XPS, FTIR, EDX, and XRD analysis of Al₂O₃ scales grown on PM2000 alloy

This work is an original example to compare the results obtained after calcination of Al2O3 hydroxides 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 Al2O3 precursors. 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 Al2O3 from the α-Al2O3 and, amongst the transition Al2O3, to differentiate the characteristic of the IR spectrum of γ-δ phases from that of the θ phase

Tantalum oxide/carbon nanotubes composite coatings on titanium, and their functionalization with organophosphonic molecular films:A high quality scaffold for hydroxyapatite growth

peer reviewedNowadays, titanium is a very commonly used biomaterial for the preparation of orthopedic and dental implants. Its excellent mechanical and biochemical bulk properties are nevertheless counterbalanced by its propensity to long term degradation in physiological conditions and its weak osseointegrative capacities. In this context, surface modifications can significantly hinder titanium weaknesses. The approach considered in this work relies on the preparation of thin composite coatings based on tantalum oxide and carbon nanotubes by sol–gel process. Tantalum is particularly interesting for its high biocompatibility and bioactivity, as well as its strong resistance to bio-corrosion. Carbon nanotubes are exploited to reinforce the compactness and homogeneity of the coatings, and can act as a favorable factor to strengthen the interaction with bone components by biomimicry. The composite layers are further modified with specific organophosphonic acid molecular films, able to chemically bind the tantalum oxide surface and improve the hydroxyapatite formation process. The characteristics and the qualities of these hybrid inorganic/organic coatings are evaluated by XPS, SEM, TEM, peeling tests, contact angle measurements, and electrochemical characterizations (free potential, polarization curves)

Reactive amine surfaces for biosensor applications, prepared by plasma-enhanced chemical vapour modification of polyolefin materials

Here we have demonstrated a solventless plasma-based process that integrates low-cost, high throughput, high reproducibility and ecofriendly process for the functionalization of the next-generation point-of-care device platforms. Amine functionalities were deposited by plasma-enhanced chemical vapour deposition (PECVD) using a new precursor. The influence of the plasma RF power and the deposition time on surfacial properties, as well as their effect on the reactivity and content of amino groups was investigated. The key process determinants were to have a sufficient power in the plasma to activate and partially fragment the monomer but not too much as to lose the reactive amine functionality, and sufficient deposition time to develop a reactive layer but not to consume or erode the amine reactivity. An immunoassay performed using human immunoglobulin (IgG) as a model analyte showed an improvement of the detection limit by two orders of magnitude beyond that obtained using devices activated by liquid-phase reaction. © 2010 Elsevier B.V. All rights reserved

Surface science of soft scorpionates

The chemisorption of the soft scorpionate Li[PhTmMe] onto silver and gold surfaces is reported. Surface enhanced Raman spectroscopy in combination with the Raman analysis of suitable structural models, namely, [Cu(κ3-S,S,S-PhTmMe)(PCy3)], [Ag(κ3-S,S,S-PhTmMe)(PCy3)], [Ag(κ2-S,S-PhTmMe)(PEt3)], and [Au(κ1-S-PhTmMe)(PCy3)], are employed to identify the manner in which this potentially tridentate ligand binds to these surfaces. On colloidal silver surface-enhanced Raman spectroscopy (SERS) spectra are consistent with PhTmMe binding in a didentate fashion to the surface, holding the aryl group in close proximity to the surface. In contrast, on gold colloid, we observe that the species prefers a monodentate coordination in which the aryl group is not in close proximity to the surface

Blocking and chemical pretreatments of platinum electrode for the electropolymerization of thiophenes

In order to deposit conductive polymers onto oxidable substrates and to reach a better understanding of the interfacial processes, we have performed an electrochemical analysis of the preadsorption of thiols CmH2m+lSH onto Pt. The blocking ability of the metal oxidation is higher with long alkyl chain and in the case of a preliminary desorption of oxygen. Pretreatments of the Pt electrode by sulfides and bipolar molecules HS-(CH2)n-Y (Y is an aromatic cycle) have been also undertaken. The polymerization process of the 3-methylthiophene and the polymer film properties have been analyzed in function of the structure of the molecule. The structural properties of the films are improved with short alkyl chains (n < 2)

Stability of self-assembled monolayers of organothiol mono and bipode on copper in presence of another organothiol solution

The stability of alkanethiol self-assembled monolayers (SAMs) on metallic substrates is an important aspect for further application. Some studies point out the poor stability of this coating and the displacement of alkanethiol from the monolayer by immersion in another alkanethiol solution. The aim of this work consists in a comparative investigation of self-exchange of three organothiols: 11-perfluorobutyl-1-thiol-undecane (or R fSH), 2-dodecylpropane-1,3- dithiol (or R(SH) 2) and n-decanedithiocarboxylic (or RS 2H). The immersion of RS 2H monolayer into R fSH solution (first approach) leads to the incorporation of thiol molecules into the defects of the initial SAMs followed by the displacement of RS 2H molecules by R fSH. While for R fSH SAM in presence of R(SH) 2 solution (second approach), longer time of immersion is required to observe the incorporation of dithiol molecules into the coating as well as the displacement of thiol molecules. © 2011 Elsevier B.V. All rights reserved

Surface modification of copper with 2-dodecylpropane-1,3-dithiol: The key effect of the solvent

Self-assembly of alkanethiol on gold in various solvents (alkane, alcohol, etc) leads to monolayers with similar properties. However when the self-assembly is performed on copper substrates, the nature of the solvent has an effect on the properties of the monolayer. This phenomenon arises from the chemical interaction of copper with the solvent, which is not the case of gold. Ethanol is a solvent widely used for self-assembly, however some studies pointed out its negative effect due to its significant chemical reactivity towards copper and its ability to chemisorb on the surface. The aim of this work consists in a comparative investigation of 2-dodecylpropane-1,3-dithiol (or R(SH)2) in various solvents and its ability to form stable SAMs, densely packed and well ordered. Characterizations of the SAMs are carried out using X-ray photoelectron spectroscopy (XPS), polarization modulation infrared reflection-absorption spectroscopy (PM-IRRAS) and cyclic voltammetry (CV). © 2009 Elsevier B.V. All rights reserved

Aminealkylthiol and dithiol self-assembly as adhesion promoter between copper substrate and epoxy resin

To improve adhesion between copper and epoxy resin in printed circuit board, a roughness treatment of copper has been widely used. Nevertheless, new adhesion promoters have to be developed to face the miniaturization and sophistication of the electronic device. Self-assembled monolayers have met increasing interest in this field by using them as coupling agent between copper and the epoxy resin. This paper presents the deposition of an epoxy resin on copper modified by amine alkylthiol and dithiol monolayers and highlights the benefit brought by the monolayer in terms of adhesion. The chemical linkage between the amine SAMs and the epoxy function has been proved by the deposition on a short epoxy fragment, the 2-(4-fluorophenoxy-methyl)oxirane. The deposition of an epoxy resin mixed with amine curing agent has then been successfully achieved on amine terminated SAMs. The resulting polymer is homogeneous and well adherent on their surface, while the adhesion is lower on bare copper and not existing on methyl terminated SAMs. The formation of chemical bond Cu-S and N-epoxy is thus essential to increase the adhesion strength between copper and the polymer. © 2011 Elsevier B.V. All rights reserved