Design And Performance Of Light-assisted Gas Sensor Based On Localized Surface Plasmon Resonance

In recent years,highly sensitive and selective detection towards trace amounts of nitrogen dioxide(NO₂)in complex outdoor air environment has been urgently needed for the guarantee of human health and safety.The effective combination of heterostructure and light illumination has been demonstrated as an effective approach to realize high-performance gas sensors.However,the influence of light illumination on gas sensing properties of heterostructure materials is not yet clear.In this paper,the influence of building heterostructure on the gas-sensing performance of MoS₂ have been studied scientifically.On this basis,the light-assisted gas detection mode is adopted to further improve the gas sensing-performance of heterostructure composite gas sensor.The absorption of MoS₂to visible light can be improved by introducing the local surface plasmon resonance(LSPR)of Au nanoparticles,which can solve the disadvantage of small absorption cross section of MoS₂.Gas sensors are fabricated to investigate the effect of the combination of heterostructure and illumination on gas-sensing performance of gas sensors.The main research contents are as follows:1.Uniform and pure MoS₂ nanosheets and Au NPs-modified MoS₂(Au-MoS₂)composites are synthesized by simple hydrothermal method.Through a series of characterization,the composition,surface morphology and optical properties of the materials are qualitatively and quantitatively analyzed.In addition,the enhancement of gas sensing performance caused by the modification of Au NPs at room temperature is investigate by fabricating MoS₂ and Au-MoS₂ materials into gas sensors.Compared with pure MoS₂ gas sensor,the response value of Au-MoS₂ gas sensor is significantly improved throughout the whole test range,and Au-MoS₂gas sensor is of better selectivity compared with pure MoS₂ gas sensor at room temperature.The response value of Au-MoS₂ gas sensor is about 11 times higher than that of MoS₂ gas sensor at 50 ppm NO₂ concentration.The recovery behavior is greatly improved,and the resistance of Au-MoS₂ gas sensor can return completely with almost no drift.Compared with pure MoS₂ gas sensor,the shift of response value of Au-MoS₂ gas sensor is reduced to 23.78%.The results show that the modification of Au NPs can effectively improve the response value and recovery behavior of MoS₂ gas sensor.The enhanced gas sensing performances of Au-MoS₂,which are superior to that of pure MoS₂,are ascribe to the following three factors.(1).Au NPs occupy most of the high-energy defects on MoS₂ surface and high NO₂ molecular activity,so Au NPs can be used as effective receptors for the adsorption of NO₂,so as to improve the response capacity of MoS₂ based gas sensor.(2).Au NPs act as an active catalyst with specific catalytic properties,which enhances the diffusion and transfer rate of adsorbed species from an active site to inactive sites.(3).The formation of heterojunctions can provide many electron transfer channels,so that more electrons can be transferred between MoS₂ and Au,which further improves the response value of MoS₂ gas sensor.2.A visible-light-assisted Au-MoS₂ gas sensor with low detection limit and robust anti-humidity ability is developed through introducing LSPR effect of Au NPs.With the assistance in visible light of 530 nm,the gas sensor can achieve limit detection of NO₂ as low as 10 ppb without operating temperature along with robust anti-humidity ability.The optical simulation and experimental results show that the modification of MoS₂ by optimized size(30 nm)Au NPs combined with matching light-assisted(530 nm)gas detection mode can make MoS₂ fully absorb visible light and effectively improve extinction cross section by taking full advantage of LSPR effect,which is the main reason for enhanced performance of the gas sensor.This work provides theoretical and experimental guidance for gas sensors to effectively enhance the ability of gas detection by means of light-assisted mode at room temperature,which opens up a new approach for the design of high-performance sensors for trace gas detection.