Gas sensing and electrical properties of metal oxide nanostructures

Abstract

This thesis consists of four parts of which Part-1 gives a brief overview of the synthesis, properties and applications of nanomaterials. Part-2 deals with the synthesis and characterization of different nanostructures of metal oxides and a detailed study of their gassensing characteristics. Nanoparticles, nanowires, nanorods and nanotubes of metal oxides such as ZnO, In2O3, WO3-x, V2O5, TiO2 and SnO2 have been prepared by different chemical routes and characterized by transmission electron microscopy, X-ray diffraction, energy dispersive X-ray analysis and Raman spectroscopy. Sensing characteristics of the thick filM.S. of oxide nanostructures for H2, ethanol, aliphatic hydrocarbons, H2S, NH3 and nitrogen oxides have been studied. Hydrogen sensing characteristics of single nanowires of ZnO, TiO2 and WO2.72 as well as hydrocarbon sensing characteristics of single WO2.72 nanowires have also been investigated by conducting atomic force microscopy. The best sensitivities are found with nanostructures of ZnO (~1720 at 125 °C, H2), (~2500 at 125 °C, Ethanol), WO2.72 (~106 at 200 °C, aliphatic hydrocarbon), WO3 (~ 3300 at 250 °C, H2S), In2O3 (~ 60 at 150 °C, NO, NO2 and N2O) and SnO2 (~ 250 at 300 °C, NH3). Part-3 of the thesis contains results of studies on the electrical properties and hydrogen-sensing characteristics of field effect transistors (FETs) based on nanorods of ZnO and WO2.72. Electroluminescence and rectifying properties of heterojunction light emitting diodes (LEDs) based on ZnO nanorods have been studied. n-ZnO NR/p-Si and n-ZnO NR/p- PEDOT/PSS heterojunction LEDs have been fabricated with ZnO nanorods (NRs) grown by a low-temperature method as well as by employing pulsed laser deposition. Part-4 of the thesis deals with the supercapacitive behavior of RuO2 and IrO2 functionalized mesoporous carbon. Results of studies on the interaction of single-walled carbon nanotubes (SWNTs) with electron donor and acceptor aromatic molecules are reported based on electrical measurements.