用于微纳米尺度温度传感的高阶激发态能量传递上转换荧光纳米晶研究

Upconversion luminescence (UCL) nanocrystals for nanothermometers based on fluorescence intensity ratio, are capable of working at the micro/nanoscale with high spatial resolution and absorbing near-infrared light and converting it into short-wavelength emission. Such characteristics make UCL nanocrystals for nanothermometers having important research value. However, there are two problems limited their applications, such as the low UCL efficiency and low temperature sensitivity. The purpose of our research is to improve UCL efficiency and increase temperature sensitivity. The high excited state energy transfer and micro-mechanism of activator and temperature sensitivity will be studied. The different morphology and crystal phase of Gd2(MoO4)3:Yb3+/Er3+ nanocrystals are prepared. In order to gain the strong green upconversion emission, mechanism of high excited state energy transfer in Gd2(MoO4)3:Yb3+/Er3+ nanocrystals and the effects of morphology and size on fluorescence intensity are studied. Based on the Judd-Ofelt theory, the micro-mechanism of the ligand field of Er3+ ion and temperature sensitivity is investigated in detail, by analyzing the temperature performance parameters ofGd2(MoO4)3:Yb3+/Er3+ nanocrystals with different morphologies and crystal phase. Project findings have important significance for enhancing the UCL intensity and improving the temperature sensitivity of nanothermometer.

基于荧光强度比型的上转换荧光纳米温度计能在微纳米尺度空间测温，并能把近红外光转换为可见光，在生物等领域有独特的优势。然而，低的上转换荧光效率和测温灵敏度成为制约该项技术推广应用的主要瓶颈。本项目以提高上转换荧光效率和测温灵敏度为研究目的，对高阶激发态能量传递上转换机制和激活离子局域配位场对测温灵敏度作用的微观机理进行基础科学研究。合成不同形貌和晶相Gd2(MoO4)3:Yb3+/Er3+纳米晶，调控钼酸根的激发态能级位置，构筑Yb3+-MoO42- → Er3+高阶激发态能量传递上转换通道，拟获得强绿光发射。研究不同形貌和晶相对测温性能的影响，采用Judd-Ofelt理论和荧光强度比测温相关理论，以阐明Er3+离子局域配位场对测温灵敏度作用的微观机制，为设计灵敏度更高的纳米温度计提供理论指导。项目研究成果对于增强上转换发光强度和提高纳米温度计的测温灵敏度具有一定意义。

基于荧光强度比型的上转换荧光纳米温度计能在微纳米尺度空间测温，并能把近红外光转换为可见光，在生物等领域有独特的优势。然而，低的上转换荧光效率和测温灵敏度成为制约该项技术推广应用的主要瓶颈。本项目以提高上转换荧光效率和测温灵敏度为研究目的，对高阶激发态能量传递上转换机制和激活离子局域配位场对测温灵敏度作用的微观机理进行基础科学研究。本项目合成不同形貌和晶相Gd2(MoO4)3:Yb3+/Er3+和SrMoO4:Yb3+/Er3+纳米晶，构筑Yb3+-MoO42- → Er3+高阶激发态能量传递上转换通道，获得了强绿光发射。通过266 nm飞秒激光激发的光致发光实验，验证了钼酸根MoO42-向Er3+离子高效能量传递的正确性。高阶激发态能量传递上转换有效减少Er3+离子低激发态的无辐射弛豫，增加高阶激发态的粒子数，进而提高上转换发光强度。结合分析上转换发光光谱和荧光衰减曲线，证明Yb3+-MoO42-二聚物是很好的敏化剂。采用Judd-Ofelt理论和荧光强度比测温相关理论，系统研究不同形貌和晶相对测温性能的影响。实验结果表明，Gd2(MoO4)3:9Yb3+/1Er3+纳米晶和SrMoO4:1Er3+纳米晶分别在466 K和554 K获得相对灵敏度为0.0092 K-1和0.0229 K-1，并探讨了共价性对测温灵敏度的影响。项目研究成果对于增强上转换发光强度和提高纳米温度计的测温灵敏度具有一定意义。