AVS 49th International Symposium
    Surface Science Friday Sessions
       Session SS-FrM

Paper SS-FrM5
pH-Dependence of the Interaction Between Functionalized Probes and Tri(Ethylene Glycol)-Terminated Self-Assembled Monolayers on Gold Studied with Force Spectroscopy

Friday, November 8, 2002, 9:40 am, Room C-110

Session: Self-Assembly at Surfaces
Presenter: C. Dicke, University of St Andrews, UK
Authors: C. Dicke, University of St Andrews, UK
G. Haehner, University of St Andrews, UK
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The understanding of protein adsorption on ultrathin synthetic surfaces has attracted considerable interest in recent years. In particular, the understanding of non-specific interactions is one of the major concerns. Functionalized self-assembled monolayers (SAMs) represent a class of ultrathin model surfaces that allow it to study the resistance to protein adsorption. Several recent investigations demonstrated the outstanding protein repelling properties of SAMs formed by oligo(ethylene glycol) (OEG) terminated alkanethiols on gold. Different suggestions have been made in order to explain this observation. Due to the strong hydration of the EG units in aqueous solutions an extended net-like structured water layer has been proposed to be responsible for the observed behaviour. The possibility of a specific incorporation of ions from solution into the self-assembled structure has also been suggested. Furthermore, it has been speculated that interactions of hydroxyl and/or hydronium ions with the synthetic interface play a major role. In order to elucidate the nature of the forces underlying the protein resistance in more detail, SAMs of methoxy-tri(ethylene glycol)-terminated undecanethiolates (EG3-OMe) adsorbed on polycrystalline gold were investigated by chemical force spectroscopy under liquids. Measurements with differently functionalised probes were performed under aqueous solutions with various ionic strengths and pH-values.