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Protein crystallization is an important tool for structural biology and nanostructure preparation. Here, we report on kinetic pathway‐dependent protein crystals that are controlled by light. Photo‐responsive crystallites are obtained by complexing the model proteins with cationic azobenzene dyes. The crystalline state is readily switched to a dispersed phase under ultraviolet light and restored by subsequent visible‐light illumination. The switching can be reversibly repeated for multiple cycles without noticeable structure deterioration. Importantly, the photo‐treatment not only significantly increases the crystallinity, but creates crystallites at conditions where no ordered lattices are observed upon directly mixing the components. Further control over the azobenzene isomerization kinetics produces protein single crystals of up to ≈50 μm. This approach offers an intriguing method to fabricate metamaterials and study optically controlled crystallization. [ABSTRACT FROM AUTHOR]

Protein crystallization is an important tool for structural biology and nanostructure preparation. Here, we report on kinetic pathway‐dependent protein crystals that are controlled by light. Photo‐responsive crystallites are obtained by complexing the model proteins with cationic azobenzene dyes. The crystalline state is readily switched to a dispersed phase under ultraviolet light and restored by subsequent visible‐light illumination. The switching can be reversibly repeated for multiple cycles without noticeable structure deterioration. Importantly, the photo‐treatment not only significantly increases the crystallinity, but creates crystallites at conditions where no ordered lattices are observed upon directly mixing the components. Further control over the azobenzene isomerization kinetics produces protein single crystals of up to ≈50 μm. This approach offers an intriguing method to fabricate metamaterials and study optically controlled crystallization. [ABSTRACT FROM AUTHOR]

Unreacted/excess lead iodide is considered to be the archcriminal for the rapid degradation of hybrid perovskite solar cells. Meanwhile, a high‐quality perovskite film with uniform and large grain size is the basis for high‐performance perovskite modules. Herein, a dual‐site molecular additive 4‐Aniline Sulfonic Acid (4A) is developed to regulate the unreacted/excess PbI2 and passivate defects through hydrogen bonding and intermolecular interactions between amino, and a sulfate groups and PbI2, respectively. Furthermore, the introduction of the 4A additive can induce perovskite seeds to grow uniformly on the substrate, yielding dense, uniform and defect‐less perovskite films with large grain sizes. This enables the fabrication of perovskite photovoltaics with a maximum power conversion efficiency of 24.09% (0.09 cm2) and 20.87% (16 cm2), respectively. This work demonstrated a new strategy to deposit high‐quality large‐scale perovskite films for photovoltaic modules. [ABSTRACT FROM AUTHOR]

A type of boron nitride–magnesium aluminum silicate (BN‐MAS) composite ceramics was fabricated by hot‐press sintering at different sintering temperatures. The relationship between the sintering temperature and microstructure was investigated by analyzing the interaction between hexagonal boron nitride (h‐BN) and the MAS phase. The main MAS phase in the composite ceramics is the α‐cordierite phase at a sintering temperature of 1300°C. At temperatures above 1400°C, the inhibitory effect of h‐BN on the crystallization of the MAS system is significant, and MAS mainly exists in the form of an amorphous phase. The composite sintered at 1700°C exhibited the highest bending strength of 218MPa. h‐BN and MAS were co‐enhanced. MAS can be used as an effective liquid‐phase sintering aid to assist in the sintering of h‐BN, whereas h‐BN can absorb the fracture energy of the composite ceramics through the pull‐out and bridging effect of the particles. [ABSTRACT FROM AUTHOR]

Abstract: Amorphous Si2BC3N nanopowders (NPs) were heated at 1000‐1700°C temperatures for 30 minutes in 1 atm N2. The changes in phases, chemical bonds, and microstructures were investigated by XRD, XPS, NMR, TEM, and first‐principles calculation. Increases in heating temperatures lead to the nucleation and growth of SiC and BN(C) grains, along with partial transformation of SiC4 units from amorphous to β/α‐SiC, and collapse of B–C–N bonds. SiC nucleates prior to BN(C) at 1 atm, while it goes in the opposite order at high pressures (≥1 GPa). High pressures also shift the initial temperatures of crystallization of amorphous Si2BC3N NPs from 1400°C (1 atm) to 1150°C (5 GPa). [ABSTRACT FROM AUTHOR]

Bi3.15Nd0.85Ti3O12 (BNdT)/CoFe2O4 (CFO) composite ceramic powders with embedded structures were successfully prepared by sol-gel processing. Their crystallization behavior was characterized by XRD, DTA, FT-IR, and HRTEM. The magnetic and ferroelectric phases of these composite ceramic powders segregate during calcination. The CFO phase forms easily at ~300°C, thereafter the BNdT matrix phase nucleates with grain growth at the CFO grain boundaries at temperatures >500°C. The CFO phase acts as a heterogeneous nucleation point for formation of the ferroelectric BNdT phase. Furthermore, the 0.5BNdT-0.5CFO composite ceramic powders go through a ferroelectric-paraelectric phase transition at 259°C, and the magnetic CFO nanoparticles (50-100 nm, under calcination at 600°C) embedded in the ferroelectric matrix, show superior magnetic behavior (Mmax = 16.50 emu/g), comparable to pure CFO nanoparticles. [ABSTRACT FROM AUTHOR]

The crystallization behavior of amorphous Si2BC3N monoliths by heating at 1000°C-1400°C and 5 GPa was investigated with the special attention to the nucleation mechanisms of β-SiC and BN(C) phases. Nanoscale puckered structures arising in particle bridging areas were found and its evolution behavior well reflected the nucleation process of nanocrystallites. The temperature-dependent crystallization of amorphous Si2BC3N monoliths at 5 GPa passes through four stages: The material remains amorphous below 1100°C. It undergoes partial phase segregation (1100°C-1200°C), followed by initiation of nucleation (1200°C-1250°C), and then nucleation and growth of β-SiC and turbostratic BN(C) crystallites (>1250°C). The first principles calculation indicates the nucleation precedence of BN(C) phase over β-SiC. BN(C) nucleates preferentially at bridges between ceramic particles causing SiC to concentrate in particle interiors thus forming capsule-like structures. [ABSTRACT FROM AUTHOR]

The fabrication of dense amorphous Si-B-C-N monoliths is a processing challenge given that it is hard to avoid crystallization at the sintering temperatures needed to attain full density up to 1900°C for conventional hot pressing and SPS methods. We report here successful densification of amorphous Si2BC3N monoliths achieved by heating at 1100°C and 5 GPa. The relationships between microstructure, types of chemical bonding, and mechanical properties were investigated. The strong amorphous 3-D networks of Si-C, C-B, C-N (sp³), N-B (sp³), and C-B-N bonds provide high densities at high applied pressure and thus amorphous Si2BC3N monoliths show high hardness of 29.4 GPa and elastic modulus of 291 GPa. The amorphous structure is lost with crystallization of β-SiC and BN(C) reducing contributions from Si-C, C-N (sp³), and C-B-N bond networks thereby decreasing mechanical properties. [ABSTRACT FROM AUTHOR]