Novel ultrathin mesoporous ZnO-SnO2 n-n heterojunction nanosheets with high sensitivity to ethanol

This work describes a facile strategy for fabricating unique ultrathin mesoporous ZnO-SnO2 n-n heterojunction nanosheets. The preparation method consists of synthesis of ultrathin SnO2/ZnSn(OH)(x) precursors and calcination at appropriate temperature. The obtained ZnO-SnO2 n-n heterojunction nanosheets were systemically characterized by various characterization techniques including X-ray powder diffraction, scanning electron microscopy, high resolution transmission electron microscopy and X-ray photoelectron spectra, manifesting the formation of n-n heterojunction between Sn-doped ZnO and SnO2. ZnO-SnO2 n-n heterojunction nanosheets have abundant mesopores in the range of 2-12 nm and show a specific surface area as high as 97.4 m(2) g(-1). The gas sensing tests demonstrated that ultrathin ZnO-SnO2 heterojunction nanosheets with a Zn/Sn molar ratio of 3 showed a response of 80 to 50 ppm ethanol gas at 240 degrees C, which is approximately 10 times higher than that of pure ZnO. Besides, the ZnO-SnO2 nanosheets exhibited fast response/recovery speed, excellent selectivity, and long-term stability to ethanol as well, which are mainly attributed to the unique nanosheet structure with abundant pores and high specific surface area as well as n-n heterojunctions between Sn-doped ZnO and SnO2.