离子导电型双网络水凝胶的气敏机理及其自修复、可拉伸器件的研究

Flexible gas sensors have given rise to many emerging applications in wearable electronics, environmental monitoring, safety, etc. Although the NO2 gas sensors with some flexibility can be fabricated by integrating existing NO2 gas sensing material on flexible substrates, it is challenging to realize both the stretchability and self-healing ability. In this work, ionic conductive hydrogel is exploited to fabricate room-temperature NO2 gas sensors, in which both the gas sensing material and devices are flexible, highly stretchable, self-healing and transparent. First, we will choose the polyacrylamide/carrageenan double network hydrogel that contains abundant -OH、SO3− and -NH2 functional groups as gas sensing material to investigate the important role of these surface functional groups played in enhancing the NO2 sensing performance. Then, the interaction between ionic hydrogel and NO2 molecules is enhanced by programming the material composition, such as the solvent (Introducing glycerol or ethylene glycol), electrolyte (Introducing NaHSO3), etc. in the hydrogel. Finally, the water-glycerol or water-ethylene glycol bi-solvent system not only increases the stability of gas sensor by preventing the evaporation of water molecules at high temperature and the freeze of water at extremely low temperature, but also increases the sensitivity of NO2 detection with the assistance of hydrogen bond. The project aims to reveal the mechanisms of gas adsorption, reaction and charge transport in ionic conductive hydrogel, and acquire the techniques of fabricating flexible, highly stretchable, transparent and self-healing NO2 gas sensors, and finally develop effective strategies to optimize the gas sensing performance.

柔性气体传感器在可穿戴式电子和环境安全等领域有广阔的应用前景。虽然现有的NO2气敏材料可通过整合柔性基底使传感器获得一定的柔性，但很难实现可拉伸性和自修复性。本项目利用离子导电型水凝胶制备常温NO2气体传感器,实现材料本身和器件的柔性、高度可拉伸性、自修复且透明性。首先，选择富含-OH、SO3−和-NH2等功能性基团的聚丙烯酰胺/卡拉胶双网络水凝胶作为气敏材料，研究功能性基团在气体检测中的重要作用；然后，通过调控溶剂(引入丙三醇/乙二醇)和电解质盐(引入NaHSO3)等材料成分，增强水凝胶和NO2气体的之间的相互作用；再利用水-丙三醇/乙二醇二元溶剂解决水凝胶里面的水分易蒸发和低温易结冰的问题，提高器件稳定性，并通过氢键作用提高NO2检测的灵敏度。本项目旨在揭示离子导电型水凝胶的气体吸附、反应机理和电荷传输机制，获得具有可拉伸、透明和自修复的NO2气体传感器的制备方法和性能优化技术。

柔性可拉伸的NO2气体传感器在可穿戴电子、健康医疗、环境监测等领域有着广阔的应用前景。本项目首次观测到离子导电水凝胶对NO2气体的电学响应，率先开发出基于离子导电水凝胶的本征可拉伸、自修复、透明的室温气敏材料，为制备新型穿戴式气体传感器提供了新的素材。本项目以聚丙烯酰胺/卡拉胶双网络水凝胶为模型研究对象，对其气敏特性、气体传感机理、稳定性以及性能的关键影响因素等开展了系统性的研究，取得了以下主要成果：.1）利用了溶液法制备出最大应变为1330%的可拉伸、自修复、透明的离子导电型双网络水凝胶，实现了传感器在大应变（例如100%拉伸）和切断并自愈合后的正常工作能力；发展简单、有效的溶剂/电解质盐置换法将吸湿性的小分子多元醇和氯化钙等盐引入到水凝胶中，同时提升了水凝胶的保湿性、抗冻性、和气敏灵敏度，提高了传感器的稳定性。.2）通过调控水凝胶的组分（溶剂和电解质盐等）优化了传感器的性能，实现了在宽温度范围内（包括常温、零下温度等）和湿度范围内的高性能NO2气体探测；例如，在常温下灵敏度达到119.9%/ppm，对0.8ppm NO2的响应大于75%，检测极限低至0.086ppb；通过调控水凝胶的电导率有效抑制了传感器对NH3、VOCs等干扰气体的响应，使其获得了良好的选择性。.3）通过实验探索、理论分析与模拟计算相结合的方式，初步明晰离子导电水凝胶的气敏机理，提出了NO2气体在水凝胶-电极界面上的氧化还原反应对其气敏响应的关键作用。..本项目为深入理解离子导电水凝胶的气敏机理和未来设计高性能的水凝胶基气体传感器提供了一定的理论和技术支撑；并为制备下一代可拉伸、可穿戴、自修复的常温NO2气体传感器提供了一类新的素材。项目的研究成果在Small, Mater.Horiz., ACS Appl. Mater. Interfaces等知名期刊发表论文20多篇（其中第一标注17篇，中科院一区论文19篇, ESI前1%高被引论文8篇）；申请中国发明专利10项（其中3项已授权）。