Controlling the polymorph and morphology of CaCO3 crystals using surfactant mixtures

Inspired by mineralization in biological organisms, fabrication of higher ordered CaCO3 crystals modified by surfactants has received much attention. In our present work, mixed surfactants of hexadecyl(trimethyl)azanium bromide and sodium dodecyl sulfate were used to mediate the nucleation and growth of CaCO3 crystals. When the concentration of sodium dodecyl sulfate in the solution is constant (0.1 mM), the polymorph of CaCO3 crystals changed from pure vaterite to pure aragonite with increase of the ratio of hexadecyl(trimethyl)azanium bromide to sodium dodecyl sulfate. Various morphologies of vaterite and aragonite were obtained. Based on the time-resolved experiments, we suggest that the flower-like CaCO3 formed via aggregation of hexagon-like vaterite induced by the surfactants. More importantly, we realized that a cluster-shaped morphology of aragonite was produced through the nucleation of aragonite at the surfaces of the hexagon-like vaterite. (C) 2011 Elsevier Inc. All rights reserved.