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International audience; Air pollution is a public health issue and the toxicity of ambient particulate matter (PM) is well-recognized. Although it does not mostly contribute to the total mass of PM, increasing evidence indicates that the ultrafine fraction has generally a greater toxicity than the others do. A better knowledge of the underlying mechanisms involved in the pathological disorders related to nanoparticles (NPs) remains essential. Hence, the goal of this study was to determine better whether the exposure to a relatively low dose of well-characterized iron-rich NPs (Fe-NPs) might alter some critical toxicological endpoints in a relevant primary culture model of human bronchial epithelial cells (HBECs). We sought to use Fe-NPs representative of those frequently found in the industrial smokes of metallurgical industries. After having noticed the effective internalization of Fe-NPs, oxidative, inflammatory, DNA repair, and apoptotic endpoints were investigated within HBECs, mainly through transcriptional screening. Taken together, these results revealed that, despite it only produced relatively low levels of reactive oxygen species without any significant oxidative damage, low-dose Fe-NPs quickly significantly deregulated the transcription of some target genes closely involved in the proinflammatory response. Although this inflammatory process seemed to stay under control over time in case of this acute scenario of exposure, the future study of its evolution after a scenario of repeated exposure could be very interesting to evaluate the toxicity of Fe-NPs better. K E Y W O R D S gene expression profiling, human bronchial epithelial cells, inflammation, iron nanoparticles, oxidative stress, physicochemical characterization 1 | INTRODUCTION Air pollution still constitutes the major threat to human health, whereas the adverse impacts and the underlying mechanisms of air pollution-derived particulate matter (PM) are not clearly defined

This study reports for the first time the use of β-carotene as a natural photosensitizer for both the cationic photopolymerization and thiol-ene click reactions under visible-light irradiation. In ...

A general approach to side-chain allyl-functionalization of three different polyelectrolytes (PEs), namely poly(allylamine hydrochloride) (PAH·HCl), branched polyethyleneimine (PEI) and poly(sodium 4-styrenesulfonate) (PSS), is reported for the first time. This functionalization does not affect the electrolytic properties of the newly functionalized PEs (named PEs-ene), as confirmed by the effective formation of PE-ene multilayer (PEM) films. The stepwise construction of these films is monitored using different techniques, including QCM, SEM, XPS, and WCA measurements. The incorporation of allyl functional groups into the PE side-chains allows for the stabilization of the resulting PEM films via thiol–ene UV photo-crosslinking in the presence of a water-soluble dithiol crosslinker. To overcome the problem of film delamination, the covalent crosslinking occurs not only between different layers of PEM films but also with the substrates preliminarily functionalized with allyl functional groups either via sulfur–gold chemistry or via chemical reduction of aryldiazonium salts using two newly synthesized anilinium derivatives. The stability of the resulting crosslinked PEM films in a strongly alkaline solution (pH = 14) is validated on gold substrates under QCM conditions (from 30 min to 3 h), while XPS and WCA measurements are used for evidencing such a stability under strongly acidic conditions (pH = 1) or at high salt concentration (saturated NaCl solution) on a modified anion-exchange membrane during a longer study time, i.e. 10 days. Finally, this stability study also gives evidence for a greater crosslinking efficiency of PEG-diSH, namely a macromolecular crosslinker, over dithiothreitol (DTT), a small molecule. The versatility and effectiveness of the approach presented here are expected to find widespread interest in different fields of emerging applications.

Different synthesis protocols have been developed to control TiO2 anatase nanoparticle packing. The diameter of TiO2 packing aggregate varies from 13 nm to a few 100 nm. Efficiency of dye-sensitized solar cells (DSSC) fabricated with the obtained TiO2 packing aggregate films was reported to depend on the size of the packing aggregate. It increases with the increase of the aggregate size (number of TiO2 nanoparticles) to a maximum of 4.3% and then it decreases. This effect was discussed in terms of a balance between the incident light scatterings, adsorbing amount of dye molecules, cracks free and the efficiency of electron transfer (reduction of recombination process).

Large biomolecule interaction with oxide surface has attracted a lot of attention because it drives behavior of implanted devices in the living body. To investigate the role of TiO2 surface structure on a large polypeptide (insulin) adsorption, we use a homemade mixed Molecular Dynamics-Full large scale Quantum Mechanics code. A specific re-parameterized (Ti) and globally convergent NDDO method fitted on high level ab initio method (coupled cluster CCSD(T) and DFT) allows us to safely describe the electronic structure of the whole insulin-TiO2 surface system (up to 4000 atoms). Looking specifically at carboxylate residues, we demonstrate in this work that specific interfacial bonds are obtained from the insulin/TiO2 system that are not observed in the case of smaller peptides (tripeptides, insulin segment chains with different configurations). We also demonstrate that a large part of the adsorption energy is compensated by insulin conformational energy changes and surface defects enhanced this trend. Large slab dimensions allow us to take into account surface defects that are actually beyond ab initio capabilities owing to size effect. These results highlight the influence of the surface structure on the conformation and therefore of the possible inactivity of an adsorbed polypeptides.

A new electrochemical synthetic method for the transition metal-catalyzed homocoupling of 2-halopyridinic compounds into symmetrical 2,2’-bipyridines is described. Experiments were carried out in a cavity cell under various reaction conditions, using a nickel complex as catalyst, and controlled-potential or constant-current electrolyses. A graphite powder/carbon nanotube 9:1 ratio mixture proved to constitute the optimal cathode material. Excellent homocoupling product yields were observed using aqueous KCl solution as anolyte. The cathode material proved to be recyclable with possible reuse three times without notable loss of activity.

The effects of iron nanoparticles on bryophytes (Physcomitrella patens) were studied following foliar exposure. We used iron nanoparticles (Fe–NP) representative of industrial emissions from the metallurgical industries. After a characterization of iron nanoparticles and the validation of nanoparticle internalization in cells, the effects (cytotoxicity, oxidative stress, lipid peroxidation of membrane) of iron nanoparticles were determined through the axenic culturing of Physcomitrella patens exposed at five different concentrations (5 ng, 50 ng, 500 ng, 5 µg and 50 µg per plant). Following exposure, the plant health, measured as ATP concentrations, was not impacted. Moreover, we studied oxidative stress in three ways: through the measure of reactive oxygen species (ROS) production, through malondialdehyde (MDA) production and also through glutathione regulation. At concentrations tested over a short period, the level of ROS, MDA and glutathione were not significantly disturbed.

International audience; Metal hydrides are promising high-capacity anode materials for Li-ion batteries but their conversion reaction with lithium suffers from low reversibility at room temperature (RT). Irreversibility issues in magnesium hydride MgH2 thin films are investigated, as well-defined model system. Films are deposited over Cu current collectors by means of microwave plasma-assisted sputtering and coated with aluminum to minimize formation of passivating MgO native oxide. Structural and chemical properties of the electrodes have been analyzed by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), and electrochemical impedance spectroscopy (EIS). Galvanostatic cycling reversibility at RT and C/50 regime is limited to 25% in the first cycle for 1 μm thick films. The lithiation of the thin film is complete and doubles its thickness. Despite drastic volume changes, neither cracks, voids, nor detachment of the thin film from the substrate are noticed. Moreover, electronic resistivity decreases upon lithiation due to the formation of metallic Mg. The origin of irreversibility phenomena in MgH2 films is attributed to sluggish mass transport of species within the electrode at RT.

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International audience; The presented work shows the development of a performing electrochemical sensor using self-organized gold nanoparticle (Au NP) modified HOPG electrode. Au NPs were functionalized with bisphosphonate-thiol receptors (BP-thiol) whose interactions with Au NP surface were investigated by XPS and FTIR-ATR experiments. It has been shown that the electrochemical stability of modified electrodes increases at potentials higher than-1.3 eV corresponding to the thiol reduction potential. In order to demonstrate the sensing performance of the prepared electrode the electrochemical analysis of copper and silver metal ions was achieved by using square wave voltammetry (SWV). The obtained results show a remarkable performance increase in terms of: the simple fabrication, simple use, and linear behaviour over the concentration range from 5 µM to 0.5 mM, with the detection limit of 5 µM.

Biobased release networks embedding active phenolic moieties were prepared by photoinduced thiol–ene reaction. The originality of this work is to design UV-cured materials as the delivery system of two phenolic compounds i.e. carvacrol (presents in thyme essential oil) and tannic acid (plants extracted). The key point of this study is to elaborate the cross-linked network and, in the same step, trapping the active phenolic molecules thanks to a rapid photoinduced process at room temperature, preserving active natural compounds. The photoactivated thiol–ene reaction was chosen to synthesize different eugenol-based networks since this process is nowadays mainly well-known as a fast and straightforward tool to prepare cross-linked materials by green chemistry. The mechanical and thermal properties of the networks were determined, and their antibacterial and antioxidant properties were investigated against two bacteria strains: Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli). The system based...

The aim of this study was to highlight the properties of novel phosphorus-containing β-cyclodextrin polymers (CDP) and mainly their dual complexing abilities toward hydrophobic guests and (bio)minerals. Affinity of CDP toward divalent metal cations, calcium, magnesium and zinc, has been investigated by isothermal titration microcalorimetry (ITC). The complexation constants K were around 1.1–6.2 × 104 L mol−1 and were in the order Ca2+ < Mg2+ < Zn2+. The K regular increase with the CDP molecular weights could be attributed to a cooperative binding of the cations by the monophosphate groups carried by the CDPs. Regarding their CD and phosphorus functionalities, the dual complexing abilities toward amphiphilic guests and divalent cations can occur independently as evidenced from ITC experiments performed in presence of both species. Finally, strong interactions between CDPs and hydroxyapatite have been highlighted by X-ray photoelectron spectrometry with adsorbed amount in the range of 2 mg/m2. CDPs are thus promising materials endowed with dual functionalities which could serve in biomaterials to simultaneously entrap bioactive molecules and capture (bio)minerals.

A green photoinduced method for the modification of a biodegradable and biocompatible polymer, poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBHV), has been successfully carried out using three types of monomers with potential antibacterial effects, i.e., 2-[(methacryloyloxy)-ethyl] trimethylammonium chloride (META), 2-[(methacryloylethyl)]-dimethyl-(3-sulfopropyl) ammonium (MESA) and 2-hydroxyethyl methacrylate (HEMA). The photografting process is conducted through a photoinduced free radical process employing a ketone-based photoinitiator in an aqueous medium. Under appropriate conditions, the photogenerated radicals abstract hydrogen atoms from the PHBHV backbone, thus initiating the UV-mediated photopolymerization of derived-(meth)acrylate monomers from the surface of PHBHV film. The photochemical mechanism of the ketones photolysis is entirely described by a electron spin resonance/spin trapping technique, and the modified-PHBHV films are extensively characterized by ATR-FTIR and water contact angle...

The knowledge of the underlying mechanisms by which particulate matter (PM) exerts its health effects is still incomplete since it may trigger various symptoms as some persons may be more susceptible than others. Detailed studies realized in more relevant in vitro models are highly needed. Healthy normal human bronchial epithelial (NHBE), asthma-diseased human bronchial epithelial (DHBE), and COPD-DHBE cells, differentiated at the air-liquid interface, were acutely or repeatedly exposed to fine (i.e., PM2.5-0.18, also called FP) and quasi-ultrafine (i.e., PM0.18, also called UFP) particles. Immunofluorescence labelling of pan-cytokeratin, MUC5AC, and ZO-1 confirmed their specific cell-types. Baselines of the inflammatory mediators secreted by all the cells were quite similar. Slight changes of TNFα, IL-1β, IL-6, IL-8, GM-CSF, MCP-1, and/or TGFα, and of H3K9 histone acetylation supported a higher inflammatory response of asthma- and especially COPD-DHBE cells, after exposure to FP and especially UFP. At baseline, 35 differentially expressed genes (DEG) in asthma-DHBE, and 23 DEG in COPD-DHBE, compared to NHBE cells, were reported. They were involved in biological processes implicated in the development of asthma and COPD diseases, such as cellular process (e.g., PLA2G4C, NLRP1, S100A5, MUC1), biological regulation (e.g., CCNE1), developmental process (e.g., WNT10B), and cell component organization and synthesis (e.g., KRT34, COL6A1, COL6A2). In all the FP or UFP-exposed cell models, DEG were also functionally annotated to the chemical metabolic process (e.g., CYP1A1, CYP1B1, CYP1A2) and inflammatory response (e.g., EREG). Another DEG, FGF-1, was only down-regulated in asthma and specially COPD-DHBE cells repeatedly exposed. While RAB37 could help to counteract the down-regulation of FGF-1 in asthma-DHBE cells, the deregulation of FGR, WNT7B, VIPR1, and PPARGC1A could dramatically contribute to make it worse in COPD-DHBE cells. Taken together, these data contributed to support the highest effects of UFP versus FP and highest sensitivity of asthma- and notably COPD-DHBE versus NHBE cells.

Thermal degradation of blue phosphor BAM:Eu 2 + under air is investigated using XPS, XRD, EPR and photoluminescence (PL) in order to analyze the loss of intensity in terms of modifications of the dopant distribution in the crystal cell and between crystal bulk and surface. This study reveals the key role played by oxidation-driven 2D diffusion of europium and barium, that results in important concentration gradients and makes degradation strongly dependent on both microstructure and cooling speed. Also based upon cation mobility, a possible regeneration effect is evidenced at moderate temperature. Flux treatments, known to increase the intensity of photoluminescence, also appear to reduce thermal degradation by lowering specific surface; they also enhance the regeneration process by forming extended single-crystal domains conducive to cation diffusion.

The influence of copper derived TiO

International audience; Nosocomial infections are often induced by the presence of pathogenic organisms on the surface of medical devices or hospital equipment. Chemical modifications of the surface are recognized as efficient strategies to prevent bacterial adhesion but they may have a negative impact on the material's interaction with living tissues. Here we have developed a photoactivated method for the modification of titanium substrates. A photoinduced technique employing a grafting-onto process has been successfully performed to covalently anchor an imidazolium-derivative siloxane onto titanium surfaces. Imidazolium surfaces showed higher bacteria-repellency performances than native titanium substrates, achieving more than 98% anti-adhesion efficiency against Escherichia coli after 24 h of incubation. In addition, these surfaces allowed for the adhesion and viability of osteoblasts cells without evidence of cytotoxicity.

Bio-based networks derived from eugenol and linalool were prepared with an eco-friendly process by photoactivated thiol-ene reactions. Allyl derivative Eugenol, AE, prepared by a nucleophilic substitution was combined with linalool, L, a monoterpene presents in the lavender essential oil, well known to its antibacterial activity or with Eugenol, E, a sustainable antioxidant molecule major component of the essential oil of clove. The photoactivated thiol-ene reaction is a quick room temperature straightforward way to obtain renewable crosslinked networks. Two bacteria strains were used in vitro to evaluate the resistance to bacterial adhesion and the DPPH method was used to determine the antioxidant properties of the networks. As expected, the results showed a promising anti-adhesion activity against Staphylococcus aureus (S.aureus) and Escherichia coli (E. coli) due to the presence of eugenol moieties. Moreover, the phenol groups of eugenol provide an antioxidant activity characterized by a radical scavenging activity of 90%.

International audience; Nosocomial infections are often induced by the presence of pathogenic organisms on the surface of medical devices or hospital equipment. Chemical or topographical modifications of the surface are recognized as efficient strategies to prevent bacteria adhesion but they may have negative impact on the material interaction with living tissues. Here we have developed a photoactivated method for the modification of a biocompatible polymer, poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBHV) under aqueous conditions. A photoinduced free-radical technique employing a grafting-from process in water media has been successfully performed to covalently anchored fluorine or PEG groups onto PHBHV surfaces. PEGylated hydrophilic surfaces showed higher bacteria-repellency performances than fluorinated hydrophobic films, achieving a >98% anti-adhesion efficiency against Escherichia coli and Staphylococcus aureus. In addition, these surfaces allowed for the adhesion and proliferation of human dermal fibroblasts without the evidence of cytotoxicity.

In this paper, we report on preliminary investigations about surface reactivity of quasicrystalline-based alloys with respect to small biological molecules such as amino-acids. The main purpose is to study potential applications for these materials in biomedical fields since biomolecules are well known to be sensitive to solid surface wettability, surface energy and charge. In that sense, quasicrystals surfaces could be attractive considering their unusual symmetry, their low surface energy and their peculiar electronic properties. Our investigations were focussed on superficial reactivity of as-quenched Ti45Zr38Ni17 (numbers indicate at.%) ribbons, whose microstructure was analysed by transmission electron microscopy and X-ray diffraction. Surfaces were then carefully polished and immersed in a solution (C = 10−2 mol l−1, pH 6) of l -glutamic acid or l -lysine for duration varying from 30 min to 6 days. Molecular vibrational modes and adsorption kinetics were investigated using infrared spectroscopy. The first results reveal that l -glutamic acid seems to display faster adsorption kinetic on quasicrystalline ribbons compared to that on pure titanium (cpTi) or on β-metastable alloys (Ti–12 Mo–6 Zr–4.5 Sn), which is quite interesting since surface energy on quasicrystals is known to be low.

Two decades of intense research on quasicrystalline materials have suggested their potential use as surface coatings, considering their low coefficient of friction, high hardness, good corrosion and wear resistances and low surface energy. In that sense, quasicrystals could be introduced into the field of biomaterials since biomolecules are well known to be sensitive to solid surface properties. In this paper we report on investigations of the early stage of oxidation of the quasicrystals forming Ti45Zr38Ni17 alloy and its surface reactivity with respect to an aminoacid. After analysing the microstructure of as-quenched ribbons both by transmission electron microscopy and X-ray diffraction, surface oxide layers were characterized by X-ray Photoelectron Spectroscopy (XPS). Oxidation of Ti45Zr38Ni17 results in the formation of a ZrO2/TiO2 barrier oxide layer, avoiding toxic Ni release. This latter is mainly present at the oxide/alloy interface. Thereafter, adsorption of L-glutamic acid has been investigated by infrared spectroscopy. Even if this biomolecule is found to adsorb to each substrate, it seems to display different adsorption mechanisms on quasicrystalline ribbons compared to that on pure titanium (CpTi) or on pure zirconium (Zr), leading to a weaker signal on Ti45Zr38Ni17. We discuss these results along with the affinities of each alloying metal to oxygen and with the peculiar electronic properties of quasicrystals which could affect the surface properties of Ti45Zr38Ni17. [doi:10.2320/matertrans.48.278]

Novel βCD-based hydrogels have been synthesized using sodium trimetaphosphate (STMP) as non-toxic reagent. Straightforward mixing of βCD with dextran and STMP in basic aqueous media led to hydrogels incorporating dextran chains, phosphate groups and βCD units. The hydrogels have been characterized by swelling measurements, XPS and (31)P NMR. The swelling ratio was correlated to the content in phosphated groups, which give a polyelectrolyte character to these hydrogels. The significant rise of the swelling ratio with the βCD content increase has been attributed to a decrease of the number of phosphate-based crosslinks, the βCD units playing the role of dangling ends in the tridimensional network. Their loading capacity and their release properties have been investigated for methylene blue and benzophenone in order to demonstrate their potentiality for drug delivery. Through different interaction mechanisms, electrostatic and inclusion complex interactions, these compounds are loaded with different efficiencies. The release involves deswelling, diffusion mechanisms and partition equilibrium.

The adsorption of S-histidine on gold and copper well-defined surfaces has been characterised by reflection absorption infrared spectroscopy (RAIRS), a surface technique that gives chemical as well as orientational information. Analyses were carried out in a UHV chamber. The RAIRS data are in agreement with the following conclusions. Under low pressure of histidine, 10−8 mbar, histidine molecules form an adsorbed molecular layer on Au (1 1 1) and Cu (1 1 0) surfaces. On gold, histidine mainly adsorbs through the depronated carboxylate group in a quasi-upright geometry that maintains the imidazole ring far from the surface. On copper, the histidine NH2 and COO− groups are involved in the interaction with the surface, with the cycle closer to the surface.

Adsorption of (S)-histidine on Cu(110), and Cu(110) modified by adsorbed oxygen, has been studied by reflection absorption infrared spectroscopy (RAIRS). The molecular form and the orientation of the histidine molecule were deduced from experimental RAIRS data; moreover, vibrational spectra were simulated with a molecular mechanics force field (MMFF) calculation to address vibrational modes and the geometry of the adsorbate. The molecule preferentially binds to the surface in its HHis- molecular form. On the metallic Cu(110) surface, the adsorption occurs via the carboxylate group (COO-), with the two oxygen atoms equidistant from the surface, and via the dehydrogenated nitrogen of the imidazole group; the latter adopts an upright position with respect to the copper surface. The amino group (NH2) is likely to be maintained close to the surface, thus facilitating the interaction with the metal. Preadsorption of oxygen (θ ≈ 0.3) on the copper surface induces minor changes in the molecular orientation: the ...

Iron nanoparticles (nFe) prepared by vaporization and cryogenic condensation process (10–100 nm) has been exposed to Hank's balanced salt solution (HBSS) and the B-Ali cell growth fluids. These media can be used for cellular growth to study nFe penetration through cell membrane and its induced cytotoxicity. Surface chemistry of nFe exposed to such complex fluids has been characterized as the nanoparticles surface can be strongly changed by adsorption or corrosion processes before reaching intracellular medium. Particle size and surface chemistry have been characterized by scanning electron microscopy (SEM) and high-resolution X-ray photoelectron spectroscopy (HR-XPS). Exposition of nFe particles to growth and differentiation media leads to the formation of an oxy-hydroxide layer containing chlorinated species. We found that the passivated Fe2O3 layer of the bare nFe particles is rapidly transformed into a thicker oxy-hydroxide layer that has a greater ability to adsorb molecular ions or ionic biomolecules like proteins or DNA.

Iron nanoparticles were produced in a radiofrequency levitation furnace and their dimensions and purity determined by scanning electron microscopy and x-ray microanalysis. Confocal microscopy revealed that these particles penetrated the leaves of Aphanorrhegma when applied to the plants as mineral water suspensions. This, the first demonstration of nanoparticle uptake by a bryophyte, opens the way to nanotoxicological studies paralleling those in higher plants. The actual penetration mechanism in both groups remains unknown.

Surface composition and electronic structure of AlPdMn quasicrystalline alloy have been studied for temperature ranging from 300 K to 873 K. The quasicrystalline nature of the in-situ prepared surface was identified by the unusual behaviour of the core level photoemission peaks of Mn as already demonstrated by Thiel et al. Quantitative estimation of surface concentration by measuring the peak on background ratio in Auger electron spectroscopy (AES) do not allow to concluded to surface segregation of one element whatever the substrate temperature. Auger transitions implying valence band electrons in the Auger relaxation reveal interesting shapes and energies modifications that can be correlated with the typical electronic structure of this alloy. The appearance of strong satellite structure in the Auger and photoemission spectrum can be attributed to bulk plasmon of the quasicrystalline phase.

In situ interactions of trivinylethoxysilane (TVES) with oxidized surfaces of silicon and aluminium was investigated at room temperature by high resolution electron energy loss spectroscopy (HREELS) and reflection-absorption infrared spectroscopy (RAIRS). The molecular interaction was held under vacuum environment. The chemical state of the substrate surfaces was characterized before and after the alkoxysilane interaction by Auger electron spectroscopy (AES), HREELS or RAIRS. Under vacuum conditions, silica surfaces are chemically inactive to the TVES molecules contrarily to oxidized aluminium surfaces where adsorption is realized successfully. Differences among adsorption mechanisms on both substrates are discussed in light of Bronsted acid properties of the oxide surfaces and of the role of physisorbed water.

Zinc oxide (ZnO) films with well-controlled morphologies have been prepared by electrochemical deposition. A seed layer of nanocrystallites of ZnO was prepared from which ZnO nanowires were grown from a low concentration of ZnCl 2 . The nanowires are rough and dense and their superhydrophilicity is enhanced. A treatment with an alkylsilane (octadecylsilane) yields superhydrophobic surfaces with very high advancing and receding contact angles 173°/172° and a very low roll-off angle. Our superhydrophobic films are stable for more than 6 months.

High resolution electron energy loss spectroscopy ( HREELS ) is used to characterize the extreme surface composition and the interfaces of silane and thiol monolayers deposed on silicon and platinum crystals, respectively. Energy losses due to impact interactions are very sensitive to the molecular groups present in the extreme surface of the film. Long range dipole interactions can supply information about buried interfacial bonds. Silicon substrates were characterized before and after molecular interactions. Energy losses assigned to interfacial siloxane bonds clearly vary with previous substrate annealing. Spectra of adsorbed thiols are dominated by losses corresponding to functional groups attached to the chain-end. An energy loss at 360 cm−1 was identified as corresponding to an interfacial S–Pt bond.

The interaction of sulfur dioxide with a Cu(110) surface, oxidized to different levels or hydroxylated, was investigated at room temperature by in situ infrared reflection−absorption spectroscopy. The initial surface chemical state was checked by Auger electron spectroscopy and photoelectron spectroscopy. Oxidation of sulfur dioxide into sulfites or sulfates was observed upon exposure to SO2, depending on the reactivity of oxygen and hydroxyls in the surface layer. The more oxidized the surface, the less reactive it becomes toward sulfur dioxide. Hydroxylation also reduces the surface reactivity as deduced from band intensities. Adsorption of SO2 on Cu(110), only partially covered with oxygen, generates sulfates whereas only sulfites are formed by interaction of SO2 with a surface copper oxide. Coadsorption of sulfur dioxide with oxygen favors the formation of sulfates whether the surface is only partially covered with oxygen or oxidized. When the surface is oxidized and hydroxylated before being exposed ...

A straightforward and versatile method for immobilizing macromolecules and silver nanoparticles on the surface of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBHV) electrospun fibers is developed with the objective of designing a new functional material having significant antibacterial activity. The approach relies on a two-step procedure: UV photografting of poly(methacrylic acid) (PMAA) on the surface of PHBHV fibers according to a "grafting from" method, and complexation of in situ photogenerated silver nanoparticles (Ag NPs) by carboxyl groups from tethered PMAA chains. The photografting process is conducted through a photoinduced free-radical process employing a ketone-based photoinitiator in aqueous medium. Under appropriate conditions, the photogenerated radicals abstract hydrogen atoms from the PHBHV backbone, thus initiating the UV-mediated photopolymerization of MAA from the PHBHV microfibrous surface. The photochemical mechanism of the ketone photolysis is entirely described by the electron spin resonance/spin-trapping technique, and the modified PHBHV microfibrous scaffold is extensively characterized by ATR-FTIR spectroscopy, water contact-angle measurements, and mercury intrusion porosimetry. In a second step, the in situ synthesis of Ag NPs within the microfibrous scaffold is implemented by photoreduction reaction in the presence of both a silver precursor and a photosensitizer. The photoinduced formation of Ag NPs is confirmed by UV spectrophotometry and XPS analysis. SEM and TEM experiments confirm the formation and dispersion of Ag NPs on the surface of the modified fibers. Finally, a primary investigation is conducted to support the antibacterial activity of the new functionalized biomaterial against Staphylococcus aureus and Escherichia coli.

The graft copolymerization of 2-hydroxyethylmethacrylate (HEMA) and methacrylic acid (MAA) onto a biodegradable and biocompatible polymer, poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBHV), has been investigated. The one-step process was conducted in aqueous media using for the first time a cationic photoinitiator, triarylsulfonium hexafluoroantimonate salts, upon UV irradiation. Under appropriate conditions, the remaining radicals abstract hydrogen from the PHBHV backbone which initiate the UV-mediated grafting of polymers from the PHBHV surface. This process provides the opportunity to adapt the functionality of the film, thus permitting the control of its wettability as a function of the time of irradiation. In the last demonstration, we demonstrated that UV-mediated graft polymerization is an effective method to micropattern coatings onto PHBHV surface to develop microdevices for biological applications.

Functionalization of a novel nanoporous monolithic alumina synthesized from amalgam is investigated. The structure is studied by X-ray diffraction, BET, MEB and IR spectroscopy, before and after chemical functionalization by trimethylethoxy silane adsorption and annealing at high temperature. These treatments retain both monolith microstructure and nanostructure while strongly improving material mechanical properties. Allyldimethoxysilane and alcohol adsorption on the annealed samples, proves that highly reactive sites are available for further polymer grafting, as demonstrated by a significant shift of allyldimethoxysilane ν(SiH) to 2,215 cm(-1) and adsorbed acetate formation. Simple quantum computations on model systems support this conclusion. Chemical processes reported in this paper, allow a nanostructured alumina monoliths functionalization to optimize ceramics-polymer bonds, and to tune new hybrid biomaterial properties.

Recent studies have shown that the particle size of fillers used for the reinforcement of dental resin composites should be multimodally distributed, in which micron-sized fillers are mixed with nanoparticles so as to achieve a higher filler level in the resin, and should be kept well dispersed so as to be functionalized by a silane. In this study, porous alumina monoliths with high specific surface area, measured by the Brunauer-Emmett-Teller (BET) method, were obtained using a novel preparation method. Structure and surface reactivity have been investigated as functions of temperature and chemical treatments. The impregnation of the as-prepared material by trimethyletoxysilane (TMES) stabilized alumina with high specific surface area at higher temperature. FTIR study has described the effect of TMES treatment and temperature on the structure of the material. The use of allyldimethoxysilane (ADMS), as a probe molecule for measuring the surface reactivity, has allowed us to show that the treatment of samples with TMES and their reheating at 1300°C results in adsorption sites which give stronger chemical bonds. This preliminary study has, therefore, allowed us to optimize the structural and surface treatment of experimental fillers before their use in the reinforcement of resin composites or resin-modified glass ionomer cements. © 2008 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2009

Low-energy electron diffraction, Auger electron spectroscopy and reflectivity measurements were used to examine the growth mode and the structure of ultrathin layers of samarium deposited from the vapour onto a (211) Cr face at ambient temperature and at 900 K. At room temperature a Stranski-Krastanov growth mode is observed. Nucleation of dense islands is followed by a compact disordered monolayer. At high temperature several structures are successively observed during formation of the monolayer. At completion of the monolayer coexistence of c(2 × 2) domains separated by antiphase boundaries and more dense p(3 × 1) domains is obtained.

Electronic and atomic structure of low index polar (0 0 1, 0 1 1, 1 1 1) spinel γ -alumina surfaces have been investigated using a modified large-scale quantum semi-empirical simulations. Atomic structure optimization and electronic structure calculation were done in the direct space on periodic large unit cells in which random distribution of cationic vacancies close to the surface were included. Predicted electronic structures match more accurate ab initio Density Functional Theory (DFT) results on aluminum oxides. We found that the restructured surfaces behave as amorphous-like shapeless planes provided unit cell dimensions are much greater than primitive translations as periodicity constraints are weakened. Aluminum ions vacancies in the surface region are shown to induce a surface atomic disordering even at 0 K, correlated with the appearance of low coordinated ions, as proven experimentally and theoretically with classical Molecular Dynamics (MD) calculation on some aluminum oxide systems. The lowering of the surface charge density is obtained from two distinct mechanisms involving large ion movements. On the oxygen rich plane termination, this results from the formation of O 2 δ − entities. On the aluminum rich plane termination, the same effect is related to a loss of co-ordination number together with a reduction of cationic charge. Furthermore, large-scale simulations allow to statistically quantify specific relaxed surface ion densities for which the Local Density of States (LDOS) is evaluated. Their inferred electronic properties are then compared to available probe molecule adsorption experiments investigated by infrared spectroscopy. We show that surface electronic states are not a simple function of ion coordination. Our large-scale quantum semi-empirical calculation fills the gap between atomic structures predicted by classical MD approach with electronic structure results obtained by DFT on small systems.

We have studied surface hydroxyls adsorbed onto (001), (011), and (111) gamma alumina surfaces using a quantum-chemistry approach in order to compare with empirical models proposed in the literature. Local electronic structures and geometries in the low OH coverage limit have been evaluated for both ideal and relaxed surfaces with the help of a large scale periodic quantum-chemical code. Hydroxyl groups are adsorbed onto surfaces, and a study of their local electronic structure, vibrational frequencies, charges, and adsorption energies is performed and analyzed as a function of their adsorption site geometry. Our results show that, even on ideal (nonrelaxed) surfaces, OH local environments are more complicated than those stated by empirical models and strongly influence the hydroxyl stretching vibrational mode. Large scale simulation shows that disorder takes place even at 0 K, and the analysis of the vibrational frequencies leads to a revision of Knözinger's empirical model. Cationic vacancies in the first surface layers have also been taken into account; they have a significant influence on the surface atomic and electronic structures, modifying the physical properties of adsorbed OH entities. This work emphasizes the necessity to perform an electronic structure calculation to better understand adsorbed OH properties on gamma alumina surfaces and reveals the difficulty to make a one-to-one correspondence between OH stretching frequencies and their other physical properties. Finally, we show that these results agree with some available experimental studies.

High-resolution electron energy-loss spectroscopy and x-ray photoemission are used to probe the fivefold AlPdMn oxidized surface. The vibrational spectrum reveals a strong increase of the Al-O stretching mode wave number while the oxygen Auger transition and photoelectron spectra prove the high ionicity of the thin alumina layer. These observations are markedly different from those made with oxidized aluminum and can be related to the low reactivity of the quasicrystal surface. The influence of the quasicrystal bulk structure on the oxidized surface vibrational mode and ionicity can be well understood by image forces theory and the static dielectric constant behavior between the pure free-electron metal and the quasicrystalline alloy.

Adsorption of lithium and hydrogen onto carbon nanotubes has been modeled using a neglect of diatomic differential overlap semiempirical calculation. Our results predict that lithium can be adsorbed on zig-zag nanotubes with a charge transfer, an adsorption energy, and a vibration frequency which depend on the tube radius and whether the adatom approaches the surface from outside (exo-way) or inside (endo-way). Adsorbed lithium allows the anchoring of molecular hydrogen on the carbon nanotube with a binding energy in a chemisorption regime compared to previous experimental and theoretical works which show that ${\mathrm{H}}_{2}$ is physisorbed. We also predict that a shift of the hydrogen stretching mode upon adsorption should be observable experimentally by vibrational spectroscopy.

Interaction of sulphur dioxide (SO 2 ) with the Cu(100) surface has been investigated by infrared reflection absorption spectroscopy (IRAS). Results have been compared with data obtained previously under similar conditions on the Cu(110) surface in order to make clear the role of the surface structure on the adsorption process. Auger electron spectroscopy and XPS were used to control the surface chemical state before and after SO 2 interaction. On Cu(100), the dissociation of SO 2 is observed for low exposure, and is then followed by the formation of SO x molecular species (x ≥ 2). On oxygen-induced reconstructed Cu(100), sulphites and sulphates are formed by interaction with SO 2 . Sulphites and sulphates are oxygen-bound to the surface, resulting from nucleophilic attack of the sulphur atoms of impinging SO 2 molecules by the surface oxygen atoms. On the oxidized Cu(100) surface, SO 2 is only converted to sulphites. The less 'oxidizing' character of a superficial oxide layer compared to an oxygen adsorbed layer is correlated to the coordination and interatomic distances of the surface oxygen atoms. The nature of the adsorbed species resulting from the interaction of SO 2 with copper strongly depends on the structure and on the chemical composition of the surface. These data confirm that this molecule is a good probe of the metallic and oxide surface reactivity.

The reactivity of sulfur dioxide with well-defined copper surfaces, has been investigated by infrared reflection absorption spectroscopy (IRRAS). Depending upon the level of oxidation of the two selected low index planes of copper, Cu(110) and Cu(100), sulfur dioxide leads to the formation of different adsorbed atomic or molecular entities. A complete dissociation of SO2 was only observed on the metallic Cu(110) surface confirming the “cracking” character of that opened surface. The nature of the molecular compounds, SO3 and SO4, which have been identified on other surfaces, is related to the amount and to the coordinance of surface oxygen atoms. Sulfites result from the interaction of SO2 with the metallic Cu(100) surface. They are partially replaced by sulfates when SO2 is coadsorbed with oxygen. On O-reconstructed surfaces, sulfites and sulfates are formed; the latter are predominant on the most “open” structure, the Cu(110)-c(2×6)O. Finally, surface oxides interact with SO2 to give rise exclusively to...

A combination of catalytic tests and surface studies has been undertaken to better understand the poisoning effect of sulfur dioxide upon the reduction of NO by a hydrocarbon. The characterization of the copper surface by photoelectron spectroscopy, at various stages of the reaction, made clear an initial oxidation of the catalyst accompanied by the formation of an oxygenated intermediate; it is followed by a reduction of the surface and a rapid reaction of NO with this species. In situ surface infrared measurements have been made on a model copper surface, Cu(110), under 10 −5 Torr of SO 2 or SO 2 +O 2 revealing the formation of molecular adsorbed compounds when the surface is oxidized, slightly covered with oxygen or hydroxylated. SO 2 is a drastic poison of the catalytic NO reduction; it reacts with the oxidized surface leading to sulfite and sulfate groups, it interacts with water, leading to hydrogenosulfoxide adsorbates which can obviously block a number of surface sites. It also dissociates on the metallic copper and occupies surface sites. It does not block the hydrocarbon adsorption completely but severely reduces the formation of the active intermediate.

The room-temperature interaction between anhydride-type molecules and oxide-covered zinc substrates has been studied using infrared reflection-absorption and high-resolution electron energy loss spectroscopies. Gas-solid interactions were carried out extensively for acetic anhydride on polycrystalline zinc substrate, either in-situ prepared, or ex-situ chemically prepared prior to its vacuum introduction. Vibrational spectroscopy revealed the formation of adsorbed carboxylate species in both cases, accompanied by the consumption of surface hydroxyls, which thus appeared to be the active sites in the adsorption process. However, other active surface sites were demonstrated on the ex-situ chemically prepared substrates, namely zinc ions covered by carbonate species which are easily displaced upon anhydride adsorption. The interaction mechanism was found to be the same for the adsorption of maleic and succinic anhydride on industrial zinc-covered substrates.