稀土掺杂氧化物光子晶体上转换发光调控研究

Rare earth (RE) doped upconversion nanocrystals have attracted extensive research interest because of their wide and great potential applications in biology and photonics fields. However, low upconversion luminescence (UCL) efficiency is still an obstacle for their practical applications, it is therefore the focus of research. This project intends to prepare a series of high quality RE doped oxide inverse opal photonic crystals (IOPCs) through self-assembly templates combined with sol-gel method. The UCL efficiency will be largely improved by the photonic modulation of IOPCs special structure. The modification of upconversion spontaneous emission by embedding RE ions in the IOPCs will be discussed, and the different modification on the spontaneous emission of different emitters (rare earth, quantum dots and dye molecules) in the same IOPCs will be compared. A variety of spectral characterization, such as excitation and emission spectra, transient dynamic analysis, power-dependent emission spectra, temperature-dependent emission spectra and dynamics, and internal quantum efficiency will be adopted to further probe the physical nature of the UCL efficiency improvement and the modification of spontaneous emission. This project not only has value for fundamental physics, but also provides theoretical guidance and experimental basis for the practical application of this kind of materials in the photonics field.

由于在生物和光电子等诸多领域的潜在应用前景，稀土掺杂上转换纳米发光材料引起了广泛地研究兴趣。然而，低的上转换发光效率成为其实际应用的瓶颈问题，同时也是研究的难点问题。本项目拟通过自组装模板结合溶胶-凝胶的方法制备一系列高质量稀土掺杂氧化物反蛋白石光子晶体。通过反蛋白石光子晶体特殊结构对发光的调制提高上转换发光效率；利用光子晶体禁带效应调控稀土离子上转换自发辐射，并在同一体系中比较光子晶体对不同发光中心（稀土、量子点、染料分子）调控的区别。采用激发和发射光谱、变功率光谱、瞬态动力学、变温光谱及动力学和内量子效率等多种光谱测试手段，深入揭示反蛋白石光子晶体提高上转换发光效率和调控自发辐射的物理本质。本项目不但具有基础物理研究价值，并为这类材料在光电子等领域的实际应用提供理论指导和实验依据。

本项目以稀土掺杂氧化物反蛋白石光子晶体制备及上转换发光调控为研究目标。首先通过自组装模版结合溶胶-凝胶的方法制备出ZnO, NaGd(WO4)2:Eu3+,Tb3+, In2O3:Yb3+, Er3+, BaTiO3:Yb3+, Er3+, NaYF4:Yb3+, Er3+等多种反蛋白石光子晶体，通过优化实验条件，光子晶体的光子带隙深度能够达到20%以上。在反蛋白石光子晶体中实现了对稀土离子自发发射的调制：当稀土离子发光位置处于光子带隙内时，自发辐射受到抑制，当发光位置处于光子带隙的带边时，自发辐射得到增强，通过光谱物理分析发现这种调制主要来源于反蛋白石光子晶体有效折射率的改变，而不是光子态密度的变化；在反蛋白石光子晶体中实现了上转换发光效率的提高，这种提高主要来源于反蛋白石光子晶体特殊结构：薄壁、高连通性和良好的开放性对稀土离子长程能量传递地抑制，另一方面这种连通结构能够有效地抑制上转换发光的局域热效应。本项目不仅探明了光子晶体中自发辐射调控的物理本质，而且为这类材料在光电领域的实际应用提供理论指导和实验依据。