Template Adaptability is Key in the Oriented Crystallization of CaCO3
In CaCO3, biomineralization nucleation and growth of the crystals are related to the presence of carboxylate-rich proteins within a macromolecular matrix, often with organized {beta}-sheet domains. To understand the interplay between the organic template and the mineral crystal it is important to explicitly address the issue of structural adaptation of the template during mineralization. To this end we have developed a series of self-organizing surfactants (1-4) consisting of a dodecyl chain connected via a bisureido-heptylene unit to an amino acid head group. In Langmuir monolayers the spacing of these molecules in one direction is predetermined by the hydrogen-bonding distances between the bis-urea units. In the other direction, the intermolecular distance is determined by steric interactions introduced by the side groups (-R) of the amino acid moiety. Thus, by the choice of the amino acid we can systematically alter the density of the surfactant molecules in a monolayer and their ability to respond to the presence of calcium ions. The monolayer films are characterized by surface pressure-surface area (p-A) isotherms, Brewster angle microscopy, in-situ synchrotron X-ray scattering at fixed surface area, and also infrared reflection absorption spectroscopy (IRRAS) of films transferred to solid substrates. The developing crystals are studied with scanning and transmission electron microscopy (SEM, TEM), selected area electron diffraction (SAED), and crystal modeling. The results demonstrate that although all compounds are active in the nucleation of calcium carbonate, habit modification is only observed when the size of the side group allows the molecules to rearrange and adapt their organization in response to the mineral phase.
- Research Organization:
- Brookhaven National Lab. (BNL), Upton, NY (United States). National Synchrotron Light Source
- Sponsoring Organization:
- Doe - Office Of Science
- DOE Contract Number:
- DE-AC02-98CH10886
- OSTI ID:
- 959770
- Report Number(s):
- BNL-82756-2009-JA; JACSAT; TRN: US1005805
- Journal Information:
- Journal of the American Chemical Society, Vol. 129; ISSN 0002-7863
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ABSORPTION SPECTROSCOPY
AMINO ACIDS
CALCIUM CARBONATES
CALCIUM IONS
CHAINS
CRYSTALLIZATION
ELECTRON DIFFRACTION
ISOTHERMS
MICROSCOPY
MINERALIZATION
MODIFICATIONS
NUCLEATION
PROTEINS
REFLECTION
SCATTERING
SUBSTRATES
SURFACE AREA
SURFACTANTS
SYNCHROTRONS
TRANSMISSION ELECTRON MICROSCOPY
national synchrotron light source