基于黑磷-氧化锌异质结的高灵敏NO2气体传感器制备与钝化材料辅助的工作稳定性研究

Nitrogen dioxide gas (NO2), mainly discharged from industrial production and automobile exhaust, will pose severe threat to human health and ecological environment due to its strong chemical activity and corrosivity. However, as the emission concentration of NO2 gas is decreased, conventional monitoring methods still suffer from low detection precision. In past decades, chemical gas sensors based on novel sensitive materials have attracted extensive attention, being a promising alternative strategy to monitor NO2 gas emission into atmospheric environment. Recently, a novel two-dimensional (2D) material-black phosphorous (BP) has been verified to possess inherent advantages of large specific surface area, strong molecular adsorption energy and small out-of-plane conductance in the field of chemical gas sensors. Given that semiconductor heterojunctions will be produced between BP and nanostructured metal oxides (MOs) in the presence of an intimate contact of both sensitive materials, sensitivity of gas sensors will be remarkably improved with the aid of such heterojunctions. This project intends to exploit the predictable advantage of detecting low-concentration NO2 gas owned by BP-nanostructured zinc oxide (ZnO) heterojunctions, combine with planar interdigital microelectrodes and specific thin-film deposition technology, and incorporate passivation materials into sensitive films, to prepare a novel NO2 gas sensor providing the capability of sensitive and steady detection of NO2 gas of low concentration. This project will enrich sensing mechanisms of BP based material, expand its monitoring application of ultralow exhaust emission, and lay the foundation for future study of gas sensors based on novel 2D materials.

工业生产和机动车尾气排放的NO2气体具有较高的化学活性和较强的腐蚀性，会给人们的身体健康和生态环境造成严重的危害。然而随着排放浓度的下降，传统的检测方法已无法实现精确监测。近年来，基于新型化学敏感材料的气体传感器受到了国内外的广泛关注，已成为下一代大气环境NO2监测系统最具潜力的备选方案之一。其中，新型二维材料黑磷（BP）具有比表面积大、分子吸附能高、面外电导低等独特优点，若BP与纳米金属氧化物结合形成半导体异质结，将很大程度地提高气体传感器的灵敏度。本项目利用BP-纳米ZnO异质结检测低浓度NO2气体的可预见优势，结合平面微电极叉指器件和薄膜工艺，并在敏感薄膜中引入钝化材料，研制出基于BP-ZnO复合薄膜的新型NO2气体传感器，实现对低浓度NO2气体的高灵敏、稳定探测。本项目将丰富BP基复合材料的气敏机理，拓展BP材料在超低排放监测领域的应用，为新型二维材料气体传感器的研究奠定基础。

本项目针对NO2气体超低排放的监测提出采用基于黑磷 (BP)-氧化锌 (ZnO)异质结薄膜的电阻式气体传感器。BP虽然比表面积大、吸附位多、室温导电性强，利于低浓度气体的室温探测 (20 oC)，但易受湿度影响而出现物理降解进而造成器件的性能退化。为了解决上述问题，作者首先采用疏水的n型聚合物联苄吡啶 (BV) 钝化BP纳米片，室温下探测强氧化性的ppb级别NO2气体，器件的响应几乎未衰减，同时器件的恢复特性和抗湿特性得到大幅加强；之后，作者又采用BP-ZnO纳米线复合薄膜结构，探测ppb级NO2气体，不仅增强了器件的响应，同时还大幅加快了响应速度，改善了器件的选择性和抗湿特性。设计基于ZnO的疏水特性以及比表面积大、吸附位多的特点。同时，二维BP纳米片和一维ZnO的有效结合，为生成多孔的复合薄膜创造条件。此外，作者还制备了石墨烯基复合材料 (rGO-Cu2O)的气体传感器，研究结果发现，通过施加不同的工作温度或优化薄膜组分形貌，传感器可分别对NO2、NH3和H2S气体选择性响应更好。而且，作者研究发现采用UV光辐照的方式能有效改进气体传感器室温工作下的恢复特性和灵敏度。对于纯金属氧化物气体传感器，湿度往往会大幅降低传感器的灵敏度，而对于弱极性的NH3和甲醛气体，作者分别采用PANI-WS2和rGO/N-MXene/TiO2复合薄膜并在湿度的触发下成功实现高灵敏和可恢复的探测。本项目研究了多种新型二维材料的气敏探测性能，并提出了湿度环境下改善气体传感器工作稳定性的方案，同时探索了湿度对传感器性能的影响及内在机理，为未来低功率、小型化的新型气体传感器的设计提供数据和理论支撑。