Two fabrication methods have been investigated to synthesize silicon oxide nanowires. One was catalytic thermal evaporation method in which silicon monoxide was used as the precursor and Au particles served as the catalysts. Using nanosphere lithography, patterned nanowires were obtained and their growth positions were controlled by the locations of Au catalysts. For the second method, without silicon monoxide as the precursor and without the aid of Au catalyst, silicon oxide nanowires directly formed along the <110> direction of the silicon substrate only with the introduction of hydrogen gas. A series of experiments were carried out to study effects of reaction time, temperature, and hydrogen on the growth of the nanowires. Also, various electron microscopy techniques were utilized to characterize their morphologies and internal structures and to analyze their compositional distributions. In this paper, the characterization of different silicon oxide nanowires and their formation mechanisms in relation to both preparation methods are discussed.

Supercritical CO2 (sc-CO2) was first time utilized to make germanium (Ge) nanocrystals by thermolysis of diphenylgermane (DPG) or tetraethylgermane (TEG) with octanol as capping ligand at 500°C and 27.6 MPa. A new approach to prepare Ge nanocrystals of high chemical yield by reduction of GeI2 with LiAlH4 in trioctylphosphine (TOP) at 300°C is also presented. In both cases, Ge nanoparticles with high crystallinity were observed with high resolution transmission electron microscopy (HRTEM), and the presence of Ge was confirmed by X-ray diffraction (XRD) pattern. Compared to the supercritical organic solvents investigated in the previous study to make Ge nanoparticles, the reaction in sc-CO2 produced much less organic contaminants and made the removal of by-products and cleaning of the nanocrystals much easier. While Ge nanoparticles were synthesized in sc-CO2 with DPG and octanol, bulk Ge instead of nanoparticles was obtained without the presence of CO2 at the same concentration of DPG and octanol. High chemical yield of up to 75% was achieved for the Ge nanoparticles made from GeI2 with TOP, and only minimal cleaning is required to obtain Ge nanocrystals with high purity.

Transition metal oxides are being considered as the next generation materials in field such as electronics and advanced catalysts; between them is Tantalum (V) Oxide; however, there are few reports for the synthesis of this material at the nanometer size which could have unusual properties. Hence, in this work we present the synthesis of Ta2O5 nanorods by sol gel method using DNA as structure directing agent, the size of the nanorods was of the order of 40 to 100 nm in diameter and several microns in length; this easy method can be useful in the preparation of nanomaterials for electronics, biomedical applications as well as catalysts.

A low-doped p-type silicon wafer was wet-etched to form macropores in a high-aspect-ratio, straight and parallel manner along the Si (100) direction. It was then plated in aqueous alkaline solution containing Ni2+. Metallic Ni was rapidly deposited in the macropores on the sidewall surface without using a reducing agent or activation treatment at slightly elevated temperature. After being immersed for certain duration, the single crystalline Si of sidewalls was replaced by polycrystalline Ni while the initial porous structure was still maintained. When Ni became dominant in the entire porous regime, the porous film more than 200 μm thick was discovered to be able to peel off very easily from the Si substrate beneath. In this way, a piece of nickel foam with straight pores of very high aspect ratio is self-formed and self-peeled.

We report the synthesis of cadmium and lead thiosemicarbazide complexes. The single x-ray crystal structure of lead complex is reported. The cadmium thiosemicarbazide complex was thermolysed in hexadecylamine (HDA) at 140°C and 180°C to give CdS nanorods. The transmission electron microscopy (TEM) and XRay diffraction (XRD) measurements show that the reaction temperature has the influence on the size and shape of the nanorods. The lead thiosemicarbazide was thermolysed in tri-n-octylphosphine oxide (TOPO) at 240°C to yield hexagonally shaped nanoparticles of PbS. The XRD confirms a face centred cubic rock salt structure.

We have succeeded in preparing submicron-sized monodisperse spherical V2O5 particles by hydrolysis of vanadium isopropoxide (VO(OiPr)3) in acetone/pyridine (Py) mixture solution for the first time. These particles had almost perfect spherical shape and were non-agglomerated. Their size could be easily controlled from 200 to 800 nm by changing the concentration of pyridine while keeping narrow size distribution (standard deviation, ca. 7%). Elemental and Fourier Transform Infrared analyses revealed that these particles have a composition of V2O5.xPy.yH2O (x ≈ 0.8, y ≈ 0.9) independent of their size. X-ray diffraction studies revealed that these particles have layered structure similar to that of V2O5.nH2O xerogel with an interlayer spacing of ca. 1.05 nm independent of their size, possibly due to the intercalation of H2O and pyridine between the V2O5 sheets.

A series of N-alkyldithiocarbamato complexes of cadmium have been synthesised and characterized. [Cd(S2CNHC12H25)2] complex was used as a single source precursor to synthesize CdS nanoparticles. Synthesis of CdS nanoparticles was carried out at various thermolysis temperatures and concentration of the precursor to observe the morphological changes. At moderate or high temperature the 1D nanostructures (single-rods, bend rods or multi-rods) are generated. The shape of CdS nanocrystals varied from longer rods to shorter rods with increased width (average size: 4nm wide and 27nm long vs. 9nm wide and 27nm long) by simply increasing the quantity of precursor in the bulk solution from 0.05g/8ml HDA to 1g/8ml HDA at 250°C.

Free-standing PZT (Lead Zirconate Titanate ) and Gold nanoparticles (ceramic and metal) have been prepared by complex process. In case of PZT, the process involves the preparation of metal ion complex (ligand) solution followed by evaporation. Complete evaporation results in fluffy dried mass. Calcination of dried mass at low temperature produces free-standing PZT nanoparticles. The concept of the process involves choice of correct metal ion complex, stoiochiometry and drying conditions to produce free-standing individual nanoparticles. Similar process has been used to prepare free-standing gold nanoparticles where individual gold form complex with the ligands (complexing agents) to produce free-standing nanoparticles.

Solvothermal reaction of a mixture of metallic barium and titanium isopropoxide in acetophenone leads to the formation of barium titanate nanocrystals. XRD measurements prove the presence of cubic BaTiO3 with traces of BaCO3 as side product. According to TEM investigations, the particles exhibit a nearly spherical particle shape with diameters ranging from 10 to 15 nm. However, due to the lack of any stabilizers, the particles are slightly agglomerated. NMR analysis of the obtained reaction solution shows that aldol condensation reactions of acetophenone and in situ formed acetone provide the water necessary for inducing crystallization and nanoparticle formation.

Two products are formed in the process of carburization of iron with hydrocarbons: iron carbide (Fe3C, cementite) and in the next stage - carbon deposit. This paper deals with the formation of carbon deposit on nanocrystalline iron from ethylene decomposition and the reduction of its product with hydrogen.

The carburization process was controlled using spring thermobalance. The samples after carburization contained cementite and some amount of carbon deposit in the form of carbon nanofibers and carbon nanotubes. In the next step iron carbide had been reduced under hydrogen flow at 400 – 500°C and pure iron was obtained. Some carbon was hydrogenated and the morphology of the remaining carbon deposit was changed – thicker carbon nanofibers were eliminated and thinner carbon nanotubes remained.

The samples after carburization and reduction processes were characterized using XRD (X-rays Diffraction) and HRTEM (High Resolution Transmission Electron Microscopy) methods.

In this work we report on the growth of cadmium sulfide and zinc sulfide nanocrystals by thermolysis, starting from a metal thiolate in a (i) solventless way, (ii) by a novel route in tryoctilphosphine oxide (TOPO), and (iii) by direct synthesis in a polystyrene matrix. The x-ray diffraction (XRD) and transmission electron microscopy (TEM) show that the nanocrystals fabricated by the different methods are under optimized growth conditions single crystals of zincblende structure and of regular spherical shape. The average size was estimated to be between 2.0-3.0 nm with a size dispersion that depends on the synthesis route and is in the range between 10% and 20%. The XPS results indicate that for the nanoparticles obtained via solventless strategy the sulfur is present both as bonded to the metal atom and to the organic residue, while in the TOPO synthesized nanoparticles the sulfur signal has only one component associated to the metal-sulfide bond. The photoluminescence spectroscopy (PL) analysis of CdS crystals clearly evidences the typical emissions of nanosized zincblende CdS monocrystalline particles. Furthermore, the optical spectroscopy data indicate that the size distribution of the Cdsulfide - TOPO nanoparticles seems to be generally larger than that ones grown directly in polymer matrix. For all the CdS samples, the metal-sulfide nanocrystals exhibit a trap-related radiative transition at about 2eV that can be attributed to the hole-electron recombination at particle surface defect-center.

The fabrication and structures of nanometer sized metal and semiconductor dots by a new “combined UHV and liquid-phase processing” (CULP) method are investigated. Ultrahigh vacuum deposition of monolayers of material, buffered and co-adsorbed along with chemically-inert working gas molecules, and subsequent pressurization in situ with high purity helium, led to self-assembly of metal and semiconductor nanoparticles in the liquid phase. The density and size distribution of nanoparticles were found to depend on processing parameters including the substrate surface condition and the dilution of the co-adsorbed film. These results are discussed in terms of surface and interface energies and kinetics.

Well-aligned ZnO nanowires were synthesized by simple physical vapor deposition using c-oriented ZnO thin films as substrate without catalysts or additives. The synthesized ZnO nanowires have two typical average diameters: 60 nm in majority and 120 nm in minority. They are about 4ím in length and well aligned along the normal direction of the substrate. Most of the synthesized ZnO nanowires are single crystalline in a hexagonal structure and grow along the [001] direction. The c-oriented ZnO thin films control the growth direction. Photoluminescence spectrum was measured showing a single strong ultraviolet emission (380 nm). Such result indicates that the ZnO nanowire arrays can be applied to excellent optoelectronic devices.

The Si nanowires were synthesized using a novel catalytic thermal reaction under Ar flow. The average diameter is in the range of 50 ∼ 100 nm. They consist of defect-free single-crystalline cubic structure with the [111] growth direction. The thickness of amorphous oxide outer layers was controllable by growth conditions or surface treatment. In order to protect the oxidation, the Si nanowires were coated with boron nitride layer by the reaction of boron oxide mixture with NH3.

Si nanoparticles have been synthesized by ablating a Si target in Ar with 355 nm laser radiation. The nanoparticle size distribution has been determined in real time by laser-induced time of flight mass spectrometry. Under these conditions, nanoparticles that are formed in 1.0 and 2.0 Torr of background Ar gas exhibit log-normal size distributions with most probable diameters of 2.6 and 3.0 nm, respectively. The speed distribution of the nanoparticles has been determined by varying the time delay between the ablation and photoionization lasers. The results indicate that the most probable speed of the nanoparticles, after formation and a 25 mm drift in background Ar, is 100 m/s. Finally, there is a deviation of the size distribution from the log-normal distribution at small nanoparticle sizes. This is attributed to multiple ionization of the nanoparticles. Confirming evidence for multiple ionization is provided by the atomic and mass spectra which show peak broadening due to Coulomb explosion.

Nickel sulphide (NiS) thin films have been deposited on glass by aerosol assisted chemical vapour deposition(AACVD) using single source precursors of the type, ([Ni(S2COR2)2], R = C2H5 or C3H7). TGA analyses showed that the precursors are highly volatile, making them suitable for AACVD studies. As deposited NiS films were polycrystalline as confirmed by XRD. The films have been characterised by xray diffraction (XRD), scanning electron microscopy (SEM), and Energy dispersive analysis of x-rays (EDAX).

This paper reports direct growth of [001] ZnO nanorod arrays on ITO substrate from aqueous solution with electric field assisted nucleation, followed with thermal annealing. Xray diffraction analyses revealed that nanorods have wurtzite crystal structure. The diameter of ZnO nanorods was 60 ∼ 300 nm and the length was up to 2.5 μm depending on the growth condition. Photoluminescence spectra showed a broad emission band spreading from 500 to 870 nm, which suggests that ZnO nanorods have a high density of oxygen interstitials. Low and nonlinear electrical conductivity of ZnO nanorod array was observed, which was ascribed to non-ohmic contact between top electrode and ZnO nanorods and the low concentration of oxygen vacancies.

In this paper, a novel mild synthetic route was tentatively designed to achieve both shape and dimension-defined nanostructure such as nanorods, nanowires and nanocircles which were fully characterized by AFM and TEM. Bubbles, which are automatically generated when water is mixed with ethanol by a simple shaking, act as a nanoreactor to produce these nanostructures. Fe containing nanowire, nanorod and nanocircle are successfully prepared by using this method. Autogenerated bubble-mediated formation of nanostructures has advantages over conventional methods in terms of short reaction time, low energy consumption and absence of complicated experimental equipments.

ZnO, which exhibits a direct bandgap of 3.37 eV at room temperature with a large exciton binding energy of 60 meV,is of considerable technological importance because of its potential use in short-wavelength devices, such as ultraviolet (UV) light-emitting diodes and laser diodes. The fabrication and application of 1-D ZnO nanostructures has attracted considerable interest in recent years. In this work, we produced single crystal nanowires of zinc oxide using a novel self-seeded growth using ultrasonic spray assisted chemical vapour deposition, in which a nanocrystalline seed layer was first deposited onto a glass substrate and the nanowires subsequently grown using a different precursor concentration and substrate temperature. The diameter of the nanowires is in the range of 20-80 nm and the length of the wires is as long as 10 μm. The single crystal nature of the nanowires was revealed by high resolution transmission electron microscopy. The formation of liquid droplets due to the reducing atmosphere and the higher temperature during the nanowire growth was found to be the key step of the ZnO nanowire formation.

GaS nanoparticles have been synthesized by thermolysis of [Ga(S2CNEt2)3] in 4- ethylpyridine. Their absorption spectrum give a band edge at 440 nm (band gap,3.0 eV). XRD pattern showed abroad peaks corresponding to cubic phase of GaS. TEM images confirmed the crystalline nature of particles with narrow size distribution (5.4 nm ± 0.7 dia). To our knowledge this the first time that GaS nanoparticles have been prepared.