Novel growth of CuO-functionalized, branched SnO 2 nanowires and their application to H 2 S sensors

A novel growth method for CuO-functionalized, branched tin oxide (SnO 2 ) nanowires was developed on the basis of a Cu-triggered tip-growth vapour–liquid–solid (VLS) process during annealing of Cu-coated SnO 2 nanowires. The variation in annealing temperature changed the morphology, in which higher temperatures (⩾500 °C) are favourable for the formation of branches. From the observation of tip nanoparticles, we revealed that the growth of branches at 500 and 700 °C was dominated by base-growth and tip-growth VLS processes, respectively. The tip nanoparticles at 700 °C were mainly comprised of a CuO phase. We have demonstrated the potential applicability of the CuO-functionalized, branched SnO 2 nanowires to H 2 S sensors. CuO functionalization significantly enhanced the response to H 2 S. In sharp contrast, it degraded the response to NO 2 , suggesting their selective sensing performance to H 2 S.