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

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/NH4F 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 Lu3+/Gd3+-based shells. The upconversion emission can be exploited to visualize in security decoding and in vivo 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.

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“…confirms visually the inner core area and outer shell layers of EMU NCs, and the energy-dispersive X-ray spectroscopy (EDS) mappings conducted on several randomly selected EMU NCs (Figs.2f, S2) verify the distribution of Yb in core, Gd, Tm in middle shell, and Tb in outer shell [52][53][54][55]. Figure2.…”

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