Hydrogel-Mediated Mineralization Generates Oriented Crystalline Films Comprising Granular-Rhombohedral Heterogeneous Structures.

Gel-mediated crystallization is a common system to produce self-organized materials, which is fundamental to the development of bottom-up approaches to functional complex materials. Mineralization in hydrogel matrices nevertheless remains empirical in the generation of crystallization products with tailored heterogeneous structures. We demonstrate that the employment of the hydrogels with proper cationic diffusivity can trigger the consecutive growth of oriented, granular-rhombohedral heterogeneous structures. The controllable morphogenesis leads to continuous calcitic CaCO3 films comprising spatial heterogeneity, where epitaxial match assumedly favors the successive deposition of both granular and rhombohedral layers. The scenario of consecutive growth is disclosed, where the thickness of the granular layers can become a valuable indicator to reflect the retardancy degree of crystallization. The evaluation of the physicochemical properties of the hydrogels finally establishes a direct correlation between the cationic diffusivity of the hydrogels and the appearance of the heterogeneous structures. The current work therefore sheds light on the implementation of rational morphogenetic approaches to crystalline materials with tailored complex architectures.