Transition Metal-doped Nanoparticles Research Articles

Optical properties of pure and doped CdS nanoparticles under solvothermal method

The synthesis of CdS nano particles have been widely studied for their potential usage in the field of optics. The Semi conductor nanoparticles doped with transition metal ions have attracted a wide attention due to their excellent luminescent properties. The transition metal doped nano particles have different optical properties corresponding to their host counter parts. These nano particles have tremendous applications in the fabrication of optical light emitting diodes and to design a suitable window material in fabrication for solar cells. The microwave assisted solvothermal method is used to prepare the nano particles in this study. The nano structured materials of CdS were characterized by XRD and UV techniques. The size of the crystallite is determined by XRD to be 18.26 nm depending on the amount of the molar ratio of the reactants present in the sample. The nanocrystalline nature of CdS particles and the diffused pattern shows the presence of hexagonal phase in the present system. The quantum size dependent effect and the optical quality of the CdS and Mn-doped CdS are studied. The optical absorption and transmitance spectrum of the Pure and Mn-doped CdS nanocrystals are synthesized in this work. CdS is a commercially important II-VI semiconductor having wide optical band gap, rendering it a very attractive material for optical application especially in nanocrystalline form. The UV-absorption edge provides a reliable estimate of the band gap of any system. It is found that the band gap of the pure CdS nanosystem in the present study is 2.45 eV and this value is found to be larger than that of bulk CdS. This variation of the band gap may be useful to design a suitable window material in fabrication for solar cells. In optoelectronics, it finds use as light emitting diode, reflector, dielectric filter and window material.

Effects of doping zinc oxide nanoparticles with transition metals (Ag, Cu, Mn) on photocatalytic degradation of Direct Blue 15 dye under UV and visible light irradiation.

Azo dyes represent the most commonly used group of dyes in the textile industry. These organic dyes are mainly resistant to biodegradation and may exhibit toxic and carcinogenic properties. The purpose of this study was to investigate the effects of doping zinc oxide (ZnO) nanoparticles (NPs) with transition metals (silver, manganese, and copper) on the photocatalytic efficiency of ZnO NPs in the removal of Direct Blue 15 dye from aqueous environments under ultraviolet (UV) radiation and visible light irradiation. One or two metals were used for doping the NPs. In total, seven types of undoped and transition metal-doped NPs were synthesized using the thermal solvent method with ZnO precursors and transition metal salts. The characteristics of the synthesized NPs were determined based on the scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, dynamic light scattering (DLS), atomic force microscopy (AFM), and zeta potential measurements. The produced ZnO NPs did not exhibit any particular photocatalytic activities under UV radiation and visible light irradiation. The highest removal efficiency under UV radiation was about 74% in the presence of silver-doped ZnO NPs, while the maximum efficiency under visible light was 70% in the presence of copper-doped ZnO NPs. The lowest removal efficiency was related to pure ZnO, which was 18.4% and 14.6% under UV and visible light irradiation, respectively. Although the efficiency of dye removal under visible light was not high compared to UV radiation, this efficiency was noteworthy in terms of both practical and economic aspects since it was achieved without the presence of ultraviolet radiation. The synthesis of transition metal-doped ZnO nanophotocatalysts (with one or two metals) under UV radiation or visible light irradiation could be used as an efficient and promising technology for the photocatalytic removal of Direct Blue 15 dye from aqueous environments.

Photocatalytic Activities of Transition Metal-Doped TiO<sub>2</sub> Nano-Powders by Sonochemical Method and their Physicochemical Properties

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.