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 ) and small aggregates of about 20 Angstrom radius. The process of CaCO3 mineralization in a 0.1 M aqueous solution of CaCl2 was initiated by thermal decomposition of solid (NH4)(2)CO3 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/cm(3) and at two temperatures. A further set of experiments was performed in solution containing a DMAP concentration of 15 mg/cm(3) 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.