Exploration of ZrO 2-shelled nanowires for chemiresistive detection of NO 2 gas

Abstract

We present novel research devoted to the synthesis of SnO2-ZrO2core-shell nanowires (C-S NWs) and in-vestigation of their NO2gas sensing properties. ZrO2shell layer was deposited on networked SnO2NWs. TheZrO2shell thickness was varied using four different numbers of atomic layer deposition (ALD) cycles (50, 100,150 and 200). Structural, morphological and chemical composition of the synthesized products were confirmedby different characterization techniques. The gas sensors showed an optimal sensing temperature at a relativelylow temperature (≤150 °C). NO2sensing results showed a strong dependence of response on the thickness of theZrO2shell, or equivalently the number of ALD cycles of ZrO2. The optimal sensor with a ZrO2shell deposited at150 ALD cycles (24.1 nm thick) exhibited a high response of (Rg/Ra) 24.7–10 ppm NO2gas and revealed a goodselectivity to NO2gas. Also, with an increase in the thickness of the ZrO2shell, the negative influence of hu-midity on the sensor response to NO2was significantly decreased. The sensing mechanism involves NO2re-moving electrons from the ZrO2shell. The dependence of responses to shell thickness was explained based ontwo different regimes, i.e., the surface-electron-limiting regime and adsorbing species-limiting regime. The re-sults obtained in this study can be used for further exploration of the sensing properties of ZrO2as a novel shell material.