Boosting Dye‐Sensitized Luminescence by Enhanced Short‐Range Triplet Energy Transfer

Abstract

Dye‐sensitization can enhance lanthanide‐based upconversion luminescence, but is hindered by interfacial energy transfer from organic dye to lanthanide ion Yb3+. To overcome these limitations, we propose modifying coordination sites on dye conjugated structures and minimizing the distance between fluorescence cores and Yb3+ in upconversion nanoparticles (UCNPs). Our specially designed near‐infrared (NIR) dye, disulfo‐indocyanine green (disulfo‐ICG), acts as the antenna molecule and exhibits a 2413‐fold increase in luminescence under 808 nm excitation compared to UCNPs alone using 980 nm irradiation. The significant improvement is attributed to the high energy transfer efficiency of 72.1% from disulfo‐ICG to Yb3+ in UCNPs, with majority of energy originating from triplet state (T1) of disulfo‐ICG. Shortening the distance between the dye and lanthanide ions increases the probability of energy transfer and strengthens the heavy atom effect, leading to enhanced T1 generation and improved dye‐triplet sensitization upconversion. Importantly, this approach also applies to 730 nm excitation Cy7‐SO3 sensitization system, overcoming the spectral mismatch between Cy7 and Yb3+ and achieving a 52‐fold enhancement in luminescence. Furthermore, we demonstrate the enhancement of upconversion at single particle level through dye‐sensitization. This strategy expands the range of NIR dyes for sensitization and opens new avenues for highly efficient dye‐sensitized upconversion systems.This article is protected by copyright. All rights reserved

Recent Advances in Triplet Energy Transfer between Organic Dyes and Lanthanide-Doped Luminescent Nanoparticles

“…Later on, Zhao and co-workers found that minimizing the distance between the luminescence core of organic dyes and lanthanide ions in upconversion nanoparticles can enhance the triplet energy transfer from organic dyes to upconversion nanoparticles (Figure 5b). 53 To demonstrate this, they specially prepared a disulfo-indocyanine green (ICG) dye with coordination binding groups at the conjugated structure of cyanine's luminescence core, which can bring the luminescence core of cyanine dyes closer to lanthanide ions in nanoparticles compared to conventional NIR cyanine dyes. After the dye was modified onto upconversion nanoparticles, the resulting dye-nanoparticle composite exhibited a 2413-fold enhancement of the brightness compared to nanoparticles alone and a 2351-fold enhancement of the dye-sensitization effect compared to the ICG-nanoparticle composite under NIR excitation.…”

“…Other factors that are involved in the triplet energy transfer should be considered and can be tuned to enhance or modulate the triplet energy transfer. Indeed, the molecular structure of organic dyes, the doping concentration of lanthanide ions in LnLNPs, the nanostructure of LnLNPs, the distance between the fluorescence core of organic dyes and lanthanide ions in LnLNPs, and the integration/coordination between organic dyes and LnLNPs have been found to affect the triplet energy transfer between organic dyes and LnLNPs. − However, there is still a lack of comprehensive understanding of the influence of these factors. To provide a better understanding, we will highlight the effect of these factors on the triplet energy transfer between organic dyes and LnLNPs when discussing specific studies in the following section.…”

“…Factors that can affect the triplet energy transfer have not been fully revealed. , Fortunately, some recent studies disclose clues to the role of some critical factors in triplet energy transfer. It was found that the attachment mechanism of dye molecules to the surface of upconversion nanoparticles, the distance between the luminescence core of the dye and lanthanide ions in the nanoparticle, impurities on the surface of nanoparticles, and the nanostructure of nanoparticles could obviously affect the triplet energy transfer from organic dyes to upconversion nanoparticles. − …”

“…(b) Dye’s chemical structure scheme and mechanism of energy transfer in different works. Reprinted with permission from ref . Copyright 2023 John Wiley and Sons.…”

“…Later on, Zhao and co-workers found that minimizing the distance between the luminescence core of organic dyes and lanthanide ions in upconversion nanoparticles can enhance the triplet energy transfer from organic dyes to upconversion nanoparticles (Figure b) . To demonstrate this, they specially prepared a disulfo-indocyanine green (ICG) dye with coordination binding groups at the conjugated structure of cyanine’s luminescence core, which can bring the luminescence core of cyanine dyes closer to lanthanide ions in nanoparticles compared to conventional NIR cyanine dyes.…”