In the current research, we are committed to solving the irreconcilable contradiction between fragmentation, agglomeration, poor size controllability, and high solid content in the preparation of BiOCl crystals. Water soluble block polymer polyethylene glycol monomethyl ether-b-polydimethylaminoethyl methacrylate (mPEG-b-PDMAEMA) was synthesized as dispersant to achieve high solid content by reducing the frequency of crystal collisions to avoid crystal fragments and agglomerates. With the reaction temperature of 80 °C, urea dosage of 40 g, bismuth salt solution addition rate of 0.45 ml/min, and variable amount of pre-added HCl in the reaction vessel, fragment-free BiOCl crystals of wide size ranges were successfully obtained with record-high solid content of above 10 wt%. Furthermore, bio-based pearlescent coatings were prepared by using as-synthesized BiOCl crystals as pearlescent pigments and polyglyceryl tetrastearate and polyphenyl polymethylene polyisocyanate (PAPI) as the formulations of two-component solvent free polyurethane . The decorative polyurethane coatings demonstrated excellent physical properties and corrosion resistance , which exhibited eye-catching gloss effects from pearl luster, glitter pearl luster, to shimmering luster derived from the size variation of 20, 50, and 70 µm, respectively. The large-scaled production of size controllable BiOCl crystals with high solid content in wide size range promises the practical applications in decorative coatings, cosmetics, clothing accessories, and car interior accessories.
Crystallization, while a common process in nature, remains one of the most mysterious phenomena. Understanding its physical mechanisms is essential for obtaining high-quality crystals. Typically, crystals grown by thermal evaporation or sublimation nucleate the substrate facing the evaporation source. Here, a novel vapor micro-turbulence mass transport mechanism in the growth process of ultrathin BiOCl single crystals has been revealed. In this mechanism, the precursor vapor bypasses the solid substrate, forming micro-turbulent vaporizing flows to nucleate on the surface of the substrate facing away from the evaporation source. Considering nucleation kinetics, fast shear flows are known to cause secondary nucleation, increasing nucleation quantity while decreasing the final size of the crystals. Thus, the nucleation and growth process of BiOCl crystals are controlled by adjusting the micro-turbulence intensity to reduce shear flow energy and dilate phase distribution, resulting in BiOCl crystals with uniform distribution and regular shape. Subsequent structural and morphological characterization confirms the high crystallization quality of the obtained crystals, and the performance of the constructed solar-blind photodetectors is comparable to that of similar devices. These findings contribute to a deeper understanding of vapor mass transport and crystal growth techniques and may be useful for applications related to metal oxide crystals. Graphical abstract
危险品化学品经营许可证（带存储）