High-temperature solid-state reaction induced structure modifications and associated photoactivity and gas-sensing performance of binary oxide one-dimensional composite system

The effects of high-temperature solid-state reactions on the microstructures, optical properties, photoactivity, and low-concentration NO2 gas-sensing sensitivity of ZnO-SnO2 core-shell nanorods were investigated. In this study, the ZnO-SnO2 core-shell nanorods were synthesized through a combination of the hydrothermal method and vacuum sputtering. According to X-ray diffraction and transmission electron microscopy analyses, high-temperature solid-state reactions between the SnO2 shell and ZnO core materials at 900 degrees C engendered an ultrathin SnO2 shell layer for transforming into the ternary Zn2SnO4 (ZTO) phase. Moreover, surface roughening was involved in the high-temperature solid-state reactions, as determined from electron microscopy images. Comparatively, the ZnO-ZTO nanorods have a higher oxygen vacancy density near the nanostructure surfaces than do the ZnO-SnO2 nanorods. The photodegradation of rhodamine B dyes under simulated solar light irradiation in presence of the ZnO-SnO2 and ZnO-ZTO nanorods revealed that the ZnO-ZTO nanorods have a higher photocatalytic activity than do the ZnO-SnO2 nanorods. Furthermore, the ZnO-ZTO nanorods exhibited higher gassensing sensitivity than did the ZnO-SnO2 nanorods on exposure to low-concentration NO2 gases. The substantial differences in the microstructure and optical properties between the ZnO-SnO2 and ZnO-ZTO nanorods accounted for the photocatalytic activity and NO2 gas-sensing results obtained in this study.