表面配体诱导金纳米团簇荧光增强的原位XAFS研究

Fluorescent gold nanoclusters (Au NCs) possess promising applications in biology, medicine and environmental science for their ultra-small size, good biocompatibility and excellent photostability. However, the low fluorescence quantum yields and uncontrolled fluorescence wavelength become the huge challenges for practical use. To solve these problems, it is essential to understand the underlying mechanisms of fluorescence variations at the atomic/electronic level. The synchrotron radiation XAFS is useful to understand the relationship of structure and fluorescence properties since it could offer three dimensional structure information of atoms. In this project, based on the in situ synchrotron radiation XAFS/UV-vis absorption spectroscopy and time-dependent fluorescence spectrometry, we aim to perform detailed kinetics studies on ligands-induced etching synthesis and ligands-induced fluorescence enhancement processes of Au NCs. Combined with theoretical calculations on the geometrical configuration, electronic structures of the clusters during these chemical reaction processes, it is hopeful to find out the critical factor affecting fluorescence properties. The execution of this project is promising to reveal at the atomic/molecular level the the fluorescence enhancement mechanisms of gold nanoclusters. It will also be hopeful to provide substantial theoretical and experimental basis for the synthesis of fluorescence nanomaterials with high quantum yields and development their applications in biology, medicine and environmental science.

荧光金纳米团簇因其尺寸较小、生物相容性高等独特优势在生物、医学等领域有广泛应用前景，却面临着荧光量子产率低及发光波长可控性差等重大挑战。表面配体修饰在团簇发光及荧光增强方面起着至关重要的作用，从分子、原子甚至电子结构层面上明确配体诱导荧光增强的机制是亟待研究的课题。同步辐射原位XAFS技术可以提供团簇原子三维结构排布的敏感信息，是深入理解团簇结构与荧光性能关系的有效方法。本项目拟利用原位XAFS技术，联合原位紫外-可见吸收谱、原位荧光谱、质谱等方法，研究金纳米团簇的配体刻蚀生长动力学演变规律和配体诱导荧光增强动力学行为，获得团簇原子组成、结构与荧光性能之间的关系，再结合对团簇几何构型、电子结构的理论计算，从原子、分子水平深入了解影响荧光性能的关键因素，阐明表面配体诱导金纳米团簇的荧光增强机制，为设计合成高量子产率的荧光贵金属材料及拓展其在生物、医学、环境科学等领域的应用提供实验和理论基础。

荧光金纳米团簇因其尺寸小、光稳定性好、毒性低、生物兼容性高等独特优势在生物医学领域有广阔的应用前景，却面临量子产率低及荧光发光机制不清楚等重大挑战。针对这些挑战，本项目通过优化表面配体及合成条件，成功构建了不同的合成策略制备了不同种类的具有高量子产率的荧光金纳米团簇，利用多种表征手段对合成的新产物进行了详细的表征，确认了产物的组成及结构特征。优化反应条件，构建了不同体系的荧光增强动力学过程，分别为表面配体辅助原位生长诱导荧光增强动力学过程、表面配体刻蚀诱导荧光增强动力学过程及表面配体交换诱导荧光增强动力学过程。利用时间分辨的X射线吸收谱、紫外-可见吸收谱、荧光光谱、动态光散射谱等多种原位光谱技术对荧光增长动力学过程进行了详细的光谱追踪，构建不同体系中随时间分辨的荧光性能与原子电子结构变化关系，提出金纳米团簇的发光机理及荧光增强的内在机制。此外，所合成的不同种类产物成功应用于细胞内的生物硫醇、重金属及温度的传感与成像。本研究工作制备出多种高量子产率的荧光金团簇解决了目前金属团簇面临的量子产率普遍偏低的重大科学问题，为未来金属团簇在分析检测、生物医药、光电器件等领域的研究提供了更广阔的空间。此外，该研究揭示了金纳米团簇荧光发光的内在机理及荧光增强机制，在一定程度上解决了目前金属纳米团簇领域发光机制不清楚、荧光增强机理存在争议的关键科学问题，为未来合成高量子产率的金属纳米团簇提供了有力的理论依据和指导。