In-depth analysis of excitation dynamics in dye-sensitized upconversion core and core/active shell nanoparticles

Abstract

Upconversion nanoparticles (UCNPs) combining both dye sensitization and core/shell enhancement are of great interest for their ability to boost the excitation efficiency of upconversion systems. Here, we report and investigate a 20-fold upconversion luminescence enhancement in dye-sensitized core/active shell UCNPs compared to that in nonsensitized core-only UCNPs. We observe a two-component luminescence rise dynamics in the upconversion kinetics of dye-sensitized UCNPs, distinctly different from the one-component rise dynamics of the nonsensitized UCNPs. For dye-sensitized UCNPs, the fast sub-microsecond component of the upconversion luminescence rise time is attributed to the radiative pumping of Er3+ ions from the dye, whereas the slow sub-millisecond component is due to the nonradiative energy transfer from the dye predominantly to Yb3+ ions, followed by the energy migration and the nonradiative energy transfer from Yb3+ to Er3+ ions. Our studies provide an insight into the interplay between radiative and nonradiative energy transfer as well as into the role of energy migration across the active shell of dye-sensitized core/active shell UCNPs.

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Identifiers

ORCID for Bigeng Chen: orcid.org/0000-0003-4925-2308

ORCID for Otto L. Muskens: orcid.org/0000-0003-0693-5504

ORCID for Antonios G. Kanaras: orcid.org/0000-0002-9847-6706

ORCID for Pavlos G. Lagoudakis: orcid.org/0000-0002-3557-5299

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