Er3+/Yb3+体系能量传递对热耦合能级荧光强度比的影响及高灵敏度测温的研究

The population ratio between 2H11/2 and 4S3/2 levels of Er3+ ions depends not only on the thermal activation process, but also on the energy transfer process. This makes the population ratio of the two green levels deviate from the Boltzmann distribution, which results in a large deviation between the actual measurement and theoretical prediction based on the green levels temperature sensing. In addition, the sensitivity of the commonly used green based thermometry is low at low temperature. In order to solve these two problems, this project intends to select common matrix materials in Er3+/Yb3+ system, analyzes the process of energy transfer, non-radiative relaxation, thermal activation as well as other luminescence dynamic processes, summarizes the influence of ion concentration on the energy population ratios of 2H11/2 and 4S3/2, revises the existing theoretical model, and optimizes the actual deviation. The sensitivity of temperature sensing is enhanced by choosing matrix materials with strong hypersensitive transition and substituting ions. The red Stark levels are investigated to detect temperature in different matrix materials. It provides a physical method of model modification for fluorescence ratio temperature sensing based on thermally coupled levels model, and provides a physical guidance for obtaining high sensitivity and accurate temperature measurement.

Er3+离子2H11/2和4S3/2能级间的布局比例不单取决于热激活过程，还要受到能量传递过程的影响。这使得两个绿光能级的布局比偏离了玻尔兹曼分布，进而造成了基于绿光能级温度探测中实际测量和理论预测存在较大偏差。并且目前常用的绿光测温模式在低温时的灵敏度较低。针对这两个问题，本项目拟在Er3+/Yb3+体系中，选取常见的基质材料，分析能量传递，无辐射弛豫，热激活等发光动力学过程，总结离子浓度对2H11/2和4S3/2能级布局比的影响规律，修正现有的理论模型，优化实际偏差。通过选取超敏跃迁较强的基质材料，离子替换等方法，增强测温的灵敏度，并在不同基质材料中研究使用红光Stark能级进行光温探测。为基于热耦合能级模型的荧光比测温原理提供模型修正的物理方法，为获得高灵敏准确测温提供物理指导。

基于Er3+离子绿光热耦合能级荧光强度比例进行测温具有自参考性，在强电磁场和生物体内等领域具有广阔应用潜力。然而在低温区测温误差大、灵敏度低的问题限制了其应用进程。本项目基于速率方程，依据发光动力学分析，修正了绿光热耦合能级的布局比例模型，减小了实际测量与理论预期的偏差。制备了一种新型上转换材料Gd2Mo4O15:Er3+/Yb3+，其测温绝对灵敏度高达0.00845K-1。在单斜相氧化锆中开展红绿双模式测温的研究，选用红光测温模式可显著提高低温区测温灵敏度，使灵敏度始终大于0.00152K-1。研究了Pr3+离子1D2能级斯塔克劈裂测温性能，其相对灵敏度在100K时可达9.8%K-1。在Er3+/Yb3+体系中采用发光中心替代策略增强近红外上转换发光1.5倍；优化材料设计，在小于100mW/cm-2范围内实现非线性系数最大为2.81的高效上转换红光。研究了NaYF4:Ho3+/Yb3+纳米晶上转换发光热增强的机理和调控，最终实现热增强倍数在3.5倍到6.7倍之间的人为可控。本项目将为稀土荧光测温的研究和应用以及发光动力学的研究提供理论和技术支持。