Pb-Doped Ag2Se Quantum Dots with Enhanced Photoluminescence in the NIR-II Window

Ag2Se quantum dots (QDs) as an effective biological probe in the second near-infrared window (NIR-II, 1000-1700 nm) have been widely applied in bioimaging with high tissue penetration depth and high spatiotemporal resolution. However, the ions deficiency and crystal defects caused by the high Ag+ mobility in Ag2Se crystals are mainly responsible for the inefficient photoluminescence (PL) of Ag2Se QDs. Herein, a tailored route is reported to achieve controllable doping of Ag2Se QDs in which Ag is exchanged by Pb via cation exchange (CE), which is unattainable by direct synthetic methods. The Pb-doped Ag2Se QDs (denoted as Pb:Ag2Se QDs) present fire-new optical features with significantly enhanced PL intensity of 4.2 folds. Photoelectron spectroscopy confirms that Pb acts as an n-type dopant for Ag2Se QDs and therefore the electronic impurities provide additional carriers to fill the traps. Moreover, the general validity of this method is demonstrated to convert different sized Ag2Se into Pb:Ag2Se QDs, so that a wide range of NIR-II PL with high intensity is obtained. The bright NIR-II emission of Pb:Ag2Se QDs is further successfully performed in lymphatic system mapping.

Automated summary

A tailored route is reported for achieving controllable doping of Ag2Se QDs by exchanging Ag with Pb via cation exchange, resulting in significantly enhanced photoluminescence intensity. The Pb:Ag2Se QDs exhibit new optical features and can be successfully used for lymphatic system mapping.