Biomimetic synthesis of hollow microspheres of calcium carbonate crystals in the presence of polymer and surfactant

Hollow CaCO3 microspheres were successfully synthesized using sodium carbonate and calcium chloride through a precipitation reaction method at room temperature. Polyvinylpyrrolidone (PVP), together with sodium dodecyl sulfonate (SDS), was employed as template for the controlled growth of hollow CaCO3 microspheres. The concentration of SDS was an important factor to control the synthesis of hollow CaCO3 microspheres. It suggested that the PVP–SDS complex micelles played a key role in controlling the growth of biominerals X-ray diffraction (XRD), FESEM and TEM confirmed that hollow CaCO3 microspheres consisting of calcite crystals were synthesized In the present work, we also proposed a hypothetical mechanism for the formation process of hollow CaCO3 microspheres.

From the experimental results, the growth mechanism of hollow CaCO3 microspheres was speculated upon. Hypothetical mechanism of hollow CaCO3 microspheres formation is illustrated in this figure. PVP could interact strongly with anionic SDS to form PVP–SDS complex micelles with long chains intermingling in the headgroup region of the SDS micelles. SDS could provide the nucleation sites for the crystallization of CaCO3 owing to the interaction of SDS and Ca2+. Not only PVP–SDS complex micelles could be formed, but also free surfactant micelles could exist in the solution.Figure optionsDownload as PowerPoint slideHighlights
► Hollow CaCO3 microspheres were synthesized by the precipitation reaction method.
► PVP and SDS were employed as a template for the controlled growth of CaCO3.
► A hypothetical mechanism of hollow CaCO3 microspheres formation was illustrated.
► This method is a useful route for the biomimetic mineralization materials.