A generic approach to chemically facilitate the interactions of nanoparticles with conventional polymers is developed to address the design and processing capability of inorganic-organic nanocomposites. This approach introduces homogeneity to the composite and can be used as a tailoring tool for microstructure architecture.

Nanoparticles produced by NanoGram's technology are excellent for such nanocomposites. Their spherical shape and narrow size distribution assist in the processing of homogeneous blends. High loads of particles within a polymeric matrix can be achieved without losing homogeneity. Alternatively, the particles can be selectively attracted into desired domains.

Recent interests on the science at nanometer-scale, have led to successful synthesis of a growing number of nanostructures such as zero-dimension semiconductor quantum dots [1] and C60 fullerene [2] and one-dimensional carbon nanotubes [3], metallic nanowires [4] and inorganic nanorods [5]. More complex structures/junctions beyond simple dots and lines that are essential for eventual molecular electronic applications, however, have not been realized via non-lithographic methods. Here we report the synthesis of a new branched silicon nanostructure which we call Silicon Nano-Dendrite (SiND) by Laser ablation.

Nanocrystalline ( particle diameter less than 50 nm) ceramic powders have been prepared by the rapid evaporation of precursor solutions containing the respective metal nitrates/ hydroxides, triethanolamine (TEA) and sucrose in stoichiometric amounts. Complete evaporation of the solutions yields a fluffy dried precursor mass. Heat-treatment of the precursor mass at low external temperatures (450-700 °C) resulted in the desired nanocrystalline oxides. The oxide system studied are: barium titanate (BaTiO3), lanthanum modified lead zirconate-titanate (PLZT), Nickel ferrite (NiFe2O4) and Calcium Tungstate (CaWO4).

Multi-pathogen biosensors that take advantage of sandwich immunoassay detection schemes usually rely on spatial resolution patterns of capture antibodies on a detector plate for pathogen recognition, and typically utilize fluorescent, organic dyes as optical labels to identify captured pathogens. An immunoassay-based, fiber optic detector that utilizes varying sized fluorescent semiconductor quantum dots (QDs) as the reporter labels for different antibodies would have the ability to detect multiple pathogens within a single fiber, using a single excitation source. Such a detector requires that QDs be attached to antibody proteins, such that the specificity of the antibody is maintained. We have been involved in efforts to develop a reproducible method for attaching QDs to antibodies for use in such a biosensor.

We synthesized CdSe/ZnS core-shell QDs of differing size, functionalized their surfaces with several types of organic groups for water solubility, and covalently attached these functionalized QDs to rabbit anti-ovalbumin antibody protein. We also demonstrated that these labeled antibodies exhibit selective binding to ovalbumin antigen. We characterized the QDs at each step in the overall synthesis by UV-VIS absorption spectroscopy and by picosecond (psec) transient photoluminescence (TPL) spectroscopy. TPL spectroscopy measurements indicate that QD lifetime depends on the size of the QD, the intensity of their optical excitation, and whether or not they are functionalized and conjugated to antibody. We describe details of these experiments and discuss the impact of our results on our biosensor program.

Nanometer sized gold patterns were produced with controlled spacings using the combination of a top-down (e-beam lithography) and a bottom-up (macromolecular chemistry) technique. Sub-10 nm nanoparticle arrays on silicon consisting of gold nano particles separated by micro meter spacings were fabricated with this approach. Using electron beam lithography, templates comprising of 150 nm to 1 μm sized trenches, holes and aperiodic patterns were made in an electron-beam resist. Block copolymer micelles were then patterned into this template by spincoating. The micelles acted as positioners for a nanometer sized gold precursor that is sequestered within its core. Subsequent removal of the resist layer left an array of Au loaded organic micelles ordered according to the pattern of the template. Exposure of this substrate to a hydrogen plasma removed the organic block copolymer and resulted in an array of sub-10 nm gold nanoparticles/nanoclusters with micron separations. The gold was then used as an anchor point for the tethering of functional molecules in order to localize fluorescent molecules.

Gold nanoparticles in the mid-nanometer size regime can undergo self-organization into densely packed monoparticulate films at the air-water interface under appropriate passivation conditions. Films could be transferred onto hydrophilic Formvar-coated Cu grids by horizontal (Langmuir-Schaefer) deposition or by vertical retraction of immersed substrates. The latter method produced monoparticulate films with variable extinction and reflectance properties. Transmission electron microscopy revealed hexagonally close-packed arrays on the micron length scale. The extinction bands of these arrays shifted by hundreds of nanometers to near-infrared wavelengths and broadened enormously with increasing periodicity. Large particle arrays also demonstrated extremely high surface-enhanced Raman scattering (SERS), with enhancement factors greater than 107. Signal enhancements could be correlated with increasing periodicity and are in accord with earlier theoretical and experimental investigations involving nanoparticle aggregate structures.

An optimum route to fabricate the Al2O3/Ni-Fe alloy nanocomposites with sound microstructure and magnetic propertieswas investigated. The composites were fabricated by the hot pressing of powder mixtures of Al2O3 and nano-sized Ni-Fe alloy, in which the alloy was prepared by solution-chemistry routes using Ni- and Fe-nitrate powders and a subsequent hydrogen reduction process. Microstructural observation of reduced powder mixture revealed that the Ni-Fe alloy particles of about 20 nm in size were homogeneously surrounded Al2O3, forming nanocomposite powder. The hot-pressed composite showed improved mechanical properties and magnetic response. The properties are discussed in terms of microstructural characteristics such as the distribution and size of Ni-Fe dispersion.

Hydrogen gas evolution from water dispersing nanoparticles induced by 60Co gamma-ray irradiation was studied. Nanoparticle of TiO2 with average size of 30 nm was examined. It was indicated that the hydrogen yields were affected significantly by pH of the dispersion. Difference in agglomeration could explain the difference in hydrogen yields. Reactions that enhance the hydrogen yields were discussed, and it was concluded that the radiolysis process is dominant in the total enhancement mechanism.

A series of BiFeO3 nanopowders were prepared by the sol-gel process. X-ray diffraction analysis shows that their rhombohedral crystal symmetry remains unchanged. However, as the particle size decreases, the edge length of the unit cell increases markedly and the angle between the edges deviates increasingly from 60°. Magnetic measurements show obvious weak ferromagnetism. The magnetization and magnetic susceptibility increase with decreasing particle size. Mössbauer studies reveal that the spin canting angles in the smaller particles are bigger and have a wider distribution. The magnetic structure in these particles is a complicated uncompensated antiferromagnetic spin arrangement.

Co-crystallization of 2,7-di-tert-butyl-9,9-dimethyl-4,5-xanthenedicarboxylic acid (1), a Rebek cleft, with 1,2-trans-bis(4-pyridyl)ethylene 2 yields a four-component molecular assembly, 2(1)·2(2), that is held together by four O-H…N hydrogen bonds. The cleft organizes the bipyridine such that two molecules of 2 lie in a stacked arrangement.

In this work an improved synthetic route that exploits a quaternary water-in-oil microemulsion has been used to obtain nanocrystals of ZnS, CdS and their mixed compounds, - CdxZn1-xS - differing by their size and composition and having high crystalline quality, small dimensions and a quite good size distribution. The opportunity offered by the use of water-in-oil microemulsion to immobilize the nanocrystals onto solid substrate by self-assembling to obtain stable adherent layers has also been exploited.

The physical and chemical properties of obtained nanocrystals and layers have been investigated by UV-vis spectroscopy, X-Ray Diffraction X-ray Photoelectron Spectroscopy and Scanning Tunneling Microscopy. The role played by the co-surfactant (pentanol) in controlling nanocrystal size and stability has been discussed.

Multilayered cold cathodes made of spin coated nanocrystalline diamond and cathodic arc process grown nanocluster carbon films, were studied. The nanocrystalline diamond was first coated on to the substrate. The nanocluster carbon films were then deposited on the seeded nanocrystalline diamond coated substrates using the cathodic arc process at room temperature. Theresultant hetrostructured microcathodes were observed to exhibit electron emission currents of 1μA/cm2 at fields as low as 1.2 V/μm. Further some of the samples seem to exhibit I-V characteristics witha negative differential resistance region at room temperature conditions. This negative differential resistance or the resonant tunneling behaviour was observed to be dependent on the nanoseeded diamond size and concentration for a given nanocluster carbon film.

The preparation and characterization of nanostructured materials and catalysts is the focus of intense study in recent years. The micro emulsion technique is one of the chemical methods known for isolation of nano-sized materials and some simple compounds such as AgCl and LiF have been prepared using this technique. However, very few attempts have been made to isolate nano-sized coordination compounds, which are known to be good catalysts.

In the present paper, nano-sized complexes of Cu(II) and Ni(II) with Leucine were prepared by the reaction of metal chloride and the ligand solution in water in oil micro-emulsion medium. N-Heptane was used as oil and sodium salt of dioctyl sulfo succinate (AOT) was used as surfactant to stabilize the emulsion. The complexes were characterized by elemental analysis and spectral studies. The crystallite sizes were determined by XRD studies using single line approximation through Scherrer equation. The X- ray diffraction studies revealed that the crystallite size of the complexes prepared by micro-emulsion technique was smaller than that of the material prepared by conventional method. The difference in particle size was also observed in differential scanning calorimetric (DSC) studies, where in, the reaction peaks were observed at lower temperatures for the complexes prepared by the micro-emulsion technique. The increased surface to volume ratio is expected to give better catalytic behavior.

Bifunctional electrocatalytic films were prepared employing a layer-by-layer assembly approach. The cation, metalloporphyrin (MP), and the anion, potassium tetrachloroaurate (KAuCl4) were alternatively assembled on glass or indium-doped tin oxide (ITO) supports. The assembled AuCl4 - ions were then converted to gold nanoparticles (Aun) under the exposure to ultraviolet light. Film growth at each adsorption step was monitored by UV-Vis absorption spectroscopy and cyclic voltammetry (CV). The formation of gold nanoparticles was characterized by UV-Vis absorption spectroscopy, X-ray diffraction (XRD) and scanning electron microscopy (SEM). Bifunctional electrocatalytic activity of the film was demonstrated in the oxidative detection of nitric oxide (NO) over Aun and the reductive detection of oxygen (O2) over Co(II)P in the same CV scan.

Nonstoichiometric precursor-ratios for the synthesis of ZnS:Mn2+ are discussed and the significant influence on the luminescence features and crystal size is explained. From the temperature quenching of the ZnS photoluminescence a luminescence excitation model is proposed. Measurements of the photoelectrochemical properties of nanocrystalline ZnS electrodes doped with Mn2+ are also presented and discussed. The observation of both anodic and cathodic photocurrent is direct evidence for the nanocrystalline nature of the system. In-situ photoluminescence measurements showed stable Mn2+ related photoluminescence over a large potential range.

Artificial hydroxyapatite with chemical formula of Ca10(PO4)6(OH)2 is the best as bioceramics due to its composition and structure being similar with inorganic part of hard tissues. The alloys especially with Ti, Ni and Co contents are very promising as a kind of biomaterials due to their high strength and high toughness. The alloys as biomaterials need good final surface properties by proper surface treatment. By using clinical treatment with machining, cleaning, sterilization, we obtained Ti-oxides surface with 4-6 nm in thickness which are very good in property with chemical composition of TiO2 + Ti2O3 + TiO. However, the Ti-alloy with an artificial hydroxyapatite surface is even much better than that with the surface of Ti-oxides due to its high bioactivity. Human bones and human teeth with a chemical composition of Ca10(PO4)6(OH)2 and the structure of hydroxyapatite are commonly considered as bio-mineral. In nature the pears and shells are also a kind of bio-minerals. Our observations showed that human bone is a complex material with a layered composite structure. The hydroxyapatite mineral crystals that reinforce the organic proteinceous component are about 35 nm wide, irregular, plate-like crystals reside initially in the hole zones of the collagen microfibris: later fill available space within the collagen fibrils. At present paper nanostructure features of both bioceramics and biominerals have been characterized with comparison between each other's.

We report on the characterization of germanium quantum dots grown on silicon (001) substrates by ultra-high vacuum chemical vapor deposition (UHV/CVD). In many applications small and uniform quantum dots are required which must be overgrown by a silicon epitaxial layer. We report here on the effect of carbon predeposition from methylsilane on the dot size and uniformity. In addition, we use reciprocal space mapping to evaluate the qualityof epitaxial layers which overgrow the quantum dots. The results show some differences from previous reports on MBE-grown dots.

To investigate the grafting of polymer chains onto nanoparticles (metal, semi-conductor, inorganic, etc) and nanostructured (patterned) surfaces, we have investigated anionic surface initiated polymerization (SIP) on a variety of surfaces. Understanding the surface chemistry issues involved is critical for future applications and protocols. SIP of polystyrene from Silicate and clay nanoparticles surfaces have been made by the living anionic polymerization method with 1,1-diphenylethylene (DPE) initiation sites attached to nanoparticle surfaces using chlorosilane and amino functional groups. Model studies were initially done on flat Si-wafer surface and recently with Au surfaces. For the nanoparticles, the grafted polymers were cleaved and characterized by FTIR, NMR, AFM, TGA and SEC. Polymers grafted from nanoparticle surfaces show higher polydispersity and lower molecular weight than those formed in solution. We observed that diffusion of the monomer, stability of the initiator attachment to the surface, and aggregation of the particles controls the properties of the grafted polymers on particle surfaces. On the other hand, the use of the anionic polymerization method on surfaces allows the possibility of combining a variety of polymers (organic) with various nanoparticle and surfaces (inorganic) for the preparation of hybrid nanocomposite materials.

In this work, we report optical and structural properties of vertical aligned self-assembled InAs quantum dots multilayers. The InAs quantum dots samples were grown by Molecular Beam Epitaxy. Employing Atomic Force Microscopy, Transmission Electron Microscopy, and Gracing Incident X-ray Diffraction we have studied the structural properties of samples with different number of periods of the multiplayer structure, as well as different InAs coverage. The optical properties were studied using Photoluminescence spectroscopy.

Current synthetic techniques to high-quality quantum dots (“QD's”) involve organometallic precursors that are hazardous and expensive and require they be rapidly injected into an extremely hot solvent to form the QD's. A new method for synthesizing high-quality CdSe QD's while circumventing these problems has been developed. Different cadmium salts were studied as Cd precursors alternative to dimethylcadmium. High-quality CdSe QD's were found possible with cadmium acetate as the Cd precursor. Changes in solvent temperature and reaction time had a systematic effect on QD particle sizes and the accompanying optical properties. These preliminary results point to a general method for producing high-quality QD's that is safer and much more versatile.