Quantum-confined CsPbBr 3 nanoplatelets (NPLs) with narrow full width at half-maximum (FWHM), large exciton binding energies, and precisely tunable thickness have become one of the promising materials for lighting and display. Still, the synthesis of CsPbBr 3 NPLs with high photoluminescence (PL) intensity and excellent stability is challenging, hindering their large-scale application in lighting devices. Herein, we present a facile post-treatment strategy to enhance the PL performance of CsPbBr 3 NPLs by surface passivation with a ZnBr 2 solution. The ZnBr 2 -treated CsPbBr 3 NPLs exhibit 90% photoluminescence quantum yield (PLQY) in the dispersion at 461 nm and 50% PLQY in thin films. Benefiting from surface defect passivation and ion migration suppression, ZnBr 2treated CsPbBr 3 NPLs exhibit outstanding stability over pristine CsPbBr 3 NPLs during long-term storage and exposure to a polar solution, light, and heating treatment. Specifically, the PL intensity of ZnBr 2 -treated CsPbBr 3 NPLs dispersion shows a little decrease after storage at ambient conditions for 50 days or after mixing with ethanol for 160 h. Under challenging conditions including exposure to ultraviolet light for 300 h or heating at 70 °C for 30 min, their PLQY decreases only slightly.
Six fractional polysaccharides were prepared by water extraction and alcohol precipitation under controlled temperature from bletillae rhizoma, a traditional Chinese medicine. Based on this, yields of bletillae rhizome polysaccharides (RBPs) were obtained. The extracting temperature impacted the characteristics of the fractional polysaccharides. The fractional polysaccharides were characterized by glucomannan (GM) content, thermal stability, scanning electron microscopy (SEM), Fourier-transform infrared (FTIR) spectroscopy, gel permeation chromatography (GPC), and x-ray diffraction (XRD). For the analysis, 2.0% w/v dispersions of the six fractional polysaccharides were prepared and their flow behaviors were evaluated using a rotational rheometer. The results showed that increased extraction temperature led to increased GM extraction yields and extraction rate, but GM content was relative stable (over 90%). The average molecular weight (Mw) of fractional polysaccharides obtained at 30, 40, 50, 60, 70, and 80 °C was 3.598 × 104, 4.188 × 104, 8.632 × 104, 8.850 × 104, 2.372 × 105, and 3.081 × 105 g/mol, respectively. SEM revealed that fractional polysaccharides had a porous structure of different sizes and densities. Thermal analysis, FTIR, and XRD results indicated that extraction temperature affects the structure and moisture content of fractional polysaccharides. All results showed that the extraction temperature has an obvious impact on the morphology, molecular weight, and polydispersity of the RBPs. This simple process is a promising method for the preparation of fractional polysaccharides.
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