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Biomimetic Synthesis of Macroscopic-Scale Calcium Carbonate Thin Films. Evidence for a Multistep Assembly Process

Summary: Biomimetic Synthesis of Macroscopic-Scale Calcium Carbonate Thin
Films. Evidence for a Multistep Assembly Process
Guofeng Xu,#, Nan Yao, Ilhan A. Aksay,, and John T. Groves*,#,
Contribution from the Departments of Chemistry and Chemical Engineering and the Princeton Materials
Institute, Princeton UniVersity, Princeton, New Jersey 08544
ReceiVed June 1, 1998
Abstract: Biologically controlled mineralization features an orchestrated balance among various controlling
factors such as spatial delineation, template promotion, crystal growth modification and cessation, and so on.
Highly ordered calcium carbonate lamellae formed in the nacreous layers of mollusk (aragonite), the foliated
calcitic layers of mollusk (calcite), or the semi-nacre of brachiopods (calcite) are excellent examples of the
outcome of such synergistic control. Mimicking the concerted interplay of template promotion and growth
inhibition as often utilized in biomineralization, we have synthesized macroscopic and continuous calcium
carbonate thin films with thickness ranging from 0.4 to 0.6 m. The thin films were prepared at air/subphase
interfaces by promoting mineral deposition with amphiphilic porphyrin templates, coupled with growth inhibition
by the use of poly(acrylic acid) as a soluble inhibitor. Films formed at 22 C were found to have a biphasic
structure containing both amorphous and crystalline calcium carbonate. The crystalline regions were identified
to be calcite oriented with the (00.1) face parallel to the porphyrin monolayer at the air/subphase interface.
Films obtained in the early stage of formation at lower temperature (4 C) displayed characteristics of a single
amorphous phase. These observations suggest that films formed through a multistage assembly process, during
which an initial amorphous deposition was followed by a phase transformation into the ultimate crystalline


Source: Aksay, Ilhan A. - Department of Chemical Engineering, Princeton University


Collections: Materials Science