Design,Preparation And Sensitive Property Of Flexible Ammonia Sensor

Ammonia?NH₃?is a kind of toxic gas which exist in industrial and agricultural fields.Therefore,it is of great significance to develop an NH₃ gas sensor that can operate at room temperature and atmospheric humidity with high sensitivity and low detection limit.Combined with the trend of the sensor in the direction of flexibility and light weight,in this paper,conductive polymer polyaniline?PANI?,new two-dimensional material MXenes?Ti₃C₂T_x?and metal semiconductor oxide titanium dioxide?TiO₂?were used to prepare flexible NH₃ gas sensors with excellent performance at room temperature and atmospheric humidity by in-situ polymerization self-assembly technology and spray method.The sensor sensitivity mechanism model was established by combining sensitive film characterization and sensor gas sensitivity test.The main contents of this paper are summarized as follows:1.The PANI/Ti₃C₂T_x flexible gas sensor was designed and fabricated by in-situ polymerization self-assembly process,and its sensitivity to NH₃ was studied.The SEM results showed that the PANI/Ti₃C₂T_x composite film has larger specific surface area,lamellar structure and rough surface,which can provide a large number of adsorption sites and beneficial to the adsorption of NH₃ gas molecules,so that the sensor obtains excellent gas sensitivity.XRD characterization confirmed the composite structure of PANI/Ti₃C₂T_x,and XPS characterization further determined the valence state and chemical bond composition of the composite element.The gas sensing properties of pure PANI and PANI/Ti₃C₂T_x gas sensors for NH₃ were investigated at room temperature.The results show that the composite film has higher sensitivity and exhibits good repeatability,selectivity,flexibility and long-term stability.The gas-sensitive response of the composite film sensor to NH₃ gas under different humidity was simulated.The results show that composite film sensor has good repetitive response characteristics under different humidity.Based on the characterization and test results,the sensitivity mechanism model of PANI/Ti₃C₂T_x composite film to NH₃ was established,and the influence mechanism of humidity on the gas sensing properties of the composite film was explained.2.A flexible TiO₂/Ti₃C₂T_x NH₃ gas sensor which can be used in room temperature and atmospheric humidity environment was prepared by spray method.SEM characterization showed that the rough surface of TiO₂/Ti₃C₂T_x which provided a large number of adsorption sites.The elemental composition of the composite films was confirmed by XRD and XPS characterization.NH₃ gas sensing properties of Ti₃C₂T_x thin films and Ti₃C₂T_x composite thin films were tested at room temperature and atmospheric humidity.Compared with pure Ti₃C₂T_x film,the composite film of TiO₂/Ti₃C₂T_x has higher sensitivity,lower baseline drift and has good repeatability,selectivity,flexibility and long-term stability.The effect of humidity on gas sensing performance of the composite film gas sensor was studied.The results showed that the ammonia sensing response of the composite film increases firstly and then decreases with the increase of humidity.Based on the characterization and gas sensitivity test,a model of the sensing mechanism of TiO₂/Ti₃C₂T_x composite film to NH₃ gas is established.It is considered that the p-n heterojunction is formed by the close contact between p-type Ti₃C₂T_x and n-type TiO₂,which resulting in more electron transfer and transmission at the interface of the heterojunction and improving the gas sensitivity of the thin film gas sensor.