Low-Saturation-Intensity, High-Photostability, and High-Resolution STED Nanoscopy Assisted by CsPbBr 3 Quantum Dots.

Stimulated emission depletion (STED) nanoscopy is one of the most promising super-resolution imaging techniques for microstructure imaging. Commercial CdSe@ZnS quantum dots are used as STED probes and ≈50 nm lateral resolution is obtained. Compared with other quantum dots, perovskite CsPbBr3 nanoparticles (NPs) possess higher photoluminescence quantum yield and larger absorption cross-section, making them a more effective probe for STED nanoscopy. In this study, CsPbBr3 NPs are used as probes for STED nanoscopy imaging. The fluorescence intensity of the CsPbBr3 sample is hardly weakened at all after 200 min irradiation with a 39.8 mW depletion laser, indicating excellent photobleaching resistance of the CsPbBr3 NPs. The saturation intensity of the CsPbBr3 NPs is extremely low and estimated to be only 0.4 mW (0.126 MW cm-2 ). Finally, an ultrahigh lateral resolution of 20.6 nm is obtained for a single nanoparticle under 27.5 mW STED laser irradiation in CsPbBr3 -based STED nanoscopy imaging, which is a tenfold improvement compared with confocal microscopy. Because of its high fluorescence stability and ultrahigh resolution under lower depletion power, CsPbBr3 -assisted STED nanoscopy has great potential to investigate microstructures that require super-resolution and long-term imaging.