Recently, quasi-two-dimensional (quasi-2D) organic–inorganic hybrid perovskites, such as those obtained by introducing long-chain organic cations like n-butylammonium (BA) into 3D MAPbI3 perovskites, have been widely investigated as optoelectronic devices owing to their high light absorption coefficient, ultra-long carrier diffusion length, and high defect tolerance. Controlling the BA content to obtain (BA)2(MA)n−1PbnI3n+1 with homogeneous n values is crucial for extraction of photo-carriers because volatile n value related interior heterojunctions are unfavorable for extraction of photo-carriers. Here, we revealed the fundamental growth mechanism of (BA)2(MA)n−1PbnI3n+1. The growth mechanism of (BA)2(MA)n-1PbnI3n+1 SCs is controlled by the evolution of macroscopic spiro dislocations and its derived growth steps. In terms of the understanding of the surface growth mechanism, we grew a series of single crystals with individual n values, avoiding interior heterojunctions, and obtained a lower dark current of 0.247 nA, a high photocurrent (74.5 nA) and high responsiveness (0.064 A W−1) and an external quantum efficiency of 19.5% for a photodetector based on the (BA)2(MA)3Pb4I13 SC. This contributes to an in-depth understanding of the growth mechanism of quasi-2D (BA)2(MA)n−1PbnI3n+1 SCs and the development and optimization of quasi-2D layered materials and devices for optoelectronics.
Li Jing,Li Ziyi,Gong Hui,Ma Mengyi,Li Shuolei,Yang Huilin,Zhang Hailin,Liu Jianguo
Abstract In this study, a novel high-activity amylosucrase from Salinispirillum sp. LH10-3-1 (SaAS) was identified and characterized. The recombinant enzyme was determined as a monomer with a molecular mass of 75 kDa. SaAS protein exhibited the maximum total and polymerization activities at pH 9.0 and maximum hydrolysis activity at pH 8.0. The optimum temperature for total, polymerization, and hydrolysis activities were 40, 40, and 45 °C, respectively. Under the optimal pH and temperature, SaAS had a specific activity of 108.2 U/mg. SaAS also showed excellent salt tolerance and could retain 77.4% of its original total activity at 4.0 M NaCl. The addition of Mg 2+ , Ba 2+ , and Ca 2+ enhanced the total activity of SaAS. When the conversion of 0.1 M and 1.0 M sucrose was catalyzed at pH 9.0 and 40 °C for 24 h, the ratios of hydrolysis, polymerization, and isomerization reactions were 11.9:77.4:10.7 and 15.3:53.5:31.2, respectively. The α-arbutin yield of 60.3% was achieved from 20 mM sucrose and 5 mM hydroquinone catalyzed by SaAS. Key points
• A novel amylosucrase from Salinispirillum sp. LH10-3-1 (SaAS) was characterized.
• SaAS has the highest specific enzyme activity among all known amylosucrase.
• SaAS has hydrolysis, polymerization, isomerization, and glucosyltransferase activities.
Graphical Abstract
Alkaline earth lithoaluminates with the UCr4C4-type structure have demonstrated considerable potential in achieving narrow-band emissions from Eu 2+ . However, obtaining single-phase powder samples with green-emitting remains challenging. In this study, we address this issue by co-doping Ba 2+ into the novel UCr4C4-type system Sr5/6-xBaxLi17/6Al7/6O4:Eu 2+ , which significantly enhances phase purity and structural homogeneity. This approach not only reduces the emission bandwidth from 66 nm (2241 cm -1 ) to 51 nm (1830 cm -1 ) but also induces a blue shift to 529 nm, fine-tuning the emission into the desired deep green region. Through detailed mechanistic studies-including low-temperature spectroscopy and luminescence decay analysis-we identify the presence of multiple Eu 2+ emission centers associated with distinct Sr 2+ sites. Ba 2+ doping is shown to promote dominant Eu 2+ emission in the green spectral region, thereby facilitating spectral narrowing.The optimized phosphor achieves a high absorption efficiency of 64.6% and an external quantum yield of 22.2%. When integrated into a white LED prototype, it enables a color gamut covering 97.6% of the NTSC (National Television System Committee) standard, outperforming a commercial β-SiAlON:Eu 2+ -based device. This study provides an effective cationic codoping strategy for designing high-performance narrow-band oxide phosphors and highlights a promising candidate for nextgeneration display technologies.
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