Dual-Function Strategy for Enhanced Quercetin Detection Using Terbium(III) Ion-Bound Gold Nanoclusters

The engineering of metal nanoclusters (NCs) that exhibit bright emissions and high sensing performance under physiological conditions is still a formidable challenge. In this study, we report a novel design strategy for realizing excellent performance metal NC-based probes by leveraging both concerted proton-coupled electron transfer (PCET) and photoinduced electron transfer (PET) mechanisms, with terbium(III) (Tb3+) ions serving as a key modulator. Our findings indicate that the binding of Tb3+ ions to the 6-aza-2-thiothymidine (ATT) ligand effectively inhibits the proton-transfer step in the concerted PCET pathway of Au10(ATT)6 NCs, giving rise to over a 10-fold enhancement in fluorescence and a quantum yield of 7.2%. Moreover, the capped Tb3+ ions on the surface of Au10(ATT)6 NCs can act as a bridge to facilitate an efficient donor-linker-acceptor type PET reaction from quercetin (Que) to the excited Au10 core by specifically interacting with the bare 3-OH group. These advancements enable the Tb3+/Au10(ATT)6 NC-based probe to achieve a significantly lower limit of detection for Que, reduced by nearly 3 orders of magnitude to 2.6 nM, while also addressing the critical difficulty of selectively detecting Que in the presence of its glycosylated analogues. This work opens new opportunities for the precise control of photoluminescence in metal NC probes at the molecular level, potentially promoting the development of next-generation metal NC-based sensing technologies.