Alloyed geometric structure strategy enables high-quality water-soluble quantum dots for ultrasensitive fluorescence immunoassay

The rapid advance and growth of the point-of-care diagnosis industry has provided an impetus for the development of novel signal labels for highly sensitive bio-molecule detections. Colloidal quantum dots (QDs) exhibit superior brightness, facile surface functionalization and exceptional photostability, making them the preferred option for these biological applications. However, the significantly reduced fluorescence intensity and limited photochemical stability in complex biological environments have greatly hampered their further use. Herein, with an innovative alloying engineering strategy, the high-quality water-soluble CdSe/Cd_xZn_1−xS QDs with near-unity PL quantum yield and monoexponential PL decay dynamics are obtained. Notably, for the first time, a record-breaking stability at the single QD level in water with nonblinking behavior persisting for an hour is achieved, which approaching those of state-of-the-art hydrophobic QDs. Furthermore, the nanocomposites formulated with these novel alloyed QDs demonstrate a remarkable PL QY of 96 % and provide an ultrasensitive detection for prostate specific antigen on lateral flow immunoassays. These findings presented here shed new light on the design of high-brightness water-soluble QDs in single-molecule level and QDs-based nanocomposites, significantly pushing ahead toward high-sensitivity biomedical detections and diagnosis.