Size effect of zno-nanowires on reversible sulfuration-desulfuration reaction for ultra-sensitive detection of ppb-level H2S gas

This paper, for the first time, reports the nano-size effect of ZnO nanowire (NW) on reversible sulfuration-desulfuration reaction process. ZnO NWs with diameter of 50nm are recently found to be sulfurated by H₂S to form ZnS, which can be latterly desulfurized by ambient oxygen back to ZnO when H₂S is removed. This sensing mechanism is different from the widely used conventional one for reductive gases like H₂S [1]. Based on the nano-material property, higher sensitivity of ZnO NW to ultra-low concentration H₂S is expected by size shrinking. A novel nano-structure of tree-branch ZnO NWs, with the branch diameter as 20nm, is in situ grown at the hot-plate of a micro-sensor. Both the 20nm ZnO-NWs sensor and the 50nm sensor are compared by experiment, resulting in good validation of the nano-size effect. The tree-branched 20nm ZnO-NWs sensor exhibits resoluble sensing to 20ppb H₂S.