基于光子晶体上转换荧光增强及固态传感性质研究

Recently, the liquid-based sensors based on rare earth (RE) doped upconversion nanocrystals are widely used in detecting DNA, metal ions and small molecules. However, the liquid-based sensors are usually unstable, irreproducible and low upconversion luminescence (UCL) efficiency, which will affect the detection limit and sensitivity unavoidably. This project intends to prepare a series of cyanine dye (hCy7) modified fluoride nanocrystals (hCy7-NaYF4:Yb, Er/Tm) using solvothermal method, and combine with self-assembly template method to prepare YVO4 inverse opal photonic crystals (IOPCs)/hCy7-NaYF4:Yb,Er/Tm composites. The UCL will be enhanced by the modulation of spontaneous emission in IOPCs, and a variety of spectral measurements, such as steady-state emission spectra, transient dynamic analysis, and internal quantum efficiency, are adopted to further probe the physical nature of the UCL enhancement. On this basis, the solid-based UCL sensor is presented for highly sensitive detection of trace methylmercury (MeHg+) via the fluorescence resonance energy transfer between RE ions and cyanine dye. This project will obtain a new kind of efficient composites, and provide important theoretical basis and experimental guidance for the practical application of solid-based detection of MeHg+.

稀土掺杂上转换纳米晶液态基传感器近年来广泛应用于DNA、金属离子和小分子检测。然而，液态基传感器的不稳定性、重复利用差和发光效率低等因素，不可避免地影响其检测限和灵敏度。本项目拟采用溶剂热法制备一系列花青染料(hCy7)修饰的氟化物纳米晶(hCy7-NaYF4:Yb, Er/Tm)，并结合自组装法制备出YVO4反蛋白石光子晶体/hCy7-NaYF4:Yb, Er/Tm复合纳米材料。通过反蛋白石光子晶体对自发辐射的调制实现上转换荧光增强，并结合稳态发射光谱、瞬态动力学和内量子效率等多种光谱测试手段，深入揭示上转换荧光增强的物理本质。在此基础上，将其作为固态基上转换荧光传感器，通过稀土离子与花青染料之间荧光共振能量传递实现对微量甲基水银（MeHg+）高灵敏检测。本项目将获得新一类高效复合纳米材料，并为其在固态条件下实现对甲基水银检测的实际应用提供重要的理论基础和实验依据。

本项目以通过反蛋白石光子晶体实现上转换荧光增强和在此基础上制备固态基荧光传感器为研究目标。研究内容主要包括：稀土掺杂反蛋白石光子晶体制备、光子晶体调控上转换自发辐射物理本质研究、固态基上转换荧光传感器制备及对甲基水银的高灵敏检测3部分。本项目通过自组装结合模版去除的方法制备出In2O3:Yb3+, Er3+, YVO4:Yb3+, Er3+, NaYF4:Yb3+, Er3+, NaGd(WO4):Eu3+, Tb3+多种反蛋白石光子晶体；反蛋白石光子晶体中稀土离子的上转换发光强度提高大约20倍，通过光谱物理分析发现这种荧光增强主要来源于光子晶体（薄壁、高连通性、良好开放性）结构对稀土离子间长程能量传递的抑制；利用光子晶体作为载体制备的固态基上转换荧光传感器有效地提高了上转换发光效率，放大了荧光信号，进而提高了检测的灵敏度，对甲基水银的检测下限达到13 nM. 本项目的研究不仅探明了光子晶体中上转换荧光增强的物理本质，而且为固态下实现甲基水银的高灵敏检测提供重要的实验依据。