The Role of Mg2 and BSA Langmuir Monolayers in Controlling Polymorph and Morphology of CaCO3 Crystal

Abstract

Mg2+ and bovine serum albumin (BSA) Langmuir monolayers were used as effective crystal nucleation and growth modifiers and template to control the crystallization of CaCO3. The polymorph and morphology of crystals were characterized using scanning electron microscopy (SEM), and X-ray diffraction (XRD). The results demonstrated that various morphologies such as abacus-bead-like particles, spherical-shaped particles, wood block-like particles, pignut-shell-like particles and the rolling pole shaped particles produced at the interface of film/solution. With the increasing of the molar ratio of Mg2+ to Ca2+, the polymorph of calcium carbonate obtained undergoes an evolvement from calcite to vaterite and aragonite. The ability of Mg2+ to induce the formation of aragonite was enhanced as the molar ratio of Mg2+ to Ca2+ increased. When the molar ratio reached 3, the crystals obtained were all aragonite. In the systems of Mg2+-BSA Langmuir monolayers, the presence of Mg2+ was helpful for the formation of aragonite. The possible formation mechanisms of CaCO3 in different systems were discussed in the paper.