Abstract
Atomic force microscopy (AFM) and chemical force microscopy (CFM) techniques have been used to characterize the chemical functionality of cholesterol monohydrate single-crystal surfaces in different solution environments. Both synthetic and natural crystals adopt a platelike habit in which the largest face is (001). Under aqueous and organic solution conditions, in situ contact mode topographical images reveal that the plate face is primarily terminated by bilayer molecular structures and therefore largely homogeneous. Adhesion force measurements obtained with chemically modified tips demonstrate that the functionality of the crystal surface can be altered by changes in the solution composition. The 3-hydroxyl end of cholesterol molecules is presented on the plate face in aqueous media, while alkyl tail groups terminate the surface in organic solutions. Contact angle measurements on (001) surfaces exposed to solvents of different hydrophilicity also show similar trends, providing additional support to the...
Published Version
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