稀土离子掺杂单颗粒纳米晶偏振荧光机理及生物应用的研究

The polarized luminescence of lanthanide ions doped nanoparticles has the potential applications in biomedicine, data storage, three-dimensional display, etc., benefiting from its unique optical properties. However, the mechanism for polarized luminescence is still unclear for its diversity and complexity. Our previous research shows the polarized luminescence is related to local crystal field and crystal orientations. Herein, we propose the hypothesis that the crystal field and energy levels of lanthanide ions modulate the polarized luminescence. In this proposal, single particle diagnose system will be used to characterize the luminescence from single nanoparticle. The subtle control of crystal orientation, local crystal field, photon-phonon coupling and magnetic-optical interaction can be realized by changing the surface ligand, replacing the ligand atoms, and applying external fields, respectively. The microscopic mechanism will be explored by modulated the degeneracy of energy levels and the distribution of electrons, which is concerned with local crystal field and energy levels. Then, we hope to understand the physical connection between external fields, crystal field, energy levels, distribution of electrons, and polarized luminescence of lanthanide ions. Furthermore, the near-infrared polarized luminescence would be used to monitor the physiological process in vivo with lanthanide ions doped nanoparticles. The research on physical mechanism of polarized luminescence has great significance for not only the great scientific value, but also the theoretical support of its applications in biomedical, optical data storage, sensors and so on.

稀土离子掺杂纳米晶偏振荧光因其独特的光学特性，在生物医学、信息存储、三维显示等领域具有重要的应用。但由于稀土离子偏振荧光的多样性和复杂性，偏振荧光的机理尚不清楚。我们前期工作发现偏振荧光与稀土离子局部晶体场、晶体取向有关，据此提出晶体场和稀土离子能级调制偏振荧光的假说。本项目采用单颗粒测试系统，表征单颗粒纳米晶光学性能。通过改变表面配体、取代配位原子、施加外场等方法，控制晶体取向、稀土离子周围局部晶体场、光声子耦合作用和磁光作用。从而精细调控稀土离子能级简并和激发态电子布局，探索晶体场、稀土离子能级作用偏振荧光的机理，建立起“外场-晶体场-稀土离子能级-电子布局-偏振荧光”的物理机制。进而，调制合成近红外偏振荧光的纳米晶，用于实时监控生物体内生理过程。稀土离子偏振荧光机理的研究不仅在光物理领域具有重要的科学价值，同时为其在生物理疗、光信息存储、探测传感等领域的应用奠定了理论基础。

稀土离子掺杂纳米晶的偏振荧光因具有窄带发射、荧光峰位可调、长寿命、光热稳定等优异的特点，潜在应用于传感、显示、生物等领域。但稀土离子偏振荧光的机理尚不明确。本项目通过本项目研究了长径比、能量传递、交叉弛豫、激发态电子布局对偏振性能的影响，提出基态吸收和激发态吸收规则激发态电子布局，提高偏振性能的理论。研究了点群作用下，稀土离子能级简并度对激发态电子布局和偏振荧光的影响，证实能级简并度越大，偏振荧光越弱，探明了简并度和稀土偏振荧光的关系。根据稀土离子偏振荧光的光谱与晶体方向的关系，使用光镊系统，成功实现了不同液体浓度下，纳米晶的旋转和偏振探测，为生物体内液体粘度和流速测试提供理论和实验基础。