Thiolate Etching Route for the Ripening of Uniform Ag₂Te Quantum Dots Emitting in the Second Near-Infrared Window: Implication for Noninvasive In Vivo Imaging

Ag2Te quantum dots (QDs) are important near-infrared (NIR) luminescent materials, which have exhibited great potential for biomedical imaging due to the narrow band gap and low in vivo toxicity. However, it remains a challenge to obtain Ag2Te QDs with uniform size and high photoluminescence quantum yield (PLQY). Herein, a thiolate etching strategy is proposed for the synthesis of high-quality Ag2Te QDs emitting in the second NIR (NIR-II) window. Taking advantage of the activity of a thiol ligand, 1-dodecanethiol, Ag(I)–thiolate could trigger the association of Ag(I) with Te on the surface of cubic PbTe QDs and subsequent decomposition of PbTe QDs, resulting in a ripening process for the formation of uniform Ag2Te nanocrystals. The as-prepared Ag2Te exhibited low toxicity and excellent optical properties in the NIR-II window (1300 nm and PLQY = 7%), allowing for the noninvasive in vivo imaging of microvessels (71 μm) with high clarity. This work not only provides a tool for deep tissue fluorescence imaging but also proposes a facile route for the preparation of metal telluride nanocrystals.