稀土纳米材料的近红外发光及敏化机制研究

In recent years, rare earth-based nanomaterials have evoked extensive attention in bioimaging and theranostic studies, and materials with near infrared emission, which show great potential in high resolution detection with long penetration depth, is just in the beginning. Efficient modulation of rare earth near infrared emissions is of great significance for extended optical applications. In this study, the composition and structure influence on the near infrared emission will be studied, and quenching routes at nanoscale will be evaluated. Energy transfer between rare earth ions which can be excited and emitted in the near infrared will be studied to establish donor-acceptor pairs in the near infrared region. In addition, organic dye, which shown large overlap via its emission and absorption of the rare earth ions, will adsorb or covalent binding to the surface of rare earth nanoparticles to set up a dye sensitized rare earth emission model. Based on the proposal of this project, the influence factors on near infrared emission of rare earth nanomaterials will be elucidated, and routed to high efficient nanomaterials will be established.

稀土上转换发光纳米材料在生物成像、医学诊疗等领域备受关注，具有近红外激发、近红外发射的纳米材料在深层组织的高分辨成像方面有更加诱人的潜力，但纳米尺度下稀土近红外发光的机理和调控途径研究尚处于起步阶段。本申请拟研究近红外光激发下，稀土纳米晶组成、结构对近红外发光的影响；研究纳米尺度下，稀土离子的猝灭浓度与尺寸的关系，揭示纳米尺度下稀土离子近红外发光的猝灭途径，提出提高稀土离子近红外发光效率的设计；研究近红外激发下，稀土离子能量传递对近红外发光的敏化方式；选择发射与稀土离子吸收匹配的近红外染料，通过静电、键联等方式拉近二者的距离，并通过共振能量转移模式实现染料敏化稀土纳米颗粒的近红外发光。通过上述研究，阐明纳米尺度下，稀土近红外发光的影响规律，建立高效敏化稀土近红外发光的途径。

近红外发光材料在光通信、安全监测以及生物医学等领域发挥了重要作用，其中基于稀土的近红外发光材料占据相关领域的主导地位。本项目针对病毒示踪、高灵敏信息检测以及生物成像需求的近红外发光材料，研究了稀土离子(Nd、Yb、Er)等掺杂的纳米晶发光与掺杂浓度、温度以及结构的关联。研究结果阐明纳米晶的表面配体(如表面吸附H2O、C-H振动等)是近红外发光猝灭的主要途径。基于此，核壳结构纳米晶主要通过将发光中心与表面猝灭中心隔离，有效提高其近红外发光强度。该结论不仅对于Nd3+、Yb3+、Er3+等离子的下转移发光适用，对于Tm3+离子的上转换近红外发光也适用。因此，核壳结构纳米晶的设计与上转换发光研究类似，仍是提高纳米晶近红外发光的主要策略；核壳结构还可以大大提高发光中心的猝灭浓度，二者的共同贡献可大大提高近红外发光强度、延长发光寿命。对于染料或量子点敏化稀土发光的研究，适合的三重态能级或暗激子能级是提高激发效率、提高二者能量传递的基础。该研究为稀土纳米晶的发光认识以及针对性地设计稀土纳米发光材料提供了基础，也将为新型稀土发光成像探针、微结构信息探测探针等提供理论支持和指导。