Eco friendly chemical synthesis and gas sensors of metal oxide nanostructures

Abstract

Eco-friendly green biosynthesis of SnO2 and TiO2 nanostructures has been carried out using medicinal mushroom, Ganoderma lucidum (G Lucidum) in the present work. The medicinal plant species, G. lucidum was used a reducing and chelating agent for the synthesis of metal oxides. SnO2 based ethanol (C2H5OH) gas sensors and TiO2 based chlorine (Cl2) gas sensors were investigated. The effects of molar concentration of precursor on the structural properties and gas sensor performance were investigated. Furthermore the effects of noble metal sensitization on the response of gas sensors were investigated. Noble metals such as Silver (Ag), Gold (Au) and palladium (Pd) were used for sensitization of SnO2 and TiO2. The change in surface energy, electronic sensitization and the chemical sensitization (spillover effect) caused by sensitization of noble metals on SnO2 and TiO2 surface were investigated. Pure SnO2/TiO2 and Ag, Au and Pd sensitized SnO2/TiO2 nanostructures were characterized using X-ray diffraction (XRD), Field emission scanning electron microscopy (FESEM), High resolution transmission electron microscopy (HRTEM), Energy Dispersive X-Ray Spectroscopy (EDAX), Ultraviolet/Visible Absorption Spectroscopy (UV/Vis spectroscopy), X-ray photoelectron spectroscopy (XPS) and Brunauer, Emmett and Teller (BET) measurements for micro structural, morphological, elemental analysis and adsorptiondesorption studies of NO2 on the surface of the resultant products. The green synthesized nanostructured SnO2 film showed excellent selectivity towards C2H5OH gas. The sensing properties of the films of different molar concentrations of precursor solution (0.1 M through 0.5 M of SnCl4) were studied, the maximum response of 69.6 % was obtained at 100 ppm C2H5OH concentration for 0.3 M SnCl4 (S3) film. However, the response was found to decrease as the molar concentration of SnCl4 solution increased. The electronic and chemical sensitization of impregnated films showed enhanced gas sensing performance of the films. Ag, Au and Pd sensiti