Formation of Hierarchical Structures of l-Glutamic Acid with an l-Arginine Additive

Abstract

Formation of hierarchical structures of organic crystals has great potential for many applications in various areas including pharmaceuticals, food, pigments, and organic catalysis. In this paper, we investigate the formation of hierarchical structures of glutamic acid using arginine as a charged additive to control the formation of the hierarchical structures. We used a reprecipitation method as a route to crystallized hierarchical structures of glutamic acid. The crystallization of hierarchical structures of glutamic acid under various experimental parameters, such as solvent compositions, arginine concentrations, and the chirality of the additive were thoroughly studied using several techniques including X-ray diffraction, scanning electron microscopy, and polarized microscopy. It was found that the formation of the hierarchical structures and their size, morphology, and porosity depend strongly on the arginine concentration. On the basis of our results, we propose a possible mechanism for the formation of hierarchical structures of glutamic acid based on the self-assembly principle. Overall, in this work we used the crystallization of l-glutamic acid hierarchical crystals in the presence of arginine as an additive as a model system to better understand the effects of polyelectrolyte additives on the crystallization of organic hierarchical crystals.