Here we report a solventless polymerization process, which involves adding catalysts on the surface of a solid substrate and polymerizing volatile monomers at the gas/solid interface. It provides an alternative to other thin-film-making processes and may lead to reduce or eliminate the use of solvents in micro/nanofabrication. On silicon or silicon dioxide substrates, solventless produced thin films show improved smoothness inside microchannels, and suits reactive ion etching (RIE) process. In addition, this process offers a simple route to generate microstructures that are inaccessible in the presence of solvent, and provides a simple and fast protocol to screen catalysts in a parallel mode.

Anovel scheme for the fabrication of large-area nanoimprint stamps has been developed based on the utilization of a combination of nanosphere lithography and reactive ion etching. Both single and double layer polystyrene beads have been employed to construct well-ordered, periodic silicon nanopillar arrays. The nanopillar arrays fabricated by this method have been successfully used as the stamps for nanoimprint lithography. Our result indicates that this approach is capable of producing large-area sub-50 nm periodic nanostructures.

One and two-dimensional colloidal crystals are assembled from aqueous suspensions of latex and silica microspheres in an alternating electric field. These crystals of size up to 25 mm2 are formed in the gap between two planar gold electrodes. They have specific axis orientation parallel to the direction of the applied field without the need for expensive micropatterned templates. The field gradient causes the particles to accumulate on the surface between the two electrodes, align into rows along the field direction, and then crystallize into hexagonal arrays. The lattice spacing can be controlled via electrostatic repulsion. The system can find application in switchable photonic devices.

We report a novel technique for micromechanical detection of biologically relevant glucose by immobilization of glucose oxidase (GOx) onto a microcantilever surface. Microfabricated cantilevers have recently attracted considerable interest in the development of a wide range of novel physical, chemical, and biological sensors. This paper describes the combination of this novel technology with enzyme specificity to construct a highly selective glucose biosensor. The enzyme-functionalized microcantilever undergoes bending due to a change in surface stress induced by the reaction between glucose and the GOx immobilized on the cantilever surface. The common interferents for glucose detection in other detection schemes have been tested and have shown no effect on the measurement of blood glucose level by this technique.

High-quality GaP, GaP@GaN and GaN@GaP nanowires were grown by a convenient vapor deposition technique. The wire-like and two-layers structures of GaP@GaN and GaN@GaP core-shell nanowires were clearly resolved using X-ray powder diffraction and high-resolution transmission electron microscopy (HRTEM) and their growth directions were identified. Photoluminescence intensity of GaP@GaN nanowires increased as temperature increased. The result was interpreted by the piezoelectric effect induced from lattice mismatch between two semiconductor layers. An unexpected peak at 386 cm-1 was found in the Raman spectra of GaN@GaP and assigned to a surface phonon mode due to the interface. Detailed synthetic conditions and possible growth mechanisms of those nanowires were proposed.

Liquid crystals (LC) are promising photonic bandgap (PBG) materials. Certain LC phases have spatially modulated ground states and effectively form self-assembled PBG structures. These structures can also be made permanent by photopolymerization. Typically, LCs respond readily to applied fields, enabling modulation and switching of the bandgap. Since classical light propagation is forbidden, fluorescent emission in the band gap can lead to population inversion and stimulated emission at the band edges. Mirrorless lasing experiments provide an effective probe of the bandgap. We discuss the underlying physics, and present the results of mirrorless lasing in a variety of cholesteric LC materials, including recent results of photon counting statistics and 3-D lasing in the cholesteric blue phase.

Cu(II) doped ZnSe nanoparticles were synthesized using molecular cluster precursors. The Cu(II) dopant had the effect of quenching the ZnSe band edge emission, yet only weak emission from Cu(II) centers was observed. An X-ray Absorption Fine Structure (XAFS) experiment was performed on the Cu(II) doped ZnSe nanoparticles. It was determined that the Cu(II) occupies a tetrahedral site in the lattice in an environment similar to that of Cu in bulk Cu2Se, and is likely to have substituted for Zn(II) in the lattice.

A general approach involved template-engaged, galvanic replacement reactions has been developed to prepare metallic nanostructures with hollow interiors by reacting solutions of appropriate salts with metallic solid nanoparticles. The reaction between aqueous chloroauric acid and silver nanoparticles was used as a typical example to demonstrate the synthesis of gold nanoshells. The morphology, void space, and wall thickness of these hollow structures were all determined by the silver templates, which were completely converted into soluble species during the replacement reaction. The extinction peaks of these gold nanoshells were considerably redshifted as compared to solid gold colloids having approximately the same dimensions. In addition, the surface plasmon resonance of gold nanoshells exhibited a much more sensitive response toward environmental changes even when compared with solid colloids with a mean size much smaller than that of gold nanoshells.

In this work we report methods of formation of three-dimensional structures of particles in a liquid crystal host. We found that, under the appropriate conditions, the particles are captured and dragged by the moving isotropic/nematic front during the phase transition process. This movement of the particles can be enhanced significantly or suppressed drastically by application of an electric field and/or by changing the conditions of the phase transition, such as the rate of cooling. As a result, a wide variety of particle structures can be obtained ranging from a finegrained cellular structure to stripes of varying periods to a course-grained “root” structure. Changing the properties of the materials, such as the size and density of the particles and the surface anchoring of the liquid crystal at the particle surface, can also be used to control the morphology of the three-dimensional particle network and adjust the physical properties of the resulting dispersions.

We report on the effects of doping on the growth of ZnO nanostructures. We find that the incorporation of dopants, such as Si, Li, and Na, usually lead to reduced quality of ZnO nanostructures. Although doping with Li and Na results in the formation of facets on ZnO nanostructures, doping of Si often reduces dramatically the quantity of ZnO nanostructures. The formation of facets on ZnO nanostructures is found to significantly affects the cathodoluminescence emissions of the nanostructures.

Nano- and micro-structured materials are a powerful tool in the development of chemical sensors. Surface imprinting of different biogenous species into pre-polymerized, highly crosslinked reaction mixtures (polyurethanes, polystyrenes, sol-gel materials etc.) yields selfassembled structures that are optimized to re-incorporate the template particle. Surface properties are tuned both on the micrometer as well as the molecular scale, as selectivity studies suggest the formation of strongly adapted interaction networks between the polymer and the species used for imprinting.

We present optical analysis concerning the redshift of the photoluminescence (PL) of ensembles of GaN nano-crystals. We found that the extent of the redshift depends on the laser power as well as on the ensemble size. For ensemble of size ∼ 30 μm, the laser power in our experimental specification impacted the PL energy and caused a redshift of up to 120 meV. This phenomena was not observed for a small ensemble of ∼ 1 νm or less. For the small ensemble the PL redshift was negligible and depended weakly on the laser power; similar behavior was found in GaN thin film. The above findings were observed in the PL of GaN nano-crystalline of Wurtzite as well as cubic structure. Our results point to a laser heating event occurring in the large ensemble; the emitted and scattered light is confined among the nano-crystallites thus causing the heating. For a small ensemble the light has a higher probability of diffusing outside the enclosure, and thus no laser heating occurs.

In this work, we present an extensive study of the oxidation process of Si/Ge nanocrystals (nc-Ge)/Si samples using SIMS (Second Ion Mass Spectroscopy), Transmission Electron Micrscopy (TEM), Atomic Force Microscopy (AFM) and electrical characterization of Metal/Oxide/Semiconductor capacitors (MOS). Various samples with different oxidation times have been studied and it is demonstrated that Silicon dry oxidation kinetics is not influenced by the presence of Ge. As shown by SIMS measurements, a pure SiO2 layer is formed on the top of the structure, while the Ge atoms are intermixed with the silicon substrate. The TEM and AFM analysis show that the nc-Ge height is drastically reduced during the oxidation process. The fabrication of MOS capacitors on the structures allowed to study electron and hole trapping in the Ge dots. From our analysis we have shown that the Ge nanostructures which covered by SiO2 are not isolated from the Si substrate.

Reactive evaporation process was introduced as a simple technique for the fabrication of aligned ZnO nanowires on a Si (100) surface. Single crystalline ZnO nanowire arrays were successfully synthesized on Au coated Si substrates via a VLS growth mechanism. The diameter of ZnO nanowires were observed to vary from 40 nm to 150 nm and the ratio of length to diameter was observed to be larger than 30. The diameter of ZnO nanowires was controlled by changing the processing temperature and by the thickness of Au catalyst film. Green emission induced from singly ionized oxygen vacancies was generated from ZnO nanowires with the excitonic emission in UV range. Higher intensity of the green emission was observed in thinner nanowires, which is attributed to their higher surface-to-volume ratio. Aligned structure formation and size control of ZnO nanowires could provide the potential for various nano-scale device applications.

Semispherical self assemblies of colloids have been fabricated on a substrate using inkjet printing with an ink of submicron-sized monodisperse silica particles. Colloidal silica has been prepared by Stöber process. The shape and monodispersity of the synthesized colloidal particles were observed by scanning electron microscopy (SEM) and laser light scattering particle analyzer. Simple test patterns on various substrates (silicon wafer, Cu foil, and Mylar film) were printed with commercial HP printer. It was found that the uniformity and spatial extent of the self-assembled colloidal silica within a dot were significantly influenced by the contact angle between ink and substrates. Ink droplets printed on the hydrophobic Mylar film maintain a higher contact angle as compared to the hydrophilic substrates such as Si wafer. Slower evaporation and high capillary stress exerted on the ink droplet allow hemispherical colloidal aggregates with an ordered internal structure on Mylar film.

Utilization of protein cages in biomimetic chemistry allows for the deposition of inorganic materials within an organic construct, controlling the size and amount of material deposited within a constrained reaction environment. Previously, protein cages such as viral capsids and ferritins have been used in the constrained synthesis of inorganic materials. The MrgA protein displays a high sequence homology to both bacterial DNA-protecting proteins (Dps) found in many bacterial genera and Ferritin-like proteins (Flp), which have been shown to functionally sequester and store iron in a biologically available form. Here we demonstrate recombinant production, purification and characterization of the MrgA protein and provide evidence that this protein self-assembles to form a multimeric complex. This complex demonstrates characteristics similar to that of ferritin-like proteins such as resistance to iron toxicity, iron incorporation, and resistance to thermal and chemical denaturation. The ability to deposit iron within the putative internal cavity of this protein cage will allow the MrgA complex to be utilized as a spatially constrained reaction vessel for nanomaterial synthesis of other inorganic materials. From a materials science perspective, it will be interesting to see if these organic/inorganic hybrid materials can be harnessed for catalysis, nanomagnetics, and other applications.

Applied wet colloidal nano-processing and thermal, physical, and chemical treatments of superconductor ceramic particles result in sintered 3D-textured crystal conglomerates to produce functionally effective macro-products, such as advanced electrical and electronic articles including superconductive adhesion coated continuous and flexible round wire. AFM images show texture evolution and confirm effectiveness of the developed combination of original ceramic-silicone material formulation and invented crystal organization methods.

Multiple layers of self assembled In0.3Ga0.7As quantum dots of different size were grown on GaAs (100) using molecular beam epitaxy. Fourier-transform infrared spectroscopy shows absorption in the long-wavelength infrared region (8–10 νm) under normal incidence. The absorbance peak shift with dot size was investigated and revealed non-monotonic behavior of intersubband transitions. The optical absorption coefficient was calculated to be in order of 3.8×103 cm-2.

High-quality single crystalline gallium nitride (GaN) nanowires are synthesized via a chemical vapor deposition (CVD) method using gold nanoparticles as the catalyst. This method enables control over several important aspects of the growth, including control of the nanowire diameter by using mono-dispersed gold clusters, control of the nanowire location via e-beam patterning of the catalyst sites, and control of the nanowire orientation via epitaxial growth on aplane sapphire substrates. Transport properties of these GaN nanowires are studied. Our work opens up new ways to use GaN nanowires as nano-building blocks.

Carbon-encapsulated ferric magnetic nanoparticles were prepared by the grain-boundary-reaction of ultrafine goethite particles. The mechanism of the grain-boundary-reaction was studied with high-resolution transmission electronic microscope, X-ray diffraction and thermo gravimetric analysis. The magnetic properties are measured with a vibrating sample magnetometer. The diameter of carbon-encapsulated ferric magnetic nanoparticles is 30~60 nm, and the coercive force and saturate magnetization are 315 Oe and 30 emu /(g powder), respectively. These composite particles are very stable in air.