesopore diameter, likely due to a diminished tendency for silica particles to aggregate in the precursor suspension prior to and during freeze-casting. Further enhancement of mesoporous/microporous surface areas and pore volumes is achieved by chemical and physical activation methods employed in the processing of the HPC.
The mechanical properties of these monolithic carbons can be tuned by varying freeze-casting conditions, precursor formulation, and post-treatment steps. Additionally, the conductivity of these carbons may be further enhanced through the process of catalytic graphitization, a process in which a transition metal salt (catalyst) that has been freeze-cast with the RF suspension leads to the formation of graphitic carbon upon pyrolysis. We are currently investigating the synthesis of graphitized HPC monoliths with high surface areas and pore volumes achieved via hard templation.

We demonstrate the fabrication of rationally designed, multifunctional ordered mesoporous core-shell nanocomposites with tunable structural characteristics using the combination of solution based block copolymer structure direction of a carbon precursor with atomic layer deposition (ALD) or surface sol-gel (SSG) synthesis of transition metal oxides. Soft-templated gyroidal mesoporous carbon materials and free-standing monoliths with uniform and tunable pore sizes were synthesized through the organic-organic self-assembly of the triblock terpolymer poly(isoprene)-block-poly(styrene)-block-poly(ethylene oxide) (ISO) and phenol-formaldehyde resols. Gyroidal mesoporous carbonaceous monoliths with an ultralarge pore size of 40 nm and large footprint areas were used as functional templates for ALD of titania. The deposition depth as a function of the ALD conditions was evaluated and the ordered free-standing composites were converted into various crystalline titania composites via heat-treatment with retention of the ordered structure and porosity. Gyroidal mesoporous carbon powders with varying degrees of activation are coated with thin transition metal oxide layers such as titania and niobia using simple solution based surface sol-gel chemistry. The composites obtained from both methods exhibit triple functionality; a conductive carbon core that is coated with a crystalline transition metal oxide such as titania or niobia in contact with a mesoporous phase in a compact monolithic architecture or as powders for electrodes with high effective densities.

Metal-organic frameworks (MOFs) or Porous coordination polymers (PCPs) are 3-D crystalline nanoporous architectures which can be compared to zeolites and carbons for applications such as gas storage and separation.
From a synthesis standpoint, MOFs are an interesting family of nanoporous solids due to the possibility to assemble almost any metal from the periodic table as nodes and a wide range of rigid organic linker units. This opens the possibility to search for, and fine tune, a given physical or chemical property, in an almost limitless fashion. However, the diversity and number of different MOFs available makes choosing the most appropriate material for a given process difficult.
In the case of gas adsorption and separation there is a need to develop a screening strategy. This step needs to be to high pressure for processes such as CO₂ recovery in natural gas purification or in pre-combustion CO₂ capture. Whilst computer methods have been developed to screen ideal materials, the experimental screening of materials to obtain high pressure gas adsorption isotherms has only recently been developed. The problem then comes down to how to extract the relevant information from a large number of entries. One approach is to develop a structure-property relationship strategy to initially choose the most interesting materials for further characterization.
After this screening step, materials taken forward can be further characterized in terms of adsorption energies, working capacities and selectivities. Here, the adsorbent performance indicator can be used to further refine the choice of materials for upscale and pilot testing.
This contribution aims address the above points. An experimental methodology able to screen materials for gas adsorption and separation will be presented. An initial data set with over 400 entries has been obtained which allows some pointers towards an experimental structure-property relationship strategy to be developed. From this screening, further characterizations will be discussed and the concept of an adsorbent performance indicator will be presented. Here, MOFs can be compared with zeolites and carbons and we will identify possible structures that have the potential to outperform current reference materials.

Hybrid mesoscale heterostructures of multiple components and controlled dimensions, capable of being tailored and assembled during the synthesis, are of substantial research interest, as they allow for realization of devices with synergetic and unconventional functions in energy and biological applications. In this talk, we will first describe the controlled growth of highly-ordered mesoporous silica, carbon and transition metal oxide thin films, via a surface-induced organic-organic assembly, for efficient solar energy conversion and electrical energy storage. Second, the synthesis of an ultralight iron oxide hierarchical mesostructure by a surfactant-free interface-driven assembly of single-crystalline Prussian blue nanocubes over macroporous polyurenthane frameworks is exhibited. Finally, we will demonstrate a bio-inspired interfacial assembly of antenna-like, mesoporous Prussian blue nanocube/titanium oxide nanowire heterostructure for sensitive cellular interfaces and enhanced photoelectrochemical detection. Mimicking the functional antennas of insects, the Prussian blue nanocubes at the tip segment catalyze electron transfer reactions that convert hydrogen peroxide into oxygen and water, while the titanium dioxide nanowires at the arm segment carries the resulting electric current to the substrate surface where it is amplified and detected. The antenna-like nanosensor heterostructures possess high surface area and porosity, thus allowing for ultrahigh sensitivity, excellent selectivity and remarkable affinity towards living cells.

Hollow micro/nanostructures have received extensive attention due to their promising potential in drug release, catalyst support, batteries and sensing. However, most of the existing methods to obtain hollow structures involve the use of a template as the growth-directing agent, which limit the general production of hollow materials with controlled complex morphologies and require post-treatment steps. In this talk, we report our recent development of a kinetically-controlled, template-free solution self-assembly of unusual silica/Au hollow mesostructures, including nanotubes, nanocrutches, nanoribbons, nanobundles and nanobells, by facile tuning the relative amount of precursors and additives. Specifically, tetraethyl orthosilicate (TEOS) species diffuse into and deposit at one side on the surface of reverse micelles, leaving a droplet at the other side; a subsequent oriented supply of TEOS species into the droplet leads to the formation of 1D structure. The growth mode can be switched between different mesostructures by fine tuning the condensation rate and the diffusion rate of silica oligomers. Detailed structural analysis reveals that the growth of these micro/nanostructures is based on a solution-solution-solid (SSS) mechanism, analogous to the classic vapor-liquid-solid (VLS) growth process. This general method opens up a novel approach for the synthesis of mesoscale silica/gold architectures, and may provide the opportunity to produce different building blocks of electronic, biomedical, and structural devices and other functional nanomaterials.

Sub-micron sized hollow and multiporous spheres are interesting building blocks for nanocomposite coatings and polymer nanocomposites [1]. Examples of nanocomposites comprising such spheres range from anti-reflective coatings [2] to materials for encapsulation and release of active agents [3]. In spite of their large potential for application, these particles are not yet widely used in commercial products. This is caused by the lack of efficient synthesis routes with stringent control over particle size and architecture that are suitable for scale up.
Here we present a facile and versatile platform approach for the synthesis of sub-micron sized hollow and multiporous organosilica spheres, which is based on an oil-in-water emulsion and merely involves one organosilica precursor that serves as monomer, precursor for a surface active species and oil phase. We studied phenyltrimethoxysilane (Ph-TMS) as model precursor [4]. After addition of Ph-TMS to aqueous ammonia of pH 11 at 60°C, we observed emulsion formation after 3 to 6 minutes reaction time. We managed to prepare hollow organosilica spheres with an average diameter between 445 and 1020 nm and a narrow size distribution, simply by varying the volume ratio Ph-TMS to water. As the particles grow from the outside inwards, the average outer diameter is fixed in an early stage of the reaction. Shell thickness and core size could be tuned through variation of the reaction time.
We studied the chemical composition of both the hollow and multiporous spheres using FT-IR, XRD and TGA. Furthermore, we performed a detailed study on the architecture of the hollow and multiporous spheres, using advanced electron microscopy (SEM, TEM, STEM) and BET analysis. Though pendant drop analyses, we studied the formation and characteristics of the surface active species formed through hydrolytic conversion of Ph-TMS. The information obtained from these studies enabled us to develop a hypothesis for the mechanism of formation of hollow and multiporous spheres. This hypothesis was validated using two other organosilica precursors: (3-acryloxypropyl)trimethoxysilane and (3-mercaptopropyl)trimethoxysilane.
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[4] M. Segers, N. Arfsten, P. Buskens, M. Möller, RSC Adv. 2014, 4, 20673.

We demonstrate an application of the electrospray to nanomanufacturing for energy conversion. The electrospray is a liquid atomization technique that generates a monodisperse population of highly charged liquid droplets over a broad size range (nanometric to tens of microns). The droplets can contain either liquid precursors for particles for in-flight synthesis or a dispersion of pre-made solid nanoparticles. The high charging level of the droplets is unique to the electrospray and provides two key advantages with respect to other atomization techniques: 1) the trajectory of these droplets or particles can be precisely manipulated with the use of electric fields to drive them to a grounded substrate, and 2) the electrostatic repulsion between droplets prevent coalescence, which preserves the monodispersity of the aerosol. As a proof-of-concept demonstration, the technique is applied to dye-sensitized solar cells by depositing clusters of TiO₂ nanoparticles for the photoanode. We show that a variety of film morphologies can be achieved by changing various experimental parameters and measure the device performance for various film microstructures and fabrication protocols. While a single electrospray suffers from low throughput that is insufficient for industrial production, the process can be scaled up by several orders of magnitude by multiplexing an individual electrospray using microfabrication techniques. The approach can be adapted to a continuous deposition process such as roll-to-roll processing.

Electric force is powerful tool for the formation and control of microstructures of ceramic films and coatings particularly via electrochemical reactions. We have studied on electrochemical ceramics films/coatings since 1989 succeeded to make BaTiO3 on Ti, then proposed for the first time in 2008 as a novel concept and technology: “Growing Integration Layer” [GIL] method for nano-/micro-structure controlled ceramics film and coating on metallic materials. Those GIL(s) can be prepared from a component of the metallic materials by electrochemical reactions in a solution at low temperature of RT-200#8451;. On a Ti-base Bulk Metallic Glass, we could succeed to prepare bioactive titanate nano-mesh layer by hydrothermal-electrochemical techniques for 1 h at 90-120#8451;. Similarly, bioactive oxide layers could be prepared on other Bulk Metallic Glasses and alloys.
The GIL strategy, where layer(s) would be grown from the Bottom to Top, is different from other Integration/Deposition methods, where every layer would be deposited by Top-by-Top or Layer-by-Layer. The GIL should be effective for many metallic alloys and bulk metallic glasses because they generally contain active component(s). [GIL] have particular features:1)Widely diffused interface(s), 2)Continuously graded layers grown from the bulk(substrate),3)Low temperature process, etc. They would be quite useful for
Chemical, mechanical, thermal and biological applications
Keywords: Ceramic;Layer:Coating;Bio-active;Metal;Integration;Solution;Electrochemistry
References
M. Yoshimura et al.,Mater. Sci. Eng. B,148,2-6(2008), 2)N.Sugiyama, M. Yoshimura et al.,Acta Biomaterialia,5,1367-1373(2009), Mater. Sci. Eng. B,161,31-35(2009)
J-J. Wu,W-P. Liao and M. Yoshimura, Nano Energy 2(6),1354(2013)
J. Senthilnathan,M. Yoshimura et al., Carbon, 71,181-187 (2014)

The electrification of modern society demands technologies that can store ever more electrical energy. From an energy density perspective, electrochemical reactions promise solutions to meet the need. Among various considerations for electrochemical energy storage, electrode design is of critical importance. In addition to high surface area and good electrical conductivity, stability against side reactions is also an important consideration. To date, the most studied electrode support has been porous carbon. Despite its obvious appeal in terms of cost and conductivity, carbon present challenges such as instability, especially at high applied potentials. The problem is particularly acute when metal air batteries are concerned because carbon not only reacts with the oxygen reduction and evaluation intermediates, it also shows reactivity toward the electrolyte. It is within this context that we have studied TiSi₂ nanonets as a new, non-carbon support for energy storage applications. Readily synthesized by a chemical vapor deposition method without the need for catalysts or growth seeds, TiSi₂ nanonets are of high surface area and excellent conductivity. When used as a support for Li ion batteries, they exhibit one of the highest performance in terms of power rates. The unique surface chemistries were found to enable site selective growth of metal nanoparticle catalysts such as Pt and Ru, allowing for applications of proton exchange membrane fuel cells and Li air batteries. The most striking advantage offered by TiSi₂ nanonets it the stability against oxidation. Superior cyclability has been observed on electrochemical cells constructed on TiSi₂ nanonets. This unique material has opened up a new door to the construction of electrochemical electrodes for high energy density, high power rate energy storage devices.

Development of high-performance lithium-ion batteries (LIBs) with ultrafast charging and discharging rates is highly demanded for portable electronic devices and electrical vehicles applications. However, several challenging bottlenecks remain to build the ideal electrodes for ultrafast rechargeable LIBs. For instances, the particulate nanostructured materials tend to aggregate during cycling, resulting in the formation of poor conduction network and loss of particle connectivity. This increases the resistance between the electrode and current collector after long-time cycling. In addition, the long-range ion diffusion path is still required due to the use of auxiliary additives such as polymer binder and conductive agent. To overcome these shortcomings, here, we reported a mechanical force-driven method to prepare elongated bending TiO₂-based nanotubes for high-rate LIBs. The formation of elongated nanotubular structure is due to the improvement of diffusion and chemical reaction rates under mechanical agitation, and the bending nature of nanotube results from the difference of force imposed on the nanotube. Furthermore, we developed a robust three-dimensional network architecture with anti-aggregation property for long-time cycling through the assembly of continuous one-dimensional (1D) TiO₂(B) nanotubes, which provides (i) direct and rapid ion/electron transport pathways and (ii) adequate electrode-electrolyte contact and short lithium ion diffusion distance comparing with other nanostructures. This novel synthetic approach could be extended to the fabrication of a wide variety of functional nanomaterials, and the current proof-of-concept study provides new avenues for the future developments of ultrafast rechargeable LIBs.

Our team designs energy-storing architectures that are scalable, manufacturable, and safer than nonaqueous lithium-based systems that persist in expressing catastrophic conflagration. We achieve high performance by rethinking the requisite multifunction#8213;mass and charge transport, electronic and ionic conductivity, and electron-transfer kinetics#8213;in light of architectural design in three dimensions [1-3], where the use of “nothing” (void space) and deliberate disorder are critical components [4]. For Zn-based batteries, we have addressed the historical Zn “dendrite problem,” which limits battery cycle life, by using a radically redesigned 3D Zn sponge architecture [5]. The interconnected Zn sponge retains an inner core of conductive metal throughout cycling that facilitates long-range electronic conductivity and provides more uniform current distribution—two properties needed for high depth-of-discharge (specific energy) and long-term, dendrite-free charge/discharge cycling. Our efforts to develop these electrode architectures and to bring them together within fully rechargeable Zn-based batteries will be described.
This work is supported by the Office of Naval Research and Advanced Research Projects Agency-Energy (ARPA-E), U.S. Department of Energy (Award Number DE-AR-0000391).
[1] J.W. Long, B. Dunn, D.R. Rolison, H.S. White, Chem. Rev. 2004, 104, 4463.
[2] D.R. Rolison, J.W. Long, Acc. Chem. Res. 2007, 40, 854.
[3] D.R. Rolison, J.W. Long, J.C. Lytle, A.E. Fischer, C.P. Rhodes, T.M. McEvoy, M.E. Bourg, A.M. Lubers, Chem. Soc. Rev. 2009, 38, 226.
[4] D.R. Rolison, Science2003, 299, 1698.
[5] J.F. Parker, C.N. Chervin, E.S. Nelson, D.R. Rolison, and J.W. Long. Energy Environ. Sci.2014, 7, 1117.

Although silicon (Si) has very high theoretical capacity (4200 mAh/g) as Li-ion battery anodes, the fast capacity fade greatly hinders its practical application. Various kinds of nanostructured Si-based materials have been developed to accommodate the large volume expansion of Si during lithiation and hence to mitigate the capacity fade. Yet, demonstration of thick electrodes with practical loading, such as ~3 mAh/cm², is limited. Here, we developed porous Si with optimized structure as stable Li-ion battery anodes. In spite of the bulk particle size of >20 micron, porous Si has demonstrated good cycling stability at a high loading of ~3 mAh/cm². The capacity retention can be 85% over 150 cycles. Fundamental understanding of the critical structural parameters of porous Si was demonstrated leveraging theoretical calculation and in-situ transmission electron microscopy characterization.

Graphene, as a two-dimensional single layer carbon material, shows great potential for supercapacitor applications due to its high specific surface area, superior electrical conductivity, high flexibility, and good mechanical properties. However, the agglomeration of graphene sheets due to the strong π-π bonding between individual graphene sheets limits its intrinsic capacitance. NiCo₂O₄ is an excellent pseudocapacitive material with a higher speci#64257;c capacitance. However, the bulk nature of NiCo₂O₄ material prevents it to achieve a high energy density and great rate performance due to the limited electroactive surface area. In this work, flexible porous 3D graphene was first prepared by a simple freezing dry method. Porous NiCo₂O₄ nanosheet arrays were then constructed on the surfaces of the porous 3D graphene film. The porous feature of NiCo₂O₄ nanosheets and 3D graphene jointly increase the amount of electroactive sites and facilitate the penetration of electrolyte ions. The hybrid nature of 3D graphene film and porous structure of NiCo₂O₄ jointly produce synergistic effect to improve the energy density and power density of the electrode.

Detailed understanding of long-range interactions, including van der Waals-London dispersion (vdW-Ld) interactions, is necessary to harness fully the potential of mesoscale self assembly for energy, optics, and biosensing technologies. We present an open-source, open-data implementation of complete mesoscopic Lifshitz theory of vdW-LD interactions based on retarded, full analytical solutions for a range of interaction geometries, with an open spectral web database to distribute optical property spectra of a variety of materials, as well as a range of results for interactions between optically anisotropic cylinders, calculated using the Gecko Hamaker software tool. Hamaker coefficients for cylindrical interaction geometry, forces, and torques are presented for interactions across a range of symmetric and asymmetric systems, for materials including DNA, collagen, single-walled carbon nanotubes (SWCNTs), and inorganic materials (silica, alumina, polystyrene).
Gecko Hamaker readily enables insights from the full-spectral method of calculating Hamaker coefficients that are not predicted by simpler or non-retarded approximations of vdW-Ld interaction strengths. DNA-silica interactions show a strong dependence on DNA composition and stacking sequence; a retardation-based attractive-to-repulsive transition is observed for certain SWCNT-DNA interactions, implying a complex, spectral detail dependent instability in such interactions. Furthermore, a local maximum is observed in the angle dependence of the Hamaker coefficients, which is linked to both the geometric and optical anisotropy in the system.
These results exhibit the power and versatility of the Gecko Hamaker software tool for scientists and mesoscale designers in the physics, chemistry, and biological communities. They provide insights to guide materials selection and design across a wide range of technologically promising mesoscale systems.

Porous assemblies of well-defined nanoparticles (NPs) are of great interest for a wide range of applications, including catalysis, solar energy conversion and optoelectronics, because of their unique properties compared to their primary counterparts [1]. Beyond individual NPs, three-dimensional porous networks assembled from uniform metal-oxide NPs hold great promise for the development of novel materials with advantageous characteristics. For instance, the unique catalytic activity of NPs will be best exploited when they are integrated into extended mesoscopic structures [2]. This is because a three-dimensional pore structure may enable fast diffusion of the target molecules along the NPs, yet could prevent interparticle sintering during catalytic reactions. In addition, the organization of catalytic or plasmonic NPs into aligned nanostructures could induce new collective properties between adjacent particles not present in the original constituents [3].
In this work, we report the synthesis of unique mesoporous Fe₂O₃ NP assemblies (Fe₂O₃-NPAs) through a surfactant-assisted aggregating assembly method. Also, we utilized post-synthetic deposition of gold on surface of Fe₂O₃-NPAs to prepare complex mesostructures of 2% Au-loaded Fe₂O₃ NPs (Au/Fe₂O₃-NPAs). The resulting Au/Fe₂O₃ hybrid mesoporous NPAs, which comprise small Fe₂O₃ nanocrystals (ca. 8 nm) and Au NPs (ca. 5 nm), possess a three-dimensional open-pore structure with a BET surface area of 123 m²/g and narrow mesopores (ca. 6 nm) These hybrid NPAs structures showed high catalytic activity and chemical stability for the selective reduction of nitroarenes into the corresponding amines using1,1,3,3-tetramethyl disiloxane (TMDS) as reducing agent under ambient conditions. We show that the electronic effect of the para-substituent has an important influence on the hydrogenation rate and nitroarenes possessing electron-acceptor group, such as methyl-4-nitrobenzoate, were quantitatively reduced to the desired amines in a shorter reaction time (30 min) than those nitro-compounds containing the electron-donating group, e.g. 4-methoxy nitrobenzene (2 h). A mechanistic study of the reduction of nitroarenes into the corresponding anilines in the presence of hydrosilanes using Au/Fe₂O₃ NPAs is also discussed.
References
[1] Z. Nie, A. Petukhova and E. Kumacheva, Nat. Nanotechnol.5, 15 (2010).
[2] I. Tamiolakis, S. Fountoulaki, N. Vordos, I. N. Lykakis, A. P. Katsoulidis and G. S. Armatas, J. Mater. Chem. A, 1, 14311 (2013).
[3] Z. Lua and Y. Yin, Chem. Soc. Rev.41, 6874 (2012).

With its self-organized high-aspect-ratio nanochannels of uniform pore size, an anodic aluminum oxide (AAO) substrate has long been accepted as an excellent template for the growth of nanocomposites with novel physical properties. An AAO template could be made even more versatile for the design and construction of sophisticated nanomaterials with local variation in their physical properties if the pore diameters and branching behavior of its nanochannels could be individually controlled. Here, we report novel processes to fabricate arrays of AAO nanochannels with individually tunable pore-sizes arranged in any custom-designed geometry and arrays of vertically fan-out curved nanochannels. Our inventions have broadened the potential applications of AAO templates and paved the way for the creation of unprecedented nanomaterials and nanodevices.

Raman scattering is a powerful tool for analyzing chemical compounds because it contains information about the vibrational and rotational motion of chemical bonds1. SERS, which enhances Raman scattering signals on the surface of noble metals through the amplification of electromagnetic fields by localized surface plasmonic resonance (LSPR), has been widely used in high-sensitivity sensors, particularly for biological assays. Because the intensity of LSPR depends on the size, shape, and arrangement of metals, a wide variety of metal nanostructures have been fabricated as efficient SERS substrates.
Recently, microparticles ranging from several tens of nanometers to micrometers with metallic nanoscale features have received increased attention because of their potential as SERS substrates. The surface-to-volume ratio of microparticles is much greater than that of 2D substrates, which increases the sensitivity of SERS for low concentration of molecules under weak excitation. Furthermore, microparticles can be dispersed in liquid media, which means that detailed in vivo analysis of biological and medical specimens can be achieved by SERS. SERS-active molecules, known as SERS tags, attached to microparticles with metal nanostructures have been used as bio-imaging probes. These biological applications require control of both the excitation wavelength and the efficiency of the enhancement. Biological specimens transmit NIR light; therefore, the excitation wavelength of SERS should be tuned to the NIR region. Furthermore, because the enhancement of SERS strongly depends on the LSPR conditions, metal nanostructures with suitable sizes, shapes, and arrangements must be formed on the microparticles.
We have demonstrated a simple fabrication method for SERS-active plasmonic nanoballs, which consisted of Au nanoparticles (NPs) and core-shell polystyrene and amino-terminated poly(butadiene) particles, by heterocoagulation and Au NP diffusion. The amount of Au NPs introduced into the core-shell particles increased with the concentration of Au NPs added to the aqueous dispersion of the core-shell particles. When the amount of Au NPs increased, closely packed, three-dimensionally arranged and close-packed Au NPs arrays were formed in the shells. Strong SERS signals from para-mercaptophenol adsorbed onto composite particles with multilayered Au NPs arrays were obtained by NIR light illumination.

The spinning of a rigid sphere in a uniform E-field has been known since Quincke¹ first developed the theory in 1896; if the induced dipole moment of a sphere is oriented opposite to the direction of the applied electric field, this configuration becomes unstable above a critical E-field strength and a small perturbation is enough to displace the dipole and make it rotate.
The physics of a Quincke rotating and weakly conducting drop is more complex since an applied E-field will deform the drop at any field strength. Taylor described the electrohydrodynamic deformation of a drop with the leaky dielectric model², while Salipante and Vlahovska³ described how different liquid and size parameters influence the rotation.
Drops fully covered by particles, so called Pickering emulsion drops, are used to stabilize emulsions and are ideal templates for producing particles and advanced capsules⁴. Recent studies show how electrohydrodynamic circulation flows in drops can structure free particles on drop surfaces⁵, but there appear to be few studies on the dynamics of Pickering drops subjected to electric field. Here we have studied how silicone oil drops covered with jammed micron sized PE particles, and suspended in castor oil, Quincke rotate, and how this compares to the case of silicone oil drops without surface particles. Upon application of a uniform electric field, the particle shell on the drop slowly deforms into an ellipsoid before a Quincke rotation starts. Our experiments show that the critical electric field strength E_c for the shell to Quincke rotate (300-350 V/mm) is remarkably lower than E_c for pure silicone oil drops (750-800 V/mm). This result will be discussed in relation to existing theories for electrohydrodynamic instability.
References:
1 Quincke, G. Ueber Rotationen im constanten electrischen Felde. Annalen der Physik295, 417-486 (1896).
2 Taylor, G. Studies in Electrohydrodynamics. I. The Circulation Produced in a Drop by Electrical Field. Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences291, 159-166 (1966).
3 Salipante, P. F. & Vlahovska, P. M. Electrohydrodynamics of drops in strong uniform dc electric fields. Phys Fluids22 (2010).
4 Rozynek, Z., Mikkelsen, A., Dommersnes, P. & Fossum, J. O. Electroformation of Janus and patchy capsules. Nature communications 5 (2014).
5 Dommersnes, P. et al. Active structuring of colloidal armour on liquid drops. Nat. Commun. 4, 2066 (2013).

A variety of chemical processes in the oil refining and petrochemical sectors are exclusively catalyzed by zeolites. These crystalline aluminosilicates possess unique properties, i.e. solid acidity, ion-exchange capacity, and unequaled shape selectivity, owing to the multidimensional network of micropores of molecular dimensions (the so-called “micro-reactor” of 0.25-1 nm in size). On the contrary, the sole presence of these micropores imposes transport/diffusion limitations and provokes rapid deactivation, thus negatively impacting the catalyst activity and lifetime. Therefore, full utilization of the zeolite`s potentials, particularly, for processing high molecular weight petroleum fractions and synthesizing large molecules used as fine chemicals, has not been fully explored. The hierarchically structured zeolites have received considerable attention as an alternative solution.
Alkaline treatment has been well-documented as a simple and economical approach for introducing well accessible networks of mesopores. However, its adoption for silica-rich Y-zeolites remains to be fully explored as compared to other industrially used zeolites. This present study subjected super dealuminated USY zeolite (molar Si/Al = 40-15) to various alkaline treatments using inorganic and/or organic bases. The extent of amorphization observed in the case of NaOH or Na₂CO₃ was significantly reduced with the organic bases (alkylammonium hydroxides) within 0.01-1.0M concentration range and the same optimized treatment conditions (65°C, 2 hrs). Among these organic hydroxides, the crystallinity preservation increases as the steric effect induced by the bulky cations increases. This trend was also maintained by the N₂ isotherms which obviously showed a better increase in the external surface area as well as preservation of microporosity for treatment with Tetrabutyl ammonium hydroxide.

Mesoporous transition metal oxides have great potential for applications in photocatalysis and electrochemistry due to their high surface area. We have developed an aerosol-assisted self-assembly pyrolysis (AASAP) method, in which metal nitrates were used as metal oxide precursors and crystalized around self-assembled pluronic F-127 in aerosol droplets during ethanol evaporation. The metal oxides were characterized by Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), Brunauer-Emmett-Teller (BET) isotherms, and X-ray Diffraction (XRD). The metal oxides were tested in cyclic voltammetry to determine their pseudocapacitive behavior.

The ongoing densification and vertical integration in microelectronic systems generates the need for high thermally conductive dielectric materials facilitating efficient heat removal from the system. Composite materials containing percolating microparticles, such as alumina and diamond, exhibit improved thermal transport properties. However, the thermal transport in such percolating microparticle frameworks is limited by point contacts, where the cross sectional area of the thermal conduction path is narrowed or even discontinuous. This work presents the assembly of inorganic nanoparticles, such as alumina and titanium oxide, in the point contacts between micron-sized dielectric particles, forming so-called necks. The directed assembly method relies on the formation of capillary bridges from a nanoparticle suspension within the percolated microparticle framework during evaporation of the solvent. The necks result in quasi areal contacts between the microparticles, allowing for tailoring of structural and transport properties of the composite material.
The site of the nanoparticle assemblies is influenced by different properties of the micro- and nanoparticles, the solvent of the nanoparticle suspension and the evaporation conditions. The influence of these parameters on the morphology of the assembled nanoparticle necks is investigated, including electrostatic double-layers on the micro- and nanoparticles, size and shape of the nanoparticles, and surface tension of the solvent. Furthermore, the parameter space leading to defect-free and robust necks with a high nanoparticle packing density is obtained. Ultimately, the change in thermal conductivity by the existence of nanoparticle necks in percolating microparticle frameworks in confined cavities, mimicking the application as underfill material in flip-chip electronic packaging, is measured and reported.
Reference: T. Brunschwiler, G. Schlottig, S. Ni, Y. Liu, J. V. Goicochea, J. Zürcher, and H. Wolf. Formulation of percolating thermal underfills using hierarchical self-assembly of microparticles and nanoparticles by centrifugal forces and capillary bridging. Journal of Microelectronics and Electronic Packaging9, 149-159 (2012)

Mesoporous metal oxides have attracted a great deal of interest in the field of materials chemistry. Tuneable structural properties such as surface area, pore size, pore volume and nanocrystalline walls make these materials potentially useful in many fields like catalysis, energy, separations, and others. Herein we report Cs promoted mesoporous manganese oxide (UCT-18-Cs) as a remarkably efficient oxidation catalyst. The synthesis of recently discovered UCT (University of Connecticut) mesoporous materials depends on unique NOx chemistry. Nitrate complexes decompose by in situ thermal decomposition producing NOx, which further dissociates to increase the pH of the solution in a controlled way to form metal oxide structures. Finally, metal oxide nanoparticles are packed in a random fashion to build the mesostructure. The surface properties and crystallinity of the material can be tuned by applying heat treatment. Trace amounts of electropositive Cs (Mn/Cs molar ratio 3000/1) create defects (basic sites) in the material and enhance electron density of the lattice oxygen. The material is found to be more active in the amorphous state than the crystalline bixbyite phase (Mn₂O₃). Smaller particle size, high surface area, and lack of large lattice energy in the amorphous state of the materials promote a more facile supply of lattice oxygen. The UCT-18-Cs catalyst can perform various organic oxidation reactions under mild aerobic conditions. For example, the material successfully converts structurally different organic alcohols to corresponding aldehydes and ketones selectively. The UCT-18-Cs catalyzes the double oxidation of 1-Decanol (53% conversion) to 1-Decanoic acid (76% selectivity) with in situ formation of Decyl Decanoate (23% selectivity). The bifunctional (oxidative and basic) UCT-18-Cs catalyst performs solvent free oxidation of Mesitylene (95% conversion) to 3,5-Dimethyl benzoic acid (90% selectivity) and the corresponding benzylic ester (10% selectivity). The material is also effective in gas phase oxidation reactions like oxidation of CO and CH₄ to CO₂ .Use of mild reaction conditions with excellent reusability make the UCT-18-Cs materials a new class of environmentally friendly oxidation catalysts.

Si small particles with porous structures on the surface has attracted much interest owing to its applicability to various application fields. There have been large numbers of methods for the preparation of Si particles with porous structures so far. However, in most cases, it is difficult to prepare the porous Si particles with controlled geometrical structures. We recently reported a new process for the preparation of small porous particles with controlled geometrical structures [1]. In this process, anodization of closed packed small Al particles, where mechanical contact between the particles enables the electrical contact between to small particle, and subsequent re-dispersion of particles generated the particles with porous oxide layers. Using a small Si particle as a starting material, porous Si particles could be obtained by anodization of Si particles in HF electrolyte [2]. In the present report, we describe the formation of porous Si particles with controlled geometrical structures by adjusting the anodizing conditions. In the experiment, commercially available spherical Si particles (p-type, 0.1 #8486;#903;cm) were used as a starting material. To obtain micrometer-size particles, the isotropic etching of Si particles was carried out using an etchant. For the electrochemical etching, the Si particles were set in a cylindrical holder made of a polymer mesh with openings of 100 × 100 mu;m², and an Ti electrode was placed on the particles to ensure the electrical contact between each particle. The electrochemical etching was carried out in an organic electrolyte solution composed of 10 wt% HF and N,N-dimethylformamide solution at 0 0C under a constant current. Form the SEM observation, it was confirmed that the Si particles with nanoporous structures on their surfaces were obtained by electrochemical etching. The depth of the pores in the porous layer could be controlled by changing the treatment time of electrochemical etching. The obtained porous Si particles are expected to be useful for various applications. [1] T. Yanagishita, S. Kimura, K. Nishio, and H. Masuda, Appl. Phys. Express, 1, 084001 (2008). [2] T. Yanagishita, M. Imaizumi, K. Nishio, and H. Masuda, ECS Sold State Lett., 2,P117 (2013).

Photonic crystals have considerable impact on passive and active optical devices and systems due to the possibility to control, modify or confine electromagnetic waves in all the three dimensions. Fabrication of 3D photonic band gap materials working in the visible and near- IR regions recently gained momentum due to development of state of the art of nanofabrication tools. Self-assembly of colloidal particles is a simple method to synthesis 3D photonic crystals compared to nanolithography. We have synthesized different sizes of polymethylmethaacrylate (PMMA) nanoparticles using surfactant free emulsion polymerization technique. These nanoparticles were characterized using DLS and UV-Vis absorption spectroscopy measurements. Self-assembly of polymer nanoparticles and metal precursors was utilized for fabricating 3D photonic crystals. Insitu reduction of metal precursor was performed to fabricate metal nanoparticles doped PMMA 3D photonic crystals. Fabricated 3D photonic crystals were characterized using SEM, HRTEM and UV-Vis Spectrophotometer. Biosensing properties of fabricated metal nanoparticles doped PMMA 3D photonic crystals will be presented.

Since Yaghi's first paper describing a Metal-Organic Framework (MOF) in 1995, research in synthesis and applications of MOFs has undergone rapid expansion, with over 7,800 articles describing MOFs being published in 2013.
Despite high interest in using these materials for applications as broad as gas separation, sensing, storage and catalysis, the near-limitless number of possible MOFs means that it is nearly impossible to naively synthesize a MOF appropriate for a given task. Therefore, there is a need to be able to calculate the structure and properties of arbitrary, hypothetical frameworks.
In this work, we present AuToGraFS, our software that employs a database of SBUs to create framework models with topologies sourced from either the Reticular Chemistry Structure Resource (RCSR) or the EPINET database. The models generated by AuToGraFS, are highly accurate, with less than 1.5% error on cell parameters, even for large unit cells such as mtn-e (MIL-101) and may be refined further our framework optimised extension of Rappé's Universal Force Field, UFF4MOF[1] .
1. Addicoat, M.A.; Vankova, N.; Akter, F.; Heine, T.; J Chem Theory Comput, 10, 880-891 (2014)

Nanoparticles and other specialized morphologies are pursued as materials with enhanced performance for applications such as catalysis, energy generation, and energy storage. Property enhancement can be attributed to increased surface area and decreased diffusion distances. Connected porosity is particularly important and can be achieved through the bulk of a material with pores sizes over various length scales, depending on the method employed in pore generation. Templating is a common technique for preparing porous ceramic materials by the use of a preformed template that is later removed. Alternatives to this time and material intensive strategy make use of inherent material reactivity rather than the dimensions and shapes of templating materials. One such alternative for preparing porous metals is dealloying, an early example of which is Raney Nickel. Another method, which is similar to dealloying, can be used to prepare metals and metal oxides with connected mesoporous and textured morphologies by the removal of a sacrificial element or phase. In particular, porosity has been observed with the removal of Zn from complex Zn-M-O compounds, where M is a transition metal. Upon heating between 500 and 900°C in a reducing atmosphere, such as 5% H₂/N₂, Zn²⁺ is reduced to the metal. Since Zn metal has a low vaporization temperature and high vaporization pressure, it is removed from the structure in the vapor phase. The remaining M is also reduced to a lower oxidation state, depending on the stability of the oxide. The resulting phase change and mass loss can result in a metal or metal oxide with 3-dimensional porosity. In this study, we relate the degree of morphology evolution to differences between the parent Zn-M-O compound and reduction product phases. Methods such as XRD, SEM, and BET/BJH are used to analyze the phase and morphology that result from heating in a reducing atmosphere. Additionally, we investigate how a material&’s electrochemistry is affected by connected porosity and pore size.

Agglomeration refers to the formation of physically attached primary particles by coagulation. It occurs in environmental and industrial processes, especially in low temperature regions where sintering or coalescence are rather slow. Understanding agglomeration is essential for optimal process design for manufacture of nanomaterials as their fractal structure affects their handling and processing and eventually their performance. The high particle concentrations encountered during nanomaterial manufacturing lead to formation of agglomerates with well-defined asymptotic structure and size distribution given by their fractal-like dimension and self-preserving size distribution, respectively.
The growth and detailed structure of fractal-like aerosol particles undergoing agglomeration is investigated here from the free molecular to the continuum regime by discrete element modeling. Particles in the free molecular regime follow ballistic trajectories described by an event driven method whereas in the near continuum (gas-slip) and continuum regimes Langevin Dynamics describe their diffusive motion. The simulations are validated by the attainment of the collision frequency and self-preserving size distribution (SPSD) of fully coalescing particles in free molecular and continuum regimes as well as the corresponding asymptotic fractal dimensions, D_f, of 1.91 and 1.78 by ballistic and diffusion-limited cluster-cluster agglomeration, respectively.
The evolution of agglomerate structure from perfect spheres (D_f = 3) to the above well-known asymptotic fractal-like structures is simulated in detail and a simplified expression is extracted that can be readily used in process design for synthesis of nanomaterials or in environmental models for ambient aerosols (e.g. air pollution and climate forcing). Fractal-like agglomerates exhibit considerably broader SPSD than spherical particles when made by coagulation-agglomeration: the number-based geometric standard deviation of the radius of gyration of agglomerates in the free molecular and continuum regimes is 2.27 and 1.95, respectively, compared to that of spherical particles of 1.45. The quasi-self-preserving geometric standard deviation of the radius of gyration of agglomerates exhibits a characteristic minimum of 1.65 in the transition regime at Knudsen numbers, Kn asymp; 0.2. In contrast, their D_f linearly shifts from 1.91 in the free molecular to 1.78 in the continuum regime.

A combined magnetization and ⁵⁷Fe spin-echo nuclear magnetic resonance (NMR) study has been carried out on highly ordered mesoporous nanostructured materials consisting of the magnetite (Fe₃O₄) and maghemite (γ-Fe₂O₃) phases. Two series of samples were synthesized using a recently developed one-step soft-templating approach¹ with variations in calcination temperature and reaction atmosphere. Nuclear magnetic resonance has been shown to be a valuable tool for distinguishing between the two iron oxide inverse spinel phases on the nanoscale² as well as monitoring phase transformations resulting from oxidation. For Fe₃O₄ at 4.2 K and zero magnetic field, the tetrahedral (A) sites and octahedral (B) sites are characterized by NMR peaks at 69.9 MHz and 67.3 MHz, respectively. The tetrahedral and octahedral peaks for γ-Fe₂O₃ are 70.9 MHz and 73.2 MHz, respectively. The magnetic field dependence of the peaks was observed and confirmed the site assignments. Fe₃O₄ nanoparticles readily oxidize to form γ-Fe₂O₃ and this was clearly evident in the NMR spectra. As evidenced by transmission electron microscope (TEM) images, the porous mesostructure is formed by a random close-packed aggregation of nanoparticles; correspondingly, superparamagnetic behavior was observed in the magnetic measurements. Although X-ray diffraction (XRD) shows the spinel structure for the two iron oxide phases, unlike NMR, it is difficult to distinguish between the phases with XRD. Nitrogen sorption isotherms were typical of mesoporous structures, i.e., Type IV with Type H1 hysteresis loops. From the isotherms, calculations were made for the BET surface area and BJH pore size distribution.
¹Altug S. Poyraz, Chung-Hao Kuo, Sourav Biswas, Cecil K. King&’ondu and Steven L. Suib, Nat. Commun. 4, 2952 (2013).
²SangGap Lee, Hyun-wook Kang, Minchan Kwak, You-Jin Lee, Gaehang Lee, Insuk Yu and Hae Jin Kim, J. Anal. Science Tech. 2 (Suppl. A), A84 (2011).

In this research, we prepared mesostructured organically modified silica (ormosil) thin films with bright pyrene excimer emission using mesostructured ormosil colloids. In the first step, ormosil colloids were synthesized via a facile template-free sol-gel method and pyrene molecules were physically encapsulated in the ormosil network during the synthesis of the colloids. In the second step, mesostructured ormosil thin films were obtained by spin-coating pyrene doped ormosil colloids onto glass substrates. Pyrene doped non-porous dense ormosil thin films were also prepared at the same conditions. Formation and stability of excimers were investigated in both mesostructured and non-porous ormosil thin films. Excimer emission was stronger and more stable in the mesostructured films, whereas it was weak and decayed rapidly in their non-porous counterparts. The hydrophobic and mesostructured ormosil network was believed to act as efficient environment for facile diffusion of pyrene molecules to form excimers.
We analyzed nitroaromatic explosive sensing performances of the mesostructured ormosil thin films for trinitrotoluene (TNT), dinitrotoluene (DNT) and nitrobenzene (NB) based on quenching of excimer emission. The films exhibited a rapid and selective fluorescence quenching response towards nitro-explosives vapors. Quenching efficiencies of the excimer emission intensity were as high as 32% and 87.4% after exposure of the films to TNT for 10 seconds and 5 minutes, respectively. Quenching of bright blue excimer emission was visually observed under UV-light illumination enabling the detection of nitro-explosives by naked-eye. Furthermore, excimer emission signal was recovered after quenching by simply washing the films with water and the films were reused for at least five times. We believe that pyrene doped mesostructured ormosil thin films present a promising sensor platform with their high surface area, easy synthesis, cost-effectiveness and reusability.

We present a alternative technology to traditional laser and e-beam based metal and alloy additive manufacturing (AM) approaches that utilizes room-temperature extrusion of particle-based liquid inks comprised of metal oxide powder(s), elastomeric binder, and graded volatility solvents to create self-supporting, complex constructs that can be thermochemically reduced and sintered, resulting in metallic constructs. This particular ink formulation results in 3D-printed green bodies that, although comprised of up to 90 vol.% oxide particles, can be bent, rolled, folded, cut, and even fused with other similar materials using the ink as an adhesive. Complex oxide objects created through physical manipulation of the 3D-printed objects, that could otherwise not be 3D-printed directly, retain their structural fidelity upon thermochemical reduction to metal and sintering. We demonstrate that this process can be applied to a variety of ferrous and non-ferrous primary metal and alloy systems to create objects as small as a single cubic millimeter and as large as many cubic centimeters, comprised of structural features as small as 100 µm. In this manner, nano- and micron-scale oxide powders, which are generally far more economical than their metallic or pre-alloyed powder counterparts, can be utilized to rapidly create large scale, user-defined architectures. Mechanical testing of 3D-printed oxide green bodies reveals that tensile and compressive strengths and moduli depend heavily on the concentration of particles within the construct, as well as the size of the comprising particles. None of the green bodies tested, including those comprised of 90 vol.% particles, catastrophically fail under compressive loads, but rather, plastically deform. Inks comprised of a variety of oxides - including but not limited to those of iron, nickel, and copper - are presented along with inks comprised of mixed oxides corresponding to desired final binary and ternary alloy compositions. Oxide green bodies are thermochemically reduced in pure H₂ atmosphere at elevated temperatures to metals and alloys, which then continue to be sintered in H₂ or inert atmosphere. The resulting metallic constructs, although volumetrically reduced due to sintering and to oxide-to-metal density changes, retain their originally shapes without warping, cracking, or sagging. Metallographic and electron microscopic analyses of the resulting metal and alloy structures reveal near fully dense metallic constructs can be achieved with the majority of the systems tested. Hardness, stiffness, and strength values for the final metallic systems are found to be similar to conventionally processed counterparts. Finally, we show how this process can be extended towards creating complex, multi-metal/alloy constructs through co-3D-printing of multiple liquid oxide inks.

It is know that micro-scale particles of Zerovalent Iron (ZVI) have been widely used for soil and groundwater remediation. ZVI is the most commonly used reactive media in PRB (Permeable Reactive Barriers) installations, since ZVI particles are very effective in the degradation of chlorinated hydrocarbons. To have more effective reaction, people have been tried to synthesis ZVI size into nano-scale to have larger specific surface area than microscale ZVI. By using nanoscale (<1 mu;m) ZVI (nZVI), It is possible to treat more than 70 environmental contaminants such as polychlorinated hydrocarbons (aliphatic and aromatic), highly toxic substances such as As(III), As(V), Cu(II), Co(II), Cr(VI), nitrite, and a wide range of toxic industrial dyes. However, three are still several limitations to commercialize this nZVI: cost, oxidation, aggregation of nano-particles.
In this study, we suggest the way of reducing the cost of nZVI particles by recycling, minimizing oxidation, and preventing aggregation using 3D Printed hierarchical structure of nZVI particles imbedded. Although it may not useful for soil remediation but it may very effective for groundwater remediation. This can be done by simple processes of cost-effective fabrication of nZVI embedded filament, structuring of macro-scale porous filters, and simple etching process of expose nZVI in micro-scale. The polymer thermal extruder fabricated base-materials for FDM 3D Printer, which is mixing of nZVI with polymer, such as PLA, PC, or ABS. Then, FDM 3D printer builds up the macro-scale structure with 200mm resolution. Reflowing or etching process generates sub-micro-scale structures for finalizing nZVI catalysis structures.
The quantitative result of 3D printed nZVI structures is not yet prepared in ground water remediation; however, we could observe the qualitative results with simple dyed water purification preliminary experiments.

INTRODUCTION
The ability to fabricate complex 3D micro-electro-mechanical-systems (MEMS) is critical for the future of the micro-devices industry. Existing techniques include complicated, time consuming, costly processes such as gray-scale e-beam or photo lithography, ion implantation, or multi-step etching. In this study, we demonstrate the fabrication of high aspect ratio, dual-angle micro-needles with sharp tips by using photoresist (PR) re-flow process and single-step deep reactive ion etching (DRIE). Arrays of micro-needles with different heights, in the range of 110-350 µm, are fabricated.
FABRICATION PROCESS
Silicon wafers with thermally grown oxide (TOX) ranging from 1-2 µm are used as the core material. The different oxide thicknesses will allow the fabrication of several arrays with different heights. Shipley&’s SPR 220-7 is used as the initial photoresist mask and is spin coated on the wafers. Pre-bake is done in a temperature controlled oven with temperature rising to 90^oC in 20 minutes, staying constant at 90^oC for 20 minutes, followed by the final slow cool down to room temperature. Conventional photolithography is used to pattern arrays of 10x10 circles on the wafer. After developing the resist, the sample is hard baked on a hotplate at 170^oC for 45 minutes. This precise step makes the resist patterns re-flow, to form semi-spherical shapes. Wyko scans of the re-flown PR give a maximum height of the resist of approximately 12 µm.
Fluorine ICP RIE with O₂, Ar, and CHF₃ as the input gases of the plasma is then used to transfer the resist profiles into the oxide. The transfer recipe is optimized to control the selectivity between PR and TOX such that the unmasked oxide surface is cleared sooner than the resist. The final oxide patterns will have flat top surfaces with curved sidewalls. This curved sidewall is extremely important to pre-define the dual-angle shape of the micro-needles. The final step of the fabrication process is the DRIE etching, to transfer the oxide patterns into the silicon, with selectivity TOX:Silicon ranging from 1:150 to 1:250.
RESULTS AND CONCLUSION
Because of the shape of the oxide masks (curved side-wall with flat top), the final silicon etched configuration will be dual-angle, resulting in micro-needles with pencil-like shapes and sharp tips. The thinner oxide masks (1 µm and 1.4 µm) produce short micro-needles, with final height less than 210 µm. As the oxide thickness increases, the height of the micro-needles also increases, up to 350 µm for oxide thickness of approximately 1.8 µm
Extensive analysis of the silicon features shows height uniformity across the arrays better then 3%. Sidewall angles of the body of the micro-needle as well as angles at the tip are also investigated. Full results will be presented and discussed.

Sub-micron sized hybrid polymer metal oxide particles are interesting building blocks for the production of nanocomposites. Examples of products comprising such particles range from optical coatings [1] to chromatographic materials [2] and chemical sensors [3]. Particularly, particles with a programmable composition, size and architecture are of interest, since they form key building blocks for advanced composites with a tailored set of functionalities.
In spite of the large application potential of sub-micron sized hybrid polymer metal oxide particles, they are not yet widely used in commercial applications. This is mainly due to the limitations of the synthesis routes developed to date. Most of these are cost intensive, multi-step routes. In some cases, tailored block-copolymers [4] are required and some processes are intrinsically difficult to perform on large scale [5].
Here, we present a facile and versatile platform approach for the synthesis of sub-micron sized hybrid particles based on an oil-in-water emulsion. We designed a one pot synthesis approach based on simultaneous radical polymerization of monomers like styrene and methyl methacrylate (MMA) and silica segregation, and prepared hybrid particles. We studied the chemical composition of these particles using FT-IR, XRD and TGA. Furthermore, we performed a detailed study on the architecture of the particles, using advanced electron microscopy (SEM, TEM, STEM) analysis. We demonstrate that particle size, composition and architecture are programmable in this synthesis route. Particle architectures range from homogeneous to multi-domain and core-shell particles. To demonstrate the versatility of this synthesis route, we prepared particles based on combinations of MMA, styrene and a variety of silica precursors. In addition, we prepared particles with reactive rest groups suited for further functionalization.
[1] (a) R. Munoz-Espi, P. Dolcet, T. Rossow, M. Wagner, K. Landfester, D. Crespy, ACS Appl. Mater. Interfaces2011, 3, 4292-4298; (b) M. Aguirre, M. Paulis, J. R. Leiza, J. Mater. Chem. A2013, 1, 3155-3162.
[2] K. J. C. van Bommel, A. Friggeri, S. Shinkai, Angew. Chem. Int. Ed.2003, 42, 980-999.
[3] L. Zhu, X. Yang, Y. Cao, Anal. Lett.2013, 46, 982-998.
[4] (a) M. Siebert, K. Albrecht, R. Spiertz, H. Keul, M. Möller, Soft Matter2011, 7, 587-594; (b) J. -J. Yuan, O. Mykhaylyk, A.J. Ryan, S.P. Armes, J. Am. Chem. Soc.2007, 129, 1717-1723.
[5] J. M. Asua, Progress in Polymer Science2014, accepted manuscript.

Nano carbon materials such as graphene and carbon nanotube have been demonstrated to be effective conductive fillers to significantly enhance the dielectric properties of polymer-based composites. However, when the filler content approaches the threshold, the dielectric loss of these composites becomes quite high, since the conductive fillers will contact with each other in the polymer matrix. Thus, preventing the conductive fillers connections is a key for increasing the dielectric constant and retaining low dielectric loss. In our works, we produced 3 nano carbon structures with insulting surfaces, including Core/Shell structure, Multilayer structure, Honeycomb structure. Experimental results indicated the dielectric properties of polymer-based composites are greatly enhanced by filling the nano carbon with insulating interface, because the connections among the nano carbon materials in polymer matrix have been greatly reduced by the insulating surfaces. Our strategy provides a pathway to achieve nano carbon materials/polymer composites with good dielectric performances.

Isoporous membranes manufactured from diblock copolymers can be successfully produced at laboratory scale under controlled conditions. Due to our present understanding complex phenomena involved in the membrane preparation, trial and error methodologies are required to find the optimal conditions, leading to a considerable demand of physical and time resources. In general, a robust identification of the most relevant variables and their interdependence is still needed.
Recent studies demonstrate that the characteristic morphology of the final membrane is defined during the self assembly of the diblock copolymer in solution, prior the membrane casting and phase inversion in water. Herein we use the meso-scale particle-based method known as Dissipative Particle Dynamics (DPD) to construct and simulate coarse-grain models of poly-4-vinylpryridine-b-polystyrene (P4VP-PS), in solution with different solvents and polymer concentrations. We model high molecular weight polymers used for the preparation of the real membranes, in a representative time and length scales using a model reduction methodology we recently proposed. This model reduction approach preserves geometric properties of the polymer chain while the total number of degrees of freedom required is reduced.
The behavior of our computational model is consistent with experimental evidence, showing morphological transition of the aggregates as the polymer concentration and solvent affinity change; passing from disordered crew-cut micelles, to hexagonal close packed crew-cut micelles, to lamellar structures. In particular, the different meta-stable structures identified support the variation in size domain evidenced by small angle x-ray scattering (SAXS) measurements. We show that hexagonal arrangement of the micelles can exists in solution within different windows of polymer concentration depending on the solvent affinity, however in all the cases the volumetric concentration of micelles is nearly the same. In this context the order of crew-cut micelles in solution can be described using rigid-sphere packing consideration.

One-dimensional (1D) nanostructures such as nanofibers have distinctive properties that can offer good opportunities for developing advanced materials and devices. Among the other nanofiber fabrication methods, electrospinning has gained growing interest in the past decade because this technique is quite versatile and cost-effective for producing functional nanofibers. Electrospun nanofibers and their nanofiber mats have remarkable characteristics including a very high specific surface area and pore sizes within the nanoscale. Because of their exceptional properties, it has been shown that these nanofibers/nanowebs have potentials for various applications in the field of membranes/nanofilters, biomedical, nanocomposites, energy, sensing, etc. Polymerminus;inorganic composite nanofibrous structures have intriguing properties which combine the advantages of polymers such as structural flexibility and lightweight with the properties of inorganic materials such as high mechanical strength, high thermal stability and excellent electrical, magnetic, optical, catalytically properties, etc. These composite nanofibers have many potential applications in filtration, protective clothing, electronics, energy storage devices, sensors, microwave absorbers, etc.
Recently, atomic layer deposition (ALD) technique has been explored to produce conformal and very thin inorganic coatings on fibrous systems. ALD, which is a special type of low-temperature chemical vapor deposition, proceeds though the sequential pulses of two or more precursors separated by purging/evacuation periods. As the substrate is exposed to a certain precursor, gaseous precursor molecules saturate the surface by reacting with available surface sites, creating new sites for the following precursor. Film growth mechanism of ALD is inherently self-limiting, which gives rise to unique properties such as high uniformity and conformality, as well as subnanometer precise thickness control. ALD process provides flexibility so that very thin conformal layers of metal oxides or metal nitrides can be coated onto different types of three-dimensional substrates. ALD was mostly studied on inorganic substrates, yet, recent studies showed that polymeric films and complex surfaces such as fibers and nonwovens can also be coated by ALD. It has also been shown that electrospun nanofibers can be used as a template for producing hollow nanofibers.
In this report we present our efforts in the fabrication of III-nitride and metal-oxide based mesoscale, highly-3D core-shell and hollow nanofiber networks and their application in photocatalysis. Among the studied ALD-grown materials are GaN, InN, ZnO, TiO₂, In₂O₃., and their multi-layered forms. The achieved results indicate a remarkable enhancement in photocatalysis with respect to conventional thin-film counterparts.

Nanocomposites of hybrid organic and inorganic material systems in diverse nanostructure forms have potential to modify the characteristics in terms of the electrical, capacitive and magnetic properties. Various nanocomposites of oxides with conducting and semiconductor polymers have applications in chemical energy storage, photovoltaic energy conversion and sensors devices. Recent focus of nanocomposites is in the supercapacitor energy storage utilizing the 2-dimensional (2-D) microporous electrode forms. In this work, we investigate nanocomposites in the 3-D nanoarchitecture using vertically aligned ZnO nanorods template to create conducting polymer (Pedot) Poly(3,4-ethylenedioxythiophene) nanotube and nanofibrous network structure using facile electrochemical synthesis approach.
Vertically aligned ZnO nanorod arrays of 60-120 nm diameter and 3-4 mu;m length serves as template are hydrothermally formed. To create Pedot in 3-D nanostructures, ZnO nanorods are coated by electropolymerization by controlled 10k short 10 ms current pulses of 4 mA.cm^-2 amplitude in the presence of surfactant to promote site selective filling. The Pedot nanotubes are obtained by etching ZnO nanorods and nanofibres by varying electropolymerization conditions and ZnO nanorods array geometry.
Interaction and response of ZnO nanorod and various Pedot nanostructures was analyzed by electrochemical impedance, cyclic voltammetry (CV) and charge-discharge techniques. Impedance results for Pedot nanofibrous network structure showed creation of highly effective charge transfer interface structure with low resistance ~ 5.4 #8486;.cm² significantly less in comparison to ZnO and Pedot structures. Raman study show highly conjugated Pedot in oxidized state. Areal capacitance, 209 and 189 mF cm^-2 is achieved in Pedot nanotubes formed with ZnO nanorods core of diameter 60 and 120 nm, respectively. Pseudocapacitive behavior of electrodes is shown by rectangular feature of CVs and diffusion controlled process at electrode-electrolyte interface is confirmed by Randles-Sevcik plots. At fast CV scans, the charge storage through anions enhances in nanostructure created over 120 nm ZnO nanorods due increased access to larger surface regions. For 60 nm ZnO rod structures, ion diffusion limitation at higher scan rates is observed. Galvanostatic charge-discharge studies at different current densities conducted on Pedot nanostructures over ZnO nanorods are symmetrical and show capacitance consistent with CV results. In conclusion, this work shows that facilitated charge transfer and electron conduction achieved through structure control of the ZnO nanorods and Pedot nanotube and fiber network at the nanoscale has significantly improved the electrochemical redox processes and hence pseudocapacitive properties for efficient energy storage in a supercapacitor device.

We demonstrated the low-temperature fabrication of macroporous scattering film for dye-sensitized solar cells. The macroporous film was prepared by polystyrene (PS)/TiO₂ composite layer. Here, we newly developed the low-temperature fabrication process via the dissolution of PS sphere for a macroporous (MP) scattering film. The dissolution of PS sphere was investigated by fluorescence images. The reflectance of the macroporous scattering film was estimated by UV-vis spectrometer. The reflectance of the MP scattering film was increased from 7% to 30%, compared to nanoparticle (NP) TiO₂ film. The performance of DSC using the MP scattering layer was estimated under the simulated solar light. The current density of DSC using the MP scattering layer was enhanced from 8.97mA/cm² to 10.67mA/cm², which is contributed to the 22% of improvement in energy conversion efficiency. This low-temperature fabrication process is expected as a promising approach for next-generation flexible DSCs.

Cotton textiles were first converted into activated carbon textiles (ACTs) for flexible energy storage applications. NiCo₃O₄ nanowires were radially anchored the ACsT by a simple hydrothermal method. The obtained brush-like NiCo₃O₄/ACT hybrids were used as the core to further deposit NiCo₃O₄ nanosheets to form the shell. Such hierarchical core/shell NiCo₃O₄@NiCo₃O₄/ACT hybrid architectures showed a superior specific capacitance of 2450 F/g at the current density of 1 mA/cm², the capacitance could be retained at 904 F/g even at the high current density of 20 mA/cm², which showed excellent rate performance. There is almost no capacitance decay after 1000 charge/discharge cycles, which showed excellent cyclic performance. The outstanding electrochemical performance is attributed to the superstructure with significantly enhanced active-surface area, favorable morphological stability and convenient ion transport path. Such hierarchical core/shell NiCo₃O₄@NiCo₃O₄/ACT hybrid architectures also showed great flexibility, which can be further used to fabricate flexible energy storage device for wearable electronics.

Photonic crystals are widely known for their light-trapping capabilities. This is often associated with the occurrence of a photonic band gap or other suppression in the electromagnetic density of states [1-3]. This enables guiding of light on an optical micro-chip and unprecedented forms of strong-coupling between light and matter. In the past, practical applications of these effects have focussed on information technology. More recently, an important opportunity has emerged in the area of energy technology. This arises from light-trapping in the higher bands of a photonic crystal, where the electromagnetic density of states is enhanced rather than suppressed. This enables unprecedented strong absorption of sunlight in a material with weak intrinsic absorption [4-10].
We describe designs of 3D photonic crystal silicon-based solar cells that enhance the overall absorption of sunlight using architectures consisting of less than 1 micron (equivalent bulk thickness) of silicon. These 3D photonic crystals exhibit an enhanced electromagnetic density of states, consisting of slow group velocity modes, in which the flow of energy is transverse to the depth of a thin film of material. The power conversion efficiencies of these sub-micron photonic crystals are predicted to be in the range of 15-25% and rival those of present-day solar cells using up to 300 microns of silicon. These photonic crystals offer additional opportunities for solar spectral reshaping to rival and possibly surpass the Shockley-Queisser power conversion efficiency limit.
References:
1. S. John, Physical Review Letters 58, 2486 (1987)
2. E. Yablonovitch, Physical Review Letters 58, 2059 (1987)
3. S. John, Physical Review Letters 53, 2169 (1984)
4. A. Chutinan and S. John, Physical Review A 78, 023825 (2008)
5. G. Demesy and S. John, J. Applied Physics 112, 074326 (2012)
6. A Deinega and S. John, J. Applied Physics 112, 074327 (2012)
7. S. Eiderman, S. John, A. Deinega, J. Applied Physics 113, 154315 (2013)
8. S. Deinega, S. Eiderman, S. John, J. Applied Physics 113, 224501 (2013)
9. K. Le and S. John, Optics Express, 22, Issue S1, pp. A1-A12 (2014)
10. S. Eiderman, A. Deinega and S. John, Journal of Materials Chemistry A,
DOI: 1039/c3ta13655h (2014)

Random mesoporous nanostructured media possess electromagnetic properties that greatly differ from those of ordinary bulk materials. The capacity to control the optical response of the material by tuning its internal structure has rendered these architectures into a promising light trapping technology for solar energy conversion. However, a rigorous electromagnetic computation of these structures in large-scale systems is computationally demanding and impractical. Here, we present a multiscale optical model approach to study random mesoporous networks (RMN) of TiO₂-nanoparticles for dye-sensitized solar cell (DSSC) applications. The building blocks of RMN are aggregated nanoparticles with the same internal structure configuration as the macroscopic photoelectrode. In this approach, Maxwell&’s electromagnetic equations are solved with the generalized-multiparticle-Mie theory for a system of aggregated TiO₂ nanoparticles in a subwavelength volume. The results are then implemented in a Monte Carlo algorithm to simulate the propagation of light within the photoelectrode. We investigate the influence of the TiO₂ crystal phase, porosity, and pore and particle size distributions on the photoelectrode transmitted, reflected and absorbed spectra. Results of the simulations agree with the observed experimental data. We show that careful engineering of the internal structure and the thickness of the photoelectrode gives accurate control on the coupling of incident light with the mesoporous film over the UV to near-IR spectrum range that can lead to enhanced DSSC conversion efficiency. Our approach provides for the first time insight into the spatial distribution of electron generation within the photoelectrode that is of great importance for the design and optimization of the photoelectrode. Finally, we show the potential of this model to investigate RMN of nanowires and other nanostructures.

The assembly of nanoscale building blocks in engineered mesostructures is one of the fundamental goals of nanotechnology. Among the various processes developed to date, self-assembly emerges as one of the most promising since it relays solely on basic physico-chemical forces. Our research is focused on a new type of self-assembly strategy from the gas-phase: Scattered Ballistic Deposition (SBD). SBD arises from the interaction of a supersonic molecular beam with a static gas and enables the growth of quasi-1D hierarchical mesostructures. Overall, they resemble a forest composed of individual, high aspect-ratio, tree-like structures, assembled from amorphous or crystalline nanoparticles, depending on the material. Moreover, when starting from an amorphous ensemble of nanometric clusters, it is possible to obtain hyperbranched hierarchical objects with single crystalline subdomains extending for hundreds of nanometers.
SBD is a general occurring phenomenon and can be obtained with different vapour or cluster sources. SBD by Pulsed Laser Deposition is a convenient physical vapor technique that allows the generation of supersonic plasma jets from any inorganic material irrespective of melting temperature, preserving even the most complex stoichiometries. One of the advantages of PLD over other vapour deposition techniques is extremely wide operational pressure range, from UHV to ambient pressure. These characteristics allowed us to develop quasi-1D hierarchical nanostructures from different transition metal oxides, semiconductors and metals: TiO2, WO3, SnO2, MoO3, Si, Al2O3, PdO, C. In the case of the first three we successfully demonstrated hyperbranching by optimized thermal annealing procedures. Potential application range from innovative solar cells and water splitting architectures to gas sensors, thermal barriers, etc. In this communication we will discuss the application of these materials to Photovoltaics, Water Splitting for H2 generation and smart surfaces with digital control of their wettability behaviour.
Finally, a novel remote plasma source developed to mimic the SBD-PLD physics on large area will be presented.

High density tree-like three-dimensional (3D) nanowire (NW) architectures are ideal for high-performance photoelectrodes that could offer long optical paths for efficient light absorption, high quality one-dimensional (1D) conducting channels for rapid electron-hole separation and charge transport, as well as high surface areas for fast interfacial charge transfer and electrochemical reactions. Such structures are typically limited by depth of the NW channels and the density of branch coverage. We developed a surface-reaction-limited pulsed chemical vapor deposition (SPCVD) technique as a derivative of atomic layer deposition (ALD), which grew titanium dioxide (TiO2) nanorods (NRs) inside dense Si NW arrays. The SPCVD technique effectively decouples the crystal growth from precursor vapor concentration, thus makes the conform growth of dense NW arrays inside highly-confined submicron-sized spaces possible. Dramatic increases of photocurrent and efficiency were obtained when the 3D TiO2 NR-Si NW architectures were applied as photoelectrochemical (PEC) anodes. Through comprehensive atomistic electron microscopy study of the TiO₂ nanostructures at designed growth cycles, we revealed that the evolution of TiO₂ nanostructures in high-temperature ALD processes follows a path from amorphous layers to amorphous particles to metastable crystallites and ultimately to stable crystalline forms. Such a phase evolution is a manifestation of the Ostwald-Lussac Law, which governs the advent sequence and amount ratio of different phases in high-temperature TiO₂ ALD nanostructures. The amorphous-crystalline mixture enables a unique anisotropic crystal growth behavior at high temperature forming TiO₂ NRs via the principle of vapor-phase oriented attachment. When ZnO nanostructures were used as the supporting templates in the high-temperature TiO₂ ALD growth, TiO₂ tubular nanostructures with well-preserved dimensions and morphology were obtained. This process involved the cation exchange reaction between TiCl₄ vapor and ZnO solid and the diffusion of reactants and products in their vapor or solid phases, which was a manifestation of the Kirkendall effect. The evolution of TiO₂ nanotubes from ZnO NW scaffolds was seamlessly integrated with TiO₂ NR branch growth, and thus realized a pure TiO₂-phased 3D NW architecture. Our discovery of high-temperature derivatives of ALD techniques opens a new route toward the design and creation of complex 3D hierarchical nanostructures, which may advantageously impact the devices performance of solar energy harvesting.

Along with new material synthesis, the smart functional nano-structuring of known materials has drawn tremendous attention from many researchers and industries in energy harvesting, conversion and storage technologies. In particular, hierarchical highly branched nanowire structures have shown great potentials because they have very large surface area and enhanced electrical properties by providing direct transport pathway for charge carriers. Additionally, the hierarchical multiscale highly branched nanowires are beneficial to solar energy harvesting applications because they can improve the light absorption due to the increased optical path as well as additional light trapping through reduced reflection and multi-scattering in comparison to 1D nanowire arrays. In this talk, recent research development and trend in hierarchical highly branched nanowires as well as applications in energy devices will be presented and future direction will be discussed.

The interconnects between the nanoparticles comprising the network in anatase TiO₂ aerogels strongly affect UV photocatalytic H₂ generation activity, while only modestly affecting the activity of TiO₂ aerogels towards the photocatalytic oxidative degradation of dichloroacetic acid (DCA). We synthesized a series of TiO₂ aerogels with different mechanical strengths by varying the sol-gel precursor concentration in the synthesis. The strongest aerogels were ~8× more active for the UV photocatalytic generation of H₂ than the weaker materials. In contrast, rates of photocatalytic DCA degradation increased only ~30% when going from the weakest to strongest materials. The series of TiO₂ aerogels were also cast as films and analyzed using dynamic photoelectrochemical methods. Intensity-modulated photovoltage spectroscopy (IMVS) revealed that excited-state electron lifetimes were ~30-50% higher in the strong TiO₂ aerogels than in the weaker aerogels; intensity-modulated photocurrent spectroscopy (IMPS) revealed that electron transport is ~30-50% slower in the stronger materials.
The modest improvement in DCA degradation in the stronger TiO₂ aerogels correlates well to the increased electron lifetimes. The more substantial improvement in photocatalytic H₂ generation suggests an increased concentration of photocatalytic active sites (for reductive water splitting) in the stronger TiO₂ aerogels. The photocatalytic and photoelectrochemical results considered together suggest that these active sites also act as electron traps, which increase electron lifetimes, but also slow electron transport. It is probable that the active sites/trapping sites arise at aerogel interparticle contacts, or “necks”. Steady state and time-resolved spectroscopic experiments are underway to determine both the identity of the active sites and the dynamics of the trapping/detrapping processes in the different materials.
This work is supported by the Office of Naval Research.

Three-dimensional battery architectures offer a new approach for powering next generation autonomous microsystems that serve such application areas as sensing/actuation, communication and health monitoring. The energy storage considerations for such autonomous devices will be difficult to achieve with traditional two-dimensional designs because of the limited footprint area available for the power source. With 3D battery architectures, one exploits the third dimension, height, to increase the amount of electrode material within a given footprint area: milliwatt hour energies can be stored in cubic millimeter packages that have footprint areas of less than 1 square centimeter. Moreover, by using 3D electrode designs which minimize the ionic path length between electrodes, there is the prospect of achieving high energy and power density within the small footprint area.
The present paper reviews recent advances in the development of 3-D microbatteries which incorporate periodic electrode arrays. The design rules for such 3D battery architectures have been established and methods for fabricating non-planar electrode structures have been developed for a variety of materials. By varying electrode features such as rod height, diameter and pitch, we can design 3D electrodes capable of reaching areal energy densities in the range of 5 to 10 mAh/cm² which is suitable for powering autonomous microsystems. Methods for fabricating positive and negative electrodes for lithium-ion batteries have been demonstrated and tested in half-cell experiments. 3-D carbon arrays are fabricated by combining silicon micromachining with colloidal processing while LiCoO₂ electrodes are prepared through sedimentation of a colloidal solution between the rods of the array. The carbon arrays exhibit good reversibility over multiple cycles and achieve areal energy densities greater than 5 mAh/cm² at rates of C/5 or higher. The development of a suitable conformal electrolyte remains as one of the key challenges facing this technology and the progress being made in this area will be reviewed.

Superhydrophobic surfaces are of immense scientific and technological interests for a broad range of applications. However, a major challenge remains in developing scalable methodologies that enable superhydrophobic coatings on versatile substrates (regardless of composition, morphology and size) with a combination of strong mechanical and chemical stability, optical transparency, and even stretchability. In this talk, we will show a new kind of superhydrophobic coatings by using a self-assembled hydrogel as the template to in situ generate silica microstructures and subsequent silanization. The superhydrophobic coatings can be enabled on virtually any substrates via large-area deposition techniques. The hydrogel based coatings exhibit high optical transparency, superior mechanical flexibility and robustness in that it can sustain contact angles ~160° with intensive sand impingement test and even after 5,000 cycles of mechanical stretching at 100% strain. These versatile coatings can be found useful for flexible water-proof coatings, self-cleaning surfaces, anti-fouling surfaces, industry oil recovery and oil spill cleaning.

Directed assembly of microscale materials has been motivated by great demands in engineering three-dimensional architectures/systems in broad fields including bottom-up tissue engineering, microelectromechanical systems and microphotonics. Conventional manufacturing approaches, such as micromolding and templated self-assembly based on solid moulds, suffer from flexibility in reconfiguring resulting structures. Here, we demonstrate a bottom-up approach to assemble microscale materials using liquid-based template established by standing waves at the air-liquid surface. This liquid-based template can be dynamically reconfigured in seconds (< 5 s), and the assembly on the template can be achieved in a scalable and parallel manner. We illustrate broad applicability of this mechanism by assembling diverse macroscopic structures ranging in area from 100 mm² to 10,000 mm² in an efficient manner from soft matter, rigid bodies and multiple biological samples in a wide range of sizes from 10 µm to 2 mm. Assembly of neuron-seeded microcarrier beads into 3D neural networks is significant for neuroscience. However, existing methods lack controllability in the global structure of generated neural network. Here, we demonstrated capability of assembling neuron-seeded microcarrier beads into 3D neuronal networks with controllable global shape. Patterning cell spheroids into various shapes is of significance for tissue engineering due to the capability of spheroid&’s fusion into micro-tissues. Existing assembly methods are all based on the strategy of pick-and-place, which suffers from low efficiency. Here, we demonstrate simultaneous assembly of ~10³ cell spheroids (mean size: 200 µm) into various patterns. Another innovative approach that we present is overcoming challenges of scaffold-free cell assembly where the microscale assembly is limited due to small cell size and requirements for cytocompatibility. We demonstrate the assembly of a large number (~10⁶) of cells simultaneously into various complex patterns. We also show that the assembled structures can be stabilized in hydrogel by chemical- and photo-crosslinking after assembly. All these results indicate that liquid-based templated assembly opens a new paradigm for cost-effective and efficient manufacturing from microscale materials. Especially, it would be a useful biomanufacturing tool that enables various applications in fields such as tissue engineering and neuroscience.

Host-Guest interactions are common phenomena in nature, such as enzyme-substrate interaction. Mimicking this process at the nanoscale is important in nanotechnology, which may facilitate the syntheses of new complex structures that possess properties associated with both the host and guest components. A guest-host pair between gold nanoparticle (AuNP) and DNA nanocage is of particular interest since AuNPs have many important physical properties in plasmonics, magnetics, and catalysis. At the meantime, the self-assembled DNA nanocages with uniform and tunable sizes and shapes have been demonstrated as host scaffolds and encapsulating/delivery agents. Herein, we report a class of core-shell complexes (AuNP@DNA cages): hard gold NPs (AuNPs) are encapsulated in geometrically well-defined, soft DNA nanocages. Particularly, the hybrid core-shell structures rely on an encapsulating mechanism (swallowing) that the pre-assembled DNA nanocages (including DNA tetrahedron, octahedron, and icosahedron) swallow AuNPs into their central cavities to form stable AuNP@DNA nanocage complexes. When AuNPs are encapsulated in the DNA nanocages, spherical surfaces of AuNPs are restricted by the host shells (DNA nanocages), affording spatially asymmetric functional sites to the hybrid nanostructures. Interestingly, the AuNP guest can be further controllably released from the host (DNA nanocages) by a fuel replacement strand, indicating the potential applications of surface engineering of inorganic NPs and cargo delivery of DNA nanocages.

We have developed a facile freeze-drying approach for preparing aligned fibrous materials using amino acid or peptide nanofibers as building blocks. Based on scanning electron microscope (SEM), circular dichroism, and nuclear magnetic resonance analysis, we have found that aromatic amino acids, such as phenylalanine, can self-assemble into distinct fibrillar structures with no secondary structures like α-helix or β-sheet. The nature of the interactions among the amino acids within the self-assembled one-dimensional nanofibers is believed to simply be non-covalent π-π interactions. We have developed a directional freeze-drying method to align the structural elements into macroscopic three-dimensional (3D) free-standing monoliths. SEM has revealed that the obtained monoliths have been made of a 3D well-aligned fibrous network structure. The directional freeze-drying method has shown great flexibility in controlling the microstructure of 3D nanofibrous architectures. The freezing temperature has been found to be a key variable in controlling the size of the initial ice crystals, which in turn control the ultimate microstructure and pore structure of the 3D nanofibrous materials. We have shown that reducing the freezing temperature has led to a decrease in pore size but an increase in fiber alignment. At minus;20°C, the freeze-dried fibrous monoliths have presented a 3D porous architecture with randomly oriented nanofibers. At minus;80^oC, the fibrous networks have been found to be denser and better aligned compared to those prepared at minus;20°C. Using liquid nitrogen, we have obtained well-aligned fibrous structures. We have also found that amino acid concentration contributes to the microstructure, since increasing amino acid concentration has resulted in denser fibrous networks. To further take advantage of the unique fibrous architectures, we have introduced polymers or nanoparticles into the fibrous networks and obtained amino acid-based aligned nanofibrous composites. The method reported here is likely applicable to create aligned nanofibrous structures using peptides and other materials for a variety of applications such as tissue engineering, organic electronics, molecular sensing devices, filtration, and energy storage. For instance, aligned nanofibrous materials may be used as scaffolds for directional growth of biological cells.
References
LI, B. Y., JIANG, B. B., BOYCE, B. M. & LINDSEY, B. A. 2009. Biomaterials, 30, 2552-2558.
LI, B. Y., ROZAS, J. & HAYNIE, D. T. 2006. Biotechnology Progress, 22, 111-117.
WANG, X. F., DING, B. & LI, B. Y. 2013. Materials Today, 16, 229-241.
WANG, X. F., DING, B., SUN, G., WANG, M. R. & YU, J. Y. 2013. Progress in Materials Science, 58, 1173-1243.
ZHANG, H. F., HUSSAIN, I., BRUST, M., BUTLER, M. F., RANNARD, S. P. & COOPER, A. I. 2005. Nature Materials, 4, 787-793.

Biotemplating is a powerful technique for producing nanowires and nanonetworks of a wide variety of oxides and some easily-reduced metals such as Cu, Ni, and Au. Templates such as the M13 bacteriophage virus have proven to be particularly versatile for not only controlling nanowire/network composition but also controlling the crystallographic structure of nanowires and integrating disparate materials, e.g., introducing carbon nanotubes into a titania matrix to improve electrical conductivity. However, there are many materials for which there are few synthetic pathways for preparing nanowires and/or nanonetworks, including many carbides, nitrides, and metals that are hard to reduce from their oxides (such as titanium and aluminum). Such materials are of high interest for applications including lightweight structures, impact dampening, and other applications.
We present a platform for synthesizing porous architectures comprised of nanowires, nanonetworks, nanosprings, and other functional nanostructures of materials including titanium, aluminum, intermetallics and alloys such as NiTi, carbides, and nitrides. Microorganisms such as spiral-shaped Spirulina algae and filamentous M13 bacteriophage serve as templates for preparing simple or mixed-matrix oxides from simple solutions of metal ions. The microorganism template is then burned off and the remaining biotemplated oxide materials are processed via magnesiothermal reduction in a specialized reactor. The resulting materials are washed of residual magnesium oxide and other residual magnesium compounds with acid and can then be used as free-floating nanostructures or assembled into mesoporous networks for use in applications such as lightweight structural materials. Example applications of these materials including nanosprings, lightweight nanoporous metal foams, and shape memory materials will be discussed.

A potential advantage of three dimensional printing (3DP) is fabricating complex structures with reduced manufacturing time and procedures. The goal in this study is to create mesh filters with various pore sizes and wetting properties for oil-water separation. We made mesh filters with the 3DP and applied plasma treatment using a radio-frequency plasma-enhanced chemical vapor deposition (rf-PECVD) to control their surface wettability and geometry. The created nanohair structures on the mesh surfaces were further coated by hexamethyldisiloxane (HMDSO) to convert the surface wetting property. The efficiency of the oil/-water separation function was evaluated by observing the behaviour of oil-water mixture droplets on the functionalized mesh filters. The HMDSO coated mesh filters exhibited sufficient superhydrophobic and superoleophilic properties resulting in excellent oil separation capability from the oil-water mixture. Furthermore, we demonstrated that filtration of mixtures through the mesh filters was influenced by mesh pore sizes directly. The combination of 3DP technique and plasma treatment by PECVD makes very promising mesh filters for practical applications like oil spill cleanup or separation.

Three-dimension (3-D) hierarchical architectures have attracted much attention because they can provide more chances for exploring novel properties and superior device performances than low dimensions including 0-D, 1-D and 2-D. In addition, solution-based approaches for self-assembling low-dimension hierarchical architectures into 3-D ones with designed chemical components and controlled morphologies are becoming attractive in recent years. Generally, synthesis of VO₂ nanostructures with hydrothermal approaches requires the presence of various surfactants and reductants. In this work, to further enhance hydrogen sensing performance, two novel nanostructures, namely, 3-D hedgehog-like and flower-like VO₂ hierarchical architectures respectively composed of highly-aligned 1-D and 2-D tiny VO₂ nanocrystals were successfully and uniformly synthesized via a facile hydrothermal method with the absence of any surfactants and templates at 180 °C. These two VO₂ hierarchical architectures act as an innovative sensing platform for demonstrating excellent responses and recovery speeds as well as stable H₂-concentration-dependent sensitivities.

For cancer immunotherapy, the usage of appropriate adjuvant is crucial for generating robust and long-lasting adaptive immune responses. As often the case, tumor antigens stimulate the immune system only weakly [1-3]. Mesoporous silica, owing to its uniform pore structure, high surface areas and adsorption ability, is considered to be a promised adjuvant to increase the immunity against cancer than commercial aluminum hydroxide (Alum) adjuvant.
Herein, mesoporous silica (MS)-based adjuvants were developed. The mesoporous silica-based adjuvant adjuvants mixed with liquid-nitrogen-treated tumor tissue (as a source of cancer antigen) markedly inhibited recurrence/re-challenge of cancer than commercial alum adjuvant [2, 3], suggesting that MS-based adjuvants can be useful to reduce the risk of cancer recurrence.
Mechanism of MS-based adjuvants was further studied. Intraperitoneal immunization of ovalbumin (OVA) with MS resulted in high titer of OVA-specific antibody in serum, especially for IgA and IgG2a, than those immunized with alum adjuvant. In addition, the MS-based adjuvants markedly stimulated the secretion of cytokines (for example IL-2, IFN-γ, etc.) in the mice. Therefore MS-based adjuvant is expected to trigger the immunostimulatory response against tumor through cell-mediated immunity also. The present MS-based adjuvants are promising as adjuvants for cancer immunotherapy to prevent cancer recurrence.
Acknowledgements:
We thank the technical assistance from Mr. Y. Watanabe, AIST. This study was supported in part by KAKENHI (Grant-in-Aid for Young Scientists B, No. 26750162, No. 23700567 and a Grant-in-Aid for JSPS Fellows, No. 21.09501).
Keywords: adjuvant, cancer immunotherapy, mesoporous silica
References:
[1] X.P. Wang, X. Li, K. Onuma, Y. Sogo, T. Ohno, A. Ito, Scientific Reports, 2013, 3: 2203
[2] X.P. Wang, X. Li, A. Ito, Y. Sogo, T. Ohno, Acta Biomater, 2013, 9: 7480-7849.
[3] X.P. Wang, X. Li, A. Ito, Y. Sogo, T. Ohno, J Biomed Mater Res A, 2014, 102: 967-974.

Textile based electronic systems could potentially be applied in the future for high-tech sportswear, health control systems, portable power and energy systems. Textile based electronics have novel properties such as flexibility, stretchability and are lightweight, which are difficult to be demonstrated by traditional thin film electronic materials. Supercapacitors, one of the most prominent energy storage components of electronic devices, can be fabricated easily through cost-effective means on textiles.
Naturally insulating textiles attain conducting properties through coating with single walled carbon nanotubes (SWNTs). SWNT coated textiles possess high conductivity, large surface area, functionable surfaces, chemical stability and superior mechanical properties. Textiles can also be coated with pseudocapacitive metal oxides, which store energy by a redox mechanism on the surface of the metal oxides. Pseudocapacitive energy storage capability of manganese oxide (MnO₂) is very high; however, MnO₂ is insulating and brittle. Conducting polymers impart excellent properties, such as good electrical conductivity and high pseudocapacitive properties, when they are integrated into textile based supercapacitors. However, problems such as low mechanical strength and short electrochemical charge-discharge cycle life remains to be resolved. Composite formation could provide a solution to overcome these problems and creates a synergistic effect. Improved electrochemical performance for supercapacitors with 3 dimensional ternary composite active electrodes using MnO₂/SWNTs/PEDOT:PSS on textile surfaces have remained elusive.
In this work, ternary nanocomposite electrodes were fabricated through simple dip-coating method. Electrochemical properties of solid-state, symmetric supercapacitors with ternary MnO₂/SWNTs/conducting polymer electrodes were then investigated using organic gel electrolytes by cyclic voltammetry, chronopotentiometry and electrochemical impedance spectroscopy. Ternary nanocomposite electrodes revealed a specific capacitance of 434 F/g that is higher than that of bare SWNTs and binary composite electrodes with respect to active material loading. We will present a detailed analysis of electrochemical properties of the fabricated supercapacitors to underline their capacitive behavior. Our results reveal the potential use of ternary nanocomposites (MnO₂/SWNTs/conducting polymer) in supercapacitor electrodes that can be fabricated through simple solution based methods and the method investigated herein can be simply adapted to industrial scale fabrication. Fabricated supercapacitors hold significant promise to be critical components in flexible and wearable devices.

Porous conducting carbons for energy applications have been derived from several natural sources by heat treatment and simultaneous activation processes. Though heat treatment and activation of biomass provide a generalized protocol to induce desired morphological features such as micro and meso-porosity in the carbonized product, this method is not entirely suitable for fine tuning of the carbon properties. It is for this reason that there has been some exploration of polymers as precursors for the synthesis of functional carbon. Polymers offer a unique platform for precursor tunablility in order to obtain desired final products for targeted applications.
In this work, we demonstrate a novel synthesis of 3D porous assembly of graphene sheets into hexagonal n-graphene cages by a direct one-step pyrolysis method. The precursor used for the pyrolysis process is a short chain polymer generated by the free radical polymerization of 4-amino-benzoic acid. The corresponding oligomer is later converted into its sodium salt form. This 3D carbon formation process does not require any templating/external activation process but instead involves the use of specific functional groups (-COONa) which give rise to an ‘in-situ&’ molecular level activation and graphene-sheet formation. Interestingly, the sheets formed during the pyrolysis process assemble themselves in graphite like cages giving rise to high surface area assembly (~1380 m²/g) at a temperature as low as 800^oC. This high surface area assembly exhibits a micro and meso pore size distribution thereby enabling the material to exhibit efficient electrochemical charge storage performance. The 3D porous carbon synthesized in this work is termed as oligomer derived carbon (ODC).
Li-ion hybrid electrochemical capacitors (Li-HEC) are the next generation electrochemical energy storage devices which are built to enhance the energy density of supercapacitors without compromising their power density. Li-HECs are fabricated with high surface area carbonaceous materials and a Li-intercalating material as the counter electrode. In this work we employ the ODC as a cathode active material for Li-HEC applications along with Li₄Ti₅O₁₂ as counter electrode in an organic medium. The ODC based Li-HEC is capable of delivering the maximum energy density and power density values of ~63 Wh kg^-1 and ~10 kW kg^-1, respectively. The observed energy density is much higher than the commercially available activated carbon (AC)/Li₄Ti₅O₁₂ based system in the same testing conditions.