ASSEMBLY OF COVALENTLY-COUPLED DISULFIDE MULTILAYERS ON GOLD

We report on the spontaneous organization of up to eight covalently attached layers formed on gold from solution phase (α,ω)-dithiols 1,6-hexanedithiol (C6), 1,8-octanedithiol (C8), and 1,9-nonanedithiol (C9). The linking chemistry between layers is the oxidative formation of a sulfur−sulfur bond that competes successfully with intralayer S−S bond formation. We have used optical null ellipsometry, FTIR, X-ray photoelectron spectroscopy (XPS), and cyclic voltammetry (CV) to characterize the multilayers. Once formed, the multilayers are stable when washed with 1 M KCl, water, ethanol, CHCl3 and n-hexane solutions, before and after prolonged exposure to ambient laboratory conditions. In addition to the formation of multilayers, our data point to the efficient oxidation of the interlayer disulfide bond to an oxidized sulfur moiety where the S−S bond remains intact. Extensive oxidation produces a sulfonate-terminated surface that reacts with Zr4+ and alkanebisphosphonates to form a hybrid multilayer assembly.