Boosting and Activating NIR-IIb Luminescence of Ag₂Te Quantum Dots with a Molecular Trigger

Near-infrared (NIR) excited and NIR-IIb emissive Ag₂Te quantum dots (QDs) display significant advantages in luminescence bioimaging and biosensing due to their unique photophysical properties. However, the poor luminescence intensity and limited strategy for constructing activatable probes severely restrict the wide bioapplications of Ag₂Te QDs. Herein, we proposed a NIR dye-sensitization strategy to solve these two problems. First, we used IR-780 as the antenna for Ag₂Te QDs to improve the ability of harvesting excitation light, obtaining 21-fold luminescence enhancement at 1620 nm under an 808 nm laser irradiation. Subsequently, by further functionalizing the heptamethine cyanine with a recognition unit of glutathione (GSH), Cy-GSH with target-triggered emission was yielded, which served as the potential sensitizer for Ag₂Te QDs to fabricate an activatable ratiometric NIR-IIb nanoprobe for visualizing GSH in vivo with high contrast. This new strategy is expected as a powerful tool to promote the bioapplication of NIR-IIb QDs in the future.