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

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。

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.