核-壳界面构造与量子点光学性质单分散

This proposal intends to establish the realationship between sytnehtic chemistry and optical propertie of colloidal quantum dots. The focal point of the project shall be on the interface, including both core-shell interface and nanocrystal-ligand interface. At present, monodispersity of colloidal quantum dots on their size and shape has benn more or less resolved due to the great advancements in the past 10 years or so. However, their emissive properties have not reached monodisperse yet in spite of tremendous efforts on the topic. This hinders some important technical applications of qauntum dots and prevents scienctists from establishing a basic model for quantum dots as emissive materials. Experimentally, even for the most develoeped II-VI and III-V core/shell quantum dots, their photoluminescence decay has been always found in multi-exponential kinetics. At single particle level, quantum dots from the same sample usually show different photoluminescence decay dyanmics and intermitency hehavior, which further revealed the optical inhomogenity of those so-regarded best quantum dots. Recently, this research team discovered that, CdSe/CdS core/shell nanocrystals synthesized under special conditions could be made in zinc blende phase and photoluminescnece decay of these newly discovered core/shell particles was strictly singel-exponential. This project proposes to systematically study this newly discovered system, cubic CdSe/CdS core/shell quantum dots, as the model system. Taking this new discovery as the starting point, we would develop general synthetic chemistry strategy, and understand the oustanding optical properties and the interface control. Eventaully, this work shall aim to develop a theoretical model for "optical properties monodisperse" quantum dots。

通过合理设计、系统理解核-壳量子点核壳界面以及纳米晶配体界面，本项目旨在建立新一代量子点合成与光学性质的关系。量子点材料尺寸单分散、形貌单分散已基本解决。但作为性能独特的新一代发光材料，其发光性质单分散则一直困扰着整个领域，这一方面阻碍了量子点的高科技应用，另一方面使这类材料的一些基本科学问题没有答案。实验上，即使是研究最多、发展最好的II-VI和III-V族半导体量子点，它们的荧光衰变依然呈多指数。单分子光谱技术展现出，即使是最好质量的量子点，同一样品中不同粒子发光性质实际不同：不同的闪烁特性、不同的荧光衰变动力学。本课题组集10多年经验，最近终于发现在特殊条件下制备出的一种特殊成分的量子点（立方CdSe/CdS核-壳量子点）的荧光成单指数衰变。以此为立足点，本课题组拟系统研究该类新型量子点、发展相关的合成化学、理解界面对光学性质的决定性影响，最终建立"量子点光学性质单分散"理论模型。

量子点作为性能独特的新一代发光材料，在显示、照明、生物标记等领域扮演着举足轻重的角色，其光学性质单分散是当今课题研究的重点和难点。本项目以“量子点激发态的合成控制”新思路为指导思想，确立了量子点“光学性质单分散”的基本指标，发展了荧光单指数衰减核-壳量子点“层与层”的外延生长模式，设计并合成出一系列几乎覆盖全可见光谱范围的非闪烁和抗光漂白量子点。本项目系统研究了核壳量子点的纳米晶-配体界面，在国际上率先提出量子点“熵配体”概念，通过调节合成过程中配体的动力学，证明了量子点的激发态性质与其表面性质密切相关。此外，本项目还扩展研究了量子点光化学性质、量子点发光二极管QLED和电激发单光子源，并取得突破性成果。上述研究为理解量子点激发态性质、全面实现量子点作为独特发光和光电材料提供关键的科学基础，为高性能器件的制备奠定了基础。特别是在量子点发光和光电领域，高性能量子点材料与器件将直接影响国际显示产业下一代产品的选择与发展方向。