Synthesis and near-infrared photoluminescence properties of Ag₂S quantum dots

Ag₂S quantum dots (QDs) have been synthesis by a new one-step wet chemistry method. The obtained water-soluble Ag₂S QDs have long-term stability without sedimentation after storage for more than one year. The nanoparticles have a monoclinic crystal structure with average sizes of ∼45 nm and display a broad absorption from visible to near infrared (NIR) wavelength region with a peak at 1060 nm. Irradiated by a NIR laser of 808 nm, the photoluminescence in NIR-II region was found with its peak centered at 1110 nm. These Ag₂S QDs may be used as new nontoxic QDs for in vitro and vivo bio-imaging.