Prototype Alarm\nIntegrating Pulse-Driven Nitrogen\nDioxide Sensor Based on Holey Graphene Oxide/In<sub>2</sub>O<sub>3</sub>

NO<sub>2</sub> seriously threatens human health and the\necological\nenvironment. However, the fabrication of highly sensitive NO<sub>2</sub> sensors with rapid response/recovery rates, low detection limits,\nand ease of integration remains a challenge. Herein, benefiting from\nthe fast carrier transfer and rich active sites, holey graphene oxide\n(HGO) was adopted to functionalize the In<sub>2</sub>O<sub>3</sub> nanosheet to construct NO<sub>2</sub> gas sensors. Characterization\nand theoretical calculations established the merits of HGO decoration\nin the NO<sub>2</sub> sensing. The optimal sample, 0.5 wt % HGO/In<sub>2</sub>O<sub>3</sub>-sheet, exhibited superior sensing properties,\nresulting in a 1.37-fold improvement in response to 1 ppm of NO<sub>2</sub> compared to the GO/In<sub>2</sub>O<sub>3</sub> counterpart.\nGas-sensing kinetics analysis revealed its lower activation energy\nand higher kinetic rate constants. Importantly, pulsed-temperature\nmodulation was employed to decouple the gas adsorption from surface\nactivation processes, achieving an ultrahigh response of 2776 to 1\nppm of NO<sub>2</sub> for the 0.5 wt % HGO/In<sub>2</sub>O<sub>3</sub>-sheet sensor. Compared to the isothermal mode, this strategy enhanced\nthe response value by 1.6 times, reduced the response/recovery time\nby 33%/70%, and enabled the detection of NO<sub>2</sub> concentrations\nas low as 1 ppb. Finally, an NO<sub>2</sub> monitoring alarm system\nbased on the 0.5 wt % HGO/In<sub>2</sub>O<sub>3</sub>-sheet sensor\nwith pulsed-temperature modulation was demonstrated for hazard warnings.