Strategy for sensitive and selective NO2 detection at low temperatures utilizing p-type TeO2 nanowire-based sensors by formation of discrete n-type ZnO nanoclusters

Abstract

Heterostructured nanomaterials have been extensively studied for gas sensing applications because of their unique properties. In this study, we synthesized heterostructured nanomaterials consisting of p-type TeO2 (p-TeO2) NWs and discrete n-type ZnO (n-ZnO) nanoclusters (NCs) to detect NO2 gas molecules. These nanomaterials were synthesized via thermal evaporation and atomic layer deposition (ALD) techniques and then systematically investigated for NO2 sensing capabilities with regard to operating temperature, NO2 response, response/recovery times, and selectivity. The successful formation of discrete n-ZnO NCs depending on ALD conditions was observed via scanning electron microscopy (SEM) and transmission electron microscopy (TEM), and these nanomaterials were characterized by energy dispersive spectrometry (EDS), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The NO2 response of the p-TeO2 NW sensors was considerably enhanced through the formation of discrete n-ZnO NCs. In addition, the synthesized sensors showed good NO2 selectivity in comparison with interfering gases such as SO2, CO, and C2H5OH. Herein, the enhanced NO2 sensing mechanisms of p-TeO2 NWs by formation of discrete n-ZnO NCs will be discussed in detail. We also believe that the formation of discrete n-ZnO NCs is an effective way to enhance NO2 sensing capabilities of p-TeO2 NW-based gas sensors.