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A novel method has been developed for the preparation of nano-sized TiO(2) with anatase phase. Nanoparticles with diameter about 6 nm were prepared at a relatively low temperature (75 degrees C) and short time. The synthesis was carried out by the hydrolysis of titanium tetra-isopropoxide (TTIP) in the presence of water, ethanol, and dispersant under ultrasonic irradiation (500 kHz) at low intensity. The results show that variables such as water/ethanol ratio, irradiation time, and temperature have a great influence on the particle size and crystalline phases of TiO(2) nanoparticles. Characterization of the product was carried out by different techniques such as powder X-ray diffraction (XRD), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM) and UV-vis spectroscopy.

Cadmium sulfide nanoparticles with a hexagonal phase (∼10 nm) were prepared at a relatively low temperature (70°C). This synthesis was carried out shortly (30 min) through a new micro-emulsion (O/W) induced by ultrasound without surfactant. Ultrasound can provide an excess energy for new interface formation and obtain emulsions even in the absence of surfactants. This technique avoids some problems that normally exist in conventional micro-emulsion synthesis such as the presence of different additives and calcinations. In addition, it was possible to tune the particle size, the band gap, and the phases of CdS nanoparticles by changing the variables such as ultrasonic irradiation time, intensity, precursor, and ratio of the components. It was also found that the synthesized nanoparticles have a band-edge emission at about 460 nm with a blue-shift to a higher energy which is due to the typical quantum confinement effects. The product was characterized by different techniques such as UV-visible absorption spectroscopy, X-ray powder diffraction, and high resolution transmission electron microscopy (HRTEM).

A core-shell nanocomposite (CdS/TiO(2)) was synthesized at relatively low temperature (70°C) with small particle sizes (~11 nm). First, CdS nanoparticles were prepared by a combination of ultrasound and new micro-emulsion (O/W) without surfactant. Then the synthesized CdS was easily combined with TiO(2) under sonication. The formation of uniform surface layer of TiO(2) with depths of 0.75-1.1 nm on the CdS led to an increase of particle size. Ultrasonic irradiation can control the hydrolysis and condensation of titanium tetra-isopropoxide (TTIP) and the formation of TiO(2) shell around the CdS core. This technique avoids some of the problems that exist in conventional microemulsion synthesis such as the presence of different additives and calcinations. It was found that nanocomposite particles extend the optical absorption spectrum into the visible region in comparison with pure TiO(2) and pure CdS. In addition, a larger depth of TiO(2) led to a red-shift of the absorption band in nanocomposite. The characterization of nanocomposites has been studied by HRTEM, TEM, XRD, EDAX, BET and, UV-vis.