Insights Into to the KX (X = Cl, Br, I) Adsorption-Assisted Stabilization of CsPbI2 Br Surface.

Despite the excellent optoelectronic properties, organic-inorganic hybrid perovskite solar cells (PSCs) still present significant challenges in terms of ambient stability. CsPbI2 Br, a member of all-inorganic perovskites, may respond to this challenge because of its inherent high stability against light, moisture, and heat, and therefore has gained tremendous attraction recently. However, the practical application of CsPbI2 Br is still impeded by the notorious phenomenon of photoinduced halide segregation. Herein, by applying first-principles calculations, the stability, electronic structure, defect properties, and ion-diffusion properties of the stoichiometric CsPbI2 Br (110) surface and that with the adsorption of KX (X = Cl, Br, I) are systematically investigated. It is found that the adsorbed KX can serve as an external substitute of the halogen vacancies on the surface, therefore inhibiting halogen segregation and improving the stability of the CsPbI2 Br surface. The KX can also eliminate deep-level defect states caused by antisites, thereby contributing to the promoted optoelectronic properties of CsPbI2 Br. The mechanistic understanding of surface passivation in this work can lay the foundation for the future design of CsPbI2 Br PSCs with optimized optoelectronic performance.

Exploring the Catalytic Flexibility and Reversibility of Plant Glycosyltransferase HtUGT72AS1 for Glycodiversification of Phenolic Compounds.

Plant bioactive metabolites such as flavonoids are usually present in glycosylated forms by the attachment of various sugar groups. In this study, a catalytically flexible and reversible glycosyltransferase (HtUGT72AS1) was cloned and characterized from Helleborus thibetanus. HtUGT72AS1 could directly accept six sugar donors (UDP-glucose/-arabinose/-galactose/-xylose/-N-acetylglucosamine/-rhamnose) to catalyze the 3-OH glycosylation of flavonols. It also catalyzed the 4' and 7-OH glycosylation of other types of flavonoids, which lacked the 3-OH group. Additionally, the HtUGT72AS1-catalyzed reaction was highly reversible when using 2-chloro-4-nitrophenyl glycosides as substrates, which could be used for one-pot or coupled production of bioactive glycosides. It is the first reported UGT for the synthesis of arabinosides and galactosides using a transglycosylation platform. Based on structural modeling and mutagenetic analysis, the mutation of Tyr377 to Ara enhanced the catalytic efficiency of HtUGT72AS1 toward UDP-N-acetylglucosamine, and the V146S mutant gained an improvement in the regioselectivity toward 7-OH of flavonoids.