Binding of ethanol on calcite: the role of the OH bond and its relevance to biomineralization

TY - JOUR

T1 - Binding of ethanol on calcite: the role of the OH bond and its relevance to biomineralization

AU - Sand, K K

AU - Yang, M

AU - Makovicky, E

AU - Cooke, David

AU - Hassenkam, T

AU - Bechgaard, K

AU - Stipp, S L S

PY - 2010/10/5

Y1 - 2010/10/5

N2 - The interaction of OH-containing compounds with calcite, CaCO(3), such as is required for the processes that control biomineralization, has been investigated in a low-water solution. We used ethanol (EtOH) as a simple, model, OH-containing organic compound, and observed the strength of its adsorption on calcite relative to OH from water and the consequences of the differences in interaction on crystal growth and dissolution. A combination of atomic force microscopy (AFM) and molecular dynamics (MD) simulations showed that EtOH attachment on calcite is stronger than HOH binding and that the first adsorbed layer of ethanol is highly ordered. The strong ordering of the ethanol molecules has important implications for mineral growth and dissolution because it produces a hydrophobic layer. Ethanol ordering is disturbed along steps and at defect sites, providing a bridge from the bulk solution to the surface. The strong influence of calcite in structuring ethanol extends further into the liquid than expected from electrical double-layer theory. This suggests that in fluids where water activity is low, such as in biological systems optimized for biomineralization, organic molecules can control ion transport to and from the mineral surface, confining it to specific locations, thus providing the organism with control for biomineral morphology.

AB - The interaction of OH-containing compounds with calcite, CaCO(3), such as is required for the processes that control biomineralization, has been investigated in a low-water solution. We used ethanol (EtOH) as a simple, model, OH-containing organic compound, and observed the strength of its adsorption on calcite relative to OH from water and the consequences of the differences in interaction on crystal growth and dissolution. A combination of atomic force microscopy (AFM) and molecular dynamics (MD) simulations showed that EtOH attachment on calcite is stronger than HOH binding and that the first adsorbed layer of ethanol is highly ordered. The strong ordering of the ethanol molecules has important implications for mineral growth and dissolution because it produces a hydrophobic layer. Ethanol ordering is disturbed along steps and at defect sites, providing a bridge from the bulk solution to the surface. The strong influence of calcite in structuring ethanol extends further into the liquid than expected from electrical double-layer theory. This suggests that in fluids where water activity is low, such as in biological systems optimized for biomineralization, organic molecules can control ion transport to and from the mineral surface, confining it to specific locations, thus providing the organism with control for biomineral morphology.

KW - Adsorption

KW - Calcium Carbonate

KW - Ethanol

KW - Microscopy, Atomic Force

KW - Minerals

KW - Molecular Dynamics Simulation

U2 - 10.1021/la101136j

DO - 10.1021/la101136j

M3 - Journal article

C2 - 20812690

SN - 0743-7463

VL - 26

SP - 15239

EP - 15247

JO - Langmuir

JF - Langmuir

IS - 19

ER -