Functionalization of self-assembled monolayers on gold by UV-induced graftpolymerization

Further modifications of self-assembled monolayers (SAMs) on gold via argon plasma-treatment and then UV-induced graft polymerization with functional monomers has been carried out. Two alkanethiols, viz., 3-mercaptopropionic acid (MPA) and 3-mercaptopropionic acid 2-ethylhexyl ester (MPAEE), were em ployed for the deposition of SAMs from ethanol solutions onto gold surfaces . The monomers used for graft polymerization were water-soluble acrylic aci d (AAc) and hydrophobic allylpentafluorobenzene (APPB). Angle-resolved X-ra y photoelectron spectroscopy (XPS) and contact angle measurements were used to investigate the surface chemical composition, surface coverage, film th ickness, and wettability. XPS result suggest that mild and brief plasma tre atmetns can be employed to generate amounts of peroxides and hydroperoxides on the SAMS for the subsequent UV-induced graft polymerization while maint aining the SAMs intact. For all the cases investigated, XPS results reveal that the graft polymer forms a thin layer of 6-7 nm in thickness on the SAM surfaces. Contact angle measurements indicate that the SAM-modified Au sur faces could be selectively made hydrophilic or hydrophobic through the graf t copolymerization with an appropriate monomer. It was also demonstrated th at the AAc graft polymerized SAMs selectively absorbed Fe3+ ions via coordi nation complexation.