Synthesis and gas sensing performance of ZnO–SnO2 nanofiber–nanowire stem-branch heterostructure

An approach was used to fabricate a ZnO–SnO2 nanofiber–nanowire heterostructure (NNH). In this approach, SnO2 nanowire branches were grown by vapor phase growth on ZnO nanofiber stems that had been synthesized by electrospinning. For the growth of SnO2 nanowire branches, a thin Au layer was deposited on the surface of the ZnO nanofiber stems and Sn powder was then evaporated on them. The SnO2 nanowire branches, which sprouted from the ZnO nanofiber stems, had diameters in the range of 40–60 nm. To test the potential use of the ZnO–SnO2 NNH as chemical gas sensors, the sensing properties with regard to NO2 and CO were investigated. The ZnO–SnO2 NNH possessed good and reproducible sensing responses to parts-per-million level NO2 and CO for repeated testing cycles, demonstrating its potential as a platform for chemical sensors. Modulations of the depletion width along the branch nanowires as well as modulations of the potential barriers at the grain boundaries in the stem nanofibers and at both networked homojunctions and heterojunctions between the stems and branches are also likely to be responsible for the good sensing ability of the ZnO–SnO2 NNH.