A step-scheme mechanism in a NiO/CdS heterojunction nanoarray for visible light-activated gas sensing at room temperature

Abstract

Developing high-performance room temperature semiconductor gas sensors through light activation has aroused great interest recently. However, the improvement in sensing performance is greatly hindered by the extremely high recombination rate of photo-generated carriers and poor response to visible light. Herein, we present a novel approach involving the fabrication of a step-scheme (S-scheme) NiO/CdS semiconductor heterojunction nanoarray sensor, grown in situ on a commercial alumina flat surface. This sensor demonstrates efficient room temperature detection of triethylamine under low-power visible light activation (0.06 W), exhibiting a high response to 27.8 to 100 ppm triethylamine and remarkable long-term stability lasting over one year. The distinctive charge transfer mechanism inherent in S-scheme heterojunctions not only significantly enhances the separation of photo-generated carriers and improves their response to visible light, but also substantially amplifies the oxidation capability, which are responsible for the enhanced sensing performance. In addition, the strategy of in situ grown nanoarrays largely streamlines the manufacturing process and ensures the stability of devices. This study not only expands the application of S-scheme semiconductor heterojunctions in the realm of gas sensing, but also offers new insights into enhancing the performance of light-activated room temperature gas sensors through comprehensive designing of gas sensing materials and device structures.