Mesocrystals, which are ordered superstructures composed of crystalline nanoparticles aligned along well-defined crystallographic directions, have recently been investigated for their novel or improved properties for different applications. All-inorganic halide perovskite CsPbX3 materials are believed to be promising materials for next generation optoelectronic devices. In this study, a facile and rapid synthesis of all-inorganic halide perovskite CsPbBr3 mesocrystals at ambient temperature in air is presented, which does not employ dimethylformamide (DMF). The results indicate that ligands have great influences on the growth kinetics and morphologies of CsPbBr3 mesocrystals with standard cubic structure and high luminescense. The destabilization of ligand matrix is responsible for the self-assembly of mesocrystals through oriented attachment into larger monocrystals because of mutual crystallographic orientations of individual building blocks with a defined long-range order on the atomic scale. Furthermore, photoactivation phenomenon was observed in CsPbBr3 mesocrystals and these intrinsic properties may help to understand the nucleation and growth mechanisms of metal-halide perovskites.
The calcium nitrate (Ca(NO 3 ) 2 ) waste generated from the production of nitrophosphate fertilizers brings about serious environment and human health issues. Using Ca(NO 3 ) 2 waste and ammonium bicarbonate (NH 4 HCO 3 ) fertilizer as raw materials, higher-value spherical calcite mesocrystals have been synthesized via precipitation method. The synthesis conditions are optimized from the aspects of dispersant, crystal control agent and reaction temperature, and the mechanism that regulates the size and morphology of calcite is illustrated. The synthesized spherical calcite mesocrystals exhibit the small particle size of ca. 5 µm and high specific surface area of 84.44 m 2 /g. Under the dispersion effect of polyvinylpyrrolidone, the adsorption of crystal control agent citric acid on the calcite particles results in the formation of the spherical mesocrystal morphology. The yield of calcite in this process could reach 94.3%. Ca 2+ ion remaining in the mother liquor are further removed in the form of CaCO 3 by addition of calcium oxide , and a mixture of ammonium nitrate and a small amount of NH 4 HCO 3 is obtained by concentrating the filtrate, which can be used as nitrogen fertilizers. This work provides a new insight into the low-cost synthesis of spherical calcite mesocrystals with the high specific surface area and the comprehensive utilization of Ca(NO 3 ) 2 waste.
A facile, low-temperature hydrothermal synthetic route was designed for fabricating rutile TiO 2 mesocrystals composed of ultra-tiny, rod-like subunits. Mesocrystals with tunable sizes and morphologies of the subunits can be simultaneously achieved through a hydrothermal re-treatment process at different temperatures. A probable mechanism for the formation of the self-assembled giant rutile TiO 2 mesocrystals of various sizes and morphologies is proposed based on the experimental results. The rutile TiO 2 giant mesocrystals as-fabricated were also tested as anode materials for sodium-ion storage, and exhibited a capacity of 129.6 mA h g −1 with a capacity retention of 97% for over 1000 cycles at a charge–discharge rate as high as 5 C and enhanced rate capability up to 30 C (64.5 mA h g −1 at 30 C), effectually demonstrating superior sodium storage properties in terms of long-term cycling stability and rate capability.
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