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

摘要

Highly sensitive and selective hydrogen sulfide (H2S) sensors based on hierarchical highly ordered SnO2 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 SnO2@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 H2S at 250-C, whose rate of resistance change (i.e., 5.24) is 2.6 times higher than that of the pristine SnO2 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 H2S, 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 SnO2@ZnO NW gas sensors demonstrate favorable potential for enhanced sensitive and selective H2S detection with long-term stability and repeatability. High performance hydrogen sulfide detection is demonstrated for SnO2 nanobowls with branched ZnO nanowires, in-situ fabricated on a MEMS device. Hydrogen sulfide is a particularly hazardous substance to human health, and its detection via MEMS has a number of advantages in practical applications. However, coating the sensing elements directly on to a device is challenging, and often leads to insufficient reliability. Now, a team led by Hong-Liang Lu from Fudan University demonstrate atomic layer deposition of ZnO film onto SnO2 nanobowls, followed by ZnO nanowire growth to create a highly branched structure as the sensing element. The process is completed on the MEMS device itself. High sensitivity and fast response is in part attributed to the large surface area of the branched nanowires, and performance is stable for a month.