表面等离子体共振增强Nd3+敏化氧化物上转换发光纳米材料研究

Recently, up-conversion nanoparticles (UCNPs) have attracted much attention for its potential application in bioimaging. However, UCNPs suffer from the low up-conversion luminescence efficiency that restricts their application prospect. In addition, the excitation light at 980 nm results in overheating in the tissue and the decreasing of penetration depth for deep-tissue imaging due to the absorption at 980 nm of water. This project aims to turn the excitation wavelength from 980 nm to 800 nm by doping Nd3+ ion as sensitizer, allowing the water absorption to be largely suppressed. We would synthesize Nd3+-sensitized oxide UCNPs by hydrothermal (solvothermal) or coprecipitation method and investigate the efficient approach to manipulate the morphology, the particle size and the luminescence properties of UCNPs. Using Yb3+ ion as the bridge to obtain cascade energy transfer between Nd3+-Yb3+-A3+ (A = Er, Tm, Ho) and realizing monochrome and multicolor UC emissions by control the doping concentration and species of the activators. The energy transfer processes of the Nd3+-Yb3+-A3+ co-doped system and the UC mechanism of the UCNPs would be investigated in detail. In order to further increase the up-conversion luminescence efficiency of the UCNPs with 800 nm excitation, we would build UCNPs-SiO2-noble metal compound nanostructure and enhance the UC emission intensity by adjusting the plasma resonance absorption peak of noble metal nano-particles and the thickness of interlayer SiO2/Al2O3. The investigation of rare earth doped oxides UCNPs with plasmon-enhanced upconversion luminescence would provide significant experimental and theoretical foundation for increase the upconversion luminescence efficiency of with 800 nm excitation oxide nanoparticles.

稀土上转换纳米材料在生物成像领域的应用倍受关注，较低的上转换发光效率是限制其应用的重要因素，生物体内水分子对980nm红外激发光的吸收造成组织发热，穿透深度降低。本项目利用Nd3+为敏化剂将激发波长移动至水分子吸收较小的800nm附近，采用水热（溶剂热）法、共沉淀法等合成Nd3+离子敏化的氧化物纳米晶，对其形貌、粒径和发光性能进行调控。通过Yb3+离子的桥梁作用实现Nd3+-Yb3+-A3+（A = Er, Tm, Ho）之间的级联能量传递，获得800nm激发下的单色、多色上转换发射，研究上转换发光机理和能量传递过程。进一步构建上转换纳米晶-中间层SiO2/Al2O3-贵金属纳米复合结构，通过对贵金属纳米颗粒形貌粒径的控制调控其等离子体共振吸收峰，并调节中间层厚度，实现800nm激发下的等离子共振荧光增强，为800nm红外光激发下氧化物上转换纳米材料发光效率的提高提供重要的实验和理论依据。

稀土上转换发光材料在生物成像及非接触光学温度传感领域的应用倍受关注，常见980nm红外激发光由于生物体内水分子的吸收造成的组织发热，穿透深度降低的问题亟待解决，较低的上转换发光效率亦是限制其应用的重要瓶颈。 本项目首先利用Nd3+为敏化剂将原有Yb3+敏化的上转换材料的光敏感区域从980nm调节至水分子吸收较小的800nm波段，有助于避免激发光对生物组织的热损伤并提高激发光穿透深度。采用溶胶-凝胶法、水热法、共沉淀法等合成一系列的稳定氧化物为基质微纳米上转换发光材料，通过Nd3+离子敏化和Yb3+离子的桥梁作用实现Nd3+-Yb3+-A3+（A = Er, Tm, Ho）的级联能量传递，获得800 nm激发下的高效上转换发射，阐明了上转换发光机理和能量传递过程。利用改变掺杂剂浓度，调节激发光脉冲宽度和共掺杂Ce3+离子等方法实现了多模式上转换发光颜色的有效调控，研究了光谱调制的内在机理，为上转换发光的稳态和非稳态发光色度调控提供了重要的实验依据。研究了基于Er3+离子热耦合能级荧光强度比（FIR）的光学温度传感性能，获得了高灵敏度的钼酸盐基质上转换温度传感材料，探究了影响温度传感灵敏度的内在因素，为实现上转换纳米材料在生物体内的非接触式温度探测提供了理论和实验基础。成功制备了Lu2O3: Nd3+/Yb3+/Er3+上转换纳米球，实现了对纳米球粒径的有效调控。合成了不同尺寸的Ag纳米颗粒，对其进行SiO2包覆，进一步构建了Lu2O3: Nd3+/Yb3+/Er3+@SiO2@Ag纳米复合体系，探究了Ag纳米颗粒的表面等离子体共振效应对上转换发光的影响。同时，利用金属离子Li+进行掺杂，实现了800nm激发下上转换发光的增强，并对荧光增强机理进行了系统研究。800nm激发下上转换发光效率的提高对稀土上转换纳米材料的生物应用具有重要意义。