Synthesis, Characterization And Gas Sensing Properties Of Quantum-sized ZnO And1d SnO₂Nanocrystals

Quantum sized ZnO nanocrystals were synthesized using zinc acetatedihydrate through a sol gel process in different mediums: water, ethanol andmethanol. Three types of modifiers: tetraethyl orthosilicate (TEOS), sodiumdodecyl sulfate (SDS) and oleic acid (OA) were added to control the growthof the ZnO nanoparticles. The crystal structure and size were characterized byX ray Diffraction (XRD) analyses and high resolution transmission electronmicroscopy (HRTEM). The reaction between modifiers and ZnO wereanalysized by Fourier Transform infrared spectroscopy (FTIR). UV visibleabsorption spectra, Photoluminescence (PL) spectra and Raman spectra wereused to analyze the optical properties of quantum size ZnO nanocrystals.Furthermore, gas sensing properties of senors based on quantum size ZnOwere measured, the influence of crystal size, operating temperature andcalcination temperature on responses to different gases in differentconcentration were investigated. The gas sensing mechanism was alsodiscussed.Flower like one dimensional SnO2nanocrystals were synthesized by hydrothermal method. The influence of different hydrothermal temperature,reaction time and surfactant such as cetyltrimethyl ammonium bromide(CTAB) and polyethyleneglycol (PEG) on the morphology of material wereinvestigated. The crystal structure, morphology, surface properties and opticalproperties were analyzed using a variety of characterization methods. Gassensing properties of SnO2nanocrystals to NO2, CO and CH4were measured.In order to improve the response of SnO2based sensors to CO, Ni dopedSnO2nanocrystals were synthesized by sol gel route. The changes in theoptical properties of the material after doping were investigated. Optimal Nidoping amount was obtained by gas sensing measurement. The gas sensingmechanism was discussed by X ray photoelectron spectroscopy (XPS)analysis and adsorption and desorption of the gas on the SnO2surface.