University of Regensburg , Institute of Analytical Chemistry, Chemo- and Biosensors, 93040 Regensburg, Germany.
BAM Federal Institute for Materials Research and Testing , Division 1.10 Biophotonics, 12489 Berlin, Germany.
Anal Chem. 2017 May 2;89(9):4868-4874. doi: 10.1021/acs.analchem.6b04662. Epub 2017 Apr 18.
Upconversion nanoparticles (UCNPs) are attractive candidates for energy transfer-based analytical applications. In contrast to classical donor-acceptor pairs, these particles contain many emitting lanthanide ions together with numerous acceptor dye molecules at different distances to each other, strongly depending on the particle diameter. UCNPs with precisely controlled sizes between 10 and 43 nm were prepared and functionalized with rose bengal and sulforhodamine B by a ligand-exchange procedure. Time-resolved studies of the upconversion luminescence of the UCNP donor revealed a considerable shortening of the donor lifetime as a clear hint for Förster resonance energy transfer (FRET). FRET was most pronounced for 21 nm-sized UCNPs, yielding a FRET efficiency of 60%. At larger surface-to-volume ratios, the FRET efficiency decreased by an increasing competition of nonradiative surface deactivation. Such dye-UCNP architectures can also provide an elegant way to shift the UCNP emission color, since the fluorescence intensity of the organic dyes excited by FRET was comparable to that of the upconversion emission of smaller particles.
上转换纳米粒子（UCNPs）是基于能量转移的分析应用的有吸引力的候选者。与经典的供体-受体对相比，这些粒子包含许多发射镧系离子，以及许多彼此之间距离不同的受体染料分子，强烈依赖于粒子直径。通过配体交换程序制备了具有精确控制尺寸在 10 至 43nm 之间的 UCNPs，并将其用玫瑰红和磺基罗丹明 B 功能化。对 UCNP 供体的上转换发光的时间分辨研究表明，供体寿命明显缩短，这清楚地表明了Förster 共振能量转移（FRET）的存在。对于 21nm 大小的 UCNPs，FRET 效率最高，达到 60%。在较大的表面积与体积比下，FRET 效率由于非辐射表面失活的竞争而降低。这种染料-UCNP 结构还可以提供一种优雅的方式来转移 UCNP 发射颜色，因为受 FRET 激发的有机染料的荧光强度与较小粒子的上转换发射相当。
