基于能量团簇的稀土掺杂上转换发光理论及其应用研究

The applications of lanthanide-doped upconversion nanocrystals in biological imaging, photovoltaics and therapeutics have fuelled a growing demand for rational control over the emission profiles of the nanocrystals. A common strategy for tuning upconversion luminescence is to control the doping concentration of lanthanide ions. However, the phenomenon of concentration quenching of the excited state at high doping levels poses a significant constraint. Recently, we have discovered a new class of upconversion nanocrystals adopting an orthorhombic crystallographic structure in which the lanthanide ions are distributed in arrays of tetrad clusters. Importantly, this unique arrangement enables the preservation of excitation energy within the sublattice domain and effectively minimizes the migration of excitation energy to defects, even in stoichiometric compounds with a high sensitier content. This proposed project is aimed to conduct investigations on upconversion emission prpoperties of lanthanide ions in aforementioned host material. We will closely examine the effects lead by changes of different parameters, such as host matrix, combination of lanthanide dopant, dopant concentration, particle size and core-shell structure. Furthermore, we will functionalize the upconversion nanoparticles which possess high efficiency for the application of dual model MRI, and explore the coupling between photonic and magnetic properties. This will lay down the foundation to develop enhanced multiphoton upconversion for the application in nanomedicine, which is extremely useful for both theoretic and applied research.

稀土掺杂上转换纳米颗粒发射光谱的有效调控使其在生物成像、光电转换和光动力学治疗领域有着广泛应用。目前，通过改变稀土离子掺杂浓度是调控纳米颗粒发射光谱的主要途径，而掺杂浓度过高会引发浓度淬灭，使上转换效率大大受限。最近，我们发现一类适用于制备稀土掺杂上转换纳米颗粒的基质材料。这类基质材料属于正交晶系，且含有四个稀土离子为一组的子晶格。该独特的晶格结构将激发能量限制在其子晶格内，形成能量团簇，大大降低能量传递到缺陷的可能性，有效地避免了浓度淬灭。本课题旨在研究基于上述正交相基质材料制备的纳米颗粒的上转换发光特性，包括掺杂离子组合、掺杂浓度、配体修饰、颗粒尺寸以及核壳结构对上转换发光光谱和效率的影响，并对上述纳米颗粒进行磁相关的功能化修饰，探索其间光磁耦合效应的物理机制，有效地将其应用于生物检测和生物医学成像。这将有助于奠定研发多功能高效上转换纳米颗的基础，具有极高的理论研究和实际应用价值。

稀土掺杂上转换纳米颗粒发射光谱的有效调控使其在生物成像、光电转换和光动力学治疗领域有着广泛应用。本项目采用热分解方法，在XRD、SEM、TEM和PL等表征技术的支撑下，成功实现了稀土掺杂纳米颗粒结构的调控。随后，通过纳米颗粒结构的设计，完成了纳米颗粒发光效率、发光颜色、激发波长和发光离子寿命方面的调控。在此基础上，利用优化上转换纳米颗粒的发光效率、发光颜色、激发波长和发光离子寿命等参数，实现了它们在生物分子检测、医学成像、信息存储和编码等领域的应用。相关研究成果对稀土纳米颗粒光学及其应用技术的发展具有积极的推动作用，也将有助于奠定研发多功能高效上转换纳米颗的基础，具有极高的理论研究和实际应用价值。此外，我们对基于稀土离子4f-5d跃迁的无机发光材料的光学性质进行了文献综述工作。为新进入该领域的科研人员提供了一个快速通道，能使其对稀土掺杂无机材料的发光机理有初步理解，为后期的科研工作提供坚实的理论基础。