Synthesis and characterization of monodispersed spheres of amorphous calcium carbonate and calcite spherules

The isotropic property of amorphous calcium carbonate (ACC) is useful for the controlled synthesis of calcium carbonate based biomaterials. A simple and efficient strategy for the synthesis of monodispersed microspheres of ACC is reported using a low-temperature precipitation of calcium carbonate in the presence of magnesium ions. The room-temperature aging of this amorphous phase yielded superstructures of self-assembled calcite crystals. The stability of the precipitated ACC is proportional to an increase in the concentration of the magnesium ions and the precipitation time. The ACC with high magnesium content was stable for a one month period at room temperature under dry conditions. The ACC aged in solution was stable for up to 48 h. It is believed that the low temperature and the presence of magnesium ions facilitated the formation of stable monodispersed spheres of ACC. The morphological studies and characterizations were carried out using SEM, FTIR, XRD, electron diffraction, and Raman spectroscopy. We expect that the low-temperature synthesis of ACC followed by structural manipulation would be an efficient method for the controlled synthesis of interesting calcium-rich biomaterials.