Stability of Tungsten Oxide Nanoparticles in Different Media

Tungsten oxide (WO 3 ) nanoparticles were synthesised by a simple chemical precipitation method in various media, such as acidic, basic and neutral. Hydrochloric acid and sodium hydroxide were used to maintain the different pH levels and tungstic acid was used as the precursor for the synthesis of tungsten oxide. The resultant nanoparticles were studied by different characterisation techniques. Powder X-ray diffraction shows that the average crystallite size of the WO 3 is about 13 nm and exhibits stable orthorhombic phase for different pH values. Particle size and the surface morphology of the synthesised material were studied by TEM analysis. Chemical composition and surface area of the nanoparticles were studied by FTIR and BET measurements. Optical properties of the synthesised nanoparticles were studied by UV-Vis absorption and photoluminescence spectroscopy. Band gap (~2.7 eV) of the synthesised WO 3 was investigated from the optical absorption spectra. At room temperature, a strong PL blue emission peak at ~440 nm was observed for the synthesised tungsten oxide nanomaterials. Thermal stability of the synthesised material was studied by TG/DTA analysis. Cyclic voltammetry illustrated the electrochemical response of the WO 3 nanoparticles using KCl as electrolyte. The peak separation of 182 mV, 153 mV and 77 mV for the acidic, basic and neutral media were observed. Thus it was confirmed that, tungsten oxide has a low peak separation, a fast reaction rate and electron transfer rate in neutral medium.

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