title: Molecular-scale surface structures of oligo(ethylene glycol)-terminated self-assembled monolayers investigated by frequency modulation atomic force microscopy in aqueous solution.
abstract: The structure and protein resistance of oligo(ethylene glycol)-terminated self-assembled monolayers (OEG-SAMs) have been studied intensively using various techniques. However, their molecular-scale surface structures have not been well understood. In this study, we performed molecular-resolution imaging of OH-terminated SAMs (OH-SAMs) and hexa(ethylene glycol) SAMs (EG(6)OH-SAMs) formed on a Au(111) surface in an aqueous solution by frequency modulation atomic force microscopy (FM-AFM). The results show that most of the ethylene glycol (EG) chains in an EG(6)OH-SAM are closely packed and well-ordered to present a molecularly flat surface even in an aqueous solution. In addition, we found that EG(6)OH-SAMs have nanoscale defects, where molecules take a disordered arrangement with their molecular axes parallel to the substrate surface. We also found that the domain size (50-200 nm) of an EG(6)OH-SAM is much larger than that of OH-SAMs (10-40 nm). These findings should significantly advance molecular-scale understanding about the surface structure of OEG-SAMs.
authors.affiliation: Division of Electrical Engineering and Computer Science, Kanazawa University, Kakuma-machi, Kanazawa 920-1192, Japan.
authors.forename: N
authors.initials: N
authors.lastname: Inada
authors.forename: H
authors.initials: H
authors.lastname: Asakawa
authors.forename: Y
authors.initials: Y
authors.lastname: Matsumoto
authors.forename: T
authors.initials: T
authors.lastname: Fukuma