A new approach is presented to introduce the fine structure of core-loss excitations into the electron energy-loss spectra of ionization edges by Monte Carlo simulations based on an optical oscillator model. The optical oscillator strength is refined using the calculated electron energy-loss near-edge structure by density functional theory calculations. This approach can predict the effects of multiple scattering and thickness on the fine structure of ionization edges. In addition, effects of the fitting range for background removal and the integration range under the ionization edge on signal-to-noise ratio are investigated.

Tungsten oxide (WO3) nanostructures receive sustained interest for a wide variety of applications, and especially for its usage as a photocatalyst. It is therefore important to find suitable methods allowing for its easy and inexpensive large scale production. Tungstite (WO3·H2O) nanoparticles were synthesized using a simple and inexpensive low temperature and low pressure hydrothermal (HT) method. The precursor solution used for the HT process was prepared by adding hydrochloric acid to diluted sodium tungstate solutions (Na2WO4·2H2O) at temperatures below 5 °C and then dissolved using oxalic acid. This HT process yielded tungstite (WO3·H2O) nanoparticles with the orthorhombic structure. A heat treatment at temperatures at or above 300 °C resulted in a phase transformation to monoclinic WO3, while preserving the nanoparticles morphology. The production of WO3 nanoparticles using this method is therefore a three step process: protonation of tungstate ions, crystallization of tungstite, and phase transformation to WO3. Furthermore, this process can be tailored. For example, we show that WO3 can be doped with cesium and that nanorods can also be obtained. The products were characterized using powder x-ray diffraction, transmission electron microscopy (including electron energy-loss spectroscopy and electron diffraction), and x-ray photoelectron spectroscopy.

Titanium oxide (TiO2) nanoparticles (NPs) were doped with vanadium using a novel, facile, and inexpensive method. The TiO2 NPs were dispersed in a vanadyl oxalate solution prepared by dissolving vanadium pentoxide (V2O5) in oxalic acid. A short heat treatment at 400 °C applied to the dried mixture resulted in the doping of TiO2 with a net measured decrease of its band gap by about 0.5 eV, making this important semiconductor material usable in the visible light spectrum.

A simple method was used to electrodeposit a metallic coating on vertically aligned carbon nanotube (CNT) arrays, herein referred to as turfs, creating an open cell, core–shell foam. The foam exhibited highly elastic behavior, approaching the amount of elastic recovery in compression of a pure CNT turf. The turfs were pre-treated with an acid bath, and were electroplated at low voltages with nickel and copper. This simple method can be expanded to prepare a large variety of nanostructured foams (e.g., the carbon support can be changed, the metal deposited selected and its thickness controlled) while maintaining their mechanical robustness.

Semiconductor quantum dots are considered very promising candidates for bio-imaging and diagnosis applications because of their tunable optical properties and good optical stability in aqueous phase. Any practical application of these materials will rely on the viability of their simple and direct synthesis in aqueous phase with no need for toxic and unstable organic media. The optical properties of CdSe quantum dots and CuS nanoparticles are desirable in bio-imaging and cell sorting applications because of their tunable photoluminescence at the visible range. The present work addresses the synthesis of CdSe quantum dots and CuS nanoparticles via an optimized, simple and scalable aqueous processing route at low temperatures. The tunability of the optical properties was achieved by a suitable control of the citrate/Cd mole ratio, temperature of synthesis (20-90°C) and reaction time (0-1 hour). In the case of CuS, the strong plasmonic absorption offers the opportunity to investigate this material as a photothermal coupling agent for photothermal therapy. The intensity of the plasmonic absorption was enhanced by selecting an appropriate sulfide precursor (Na2S, Thioglycolic acid), temperature of synthesis (90-120°C) and reaction time. Nanocrystals were characterized by x-ray diffraction, UV-VIS, photoluminescence (PL) spectroscopy techniques and electron microscopy. The effects of the synthesis conditions on the crystal size and the corresponding functional properties of synthesized quantum dots are presented and discussed.

A nanofluid is a solid-liquid composite material consisting of a stable suspension of nanometric particles in a conventional refrigerant liquid expected to exhibit enhanced heat transfer properties. Elemental silver (Ag) was selected in this research because of its high electrical and thermal conductivity that are likely to be dependent on the crystal size and shape at the nanoscale. Accordingly, we have synthesized highly monodisperse silver nanowires and nanocrystals by reducing silver nitrate solutions with ethylene glycol in presence of polyvinylpyrrolidone, (PVP). The shape-control in the silver nanostructures was achieved by a proper selection of the type and level of chloride salts, e.g. KCl and CaCl2, and specific PVP/Ag mole ratios in starting solutions. The development of the metal phase was confirmed by X-ray diffractometry. Transmission electron microscopy analyses evidenced the formation of silver nanowires exhibiting a very uniform thickness that could be tuned in the 40-130nm range. UV-vis measurements evidenced the plasmon peak at ∼387nm and clear shoulders at ∼357nm that are indicative of the formation of elongated nanostructures.

This study reports on the structural and magnetic characterizations of free-standing bismuth ferrite, BiFeO3, nanoparticles synthesized in polyol medium. Fine tuning of the ferrite magnetic properties was achieved by adding an excess bismuth species or doping with cobalt ions, coupled with thermal annealing. Crystalline Bi1-yCoyFeO3 powders (where ‘y’ ranges from 0.00 to 0.10) were produced after annealing the precursors for one hour at 700οC. The average crystallite size was calculated to be approximately 22 nm. We found that the synthesis under stoichiometric excess of Bi species (up to 10 at.%) promoted a more complete crystallization of the material, i.e., no precursor phases remained. Furthermore, both the saturation magnetization and the coercivity of the synthesized powders were strongly influenced by the concentration of Co. They increased from 0.13 emu/g and 19 Oe to 3.5 emu/g and 1183 Oe for pure BiFeO3 and 10 at.% Co-doped BiFeO3, respectively.

A systematic study was carried out to determine the effects of composition and grain size on the structural, optical and magnetic properties of pure ZnO and vanadium-doped ZnO nanocrystalline powders and films in the 0.0 at.% V - 6 at.% V range. The powders and films were synthesized via a sol-gel approach, where ethanolamine was used to increase the viscosity of the precursor solutions and promote the adhesion of the films onto quartz substrates. Powder X-ray diffraction confirmed the formation of ZnO (host oxide) after annealing of the precursors in air. The average grain size in the thin films ranged from 11 nm to 23 nm when the samples were annealed in air for one hour between 450ºC and 550ºC. UV-vis and photoluminescence confirmed the formation of the host oxide. Also, the photoluminescence intensity was found to be strongly dependent on the amount vanadium. Furthermore, it was found that the vanadium concentration and the annealing temperature play an important role in the ferromagnetic behavior of the material.

The oxidation of both single crystal and relatively pure polycrystalline silicon carbide, between 973 and 2053 K, resulted in the formation of cristobalite, quartz, or tridymite, which are the stable crystalline polymorphs of silica (SiO2) at ambient pressure. The oxide scales were found to be pure SiO2 with no contamination resulting from the oxidizing environment. The only variable affecting the occurrence of a specific polymorph was the oxidation temperature. Cristobalite was formed at temperatures ≥1673 K, tridymite between 1073 and 1573 K, and quartz formed at 973 K. The polymorphs were determined using electron diffraction in a transmission electron microscope. These results were further confirmed using infrared and Raman spectroscopies. Cristobalite was observed to grow in a spherulitic fashion from amorphous silica. This was not the case for tridymite and quartz, which appeared to grow as oriented crystalline films. The presence of a thin silicon oxycarbide interlayer was detected at the interface between the SiC substrate and the crystalline silica using x-ray photoelectron spectroscopy.

Electronic devices based on single crystal SiC represent a good choice for a variety of new high temperature, high power electronics applications. The challenge is to develop a package that is resistant to thermal degradation in harsh environments. Conditions are extreme and this all but rules out only a handful of materials and materials systems. Polycrystalline SiC is the material that we have chosen to study as a suitable package and materials suitability/compatibility has been considered on several levels.