Green emitted CdSe@ZnS quantum dots for FLIM and STED imaging applications

Inorganic quantum dots (QDs) have excellent optical properties, such as high fluorescence intensity, excellent photostability and tunable emission wavelength, etc., facilitating them to be used as labels and probes for bioimaging. In this study, CdSe@ZnS QDs are used as probes for Fluorescence lifetime imaging microscope (FLIM) and stimulated emission depletion (STED) nanoscopy imaging. The emission peak of CdSe@ZnS QDs centered at 526[Formula: see text]nm with a narrow width of 19[Formula: see text]nm and the photoluminescence quantum yield (PLQY) was 64%. The QDs presented excellent anti-photobleaching property which can be irradiated for 400[Formula: see text]min by STED laser with 39.8[Formula: see text]mW. The lateral resolution of 42.0[Formula: see text]nm is demonstrated for single QDs under STED laser (27.5[Formula: see text]mW) irradiation. Furthermore, the CdSe@ZnS QDs were for the first time used to successfully label the lysosomes of living HeLa cells and 81.5[Formula: see text]nm lateral resolution is obtained indicating the available super-resolution applications in living cells for inorganic QD probes. Meanwhile, Eca-109 cells labeled with the CdSe@ZnS QDs was observed with FLIM, and their fluorescence lifetime was around 3.1[Formula: see text]ns, consistent with the in vitro value, suggesting that the QDs could act as a satisfactory probe in further FLIM-STED experiments.