Surface Copassivation Strategy for Developing Water-Soluble InP Colloidal Quantum Dots with High Luminescence and Suppressed Blinking.

Colloidal quantum dots (QDs) are promising emitters for biological applications because of their excellent fluorescence, convenient surface modification, and photostability. However, the toxic cadmium composition in the state-of-the-art QDs and their inferior properties in the aqueous phase greatly restrict further use. The performance of water-soluble indium phosphide (InP) QDs lags far behind those of Cd-containing counterparts due to the lack of effective surface protection. Here, we present an efficient copassivation strategy via dual hydrophilic ligands to achieve water-soluble InP-based QDs with ideal optical properties. A record photoluminescence quantum yield of near-unity and monoexponential decay dynamics for water-soluble InP-based QDs are achieved. For the first time, we realize a single water-soluble InP-based QD with significantly suppressed blinking. Furthermore, the novel QDs exhibit superior cellular imaging capabilities and high resistance to photobleaching compared with commonly used organic dyes. The results presented here will inspire the development of environmentally friendly water-soluble QDs as a promising class of fluorescence labels for biological applications.