Low‐Saturation‐Intensity, High‐Photostability, and High‐Resolution STED Nanoscopy Assisted by CsPbBr₃ Quantum Dots

Abstract 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.