Aqueous synthesis of bright near-infrared-emitting Zn-Cu-In-Se quantum dots for multiplexed detection of tumor markers

Aqueous synthesis is a green but challenging pathway to produce cadmium-free,bright,and near-infrared(NIR)emitting quantum dots(QDs).Herein,we develop a straightforward aqueous phase approach to prepare Zn-Cu-In-Se QDs with tunable emission from 630 to 800 nm through varying the molar ratio of Zn and Cu.The ultrasmall nanoparticle size remains nearly fixed(~2.6 nm)when the QD composition is varied,allowing for the effects of composition on the optical properties of QDs to be decoupled from the impact of particle size.By leveraging the off-stoichiometric effect on photoluminescence(PL),Zn-Cu-In-Se QDs with a Zn:Cu molar ratio of 1.0 show a long PL decay lifetime of 211 ns and an absolute photoluminescence quantum yield(PLQY)of 14.2%.The PLQY is further enhanced by overcoating a ZnS shell,reaching up to 25.8%.Based on the bright,biocompatible,and emission-tunable QDs,nanoprobes with targeting capability for multiple tumor markers are further constructed and employed to simultaneously ascertain targets in the cytoplasm and cell membrane.This study provides a green and effective strategy for achieving bright and biocompatible NIR quantum dots for multiplexed biodetection applications.