Mohamed M. Chehimi

Adsorption of H2S or SO2 on an activated carbon cloth modified by ammonia treatment

The aim of this research is to investigate how ammonia treatment of the surface can influence the activity of a viscose-based activated carbon cloth (ACC) for the oxidative retention of H2S and SO2 in humid air at 25 8C. Surface basic nitrogen groups were introduced either by treatment with ammonia/air at 300 8C or with ammonia/steam at 800 8C. The pore structure of the samples so prepared was examined by adsorption measurements. Changes in the surface chemistry were assessed by X-ray photoelectron spectroscopy, X-ray absorption spectroscopy and temperature programmed desorption (TPD). The change of ACC activity could not be merely attributed to surface nitrogen groups but to other changes in the support. Ammonia/steam treatment improved ACC performance the most, not only by introducing nitrogen surface groups, but also by extending the microporosity and by modifying the distribution of surface oxygen groups. Successive adsorption–regeneration cycles showed important differences between oxidative retention of H2S and SO2 and the subsequent catalyst/support regeneration process.

Thermo-induced electromagnetic coupling in gold/polymer hybrid plasmonic structures probed by surface-enhanced raman scattering.

This paper describes a general stepwise strategy combining diazonium salt, surface-initiated atom transfer radical polymerization (SI-ATRP), and click chemistry for an efficient gold surface functionalization by poly(N-isopropylacrylamide) (PNIPAM) brushes and gold nanoparticle assemblies. We designed by this way a new plasmonic device made of gold nanoparticles separated from a gold film through a thermoresponsive polymer layer. This organic layer responds to temperature variations by conformational changes (with a characteristic temperature called the lower critical solution temperature, LCST) and is therefore able to vary the distance between the gold nanoparticles and the gold film. The optical properties of these stimulable substrates were probed by surface-enhanced raman scattering (SERS) using methylene blue (MB) as a molecular probe. We show that an increase of the external temperature reversibly induces a significant enhancement of the MB SERS signal. This was attributed to a stronger interaction between the gold nanoparticles and the gold substrate. The temperature-responsive plasmonic devices developed in this paper thus provide a dynamic SERS platform, with thermally switchable electromagnetic coupling between the gold nanoparticles and the gold surface.

Protein-Functionalized Hairy Diamond Nanoparticles

Diazonium salt chemistry and atom transfer radical polymerization (ATRP) were combined in view of preparing new bioactive hairy diamond nanoparticles containing, or potentially containing, nitrogen-vacancy (NV) fluorescent centers (fluorescent nanodiamonds, or fNDs). fNDs were modified by ATRP initiators using the electroless reduction of the diazonium salt BF(4)(-),(+)N(2)-C(6)H(4)-CH(CH(3))-Br. The strongly bound aryl groups -C(6)H(4)-CH(CH(3))-Br efficiently initiated the ATRP of tert-butyl methacrylate (tBMA) at the surface of the nanodiamonds, which resulted in obtaining ND-PtBMA hybrids. The grafted chain thickness, estimated from X-ray photoelectron spectroscopy (XPS), was found to increase linearly with respect to time before reaching a plateau value of ca. 2 nm. These nanoobjects were further hydrolyzed into ND-PMAA (where PMAA is the poly(methacrylic acid) graft) and further decorated by bovine serum albumin through the 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide/N-hydroxysuccinimide (EDC/NHS) coupling procedure.

Preparation and characterisation of gold nanoparticle assemblies on silanised glass plates

Abstract Gold nanoparticles were prepared by the chemical reduction of AuCl 4 − and attached to aminopropyltrimethoxysilane-treated glass plates. The assemblies of gold nanoparticles on silanised glass were characterised by UV spectroscopy, X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM) and surface-enhanced Raman scattering (SERS). The gold nanoparticles had a diameter in the range 40±10 nm as estimated by AFM. Gold was found to be in the metallic state as judged from XPS measurements of the Au 4f 7/2 core electron binding energy. AFM showed that the gold nanoparticles experience a self-organisation on the silanised surface in such a way that the final assemblies have a certain degree of roughness and compactness. These characteristics are intimately related to the SERS effect as determined using the molecular probe bi-ethylene-pyridine at very low concentration. A huge enhancement of the Raman signals was observed and assigned to a coupling between gold particles. However, this SERS effect critically depends on the surface treatment of the substrate by the silane coupling agent, a procedure that is necessary for the attachment of the gold nanoparticles.

The determination of the surface energy of conducting polymers by inverse gas chromatography at infinite dilution

Abstract Inverse gas chromatography (IGC) has been used at infinite dilution to determine the dispersive and acid–base contributions to the surface energy of inherently conducting polymer (ICP) powders and nanocomposites, with an emphasis on polypyrrole bulk powder. New and previously published results are discussed and show that polypyrrole and polyaniline are high-surface energy materials by contrast to conventional polymers and undoped poly(3-octyl thiophene), thus reflecting a behaviour comparable to that of metals or graphite. In the case of polypyrrole, it was found that the dispersive and acid–base properties are correlated, and that the high energetic sites are predominantly acidic. Ageing and low doping levels have a significant impact on polypyrrole surface thermodynamics as they resulted in low surface energy and acidity of this ICP.

DNA adsorption onto conducting polypyrrole

Abstract Deoxyribonucleic acid (DNA) adsorption onto chemically synthesized polypyrrole powders was investigated as a function of pH, buffer nature, ionic strength and substrate nature. DNA adsorption was found to be in the range of 0.13–0.55 mg m −2 for the conditions under investigation. Strong DNA adsorption was obtained at low pH and high ionic strength. The decreasing order of adsorption as a function of the native dopant was nitrate, chloride>sulfate. The isotherms were found to be of the Langmuir type or sigmoid, depending on the combination of (at least) substrate and buffer natures. Affinity constants determined using Scatchard and Hill plots were found to be as high as 10 6 M −1 .

Hairy carbon nanotube@nano-Pd heterostructures: design, characterization, and application in Suzuki C-C coupling reaction.

Poly(glycidyl methacrylate), PGMA, was prepared via ATRP in bulk solution, and its epoxy groups were further acid-hydrolyzed in order to obtain a polymer with glycerol moieties (noted POH). The POH chain end C-Br bonds were subjected to a nucleophilic attack by NaN(3), resulting in azide-terminated POH (POH-N(3)). The CNTs were modified by in-situ-generated alkynylated diazonium cations from the para-alkynylated aniline of the formulas H(2)N-C(6)H(4)-C≡C-H, yielding CNT-C(6)H(4)-C≡C-H nanotubes. The azide-functionalized polymer POH-N(3) was clicked to the alkynyl-modified CNTs giving CNT@POH hybrids, which were further subjected to an oxidation resulting in carboxylated polymer-modified CNTs (noted CNT@PCOOH). The as-designed hairy CNTs served as efficient platforms for the in-situ synthesis and massive loading of 3 nm sized palladium nanoparticles (NPs). The CNT@PCOOH@Pd heterostructures prepared so far exhibited an efficient catalytic effect in the C-C Suzuki coupling reaction and were regenerated up to four times without any significant loss of catalytic activity.

Adsorption of aminopropyltriethoxy silane on quartz: an XPS and contact angle measurements study

Aminopropyltriethoxy silane (APS) adsorption onto quartz has been monitored by XPS and found to be of the Langmuir type. XPS brings evidence for the partial protonation of the coupling agent amino group. It is shown by angular dependent XPS that the ammonium group is in that case oriented towards the quartz substrate. Contact angle measurements of water indicated that the quartz surface wettability has decreased following APS treatment.

Multiple internal reflection FT-IR spectroscopy (MIRFTIRS) study of the electrochemical synthesis and redox process of poly (1,5-diaminonaphthalene)

Abstract The electrooxidation of 1,5-diaminonaphthalene (1,5-DAN) in acidic acqueous, methanol and organic media leads to polymer film on glassy carbon and Pt electrodes. The in situ infrared study during film growth and X-ray photoelectron spectroscopy (XPS) analysis indicate that the polymer structure consists of amine (-NH-C) and imine (-N=C) units, bearing free -NH 2 groups in the chain. The polymer structure was confirmed by a multiple internal reflection FT-IR spectroscopy (MIRFTIRS) study of the film redox process and by the ability of poly(1,5-DAN) film to chelate copper ions.

Site-specific immobilisation of gold nanoparticles on a porous monolith surface by using a thiol–yne click photopatterning approach

A monolith surface with alkyne functionality was reacted with cysteamine through radical-mediated thiol-yne addition reaction providing a hydrophilic and chelating interface. Photochemical initiation affords spatial control over the reaction site and further site-specific immobilisation of gold nanoparticles.