Self-assembled hexasaccharides: Surface characterization of thiol-terminated sugars adsorbed on a gold surface

A thiol-terminated hexasaccharide, protected with acetyl groups (AHS) was synthesized for the purpose of depositing self-assembled monolayers (SAMs) from solution onto gold surfaces. S-ray photoelectron spectroscopy (XPS), ellipsometry, contact angle measurements, and imaging time-of-flight secondary ion mass spectroscopy (iToF-SIMS) were used to determine coverage, homogeneity, chemical composition, film thicknesses, and kinetics of film growth. Deprotection of the molecules, i.e. replacing acetoxy groups by hydroxyl groups, was performed following adsorption of AHS onto the surface, as well as prior to adsorption from solution. The chemical composition of the resulting films, the film thickness, the density of molecules, and the nature of the surface functional groups were determined. Adsorption of the deprotected molecules (DHS) from solution was found to lead to a higher density of adsorbed species.