基于热增强型稀土离子荧光的温度传感方法研究

Temperature sensing technique based on the fluorescence intensity ratio of the rare earth ions possesses outstanding advantages, such as intrinsic safety, anti-electromagnetic interference, high accuracy, and good stability, and so on. These advantages make such technique has potential application in the electric industry, petrochemical engineering, biomedicine, and so on. However, the limited study on the activators as well as the thermal quenching effect caused by the temperature increment blocks the enhancement for the measurement sensitivity and accuracy. In this project, a series of Nd3+-Yb3+ codoped phosphate glasses will be synthesized through the high temperature solid-state method. Under the near infrared laser excitation, the thermally enhanced near-infrared emissions from Nd3+ ions will be designed via the multi-phonon assisted energy transfer and further used for the optical temperature sensing. The effect of the coordination environment and the rare earth ions doping content on the luminescence properties and the thermometry behavior of Nd3+ will be systematically investigated. Through designing the component and the structure of the luminescent materials, the temperature sensing properties will be optimized. The effect of the fluorescence trapping on the thermometry behavior will be emphasized. Additionally, the effect of temperature on the energy transfer dynamics processes between the rare earth ions will be studied, and the changing in the population of the thermally coupled levels during the temperature measurement will be investigated. The solution of the above problem is of great importance in the theoretical research and practical applications, which will promote the development of the optical temperature sensors with high sensitivity and good accuracy.

基于稀土离子荧光强度比的测温技术具有本质安全、抗电磁干扰、精度高、稳定性强等突出优势，在电力工业、石油化工和生物医学等重要领域存在巨大的应用价值。然而，目前对发光中心研究的局限性以及温升引起的荧光热猝灭效应，导致该方法灵敏度与准确性的提升遭遇瓶颈。本项目拟采用高温固相法制备系列Nd3+-Yb3+离子对掺杂的磷酸盐玻璃材料，在红外激光驱动下，依据声子辅助能量转移机制实现热增强的Nd3+离子近红外荧光发射，进而用于光学温度测量。系统研究配位环境与稀土掺杂对Nd3+离子荧光特性及测温性能的调控，通过控制玻璃体的结构、组分，优化材料的感温性能；分析荧光俘获效应对稀土荧光测温行为的影响，探索温度对稀土离子能量传递动力学过程的作用，清晰热耦合能级粒子布居状态随温度变化的微观物理图像。以上关键问题的解决，将促进灵敏、精准的荧光温度传感器件的研发，具有重要的理论意义与实际应用价值。

温度是一个非常重要的物理量，能够影响和反映许多物理现象、化学反应以及生物动力学过程。基于稀土发光材料的荧光强度比（FIR）测温技术，由于其设计方式灵活、响应快、误差小、灵敏度高、抗电磁干扰，在电力系统、生物医学等领域存在广阔的应用前景。然而，FIR技术目前主要处于研究阶段，实现实际应用还有一些问题亟待解决：（1）温度升高导致荧光热猝灭；（2）激光热效应影响测温过程；（3）测温能级热耦合条件不明确。本项目围绕以上科学问题，展开相关研究。980 nm激光激发下研究了Nd3+-Yb3+共掺杂磷酸盐玻璃NIR-NIR发光特性，并分析了Nd3+近红外荧光的温度传感行为。研究发现，基于Yb3+向Nd3+的声子辅助能量传递过程，能够获得高效率的随温度升高而增强的近红外荧光，可有效解决热猝灭现象，同时可获得较高测温灵敏度。为进一步扩大测温范围、提升荧光效率，高温固相法制备了CaWO4：Nd3+-Yb3，通过掺杂Li+调控稀土离子所在晶格环境，降低无辐射跃迁几率，增强Nd3+近红外荧光辐射强度，荧光热增强效果更加明显，为得到高精度荧光测温提供保障；此外，探索了Nd3+-Yb3+共掺系统在生物领域测温的潜在价值，溶剂热方法制备了形貌规则、尺寸均匀的NaYF4：Nd3+-Yb3+纳米粒子，980nm激光激发下，抑制了短波长区域的荧光跃迁，同时获得了强近红外荧光辐射；根据FIR方法研究了NaYF4：Nd3+-Yb3+近红外荧光测温特性，其结果优异于以往文献中报道的参数。基于速率方程和温度依赖的荧光动力学过程，讨论了激光热效应对上转换物理过程的影响，发现激光热效应是功率饱和现象的重要因素。为解决光热效应所引入的测温误差，采用非共振方式泵浦Er3+-Yb3+共掺微晶玻璃，绿色上转换荧光随温度升高增强，吸收声子的能量转换过程有效避免了激光热效应对测温的影响。此外，研究发现稀土离子的温度、无辐射跃迁、能量传递等物理因素明显影响测温能级热耦合状态，通过控制相关物理参数，实现特定温度区间的完全热耦合状态，对提高测温精度具有重要意义。