Nucleation and growth of CaCO₃ minerals on biomimetic templates studied by small-angle scattering

The process of mineralization of CaCO₃ on surfaces built up with DMAP (4-dimethylamino-pyridine) molecules was explored by time resolved SANS experiments. In most samples the DMAP molecules were attached to colloidal gold representing a model system of biomimetic template structures. The small-angle neutron scattering (SANS) data, however, show that DMAP forms in water a more complex structure built up of large (>1000 Å) and small aggregates of about 20 Å radius. The process of CaCO₃ mineralization in a 0.1 M aqueous solution of CaCl₂ was initiated by thermal decomposition of solid (NH₄)₂CO₃ in a closed vessel. This process was followed in-situ by SANS over a time period of about 12 h. Experiments were performed with colloids plus DMAP concentrations between 0 and 49 mg/cm³ and at two temperatures. A further set of experiments was performed in solution containing a DMAP concentration of 15 mg/cm³ without colloidal gold. The process of mineralization could be characterized by the time evolution of size and number density of the mineralized particles as will be presented and discussed in this paper.