Phase transfer-based synthesis of highly stable, biocompatible and the second near-infrared-emitting silver sulfide quantum dots

摘要

Previously reported silver sulfide (Ag_2S) quantum dots (QDs) emitting in the second near-infrared window (NIR-Ⅱ, 1000-1400 nm) showed the capacity of in vitro and in vivo bioimaging. Herein, we reported a facile phase transfer- based synthesis to achieve water-dispersed NIR-Ⅱ-emitting Ag_2S QDs. After undergoing phase transfer of Ag~+ ions from water to toluene, and the synthesis of Ag_2S in toluene followed by ligand exchange, Ag_2S QDs were favorably prepared. A series of characterizations confirmed that the prepared products were monoclinic α-Ag_2S, showing an average size of 3.7 nm. The Ag_2S QDs exhibited the maximum emission located at 1045 nm, high PL stability and low cytotoxicity, indicating the feasibility of Ag_2S QDs for effective bioimaging in NIR-Ⅱ biological window.