In this paper, we describe a simple and rapid solution-phase chemical reduction method with no inert gas protection, for preparing stable copper nanoparticle colloid with average particle size of 3.4 nm and narrow size distribution. In our synthesis route, ascorbic acid, natural vitamin C (VC), serves as both a reducing agent and an antioxidant to reduce copper salt precursor and effectively prevent the general oxidation process occurring to the newborn nanoparticles. XRD and UV/vis confirm the formation of pure face-centered cubic (fcc) copper nanoparticles and the excellent antioxidant ability of ascorbic acid.

A scaleable synthesis of metal nanowires has been developed using ac electrodeposition into the pores of porous aluminum oxide (PAO) templates, through the resistive barrier layer. Gram quantities of high aspect-ratio Cu nanowires (25 nm in diameter by ∼20,000 nm in length) were liberated by dissolving the PAO film with sodium hydroxide solution. The agglomerated nanowires were dispersed in methanol by ultrasonication and collected by centrifugation or filtration. The nanowires were blended into amorphous polyamide by melt processing. The dispersion and percolation of the nanowires in the polymer was investigated by electron microscopy and conductivity measurements as a function of nanowire loading and processing route. Mechanical properties were evaluated by tensile testing of miniature dog bone specimens.

Zinc sulfide nanoparticles, prepared employing a non-equilibrium route, are investigated for surface related effects. Water has been shown to induce a structural transformation in nanoparticles prepared this way, which is not related to their particle size. Employing Fourier transform infrared spectroscopy and x-ray powder diffraction, we show here the importance of S-H interaction in the buildup to the final ZnS structure of these nanoparticles. These particles hold promise as water sensors.

Nanocrystalline metal carbides (MC: M=Si, Ti) have been prepared using cellulose network mineralized with silica and titania by carbothermal reduction at high temperature in Ar. Hierarchical biological structures indigenous to the cellulose precursor were completely replicated after the reaction. Cubic phase MC composites show relative low oxygen content 0.24 wt% and a high lattice parameter of 4.327Å in TiC. The particle sizes of the MC composites are 200-700nm for SiC and 10-50nm for TiC, and high BET surface area, up to 150m2/g.

Nanotube arrays of amorphous vanadium pentoxide (V2O5) were synthesized through the template-based electrodeposition and its electrochemical properties were investigated for Li-ion intercalation applications. The nanotubes have a length of 10 μm, outer-diameter of 200 nm and inner-diameter of 100 nm. Electrochemical analyses demonstrate that the V2O5 nanotube array delivers a high initial capacity of 300 mAh/g, about twice that of the electrochemically-prepared V2O5 film. Although the V2O5 nanotube array shows a more drastic degradation than the film under electrochemical redox cycles, the nanotube array reaches a stabilized capacity of 160 mAh/g which remains about 1.3 times the stabilized capacity of the film.

The use of alternating current (ac) electrodeposition permits deposition through the resistive Al2O3 barrier layer, enabling the use of the as-grown porous aluminum oxide (PAO) template. This results in a process that is cost effective, simple, and scalable. However, achieving uniform filling using this technique is challenging. We have carried out a systematic study of the effect of multiple variables on the ac electrodeposition of copper nanowires using a fractional factorial design of experiment (FFDOE). This experiment led to the identification of template damage that occurs when continuous wave ac deposition conditions are employed, as well as to effective pulsed wave ac electrodeposition conditions. Subsequent examination of the effect of wave shape has identified the impact of this variable on electrodeposition, producing a further optimized set of ac electrodeposition conditions. The utility of these electrodeposition conditions has also been extended to the deposition of iron nanowires with similar results.

Two longitudinal superlattice structures of In2O3(ZnO)4 and In2O3(ZnO)5 nanowires were exclusively produced by thermal evaporation method. The diameter is periodically modulated in the range of 50-90 nm. They consist of one In-O layer and five (or six) layered Zn-O slabs stacked alternately perpendicular to the long axis, with a modulation period of 1.65 (or 1.9) nm. These superlattice nanowires were doped with 6-8 % Sn. X-ray diffraction pattern reveals the structural defects of wurtzite ZnO crystals due to the In/Sn incorporation. High-resolution X-ray photoelectron spectrum suggests that In/Sn withdraw the electrons from Zn, and enhance the number of dangling-bond O 2p states, resulting in the reduction of band gap. Photoluminescence exhibit the peak shift of near band edge emission to the lower energy as the In/Sn content increases.

Nanocapsules of Bi2S3 with diameters between 5 and 10 nm and shells with an amorphous atomic distribution were synthesized at room temperature, with bismuth nitrate and thiourea as precursors. Aging the solution for several days a black powder precipitated made of a mixture of one amorphous phase and crystalline Bi2S3. When two capsules interacted between each other, the capsule regions in contact crystallized into bismuth sulfide, which explains the origin of the crystalline phase observed in the X-ray diffraction pattern. At this temperature, aggregation of the small nanocapsules also gave rise to necklaces of capsules, which eventually gave rise to nanotubes; these necklaces ordered forming bundles parallel to their largest dimension. When the solution was annealed at temperatures lower than 100 °C, aggregation gave rise to capsules as large as 1 μm in diameter, and tubes with similar diameters; in this case aggregation occurred between small and large nanocapsules. Because of the monomers aggregating had an external spherical symmetry and the low annealing temperatures, which were not high enough to produce sintering, all capsules and tubes formed during aggregation had porous walls, making these materials interesting for many applications.

We describe the growth of amorphous carbon nanofibers (CNFs) from iron-encapsulated dendrimer catalysts at ambient temperature and pressure conditions. Both fourth-generation poly (propyleneimine) (PPI) and poly(amidoamine) (PAMAM) dendrimers were suitable macromolecular hosts for the catalytic species. Average nanofiber diameters range from 10 - 15 nm, with lengths in excess of 20 microns.

Certain forms of monohydrate aluminum oxide, commonly known as boehmite or pseudoboehmite alumina, are known to disperse in water at low pH to nano-scale dimensions. The upsurge of interest in nano-scale structures has prompted our study of the surface modification of nano-scale boehmite aluminas with organic acids in order to achieve dispersion of these materials in non-aqueous systems and alkaline aqueous systems.

This paper discusses the variety of modifiers used to achieve compatibilization and dispersion of nano-sized particles of these boehmite aluminas in aqueous and organic matrices. Organic modification of a variety of crystallite sizes (5-60 nm) and shapes (plates, needles, blocks) has been achieved, including materials of high aspect ratio. We describe the properties of these dispersions, including primary particle size, dispersed particle size, and surface charge. Finally, we present physical property data of polymer nanocomposites prepared from these materials. These materials are based on a commercial process which has been in operation for over 40 years and which has global production capacities of 70,000 tons per annum.

By simply controlling temperature and atmosphere, tetraleg ZnO nanostructures with different morphologies and sizes have been fabricated respectively through pure zinc powder evaporation without catalysts at temperature of 600∼800 oC. The growth mechanisms of the nanostructures were proposed and discussed. Photoluminescence spectra showed a UV and green emission peaks at room temperature. Field emission measurements revealed that the turn-on field is very low and the emission current density is relative to the morphology and size. Such ZnO nanostructures are likely to be candidates as building blocks for constructing photonic and field emission crystals.

Yttria-stabilized zirconia nanopowders were synthesized using AOT/isooctane reverse micelles. XRD results showed that the powders were tetragonal with crystallite sizes ranging between approximately 1-50 nm depending on the thermal treatment given to the powders. BET surface area analysis of the powders gave a specific surface area of 230 m2/g for the assynthesized powders and 19.3 m2/g for the powders treated at 1000°C. This results in equivalent powder particle diameters of 4 nm and 52 nm, respectively. Washing of the powders is a very significant step for successful post-processing of powders obtained by AOT/isooctane reverse micelles. The use of ethanol and dry ether did not remove AOT, as determined from EDS measurements. Subsequent experiments showed that a novel solvent (hydrogen peroxide) was effective in removing AOT from the powders. The reason for the effectiveness of the new solvent is its capacity to decompose the AOT into weak acids, which are easily washed away with deionized water.

A low temperature method for uniform growth of In2O3 nanostructures on Si wafers that does not require separate catalyst materials or template-assistance is investigated. Nanostructures are uniformly deposited on either bare or SiO2 thin film coated Si substrates via DC magnetron sputtering at 200-400°C using a 90% In2O3 / 10% SnO2 (ITO) target. The nanostructures are approximately 500 nm long, sit atop an accompanying underlying 100 nm conductive film, and are conically shaped, with a diameter of about 80 nm at the base, tapering to a point that is capped with a spherical “ball”. X-ray diffraction (XRD) indicates a cubic In2O3 phase. Field emission from the tips is observed at a base pressure of 10-8 Torr with turn-on fields in a range between 45-75 V/cm and threshold fields from 64-105 V/cm. Nanocone growth is investigated with respect to O2 and Ar flow rates, temperature, power, pressure, wafer rotation, and time.

Silicon Nanowires (SiNWs) have many potential applications that include diodes, transistors, logic gates, circuitry, and sensors. SiNWs also open the possibility for integrating optoelectronics with microelectronics, since silicon has semiconducting properties and amorphous silicon nanowires have been shown to emit blue light. It has been demonstrated that SiNWs have tunable electrical properties, depending on the dopant used. With such a range of applications, the ability to mass-produce silicon nanowires simply and easily with no other source of silicon needed other than the substrate itself will prove very useful. Such methods have previously been reported, but our method involves production of the SiNWs at a lower temperature than those widely observed. A (100) silicon substrate was cleaned for five minutes each in ethanol followed by acetone. Films with thicknesses of less than 20 nm of either gold or 60/40 gold/palladium were deposited on the substrate through physical vapor deposition to serve as the growth center for the SiNWs. The samples were placed in a furnace and annealed to 900° C, under a 1500 sccm flow of argon at atmospheric pressure. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used for characterization of the SiNWs. The resulting SiNWs were amorphous in structure and very convoluted, with lengths on the order of tens of microns, diameters of 40 nm and a bed thickness of approximately 10 m. The effect of varying gold concentration, annealing time, temperature, and gas flow rate were then investigated. The results, which will be discussed in further detail, indicate that adjusting these parameters allows for control over the length, thickness, density, and morphology of the nanowires.

The key hurdle in nanoscience and nanotechnology is the large-scale integration of nanoscale materials with micron scale electronics and structures to form functional devices and sensors. We have developed an innovative bottom-up wafer scale fabrication method that combines nanopatterning and nanomaterials synthesis with traditional silicon micromachining technologies. We have achieved nano-micro integration through catalyst nanopatterning and registration at wafer scale and through effective nanocatalyst protection and release before and after microfabrication. Our wafer scale fabrication process has produced 244 carbon nanotube (CNT) probes per 4-inch silicon wafer with control over the CNT location, diameter, length, orientation, and crystalline morphology. CNT probes with diameters of 40-80 nm and lengths of 2-6 μm are found to be functional nano probes for atomic force microscopy (AFM) imaging. In this paper, we will address our nano probe design and fabrication considerations in detail. CNT tip locations and diameters are defined by e-beam lithography. CNT length, orientation, and crystalline quality are controlled by the plasma enhanced chemical vapor deposition (PECVD) method. With effective catalyst protection schemes, this fabrication process is very similar to the conventional approach for fabricating wafer-scale silicon AFM probe tips. Process control is feasible and the overall yield is greatly improved. Our method and technology can be easily adapted to many other nanomaterials (nanotubes and nanowires) synthesis and processes for their rational design, fabrication, and integration in their applications.

Nano-sized TiO2 particles are of interest for many applications, including use as photocatalysts and in heat transfer fluids (nanofluids). In the present study, TiO2 nanoparticles with controllable phase and particle size have been obtained through homogeneous gas-phase nucleation using chemical vapor condensation (CVC). The phase and particle size of TiO2 nanoparticles under various processing conditions have been characterized using x-ray diffraction and transmission electron microscopy. Chamber temperature and pressure were found to be two key parameters affecting particle phase and size. Pure anatase phase was observed for synthesis temperatures as low as 600 °C with chamber pressure varying from 20-50 Torr. When the furnace temperature was increased to 1000 °C at a pressure of 50 Torr, a mixture of anatase and rutile phases was observed, with the predominant phase being anatase. The average particle size under all the experimental conditions was observed to be less than 20 nm.

Following the theory, ferromagnetism is predicted in Mn- doped ZnO, Indeed, ferromagnetism above room temperature was recently reported in thin films as well as in bulk samples made of this material. Here, we have prepared Mn doped ZnO by electrodeposition. The samples have been characterized by X-ray diffraction and spectroscopic methods to ensure that the dopants are substitutional. Some samples exhibit weak ferromagnetic properties at room temperature, however to be useful for spintronics this material need additional carriers provided by others means.

We present a novel spray based method for the formation and production of semiconductor nanocrystals that provides an attractive alternative to the commonly used epitaxial and colloidal procedures. According to this spray-based method, mainly thermospray, solutions of semiconductor salts are first sprayed into monodispersed droplets, which subsequently become solid nanoparticles by solvent evaporation. A semiconductor nanoparticle is produced from a single spray droplet upon the full vaporization of the solvent. The average diameter and size distribution of the final nanocrystals are controlled and determined by the solute concentration of the sprayed solution and by the droplet size, hence by the spray production parameters. The spray-produced nanocrystals are collected on any selected solid support. Representative results, shown in this paper, reveal the formation of CdS nanocrystals in the size range of 3 to 6 nanometer and with a size distribution of as low as five percents. A further structural analysis of these nanocrystals showed that they were formed in the zinc blend phase with high degree of crystallinity.

The creation of two dimensional large-areas of nanoparticles of different morphology and ordering is still a not fully solved problem. The presented paper shows new outstanding methods based on nanosphere lithography for controlling the mask morphology to improve fabrication of nanoscales perfectly ordered over some cm2 dots, rods and rings. An annealed mask with 30nm aperatures was used for the fabrication of ferromagnetic iron nanorings. These nanosystems are expected to find various unique applications. Our method permitted fabrication of nanostructured materials with unique morphology and properties. This field is expected to open new venues in science and technology.

Ge is deposited on HfO2 surfaces by chemical vapor deposition (CVD) with GeH4. 0.7-1.0 ML GeHx (x = 0-3) is deposited by thermally cracking GeH4 on a hot tungsten filament. Ge oxidation and bonding are studied at 300-1000 K with X-ray photoelectron spectroscopy (XPS). Ge, GeH, GeO, and GeO2 desorption are measured with temperature programmed desorption (TPD) at 400-1000 K. Ge initially reacts with the dielectric forming an oxide layer followed by Ge deposition and formation of nanocrystals in CVD at 870 K. 0.7-1.0 ML GeHx deposited by cracking rapidly forms a contacting oxide layer on HfO2 that is stable from 300-800 K. Ge is fully removed from the HfO2 surface after annealing to 1000 K. These results help explain the stability of Ge nanocrystals in contact with HfO2.