Self-assembled monolayers of n-hexanethiol and 6-[2′,5′-di(2"-thienyl)pyrrol-1′-yl]hexanethiol on polycrystalline nickel substrates

It is shown in this work that n-hexanethiol and 6-[2',5'-di(2 "-thienyl)pyrrol-1'-yl]hexanethiol form stable monolayers on electrochemically reduced polycrystalline nickel substrates, but not on the oxidised ones. Both thiols, when directly adsorbed on the nickel surfaces without electrochemical pretreatment, show significant proportions of oxidised sulfur species (sulfinates and sulfonates) in their XPS spectra. In contrast, the electrochemical pretreatment leads to monolayers exhibiting S 2p levels essentially characteristic of sulfur atoms bound to metallic sites and corroborating the good chemical stability and resistance to electrochemical oxidation of such monolayers.