UV light driven high-performance room temperature surface acoustic wave NH_(3) gas sensor using sulfur-doped g-C_(3)N_(4) quantum dots

Nanomaterials integrated surface acoustic wave(SAW)gas sensing technology has emerged as a promising candidate for realtime toxic gas sensing applications for environmental and human health safety.However,the development of novel chemical interface based on two-dimensional(2D)sensing materials for SAW sensors for the rapid and sensitive detection of NH_(3)gas at room temperature(RT)still remains challenging.Herein,we report a highly selective RT NH_(3)gas sensor based on sulfur-doped graphitic carbon nitride quantum dots(S@g-C_(3)N_(4)QD)coated langasite(LGS)SAW sensor with enhanced sensitivity and recovery rate under ultraviolet(UV)illumination.Fascinatingly,the sensitivity of the S@g-C_(3)N_(4)QD/LGS SAW sensor to NH_(3)(500 ppb)at RT is dramatically enhanced by~4.5-fold with a low detection limit(~85 ppb),high selectivity,excellent reproducibility,fast response/recovery time(70 s/79 s)under UV activation(365 nm)as compared to dark condition.Additionally,the proposed sensor exhibited augmented NH_(3)detection capability across the broad range of relative humidity(20%–80%).Such remarkable gas sensing performances of the as-prepared sensor to NH_(3)are attributed to the high surface area,enhanced functional groups,sulfur defects,UV photogenerated charge carriers,facile charge transfer in the S@g-C_(3)N_(4)QD sensing layer,which further helps to improve the gas molecules adsorption that causes the increase in conductivity,resulting in larger frequency responses.The gas sensing mechanism of S@g-C_(3)N_(4)QD/LGS SAW sensor is ascribed to the enhanced electroacoustic effect,which is supported by the correlation of resistive type and COMSOL Multiphysics simulation studies.We envisage that the present work paves a promising strategy to develop the next generation 2D g-C_(3)N_(4)based high responsive RT SAW gas sensors.