Department of Chemistry, National University of Singapore, Singapore 117543.
Nanoscale. 2012 Aug 21;4(16):5132-7. doi: 10.1039/c2nr31241g. Epub 2012 Jul 13.
NaYF(4):Yb,Er@SiO(2)@Ag core-shell nanocomposites were prepared to investigate metal-enhanced upconversion luminescence. Two sizes (15 and 30 nm) of Ag nanoparticles were used. The emission intensity of the upconversion nanocrystals was found to be strongly modulated by the presence of Ag nanoparticles (NPs) on the outer shell layer of the nanocomposites. The extent of modulation depended on the separation distance between Ag NPs and upconversion nanocrystals. The optimum upconversion luminescence enhancement was observed at a separation distance of 10 nm for Ag NPs with two different sizes (15 and 30 nm). A maximum upconversion luminescence enhancement of 14.4-fold was observed when 15 nm Ag nanoparticles were used and 10.8-fold was observed when 30 nm Ag NPs were used. The separation distance dependent emission intensity is ascribed to the competition between energy transfer and enhanced radiative decay rates. The biocompatibility of the nanocomposites was significantly improved by surface modification with DNA. The biological imaging capabilities of these nanocomposites were demonstrated using B16F0 cells.
NaYF(4):Yb,Er@SiO(2)@Ag 核壳纳米复合材料被制备用于研究金属增强上转换发光。使用了两种尺寸（15nm 和 30nm）的 Ag 纳米颗粒。发现上转换纳米晶体的发射强度受到纳米复合材料外壳层上 Ag 纳米颗粒（NPs）的强烈调制。调制的程度取决于 Ag NPs 和上转换纳米晶体之间的分离距离。在 Ag NPs 具有两种不同尺寸（15nm 和 30nm）时，分离距离为 10nm 时观察到最佳的上转换发光增强。当使用 15nm Ag 纳米颗粒时，观察到上转换发光增强了 14.4 倍，当使用 30nm Ag NPs 时，观察到上转换发光增强了 10.8 倍。发射强度随分离距离变化归因于能量转移和增强的辐射衰减速率之间的竞争。通过 DNA 表面修饰，显著提高了纳米复合材料的生物相容性。使用 B16F0 细胞证明了这些纳米复合材料的生物成像能力。
