Combined effect of ion concentration and functional groups on surface chemistry modulated CaCO3crystallization

Abstract

The effects of self-assembled monolayer templates terminated with carboxyl, hydroxyl, amino and methyl groups (–COOH, –OH, –NH₂ and –CH₃) on CaCO₃ crystallization are compared in aqueous solutions of low, medium and high Ca²⁺ concentrations. On the –COOH surface, only calcite rhombohedra are crystallized in the solutions at three different concentrations, while size, shape and orientation of the formed calcites are distinct in various Ca²⁺ concentration solutions. In low Ca²⁺ concentration solution, vaterites (111) and (200) are formed on –OH and –NH₂ surfaces respectively while no crystals are observed on –CH₃ surface. In high Ca²⁺ concentration solution, calcite (104) is formed on the –OH surface. Calcites and small amounts of vaterites and aragonites are formed on –NH₂ and –CH₃ surfaces. In medium concentration solutions, the results are similar to the case of high concentration with a lower density of crystals. From the view of the two well-known mechanisms for biomineralization, ion absorption and particle-based crystallization, the results in our study are discussed. Our findings can advance the understanding of CaCO₃ biomineralization in nature and also supply guidance for the design of advanced biomaterials.