Surface modification of ZnO nanopillars to enhance the sensitivity towards methane: The studies of experimental and first-principle simulation

Abstract The versatile patterned micro-shell fully covered with ZnO vertical nanopillars of length 2 µm and diameter 100 nm have been successfully synthesized and employed as a CH4 sensor. The sample has been characterized by Field Emission Scanning Electron Microscope (FE-SEM) and X-ray Diffraction (XRD). The bandgap of synthesized ZnO nanopillars has been calculated by using UV–visible spectroscopy and found to be 3.37 eV. Marvelous sensor response of ZnO nanopillars was observed for UV light and found to be 302 with a response time of ~ 1 s. ZnO nanopillars have an excellent sensing property so they can detect CH4 at a low concentration (100 ppm) at room temperature. Under UV light, it exhibited higher performance with an outstanding characteristic with an adequate gas sensor response 1.02 at 100 ppm of methane gas with response/recovery time ~ 132/13 s. The characteristics of ZnO and CH4 molecules were also calculated by first-principles based on density functional theory (DFT). The comparison of ZnO binding energy before and after interaction of methane gas molecule was calculated and found to be 3.68 eV and 3.1904 eV respectively, which show -0.7021 eV absorbance energy. Experimental and theoretical studied evidence that ZnO molecules have an excellent bustle with CH4 molecules.