Suppression of Photoexcited Small Polarons-Mediated Energy Transfer to Boost Photoluminescence of Lanthanide-Titanium Nanoclusters.

Jiang, Feng; He, Shengrong; Ji, Yuan; Yin, Jun; Cong, Yan; Dong, Weinan; Li, Xin; Zhang, Yu et al. · Nano Lett · 2025

basic_science · Level V

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Abstract

Lanthanide (Ln<sup>3+</sup>)-titanium-based molecular nanoclusters (NCs) have attracted much attention due to their atomically precise total structure and promising optical behavior, while there is still minimal cognition of structure-dictated electron relaxation dynamics in such an NCs regime with unsatisfied photoluminescence quantum yield (PLQY, in general below 20%). Herein, the photoexcited small polarons (i.e., local electron-phonon coupling) are identified and emphasized in modulating the emission of Ln<sup>3+</sup> NCs. Taking 4-<i>tert</i>-butylbenzoate coordinated Eu<sub>2</sub>Ti<sub>4</sub> NCs as a model, the excited electron is capable of being captured by the Ti<sup>4+</sup> to form the Ti<sup>3+</sup>-dominated small polarons, which allows influencing the ligands-sensitive antenna effect for Eu<sup>3+</sup> emission. Most importantly, by chelating the Eu<sub>2</sub>Ti<sub>4</sub> NCs with Eu<sub>3</sub>Ti<sub>3</sub> units bilaterally, the evolved Eu<sub>8</sub>Ti<sub>10</sub> NCs perform suppressed lattice vibration and therefore eliminate the photoexcited small polaron-mediated energy transfer, giving a remarkable enhancement in PLQY, from 17.6% to 73.1%.