-
[show abstract]
[hide abstract]
ABSTRACT: Macromolecular layers rich in amino acids and with some sulfated polysaccharides appear to control oriented calcite growth in living organisms. Calcite crystals nucleating under floating acid monolayers have been found to be unoriented on average. We have now observed directly, using in situ grazing incidence X-ray diffraction, that there is a 1:1 match between the monolayer unit cell and the unit cell of the (001) plane of calcite. Thus, sulfate head groups appear to act as templates for the growth of (001)-oriented calcite crystals, which is the orientation commonly found in biominerals.
Langmuir 10/2008; 24(19):10579-82. · 4.19 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: X-ray studies performed during the growth of CdCO(3) and MnCO(3) crystals from supersaturated aqueous solutions, at fatty acid monolayer templates, reveal that the nucleates are nearly three-dimensional powders below a threshold supersaturation. However, at higher supersaturations, the crystals are preferentially oriented with the {0 1 2} direction vertical. Scanning electron microscope images of samples transferred to substrates show discrete crystals at low concentrations, while at higher concentrations the crystals self-aggregate to form linear chains and sheets. The authors speculate that preferential alignment at the organic-inorganic interface is enhanced as a consequence of oriented aggregation of crystals. The role of monolayer-ion interactions in governing the morphologies and the resulting orientation of the inorganic nucleate is discussed.
The Journal of Chemical Physics 01/2007; 125(22):224713. · 3.33 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Oriented inorganic films can be grown under Langmuir monolayers floating on supersaturated aqueous solutions. This process mimics biomineralization, and is potentially an easy method for growing designed inorganic films. Grazing-incidence X-ray diffraction (in situ) and scanning electron microscopy (of films transferred to substrates) reveal that oriented growth occurs via two distinct mechanisms. First, there can be epitaxial growth, with organic and inorganic lattices relaxing to allow an exact match. A variant is the appearance of a reconstructed surface superlattice that mediates between the unstrained organic and bulk inorganic structures. Second, the alignment of crystals already formed can be enhanced via spontaneous self-aggregation into oriented chains.
Thin Solid Films 515(14):5627-5630. · 1.89 Impact Factor
