自洁净SERS基底Ag/AgX/GO的制备及其原位光催化过程监测研究

Photocatalytic degradation of organic pollutants has become an effective method to reduce environmental pollution. However, the degradation process of pollutants on the surface of photocatalysts is not clear. It is mainly through the analysis of degradation products to deduce the degradation pathway and mechanism, but it is lack of the most direct solutions-in situ monitoring. The objectives of this program are to (a) fabricate the self-cleaning SERS substrates Ag/AgX/GO, which can be simultaneously excited the photocatalytic activity and surface-enhanced Raman scattering (SERS) activity. (b) in situ monitoring the photocatalytic process of chlorophenols, polychlorinated biphenyls, polybrominated diphenyl ethers and other typical pollutants by using SERS technology for revealing the degradation pathway. (c) use density functional theory (DFT) calculations to verify its degradation pathway and identify intermediates, and assess the intermediates toxicity by using quantitative structure activity relationship (QSAR) methods. (d) analyse the charge transfer and separation behavior on the surface of Ag/AgX/GO; examine the environmental factors in the degradation process and the resultant changes of spectra; investigate the transformation rules of Ag/AgX/GO in the environmental conditions; harmless conversion of pollutants by optimizing the reaction conditions of system. The study will be helpful in understanding the photocatalytic degradation mechanism, exploiting a new material for the detection and remediation of environmental pollutants and providing a theoretical and experimental bases.

光催化降解有机污染物已成为缓解环境污染的一种有效方法，但目前对于污染物在光催化剂表面的降解过程尚不清楚，主要通过对产物的分析来推测降解途径和机理，缺乏最直接的原位监测手段。本项目拟采用氧化石墨烯（GO）为载体，构建可同步激发光催化活性和表面增强拉曼散射（SERS）活性的Ag/AgX/GO复合结构作为自洁净基底；利用SERS技术原位监测氯酚、多氯联苯、多溴联苯醚等典型污染物的可见光催化过程，揭示降解途径；利用DFT量化计算验证其降解途径及识别中间产物，并结合QSAR方法评估上述中间产物的毒性；分析Ag/AgX/GO表面上的光生电荷的转移、分离行为，考察环境因素对降解过程的影响以及引起的光谱学变化，探索Ag/AgX/GO复合结构在环境条件下的迁移转化规律，调控反应条件使污染物定向无害化转化。项目的实施，可为推进可见光催化机理的深入理解、研究开发新型污染物检测与治理材料提供理论依据和实验示范。

污染物光催化过程的监测对于污染物的降解途径、降解进程的控制、中间产物的识别、催化剂的迁移转化乃至反应机理的深入研究具有重要意义。本项目制备了多种自洁净SERS基底（Ag/AgX/GO、Ag/AgBr/TiO2/GO、Ag/TiO2/纸纤维、碳载Au/TiO2）, 此类基底可借助光催化降解“清洗”表面吸附的化合物分子，实现SERS基底的循环使用。该类基底即具有光催化活性，又具有SERS活性。基于这点，可以利用SERS光谱来原位监测污染物分子的光催化降解过程。采用SERS技术原位监测了4-氯苯酚在基底表面光催化降解过程，结合DFT 量化计算验证，研究结果揭示4-氯苯酚在基底表面经历了去氯、成醌/酚、去苯环的降解过程，反应了中间产物对苯醌、对苯酚的生成以及成醌过程对光降解过程的影响。同时考察了碳链长度对Ag/AgBr/GO的结构与光催化活性、SERS活性的影响。该研究对于氯苯酚难降解有机污染物的光降解途径、降解进程的控制、中间产物的识别、催化机理的深入研究，以及拓展SERS 光谱的应用、发展原位SERS技术、实时检测等潜在应用均具有十分重要的理论意义和实际意义。