Strained calcite crystals from amorphous calcium carbonate containing an organic molecule

Amorphous calcium carbonate (ACC) is regarded as an important precursor of biogenic crystal phases having specific shapes and mechanical properties. In the present work, calcite that was produced from ACC nanoparticles containing aspartic acid was characterized by Raman scattering spectroscopy and nanoindentation techniques. The tensile strain of the calcite lattice that was estimated from the vibrational spectroscopy varied with the organic content and the mild calcination condition of ACC nanoparticles. Calcite was found to be hardened by the presence of residual organic components inside the crystal lattice. On the other hand, the modulus of calcite decreased as the content of external organic components increased. Here, the mechanical properties of the calcite framework are successfully tuned by the crystallization of the specific amorphous phases containing organic molecules. The mechanical modulation of calcite can be associated with lattice expansion by using vibrational spectroscopy.