Artificial Atomic Vacancies Tailor Near-Infrared II Excited Multiplexing Upconversion in Core-Shell Lanthanide Nanoparticles.

Huang, Jinzhao; Li, Jingqiu; Zhang, Xuefei; Zhang, Wanmei; Yu, Zhongzheng; Ling, Bo; Yang, Xiangliang; Zhang, Yan · Nano Lett · 2020

basic_science · Level V

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Abstract

Epitaxial growth of an inert shell around the optical active lanthanide upconversion nanoparticles (UCNPs) is a general strategy to enhance their brightness. Yet, its potential as a tool in multiplexing emission tailoring has rarely been reported. Here, by developing the atomic vacancies into color selectivity actuators, we present an efficient strategy to achieve inert-shell-modulated multiplexing upconversion in 1540 nm activated UCNPs. Artificially generated fluoride atomic vacancies, owing to the decreased NaOH/NH<sub>4</sub>F dosage during shell growth, reduce the coordination number of Y-F and lattice densities in the inert shell, leading to the core-engineered shell nanoparticles with distinctive emission profiles. The multicolor tailoring is independent of shell thickness and can be readily applied to Lu<sup>3+</sup>/Gd<sup>3+</sup>-based shells. The upconversion emission can be exploited to visualize in security decoding and <i>in vivo</i> multiplexing bioimaging. This method of regulating atomic vacancies based on the inert-shell engineering opens new insights of upconversion modulation in core-shell lanthanide nanostructures.