基于稀土上转换发光纳米晶的二元自组装体系的协同光学性质研究

Rare earth upconversion luminescent materials can convert infrared light to visible or ultraviolet light based on multiphoton process, and they find applications in many fields such as lighting and display, photoelectric conversion, biological imaging and therapy. However, their low upconversion luminescent efficiency greatly limits their applications. Based on our previous work, we propose to construct the binary nanocrystal self-assembly system based on rare earth upconversion luminescent nanocrystals and noble metal nanocrystals, select the appropriate building blocks based on the composition, crystal structure, size, morphology and optical properties of these two distinct nanocrystals, explore the efficient route to adjust the type and length of nanocrystal surface ligands, uncover the factors determining nanocrystal assembly process, and then prepare a series of binary nanocrystal superlattices with different symmetries and interparticle spacing. Furthermore, we will utilize the high-pressure technique integrated with multiple optical characterizations to investigate the quantitative relationship between the collective optical properties of binary nanocrystal assemblies and their superstructure and interparticle spacing, and finally greatly improve the quantum efficiency of rare earth upconversion luminescent nanocrystals.

稀土上转换发光材料可以通过多光子过程将近红外光转换成可见光和紫外光，被应用于照明与显示、光电转换、生物成像与治疗等多个方面，但是目前的稀土上转换发光材料存在的问题是发光效率太低，极大地限制其应用。本项目拟在已有工作基础上，设计稀土上转换发光纳米晶与贵金属纳米晶组建二元纳米晶自组装体系，从两种纳米晶的组成、结构、尺寸、形貌及其光学性质入手选择合适的组装基元，同时探索纳米晶表面配体置换的有效途径来实现表面配体种类和长度的多样性，进而揭示胶体溶液自组装方法制备二元纳米晶自组装结构的影响因素，从而制备一系列具有不同对称性和结构参数的二元纳米晶超晶格。本项目旨在利用整合多种光学表征手段于一体的高压实验与测试技术，明确二元纳米晶超晶格协同光学性质与其组装结构和纳米晶间距两个方面的定量关系，最终实现稀土上转换发光纳米晶量子效率的有效提高。

本项目通过设计基于稀土上转换发光纳米晶与贵金属纳米晶的二元纳米晶自组装体系，综合利用胶体纳米晶的可控合成、溶液自组装的简便易行以及高压技术的独特性等多种优势，开展深入研究，致力于提高稀土上转换发光纳米晶的量子效率。主要包括1）从稀土上转换发光纳米晶与贵金属纳米晶的可控合成和光学性质调控入手，实现发光效率高且发光颜色可调的多种尺寸的单分散纳米晶的可控制备；2）针对纳米晶组装单元开展表面修饰，基于表面配体置换实现纳米晶的溶解性和自组装行为的调节；3）开展二元纳米晶超晶格的制备与组装结构的调控，制备出具有多种结构对称性和结构参数的高质量二元纳米晶超晶格；4）结合高压光学等测试手段，揭示出二元纳米晶超晶格的协同光学性质与其组装结构的内在关系，有效提高稀土上转换纳米晶的发光效率。