Optical, electrical and sensing properties of ZnO nanoparticles synthesized by sol-gel technique

Optical, electrical and sensing properties of ZnO nanoparticles, prepared by sol-gel process and subsequent dried in supercritical conditions, are presented. To investigate the morphological and microstructural properties, transmission electron microscopy (TEM), X-ray powder diffraction (XRD), UV-visible spectroscopy and photoluminescence (PL) spectroscopy analysis have been used. From microstructure analysis we showed that pure ZnO nanoparticles were polycrystallines and exhibited the hexagonal wurtzite structure. Chemoresistive sensor consisting of a thick layer of ZnO nanoparticles annealed at 400 °C for 2h in air on interdigitated alumina substrate has been fabricated and its electrical and sensing characteristics were investigated. The sensor performances towards carbon monoxide (CO) with and without UV illumination were reported. An increase of sensitivity, along a reduction of ZnO thick film resistance, was observed when the sensor operates under UV irradiation.