T. Laiho

XPS study of irradiation damage and different metal–sulfur bonds in dodecanethiol monolayers on gold and platinum surfaces

The X-ray induced irradiation damage is studied in the CH3(CH2)11SH monolayers on gold and platinum surfaces to get information on the metal–sulfur bonds. This is important because the sulfur–substrate bond is one of the crucial factors in thiol SAMs. The X-ray photoelectron spectra (XPS) of the S 2p and C 1s emission were analyzed. During the modification of the surface the thiol/platinum system behaves differently than the thiol/gold system. In the latter case the S 2p spectrum changes as a function of time during the measurement and two chemically different sulfur species, associated with Au-thiolates and irradiation induced sulfur species, can be identified in the spectra. On platinum, there are two chemically different sulfur species in pristine monolayers and their ratio remains unchanged as a function of measurement time. This trend is obviously surface induced and is related to the nature of the metal–sulfur bonds in the self-assembled thiol layers.

Effective low temperature reduction of graphene oxide with vanadium(III)

Reduction of graphene oxide (GO) with vanadium(III) trichloride under various reaction conditions has been investigated. The results show that V(III) can be used as an efficient reducing agent for GO in aqueous solutions at low concentrations and in moderate temperatures under ambient conditions. The IR spectroscopy and X-ray photoelectron spectroscopy (XPS) show that the structure of the vanadium-reduced material is similar to reduced graphene oxide prepared using TiCl3 or hydrazine as a reducing agent. The electrical conductivity of the material is also similar in all cases. However, on the basis of the XPS results, vanadium-based reduction does not leave significant reductant impurities in the product and does not lead to graphene substitution reactions. The success of vanadium(III) is somewhat surprising because the formal redox potential of the V(IV)/V(III) pair is rather anodic, but spectrophotometric studies of the reaction unambiguously showed that the process is a redox reaction. This method introduces a new facile graphene oxide reduction technique, which can be applied under ambient aqueous conditions.