Department of Chemistry and Biochemistry, Concordia University, Montreal, QC, Canada.
Nano Lett. 2011 Feb 9;11(2):835-40. doi: 10.1021/nl1041929. Epub 2011 Jan 18.
The synthesis using the thermal decomposition of metal trifluoroacetates is being widely used to prepare oleate-capped lanthanide-doped upconverting NaYF(4):Er(3+)/Yb(3+) nanoparticles (Ln-UCNPs). These nanoparticles have no inherent aqueous dispersibility and inconvenient postsynthesis treatments are required to render them water dispersible. Here, we have developed a novel and facile approach to obtain water-dispersible, ligand-free, brightly upconverting Ln-UCNPs. We show that the upconversion luminescence is affected by the local environment of the lanthanide ions at the surface of the Ln-UCNPs. We observe a dramatic difference of the integrated upconverted red:green emission ratio for Ln-UCNPs dispersed in toluene compared to Ln-UCNPs dispersed in water. We can enhance or deactivate the upconversion luminescence by pH and H/D isotope vibronic control over the competitive radiative and nonradiative relaxation pathways for the red and green excited states. Direct biofunctionalization of the ligand-free, water-dispersible Ln-UCNPs will enable myriad new opportunities in targeting and drug delivery applications.
采用金属三氟乙酸盐的热分解法合成油酸盐封端的镧系掺杂上转换 NaYF(4):Er(3+)/Yb(3+)纳米粒子（Ln-UCNPs）被广泛应用。这些纳米粒子本身没有固有的水分散性，需要进行不方便的后合成处理才能使其水分散。在这里，我们开发了一种新颖且简便的方法来获得水分散性、无配体、上转换发光性能强的 Ln-UCNPs。我们表明，上转换发光受到 Ln-UCNPs 表面镧系离子局部环境的影响。我们观察到分散在甲苯中的 Ln-UCNPs 的上转换红：绿发射积分比与分散在水中的 Ln-UCNPs 有明显差异。我们可以通过 pH 值和 H/D 同位素振动控制来增强或失活上转换发光，从而控制红、绿激发态的辐射和非辐射弛豫途径的竞争。对无配体、水分散性的 Ln-UCNPs 进行直接生物功能化将为靶向和药物输送应用带来无数新机会。
