超薄金壳包覆NaYF4:Yb,Er@SiO2纳米结构的可控合成与表面增强上转换荧光

利用原位还原法成功制备了尺寸均一、超薄完整金壳包覆的NaYF₄:Yb，Er@SiO₂@Au（NSA）纳米结构，其XRD、TEM、EDX、HRTEM-HAADF、Mapping及吸收光谱表征结果表明，SiO₂壳及纳米金壳的平均厚度分别约为5 nm和2 nm。在980 nm连续激光激发下，系统研究了核壳结构的上转换荧光强度与氯金酸浓度的依赖关系。稳态光谱结果显示，NSA与仅SiO₂包覆样品（NS）相比Er³⁺的红绿荧光强度均增强了~2.8倍。通过分析上转换荧光动力学过程及利用FDTD方法模拟，讨论了表面等离激元增强上转换荧光的机制。

Controllable Synthesis and Surface-enhanced Upconversion Luminescence of Ultra-thin Gold Shell Coated NaYF4:Yb,Er@SiO2 Nanostructures

The in-situ reduction method was successfully used to prepare the uniform and ultrathin gold shell-coated NSA nanostructures. The microstructure and composition characterizations such as XRD, TEM, EDX, HRTEM-HAADF, mapping as well as absorption spectra data indicated that the average thicknesses of SiO₂ shell and gold nanoshell are about 5 nm and 2 nm, respectively. Under the excitation of a CW diode laser of 980 nm, the dependence of the upconversion fluorescence intensity of the core-shell structure on the concentration of chloroauric acid was systematically investigated. The steady-state spectral results show that the red and green upconversion luminescence intensities of NS samples are 2.8 times enhanced simultaneously by coating the gold shell. The upconversion lifetime of the red and green emission levels before and after the gold shell cladding is obtained by fitting the fluorescence decay curves. The mechanism of enhanced upconversion fluorescence by the surface plasmons is discussed based on the spectral analysis and FDTD method simulation.