Congratulations to M. S. student Li-Yuan Zhu for publishing her work on Microsystems & Nanoengineering 
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Hierarchical Highly Ordered SnO2 Nanobowls Branched ZnO Nanowires for Ultrasensitive and Selective Hydrogen Sulfide Gas Sensing
        Hydrogen sulfide (H2S), one of the most dangerous hazardous gases, has aroused widespread concern for its severe toxicity to human body as well as being normally generated from industries. Trace levels of H2S are sufficient to damage the human respiratory system as well as cause unconsciousness neurological sequelae and cardiovascular-related death. In view of this, it is of great significance to effectively detect and monitor H2S in the surrounding living environment.
        Herein, a novel synthetic route for the large-scale fabrication of hierarchical highly ordered SnO2 nanobowls branched ZnO NWs with excellent H2S sensing performance is proposed combining a hard template method for the preparation of highly ordered SnO2 nanobowls, an atomic-layer-deposition (ALD) processing of nanoscale ZnO seed layers on the surface of SnO2 nanobowls, and a modified hydrothermal processing for the growth of branched ZnO NWs. More importantly, the hierarchical sensing materials were synthesized in situ on MEMS devices, which are expected to achieve high performance gas sensors with superior sensitivity, long-term stability and repeatability, as well as low power consumption. As a result, substantially enhanced sensing performance of hierarchical nanobowl SnO2@ZnO NW gas sensors to H2S were demonstrated comparing to the pristine SnO2 nanobowl sensor and the heterostructured nanobowl SnO2@ZnO film sensor. Specifically, the hierarchical nanobowl SnO2@ZnO NW sensor displayed a high sensitivity (Ra/Rg) 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 oC, whose rate of resistance change (i.e. 5.24) is 2.6 times higher than the pristine SnO2 nanobowl sensor. Moreover, the well-structured hierarchical sensors kept stable performance after a month, suggesting great stability and repeatability. The combined diversity of hierarchical heterogeneous nanocomposites with low-power MEMS hold favorable potential for highly sensitive and selective H2S gas sensors with long-term stability and repeatability.
a The synthetic protocol for the hierarchical highly ordered nanobowl SnO2@ZnO NWs in situ on MEMS and its gas sensing schematics; b SEM and TEM characterization of the hierarchical highly ordered nanobowl SnO2@ZnO NWs; c Gas sensing properties of the hierarchical highly ordered nanobowl SnO2@ZnO NWs.