含羧基功能化极性侧基聚苯胺修饰CdS量子点界面作用及可见光范围光活性

Semiconductor capped polymers nanocomposites have been widely studied due to their wide range of possible applications. The conductive polymer-quantum dots(QDs) inorganic-organic hybrid composites having dual properties, those of the QD and the conductive polymers, are expected to be promising materials for photovoltaic material. To achieve high power conversion efficiency, a new preparation method will be adopted by hybridizing quantum dots with the carboxyl-modified polyaniline. In this project, N-substituted carboxyl polyaniline (NPANI) would be prepared by the oxidative polymerization of N-phenylglycine as monomer using ammonium peroxydisulfate in 1M HCl solution. The CdS nanostructure with various diameter can be formed by controlling the molar ratio of CdCl2 to Na2S in methanol solution including the N-substituted carboxyl polyaniline as a surfactant. These structures of CdS/NPANI nanocomposites will be characterized by the spectra of FT-IR, Raman, UV-vis, TEM and XRD, and their interfacial structures will be also investigated by comparing with the pure CdS and blending CdS/NPANI. The high separation and transferring efficiency of charge carriers is mainly related to the interface property of CdS/ NPANI nanocomposite, so, it is a crucial to determine the interfacial factor between CdS and NPANI. On the basis of the result of the high efficiency of charge separation induced by the hybrid effect of NPANI and CdS, A possible mechanism of the charge separation and photocatalytic process over the NPANI-CdS photoactive material is proposed. In order to understand the efficiency of energy transfer of CdS, the fluorescent property of CdS with -COOH will be studied in comparison with the grafted CdS with mercaptoethylamine. These studies will demonstrate that CdS/NPANI nanocomposite can be used as an efficient photoactive material to degrade organic pollutants or bioimage applications in the future.

采用羧基功能化极性侧基聚苯胺修饰量子点目的在于改善聚合物与量子点之间的界面结构，以达到量子点光产激子的有效分离。本项目采用N-苯基甘氨酸为单体，利用化学氧化法制备溶解性增强的N-取代羧基聚苯胺（NPANI）。利用羧基功能化聚合物为模板和前驱体，通过控制CdCl2和Na2S摩尔比例，制备不同尺寸CdS。采用与简单机械混合的比较，研究含功能化羧基聚苯胺与CdS量子点界面的作用，探索CdS和NPANI之间的界面结构与电子-空穴分离及传输效率的关系，结合CdS中的价带和导带以及NPANI聚合物的最高分子被占轨道（HOMO）和最低分子未占轨道（LUMO），提出CdS/NPANI纳米复合电荷传输机理。通过对复合材料荧光发射规律的研究，探索CdS/NPAN杂化复合物光吸收效率及能量转移效率，为CdS/NPANI纳米复合材料应用于太阳能电池提供理论指导，对于拓展该光学活性材料具有非常重要的意义。

本项目拟采用N-取代羧酸改性聚苯胺，利用羧基功能化共轭共聚物为模板和前躯体，在聚合物基质中原位生长半导体催化剂，原位制备有机无机杂化半导体纳米复合材料。主要研究内容从以下三个方面的展开：.1、利用N-取代羧酸聚苯胺镉的前驱体，制备具有均匀分散的量子点的CdS量子点/N-取代羧基聚苯胺复合催化剂，并对其光催化活性作了进一步的探索；羧基作为反应和保护基团，对CdS的稳定起着非常重要的作用，羧基和CdS之间产生的复合效益使得催化剂具有优越的光电转移效率和抗光腐蚀的性能。结构分析表明CdS量子点除了与N结合之外，还与羧基结合，TEM和XRD也充分地证明聚苯胺链上的羧基完全能够阻止CdS半导体催化剂的光腐蚀。.2、利用石墨烯的结构特点和优良的导电性能，采用N-取代羧酸聚苯胺接枝氧化石墨烯为共轭材料，再形成镉的前驱体，最后制备CdS量子点/N-取代羧基聚苯胺/还原氧化石墨烯复合光催化剂，并对其光催化性能也作了进一步的探索；将硫化镉量子点、石墨烯、N-取代羧酸聚苯胺三组分有机地结合在一起，能够产生优良的协同效应，改善了单一材料易团聚、易腐蚀、电子空穴易复合、导电性不足等缺陷，且相较于其他类CdS光催化剂，其具有更好的溶解性能、光电转换性能和界面稳定性。.3、同样以N-取代羧基聚苯胺为导电共轭材料，将CdS半导体催化剂改为具有相类似带隙的Ag3PO4作为催化剂，并对其光催化性能作了进一步的探索，在接枝过程中，一些银离子被还原成银单质，最终得到的复合光催化剂为 NPAN/Ag/Ag3PO4复合材料。通过FT-IR、XPS、PL、TEM、TG、PL等检测手段对材料的结构、形貌等进行分析，并对其光催化性能进行研究，其中，以1/10 NPAN/Ag/Ag3PO4复合材料对RhB染料的降解效率最高，经过五次循环后其光催化降解RhB染料效率仍能保持在93.6%，而单纯磷酸银的降解效率却由83.2%下降至54.12%；另外，NPAN的引入可以加速光生电子空穴的分离，增强复合材料的光催化效果及循环稳定性，在光催化过程中复合材料具有高催化降解效率能力的主要来源是光生空穴与O2·-的强氧化性。不同复合材料修饰电极的光电化学性质表明，结果表明NPAN的引入可以改善复合材料的光电转移、界面距离和光电化学的稳定性。