Responsive Optical Materials Based on Ligand-Free Perovskite Quantum Dots Embedded in Mesoporous Scaffolds

Herein we show that dispersing inorganic cesium lead bromide (CsPbBr₃) perovskite quantum dots (QDs) in optical quality films, possessing an accessible and controlled pore size distribution, gives rise to fluorescent materials with a controlled and highly sensitive response to ambient changes. A scaffold-based synthesis approach is employed to obtain ligand-free QDs, whose pristine surface endows them with high sensitivity to the presence of different vapors in their vicinity. At the same time, the void network of the host offers a means to gradually expose the embedded QDs to such vapors. Under these conditions, the luminescent response of the QDs is mediated by the mesostructure of the matrix, which determines the rate at which vapor molecules will adsorb onto the pore walls and, eventually, condensate, filling the void space. With luminescence quantum yields as high as 60%, scaffold-supported ligand-free perovskite nanocrystals display intense photoemission signals over the whole process, as well as high photo- and chemical stability, which allows illuminating them for long periods of time and recovering the original response upon desorption of the condensed phase. The results herein presented open a new route to explore the application of perovskite QD-based materials in sensing.

Pure green emission self-crystallization CsPbBr3 quantum dot glass with Ag+ doping for stable light-emitting devices

Recently, cesium lead bromide perovskite glass has been recognized as a potential material to fabricate green light emission devices because of their high stability and excellent optical performance. However, the low photoluminescence efficiency and poor color purity ($\lt\! 525\,\,{\rm nm}$) of ${{\rm CsPbBr}_3}$ quantum dot (QD) glass restricts its practical application. In this work, self-crystallization ${{\rm CsPbBr}_3}$ QD glasses are successfully prepared via the melt quenching method, and the photoluminescence efficiency increases 10-fold compared with regular thermal treatment ${{\rm CsPbBr}_3}$ QD glass without ${\rm Ag}^+$ doping. The green light-emitting devices based on bulk self-crystallization ${{\rm CsPbBr}_3}$ QD glass with 0.4 mol.% ${\rm Ag}^+$ doping achieves a luminescence efficiency of 20.85 lm/W with a CIE (0.2084, 0.6026) under a 20 mA driving current. The present results provide new, to the best of our knowledge, insight into the application of ${{\rm CsPbBr}_3}$ QD glass in the optoelectronic field.

Highly efficient and blue-emitting CsPbBr3 quantum dots synthesized by two-step supersaturated recrystallization

Highly efficient and blue-emitting CsPbBr₃ quantum dots were successfully synthesized by two-step supersaturated recrystallization under ambient condition. This method could control the particle size within 2.8 nm, thus resulting in strong quantum confinement effect of the products. The as-synthesized CsPbBr₃ quantum dots presented outstanding optical properties with highest photo-luminescence quantum yield of 87.20% and longest PL lifetime of 12.24 ns. The blue light-emitting diode made from the CsPbBr₃ quantum dots exhibited a CIE coordinate (0.14, 0.10), in good agreement with the standard blue CIE coordinate (0.14, 0.08) of National Television System Committee (NTSC).

Highly luminescent biocompatible CsPbBr3@SiO2 core-shell nanoprobes for bioimaging and drug delivery

The encapsulation of lead halide perovskite nanocrystals (PNCs) with an inert protective layer against moisture and the environment is a promising approach to overcome hinderances for their practical use in optoelectronic and biomedical applications. Herein, a facile method for synthesizing highly luminescent and biocompatible CsPbBr₃@SiO₂ core-shell PNCs with a controlled SiO₂ thickness, which are suitable for both cell imaging and drug delivery, is reported. The synthesized CsPbBr₃@SiO₂ core-shell PNCs exhibit bright green emission at 518 nm upon excitation of 374 nm. Interestingly, a significant increase in the photoluminescence intensity is observed with an increase in the SiO₂ shell thickness, which varies with the increasing reaction time. Cytotoxicity results indicate that the CsPbBr₃@SiO₂ core-shell PNCs are nontoxic, making them suitable for in vitro cell imaging using HeLa cells. Furthermore, doxorubicin physically adsorbed on the surface of CsPbBr₃@SiO₂ core-shell PNCs is efficiently released in cells when the drug-loaded perovskite nanoprobes are injected in the cells, indicating that these core-shell nanoparticles can be used for drug loading and delivery. The results of this study suggest that the CsPbBr₃@SiO₂ core-shell PNCs can pave the way for new biomedical applications and processes.

Higher quantum efficiency and moisture resistance of all-inorganic halide perovskite nanocrystal films in situ fabricated with cyclodextrin

β-Cyclodextrin confines the growth of CsPbBr₃ nanocrystals, generating a smooth film with a higher quantum efficiency and a longer moisture resistance.