In-situ growth of CdS QDs on ZnO porous microrods for highly sensitive detection of TEA at lower temperature

Abstract

Driven by the growing issues of environmental degradation, gas sensor constructed with metal oxide semiconductor (MOS) has witnessed a rapid development owing to its suitability for monitoring different kinds of hazardous gases. In this paper, we report a CdS–ZnO n-n heterojunction approach to boost the triethylamine (TEA) sensing performance of ZnO. To expound it, ZnO porous microrods (PMRs) that assembled with secondary nanoparticles (about 25 nm in size) were prepared via an oxalate precursor method, on which CdS quantum dots (QDs) with dominant size of 7.92 nm were in-situ decorated via a facile hydrothermal route to construct nanoscale CdS–ZnO heterojunctions. Compared to the sensor constructed with pure ZnO, the hybrid CdS/ZnO sensor showed significant enhancements in TEA sensing performance, including lower operating temperature (decreased from 200 to 160 °C), higher sensitivity (0.214/ppm vs 0.068/ppm to 1–200 ppm TEA), better selectivity, and faster response speed. These improvements were well explained by the sensitization functions of CdS–ZnO heterojunctions, whose mechanism was comprehensively understood and discussed.