Attachment of alkyltrichlorosilanes to the terminal 3,5-dihydroxyphenyl moiety of a self-assembled thiol monolayer on gold

The synthesis of 5-(6-mercaptohexyloxy)-1,3-dihydroxybenzene and the formation of a self-assembled monolayer on polycrystalline gold using this compound are described. Methyltrichlorosilane and (tridecafluoro-1,1,2,2-tetrahydrooctyl)trichlorosilane were attached to the 3,5-dihydroxyphenyl terminus of the monolayer. The modified surfaces were studied by contact angle measurement, XPS, and cyclic voltammetry. High contact angles of 119degrees-128degrees were observed for the semifluoroalkylsilyl-functionalized monolayer. These high contact angles were maintained after subjecting the surface to, e.g., boiling in water or heating in air to 300degreesC. Characterization of the silane-modified monolayers by XPS indicated more than one layer of silane present at the top of the monolayer. The thickness was reduced after boiling the cross-linked monolayers in H2O, however, maintaining high contact angles. Cyclic voltammetry studies revealed that the semifluoroalkylsilyl-functionalized surface showed a higher blocking capability and a higher electrochemical stability than the parent monolayer. (C) 2002 Elsevier Science (USA).