Controlled crystallization of calcium carbonate superstructures in macroemulsions

In this paper we describe the nucleation and growth of calcium carbonate (CaCO₃) in a reverse macroemulsion system based on N-stearoyl acid surfactant with head group of serine. The CaCO₃ nanocrystals crystallized in the macroemulsions were characterized by scanning electron microscopy (SEM), Fourier transform infrared spectrometer (FT-IR) and X-ray diffraction. Our results indicated that crystallization of CaCO₃ in macroemulsions leads to the formation of vaterite and calcite nanocrystals with a uniform size of rod-like morphology and also to the formation of amorphous CaCO₃. Based on our results we propose a growth mechanism in which the stabilization of the rod-like vaterite nanocrystals is via interactions with the serine head group of surfactant. Our study demonstrates the potential application of macroemulsions to control crystals morphology and polymorphism.