COMPARISON OF ORGANIC MONOLAYERS ON POLYCRYSTALLINE GOLD SPONTANEOUSLY ASSEMBLED FROM SOLUTIONS CONTAINING DIALKYL DISULFIDES OR ALKENETHIOLS

This paper compares the properties of self-assembled monolayers (SAMs) on polycrystalline gold formed at 24-degrees-C from 1 to 1000 muM eth anolic solutions of dialkyl disulfides and of alkanethiols. The paper also describes an exploratory study of the kinetics of formation of th ese SAMs. The SAMs were characterized by ellipsometry, X-ray photoelec tron spectroscopy (XPS), and wettability by water or hexadecane. SAMs derived from dialkyl disulfides or alkanethiols were indistinguishable when examined by ellipsometry and XPS; the contact angles of water or hexadecane were largely independent of the oxidation state-disulfide or thiol-of the organosulfur precursor. The rates of formation of SAMs from dialkyl disulfides or alkanethiols were indistinguishable. The r ates of replacement of molecules from SAMs by thiols were much faster than by disulfides. This difference in the rates of replacement may ac count for the large preference for thiols in the competitive adsorptio n of disulfides and thiols on gold.