Monolayers of n-dodecanethiol molecules on surfaces of polycrystalline nickel electrochemically pretreated are obtained by immersion either in pure n-dodecanethiol or in a solution of the mercaptan in absolute ethanol. The influence of the electrochemical pretreatment on the quality of the organic layer has been studied by contact angle measurements, electrochemistry, and X-ray photoelectron spectroscopy. It is found that n-dodecanethiol monolayers directly adsorbed on nickel surfaces without electrochemical pretreatment are of poor quality and exhibit a significant proportion of the thiols oxidized into sulfonates and sulfinates. On the contrary, the electrochemical pretreatment leads to monolayers with significantly improved physicochemical properties such as better chemical stability, resistance to electrochemical oxidation, and molecular order.

Self-assembled monolayers (SAMs) of n-alkanethiols on mechanically polished polycrystalline nickel substrates are presented. The effects of several preparation conditions of the surface upon the metal/sulfur bonds and monolayer properties are evidenced. Of particular importance are the electrochemical reduction of the native oxide, the thiol concentration (10 -3 versus 10 -1 M), and the nature of the solvent (ethanol, acetonitrile, n-heptane, toluene, and carbon tetrachloride).

No abstract

This work is an original example to compare the results obtained after calcination of Al2O3hydroxides and oxidation of alumino-formers alloys. FTIR and XPS signatures were obtained for various oxidation temperatures and compared with those known from the literature about calcination of Al2O3precursors. The aim of this work is to evaluate the use of IR spectroscopy and XPS analysis to probe the structural varieties of Al2O3. For this objective, a study of the PM2000 oxidation at various temperatures was conducted by means of XRD, IR spectroscopy, XPS analysis, EDX analysis, and SEM observations. This allowed us to clearly differentiate the transition Al2O3from theα-Al2O3and, amongst the transition Al2O3, to differentiate the characteristic of the IR spectrum ofγ-δphases from that of theθphase.

No abstract

The self-assembly of aliphatic thiol (RSH), dithiol (R(SH)(2)), and dithiocarboxylic acid (RS(2)H) onto mildly oxidized and highly oxidized copper was studied in real time by in situ electrochemical impedance spectroscopy (EIS). Ex situ characterization of the films was carried out using linear sweep voltammetry (LSV), polarization modulation infrared reflection absorption spectroscopy (PM-IRRAS), and X-ray photoelectron spectroscopy (XPS). In situ EIS studies found a very fast adsorption of RSH, R(SH)(2), and RS(2)H (within 10-15 s). This fast adsorption step is followed by the long-term additional adsorption and consolidation of SAM. However, the self-assembly of RS(2)H passes through an intermediate step of molecule rearrangement for around 10 to 30 min after around 2 to 7 min of self-assembly. The binding of both sulfur moieties of R(SH)(2) with Cu happens simultaneous. The oxide reduction capacity of RSH, R(SH)(2), and RS(2)H was good. However, the XPS studies showed the decomposition of RS(2)H-based SAMs to Cu(2)S. Monolayers prepared on both mildly oxidized and heavily oxidized Cu with R(SH)(2) had the highest stability. Monolayers of RS(2)H showed the least stability on both mildly oxidized and heavily oxidized Cu. Although RSH-based SAMs had good organization on both mildly oxidized and highly oxidized Cu, R(SH)(2)-based SAMs did not show good organization in either case. The RS(2)H monolayer had good organization only on mildly oxidized Cu.

No abstract

In this paper, the chemical functionalization of multi-walled carbon nanotubes by a fluorinated trichlorosilane ((tridecafluoro-1,1,2,2-tetrahydrooctyl)trichlorosilane) is investigated. The chlorosilane has been shown to react with carboxylic acid moieties, created by an oxidative process on the nanotube walls, as well as with alcohol groups obtained by a reductive reaction of these previous oxidized nanotubes. The derivatizations were directly confirmed by x-ray photoelectron spectroscopy and thermogravimetry analyses. Little difference in the functionalization was observed for the oxidized or reduced nanotubes. However, the amount of grafted silane seems to be slightly more important when the silanization is carried out with reduced nanotubes.