Department of Biomedical Engineering, Faculty of Engineering, National University of Singapore, 4 Engineering Drive 3, 117583 Singapore.
Nanoscale. 2017 Dec 21;10(1):250-259. doi: 10.1039/c7nr06900f.
Lanthanide-doped upconversion nanoparticles (UCNPs) are of great interest for biomedical applications. Currently, the applicability of UCNP bionanotechnology is hampered by the generally low luminescence intensity of UCNPs and inefficient energy transfer from UCNPs to surface-bound chromophores used e.g. for photodynamic therapy or analyte sensing. In this work, we address the low-efficiency issue by developing versatile core-shell nanostructures, where high-concentration sensitizers and activators are confined in the core and shell region of representative hexagonal NaYF:Yb,Er UCNPs. After doping concentration optimization, the sensitizer-rich core is able to harvest/accumulate more excitation energy and generate almost one order of magnitude higher luminescence intensity than conventional homogeneously doped nanostructures. At the same time, the activator ions located in the shell enable a ∼6 times more efficient resonant energy transfer from UCNPs to surface-bound acceptor dye molecules due to the short distance between donor-acceptor pairs. Our work provides new insights into the rational design of UCNPs and will greatly increase the general applicability of upconversion nanotechnologies.
镧系掺杂上转换纳米粒子（UCNPs）在生物医学应用中具有重要意义。目前，UCNP 生物纳米技术的适用性受到 UCNPs 通常较低的发光强度和从 UCNPs 到用于光动力疗法或分析物传感的表面结合发色团的低效能量转移的限制。在这项工作中，我们通过开发多功能核壳纳米结构来解决低效率问题，其中高浓度敏化剂和激活剂被限制在代表性六方 NaYF:Yb,Er UCNPs 的核和壳区域。经过掺杂浓度优化，富敏化剂的核能够收集/积累更多的激发能，并产生比传统均匀掺杂纳米结构高一个数量级的发光强度。同时，由于供体-受体对之间的短距离，位于壳中的激活剂离子使得 UCNPs 到表面结合的受体染料分子的共振能量转移效率提高了约 6 倍。我们的工作为 UCNPs 的合理设计提供了新的见解，并将极大地提高上转换纳米技术的普遍适用性。
