Synthesis and characterization of polymer-mediated biomimetic calcium carbonate materials

Abstract

Synthesis of inorganic nanoparticles is currently recognized as an important theme in nanoscience. Calcium carbonate (CaCO3) nanoparticles (< 100 nm) have many unique properties compared to regular CaCO3 particles. CaCO3 is an important mineral, exhibits different shapes and colors, depending on the conditions at its formation and the nature of additives present during growth. Many living organisms are well able to synthesize highly optimized composite materials by means of template controlled mineralization as in pearls, shells, etc. For example, amorphous calcium carbonate (ACC) deposits of Porcellio scaber (land-based woodlice) are built of numerous spherules associated with an organic matrix that consists of radial and concentric elements, suggesting that the organic components function as a template for spherule formation. Recent efforts to duplicate the natural process of biomineralization in the laboratory have come to be known as biomimetic methods for synthesis. An understanding of the mechanism involved in such a matrix-mediated synthesis has been recognized to be of great potential in the production of engineered materials. In the present study, Porcellio scaber is used as a model to investigate the dissolution behavior of biogenic ACC by atomic force microscopy which provides a new way to investigate the stabilizing properties of matrix components. Biological systems manage to control crystal growth to high degrees of specificity by using a wide range of natural additives: from basic metal ions to complex organic polymers. In this context, an examination of how CaCO3 growth is affected by water-soluble polymers and low molecular weight additives will provide further insight and information. Here the synthesis of CaCO3 was followed by two synthetic routes: double decomposition reaction (a simple route, but it is difficult to control the shape and modification of CaCO3) and miniemulsion method (CaCO3 synthesis was performed in 1018 - 1020 nanocompartments which are separated from each other by a continuous phase). ACC is a fascinating form of CaCO3 that may well be of much interest to materials science and biomineralization. ACC in its pure form is highly unstable, yet some organisms produce stable ACC, and cases are known in which ACC function as a transient precursor of more stable crystalline CaCO3. By using miniemulsion technique, I have synthesized ACC nanoparticles which are stable in solution and also in the dry state for several days.