Papers by Keyword: Sonochemical

Abstract: With respect to metal doping into TiO₂, the doping limits for V, Cr, Zr, Nb, Mo, and W are predicted to be higher than other transition metals according to the binding energy calculations in a unit cell model of anatase TiO₂, which suggests that Cr and W can be doped into anatase structure more easily than Ag or Pt, for example. Our investigation has twofold research objectives. One is to prepare metal-doped TiO₂ nano-powders from these transition metals, and the other is to test photocatalytic activity of each resulting powder. For the former, sonochemical process has been used to produce Cr-doped, W-doped, Ag-doped, and Pt-doped TiO₂ nanoparticles. For the latter, we have performed photocatalytic oxidation of methylene blue. The combined results of the morphology and photocatalytic activites have enabled characterization of the physicochemical properties of these transition metal-doped nanoparticles.

Abstract: Hydroxyapatite (HA) is a bioactive ceramic, employed mainly in bone tissue engineering since it exhibits superior biocompatibility and osteoconductivity. Attempts have been made to synthesize HA nanoparticles with chemical composition, morphology, crystallinity and Ca/P ratio similar to that of natural bone. While wet chemical methods are becoming more popular for synthesis of HA nanoparticles, ultrasound irradiation has shown to be an effective method to increase the rate of production and also to decrease particle size. However, process variables must be carefully selected. In the present study, HA nanoparticles with desirable characteristics have been synthesized by the aid of ultrasound irradiation and characterized by powder X-ray diffraction (XRD) and electron microscopy techniques.

Abstract: In this work, we present the synthesis of silver nanoparticles by ultrasonic irradiation of a solution containing silver nitrate as precursor and sodium citrate as reducing agent. These nanoparticles were characterized by ultraviolet-visible spectroscopy and transmission electron microscopy (TEM) and then were tested as SERS-active colloids.

Abstract: Solid-state lighting (SSL) is emerging as a highly competent field and a possible alternative to existing lighting technologies. Development of a suitable phosphor is an important aspect of SSL. The aim of this review is to summarize status of Inorganic Phosphors towards SSL applications. Various examples have been taken from oxide, fluoride, nitride, sulfide and phosphate based host lattices. The important concepts like CIE coordinates and Color Correlated Temperature (CCT) will also be discussed. The sections encompasses of red, blue and green light emitting phosphors. The white light emitting phosphors will also be discussed in details.

Abstract: A novel and simple approach has been developed for a large-scale synthesis of ZnO nanorods using ultrasound radiation. Double-pod-like ZnO nanorods were directly grown from the starting precursors of zinc nitrate hydrate [Zn(NO3)26H2O] and hexamethylene tetramine (HMT) in deionized water without any templates or seeds. The obtained double-pod-like product had a diameter ranging from 80 to 150 nm and length ranging from 1 to 5 um. Scanning electron microscope (SEM), X-ray diffraction (XRD) and transmission electron microscope (TEM) revealed that these products are of high purity, hexagonal and of single-crystalline structure. The ZnO nanorods synthesized were utilized for gas sensing application. Alumina plate consists of Pt interdigitated electrode was used as sensor substrate. The as-prepared products were transferred to the surface of substrate by screen printing method to fabricate the gas sensor. The sensing properties of the sensor were investigated toward methyl mercaptan (CH3SH). The sensor shows good and fast response towards methyl mercaptan at a fixed operating temperature. The high sensitivity may be ascribed to the high surface area and aspect ration of the double-pod-like nanomaterial.

Abstract: A simple sonochemical synthesis of tungsten trioxide hydrate with various morphologies has been developed by using tungsten hexachloride (WCl6) as precursor and water, ethanol and their mixture as solvent, followed by annealing in a tube furnace. The resulting products were structurally characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transition electron microscopy (TEM) and differential thermal analysis (DTA). Results show that nanowhiskers emanating from the core of nanoparticles have been obtained with ethanol as solvent, and that nanoplates and nanosheets were formed when water and/or mixed ethanol and water was used as the solvent, respectively. The continuous changing supersaturation of tungsten trioxide may account for the formation of nanowhiskers. The formation of nanoplates or nanosheets may be associated with the selective adsorption of solvent molecules on the WO3 crystals. Due to a combination of the loss of chemical bonded water and crystal growth, the as-synthesized tungsten trioxide hydrate underwent apparent morphological evolution during thermal processing.

Abstract: Nanometer oxides e.g. SnO2, ZnO, TiO2, ZrO2, etc. have photocatalytic and gas sensing properties which can be different in nanometer range. They have been produced by several methods such as Chemical Bath Deposition (CBD), Pulsed-laser deposition, Chemical Vapor Deposition (CVD), screen printing and firing process, spray pyrolysis technique, magnetron sputtering, mechanical alloying, etc. It was found that the production method and its parameters would affect the size and morphology of these oxides. By using a composite of these oxides their properties would also be affected. In this paper the effects of sonication and reaction temperatures on SnO/ZnO coupled oxides' morphologies were investigated. These coupled oxides were characterized by X-Ray Diffraction (XRD), X-Ray Florescence (XRF), Scanning Electron Microscopy (SEM), and Differential Thermal Analysis (DTA). As a result of using the ultra sound source, the sizes of nano oxides decreased, which is one of the most important advantages of sonochemical synthesis in comparison with chemical bath deposition synthesis of these nano-composites.

Abstract: Nano-sized metal particles have recently attracted considerable interest owing to their application potential. Such particles can be synthesized using physical and chemical methods. In this study, nano-sized noble metals were synthesized through the reaction of metal oxides by ultrasonic. This means that the chemical reactions which take place under conventional conditions can be accelerated by ultrasonic cavitations. In general, the chemical effects of ultrasonic irradiation fall into three areas: homogeneous sonochemical efffects of liquids, heterogeneous sonochemical effects of liquid-liquid or liquid-solid systems, and sonocatalytic effects. It has been proposed that liquid-liquid systems are used for the fabrication of nano-metal particles in the past. In this study, the fabrication of nano-metal particles and supported composites was investigated for the liquid-solid system from a viewpoint of economy and ecology. By choosing suitable conditions, it is reasonable to expect that these simple ultrasonic processes can be extended to obtain nano-sized metal particles. Thus applications by using these reactions were investigated to prepare the nano-sized metal particle supported materials, and mechanisms were investigated.