多酸在二氧化钛纳米晶表面的自组装

Self-assembly of anions on surfaces of solid materials is an important technique for surface modification and functionalization, catalysis, electron-transfer, nano-analysis, electrochemistry. Succesful studies on self-assembly processes used to involve large and planar surfaces as well as strong adsorbants. However, research based on direct-imaging of highly-curved nanoparticle surfaces is extremely difficult and has rarely been carried out. In this proposal, we will focus on the self-assembly of polyoxometalate anions on TiO2 nanoparticle surfaces. A series of polyoxometalates will be used to assemble to varies surfaces of TiO2 nanocrystals. Cryo-TEM will be used as the main technique to image the self-assembled structures, and detailed structural information is expected to be obtained, including structures of 2D unit cells, orientations of polyoxometalates, and bonding. Quantitative thermodynamic and kinetic analysis will also be carried out. These detailed information will be used to quantitively evaluate the structural roles of cations, anions, and TiO2 lattice, etc. Our study may supply direct structure-function relationships for anchoring and dynamics of anions on nanostructures. It will also be useful in guiding the syntheses of polyoxomtalate/nanocrystal composites, as well as in decoration of nanometarial surfaces with anionic species.

阴离子在固体材料表面的自组装，是材料表面修饰和功能化、催化、电荷转移、纳米检测、电化学等领域的重要内容。以往成功的阴离子自组装的基本前提是必须使用大尺寸晶面和强吸附的阴离子。在极小尺寸（d< 10 nm）和高度弯曲的纳米晶表面上的自组装较少涉及，尤其缺少成像观察。本项目我们将使用并拓展以往建立的低温透射电镜成像和热力学分析方法，以弱吸附的的多酸阴离子在TiO2纳米晶表面的自组装为重点研究对象，获取多酸在纳米晶表面形成单分子层的二维排列、分子构象、多酸-TiO2成键等结构信息，定量获取自组装的热力学参数，找到多酸在各种晶面及高曲率、不规则表面上自组装过程和结构的决定因素。本项目的研究成果能为阴离子对半导体纳米晶催化的调控行为提供直接的构-效关系，也能为创造功能化的阴离子/纳米晶表面的自组装结构、以及指导纳米材料的表面阴离子修饰提供依据。

离子簇在二氧化钛材料表面的单分子层自组装，是二氧化钛表面修饰和功能化、光催化、电荷转移、纳米检测、电化学等领域的重要内容。本项目的研究中，我们首先通过全新的合成策略，即在溶胶凝胶法合成二氧化钛纳米晶过程中捕获中间体，成功获得了一系列新型的钛氧团簇，如{Ti3}、{Ti4}a、{Ti4}b、{Ti6}、{Ti12}、{Ti18}、{Ti22}等分子，这些分子跟TiO2的结构具有密切的关系。一方面，以这些分子为模型，围绕理解TiO2成核-生长机理和光催化相关的构-效关系，我们开展了详细的研究工作；另一方面，以这些分子为基础，我们构建了氧化钛量子点修饰纳米颗粒的方法，并对复合材料的结构和性质做了细致研究；我们在TiO2用于光催化C-C偶联研究中也取得了重要进展。这些研究，对二氧化钛纳米材料的合成机理、结构调控和光催化应用具有重要的意义。