Silicon-based Gas Sensor Synergistically Modified By Noble Metal And Conducting Polymer

The use of high-performance gas sensors to detect trace specific biomarker gases in exhaled breath gases enables non-invasive rapid diagnosis of a wide range of diseases.Therefore,new high-performance gas sensor for breath diagnostic applications are important in the field of health care.The one-dimensional silicon nanowire material formed by silicon wafer is sensitive to gas at room temperature,and its specific surface area is high.The preparation process is compatible with modern semiconductor processes,and silicon nanowire has shown good application prospects in the field of gas sensors.However,the performance of silicon nanowire-based gas sensors is obviously affected by environmental humidity.It is difficult to achieve sensitive detection of ppb-class rare gases under high humidity conditions.In this paper,the surface modification of silicon nanowires is used to improve the gas sensing performance in high humidity environment.The core-shell nanowire structure modified by polypyrrole film-noble metal silver nanoparticles is prepared in one step by vapor phase polymerization.The co-modulation of noble metal and organic/inorganic heterogeneous effect achieves a significant improvement in the NH₃ sensing performance of the silicon-based sensing material in the high-humidity environment.Firstly,silicon nanowires(SiNWs),silver nanoparticle-modified silicon nanowires(Ag@SiNWs)and polypyrrole film-modified silicon nanowires(PPy@SiNWs)were prepared by dual metal-assisted chemical etching methods and vapor phase polymerization.Then the sensing tests were comparatively studied at room temperature and 80%relative humidity,and found that the single modification silver nanoparticles or polypyrrole film is difficult to meet the requirements in exhaled breath detection.Secondly,one-step preparation of polypyrrole film-silver nanoparticle synergistically modified structure(Ag-PPy@SiNWs)was realized on the surface of silicon nanowires by pyrrole vapor phase polymerization using silver nitrate as oxidant.Gas sensitivity test results show that Ag-PPy@SiNWs sensor has a78%-208%higher response to 6 ppm NH₃ gas than unmodified or single-modified silicon nanowires at 80%relative humidity.At the same time,Ag-PPy@SiNWs sensors also feature fast response,good stability,repeatability and good selectivity for NH₃.Finally,the NH₃ sensitive mechanism of Ag-PPy@SiNWs was systematically expounded by establishing a resistance model.The humidity sensitivity tests combined with the swelling effect of organic polymer,the coordination relationship between silver nanoparticles and conductive polymer and the unique hydrophobicity of noble metal explained the effectiveness of silver nanoparticle modification to improve the anti-humidity interference characteristics of silicon nanowires.In addition,the W₁₈O₄₉ nanorods were prepared by solvothermal method,and the co-modification process was applied to W₁₈O₄₉ nanorods to verify the universality of the process for improving the gas sensitivity of semiconductor gas sensing materials under high humidity.