Band gap engineering in ZnO based nanocomposites

Abstract

Abstract In the present work, individual zinc oxide (ZnO), tin oxide (SnO2) and vanadium oxide (V2O5), their binary and ternary combinations were prepared via hydrothermal route. The structure and the morphology of all the samples were characterised using X-ray Diffractometer (XRD) and Field Emission Scanning Electron Microscopy (FE-SEM) and Raman spectroscopic tools. UV–Visible spectroscopic analysis was recorded for all the samples. The samples were also tested for ethanol sensing (0 ppm–300 ppm) at room temperature. It has been focussed on to investigate the Raman and UV spectroscopic studies on the ethanol sensing properties of these oxides. It is observed that the Raman peaks of the binary and ternary systems shifted to lower wavenumber compared to their bulk and it is attributed to the tensile stress experienced by the nanocomposite. The peculiar hierarchical nanostructures of zinc – tin – vanadium oxide (ZTV) nanocomposite with larger surface area (167.3 m2/g) provided the required active surface sites for the adsorption of ethanol molecules. The band gap of ZTV is calculated as 1.97 eV. This band gap narrowing observed in ZTV might be due to the competing effects of high free carrier concentration and Burstein-Moss shift. Hence ZTV shows pronounced sensitivity of 98% at a response time of 32 s and recovery time of 6 s. Moreover the synergistic effect of ZTV nanocomposite enhanced the sensitivity at a faster rate by overcoming the problems associated with the energy consumption, reversibility, adsorptive capacity and fabrication cost.