Hierarchical highly ordered SnO_(2) nanobowl branched ZnO nanowires for ultrasensitive and selective hydrogen sulfide gas sensing

Highly sensitive and selective hydrogen sulfide(H_(2)S)sensors based on hierarchical highly ordered SnO_(2) nanobowl branched ZnO nanowires(NWs)were synthesized via a sequential process combining hard template processing,atomic-layer deposition,and hydrothermal processing.The hierarchical sensing materials were prepared in situ on microelectromechanical systems,which are expected to achieve high-performance gas sensors with superior sensitivity,long-term stability and repeatability,as well as low power consumption.Specifically,the hierarchical nanobowl SnO_(2)@ZnO NW sensor displayed a high sensitivity of 6.24,a fast response and recovery speed(i.e.,14 s and 39 s,respectively),and an excellent selectivity when detecting 1 ppm H_(2)S at 250°C,whose rate of resistance change(i.e.,5.24)is 2.6 times higher than that of the pristine SnO_(2) nanobowl sensor.The improved sensing performance could be attributed to the increased specific surface area,the formation of heterojunctions and homojunctions,as well as the additional reaction between ZnO and H_(2)S,which were confirmed by electrochemical characterization and band alignment analysis.Moreover,the well-structured hierarchical sensors maintained stable performance after a month,suggesting excellent stability and repeatability.In summary,such well-designed hierarchical highly ordered nanobowl SnO_(2)@ZnO NW gas sensors demonstrate favorable potential for enhanced sensitive and selective H_(2)S detection with long-term stability and repeatability.