Improving the Performance of Near-infrared CuInSe2 Quantum Dots by Two Strategies: Doping and Ligand Exchange

Oil phase CuInSe 2 quantum dots (CISe QDs) were synthesized via a hot-injection method, exhibiting a near-infrared (NIR) emission wavelength of 710 $$ nm with poor fluorescence intensity. Therefore, we address this challenge by introducing two strategies: doping and ligand exchange. First, Zn was used as a dopant to improve the fluorescent properties of CISe QDs synthesized by the same method. The PL peak position of the resulting Zn–CuInSe (ZnCISe) QDs could be tuned from 600 $$ nm to 662 $$ nm, and the PL intensity of the QDs was greatly improved. Except that, this Zn doping strategy can help to improve the fluorescence lifetime and reduce defects, leading to increased quantum yield. Next, the aqueous phase transfer of ZnCISe QDs was achieved through an efficient ligand exchange strategy using glutathione (GSH) as the bifunctional ligand. Mercaptoacetic acid (MPA) was also used as an essential additive for GSH ligand exchange. With this method, we obtained high-quality hydrophilic ZnCISe QDs with particle sizes less than 3 $$ nm and good monodispersity. In addition, DLS measurements showed a unimodal peak shape of the hydrated ZnCISe QDs in ultrapure water with particle sizes ranging from 7 $$ nm to 40 $$ nm. Finally, the cytotoxicity studies revealed that the viabilities of the cells incubated with ZnCISe QDs from 1 $$ μ $\mu$ g/mL to 18 $$ μ $\mu$ g/mL remained at levels greater than 90%, which indicates that QDs with good biocompatibility are promising fluorescent probes.