Bi-functional mechanism of H2S detection using CuO–SnO2 nanowires

Abstract

In this study, a bi-functional mechanism is proposed and validated, which may be used to explain all of the reported experimental observations and to predict new sensing control parameters. Fast response and recovery in H₂S sensing was then realized by using bi-functional SnO₂ nanowires which have been radially modulated with CuO. Firstly, Cu metal nanoparticles were synthesized by applying γ-ray radiolysis. The Cu nanoparticles (attached to the surface of the SnO₂ nanowires) were oxidized to the CuO phase by a thermal treatment at 500 °C in air. The H₂S sensing characteristics of the CuO-functionalized SnO₂ nanowires were compared with those of bare SnO₂ nanowires. The results demonstrated that γ-ray radiolysis is an effective means of functionalizing the surface of oxide nanowires with CuO nanoparticles, and CuO functionalization greatly enhanced the ability of the SnO₂ nanowires to detect H₂S in terms of the response and recovery times. In addition, two control parameters, a 0.5 CuO to SnO₂ surface ratio and a sensing temperature range of 80–220 °C, are predicted. The radially modulated nanostructures achieve two functions: (1) the formation and break-away of p–n (CuO–SnO₂) junctions, and (2) the formation and dissolution of CuS using CuO–SnO₂ solid solutions.