Understanding the fundamental properties of metal-halide perovskite materials is driving the development of novel optoelectronic applications. Here, we report the observation of a recoverable laser-induced fluorescence quenching phenomenon in perovskite films with a microscopic grain-scale restriction, accompanied by spectral variations. This fluorescence quenching depends on the laser intensity and the dwell time under Auger recombination dominated conditions. These features indicate that the perovskite lattice deformation may take the main responsibility for the transient and show a new aspect to understand halide perovskite photo-stability. We further modulate this phenomenon by adjusting the charge carrier recombination and extraction, revealing that efficient carrier transfer can improve the bleaching resistance of perovskite grains. Our results provide future opportunities to attain high-performance devices by tuning the perovskite lattice disorder and harvesting the energetic carriers.

Many kinds of nanoparticles and organic dyes as fluorescent probes have been used in the stimulated emission depletion (STED) nanoscopy. Due to high toxicity, photobleaching and non-water solubility, these fluorescent probes are hard to apply in living cell imaging. Here, we report a new fluorescence carbon dots (FNCDs) with high photoluminescence quantum yield (56%), low toxicity, anti-photobleaching and good water-solubility that suitable for live-cell imaging can be obtained by doping fluorine element. Moreover, the FNCDs can stain the nucleolus and tunneling nanotubes (TNTs) in the living cell. More importantly, for STED nanoscopy imaging, the FNCDs effectively depleted background signals and improved imaging resolution. Furthermore, the lateral resolution of single FNCDs size under the STED nanoscopy is up to 22.1 nm for FNCDs deposited on a glass slide was obtained. And because of their good water dispersibility, the higher resolution of single FNCDs size in the nucleolus of a living cell can be up to 19.7 nm. After the image optimization steps, the fine fluorescence images of TNTs diameter with ca. 75 nm resolution is obtained living cell, yielding a threefold enhancement compared with that in confocal imaging. Additionally, the FNCDs show excellent photobleaching resistance after 1, 000 scan cycles in the STED model. All results show that FNCDs have significant potential for application in STED nanoscopy.

Halide perovskite (CsPbX₃, X = Cl, Br, or I) quantum dots have received increasing attention as novel colloidal nanocrystals (NCs). Accurate control of emission bands and NC morphologies are vital prerequisites for most CsPbX₃ NC practical applications. Therefore, a facile method of synthesizing CsPbX₃ (X = Cl, Br, or I) NCs in the nonpolar solvent octane was developed. The process was conducted in air at ~ 90 ℃ to synthesize high-quality CsPbX₃ NCs showing 12–44 nm wide emission and high photoluminescence quantum yield, exceeding 90%. An in situ anion-exchange method was developed to tune CsPbX₃ NC photoluminescence emission, using PbX₂ dissolved in octane as the halide source. NC morphology was controlled by dissolving specific metal–organic salts in the precursor solution prior to nucleation, and nanocubes, nanodots, nanosheets, nanoplatelets, nanorods, and nanowires were obtained following the same general method providing a facile, versatile route to controlling CsPbX₃ NC emission bands and morphologies, which will broaden the range of CsPbX₃ NC practical applications.