Preparation And Sensing Performance Of Gas Sensor Based On Layered Double Hydroxide

Due to the urgent need of environmental protection and human health,safe and reliable gas detection has always been an important research topic.As a matter of fact,the development of gas sensors is progressing with the actual demand.Early gas sensors were mainly used to detect toxic and harmful gases or flammable and explosive gases in the air,so as to ensure human health and safety as much as possible.The continuous development of ecological environment and human needs has promoted the diversification of gas sensors.In addition,the application direction of gas sensors has gradually shifted from a single high concentration environmental detection to other fields.Such as food safety,medical diagnosis and alcohol drive testing that require lower limit of detection.In view of the current research and development trend of gas sensors,layered dobule hydroxide-based gas sensors with high sensitivity,fast response-recovery characterisitic and low limit of detection have been developed in this paper.They can be used for the selective detection of low concentration ethanol and ammonia at room temperature,respectively.Firstly,the controllable preparation of layered double hydroxides with three-dimensional floral layered hierarchical structure has been achieved by hydrothermal method.Then,the layered double hydroxides were modified from two aspects.On the one hand,the surface modification of layered double hydroxides by silver nanoparticles was realized by glucose reduction method.By adjusting the coverage of silver nanoparticles,the composite structure with optimum silver coverage was obtained.The experimental results show that the layered double hydroxides gas sensors with three-dimensional flower-like layered hierarchical structure have fast dynamic response to ethanol gas at room temperature.The response of the composite structure sensor modified by silver nanoparticles to 5 ~200 ppm ethanol gas is about twice as high as that of pure layered double hydroxide sensor at room temperature.The response time and recovery time are less than 10 s and 50 s respectively.On the other hand,polyaniline/layered double hydroxide composite structure gas sensors were prepared by in-situ chemical oxidation polymerization.The experimental results show that the response value of the composite structure gas sensor to 50 ppm ammonia is 20 times and 2 times higherthan that of pure layered double hydroxide and polyaniline with a single component at room temperature.The limit of detection reaches 200 ppb.The composite sensors exhibit good long-term stability and transient response(response time is less than 3s).In addition,the gas sensing mechanism of the two kinds of composite sensors was explained in detail by constructing the corresponding gas sensing model in this paper.