Ab initio study of structural, electronic and dielectric properties of free standing ultrathin nanowires of noble metals

Arrays of vertically aligned zinc oxide nanorods were grown on a quartz substrate by microwave-assisted chemical bath deposition. Polyvinyl alcohol (PVA)–Zn(OH)2 nanocomposites were used to seed the quartz substrate prior to the growth of the ZnO nanorods. X-ray diffraction analysis and field-emission scanning electron microscopy revealed that the grown ZnO nanorods had a hexagonal structure along the c-axis direction. The absence of a seed layer and the coalescence of ZnO nanorods were the key factors responsible for the high sensitivity of the gas sensor. The hydrogen-sensing capabilities of the ZnO nanorod arrays were investigated at room temperature, and their sensitivity was 110% in the presence of 1000 ppm H2. This high sensitivity can be attributed to the high surface-area-to-volume ratio of the nanorods between the Pt interdigital contacts of the metal–semiconductor–metal (MSM) configuration. The sensing measurements for hydrogen gas at various temperatures (25–250 °C) were repeatable over a period of 100 min.