Oxide-catalyzed growth of Ag2O/Zn2SnO4 hybrid nanowires and their reversible catalytic ambient ethanol/oxygen detection

Abstract

Large scale hybrid nanowires consisting of Zn₂SnO₄ periodic nanowires and Ag₂O nanoparticles on both nanowire surfaces and tips have been successfully synthesized at 650 °C using a unique one-step silver oxide catalyzed vapor-solid-solid (VSS) growth process. The single crystal Zn₂SnO₄ nanowires mainly grew along the [13] direction with three major morphologies including straight linear, L-shape, and radiative sparse. Two-dimensional nucleation and periodic ledge growth processes were proposed to be responsible for the Zn₂SnO₄ periodical nanowire formation. These Ag₂O/Zn₂SnO₄ hybrid nanowires were responsive to ethanol at ∼150 °C upon ∼150 ppm ethanol pulses, with one order of magnitude electrical conductivity decrease. This surprising decrease might be triggered by ethanol pulses associated with Ag₂O nanoparticles on nanowire surfaces and electrode-nanowire film interfaces, leading to a catalytic activation of ambient oxygen detection. Ar plasma treatment on the nanowire surface inversely leads to conductivity increase upon ethanol pulses, which suggests a successful plasma removal of catalytic Ag₂O and oxygen ions, therefore enabling the detection of ethanol molecules, instead of ambient oxygen. This reversible catalytic ambient ethanol/oxygen detection mechanism enabled by the hybrid nanowire configurations could provide a new path for designing smart gas detection devices compatible with multiple-transient-gas detection.