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New antimicrobial polymer composite based on commercial polyurethane (PU) Laripur®LPR9020 and polymeric biocide polyhexamethylene guanidine hydrochloride (PHMG-Cl) has been prepared by solvent casting method. Modified PU films containing from 1 to 4 wt% of PHMG-Cl were characterized in terms of mechanical, thermal and surface properties, biocide release behavior, as well as antibacterial activity against Gram-negative (Escherichia coli) and Gram-positive (Bacillus subtilis) bacterial strains. The results of mechanical testing indicate that the introduction of PHMG-Cl did not cause noticeable changes in the tensile strength of PU films, but improved their elasticity by at least 20–30%. The surface of PU/PHMG-Cl films was found to possess significantly higher hydrophobicity than neat polymer that is manifested in sharply increased water contact angle value from 72° for neat PU to 95° for PU/PHMG-Cl (2%). According to thermogravimetric analysis data, PU/PHMG-Cl composites are thermally stable to at least 300 °C which indicate their availability for melt processing by common methods. The results of differential scanning calorimetry showed reduction of both glass transition and melting temperatures of PU by more than 7 °C when contained only 1% of PHMG-Cl. Gradual release of polymeric biocide from modified PU films into water has been detected spectrophotometrically. The total biocide release ratio was found to be in the range from 29% to 48% after 50 hours immersion, depending on its content in polymer composite. PU/PHMG-Cl films showed much lower leaching rate into physiological saline solution compared to pure water (from 10% to 21% after 50 hours), which may be caused by poor solubility of polymeric biocide in sodium chloride solutions. The study of antibacterial activity of modified PU films using both disc agar diffusion and contact methods indicate high efficacy against tested microorganisms when contained 3% of polymeric biocide. So, this approach, based on the modification of PU resin with polymeric biocide PHMG-Cl, has been discussed in terms of potential medical applications when biocide release system or contact active material are necessary.

Plastic pollution has become one of the most visible environmental issue. Studying the aging and the fragmentation mechanism of polymers therefore raises environmental and health issues. Since it is particularly difficult to monitor all these processes in the real environment, laboratory studies are still necessary to obtain more accurate data and to identify the pathways leading to the outcome of plastic debris in the environment. In this paper we present a new method to prepare micrometer thick LDPE films with different thicknesses and controlled crystalline morphologies (i.e. spherulite size) using dip-coating process. LDPE films presenting different spherulite dimensions were submitted to an accelerated weathering test which indicates that spherulite size has only a weak influence on the rate of photo-oxidation. However, films presenting large spherulites morphologies seem to be more sensitive to surface erosion and crack initiation. We believe that the method developed in this paper can be used to study with more control and more rapidly (i.e. thin film and accelerated weathering) the influence of crystalline morphology on a wide range of semi-crystalline polymers in different ageing conditions and thus help to better understand the fragment production of plastics in the environment.

The present study focused on the physical and electrochemical properties of stannic sulfide SnS2 synthesized by a template-free chemical route using thiourea as a precursor. SnS2 powder was characterized by X-ray diffraction (XRD), diffuse reflectance and Raman. The XRD pattern confirmed the formation of the hexagonal phaseSnS2 (SG: P-3m1) with the lattice parameters a = 3.639 A, c = 5.868 A and a mean crystallite size of ~ 60 nm. The optical measurements gave a direct transition of 2.26 eV, further transition indirectly allowed was observed at 1.63 eV. The Mott-Schottky plot recorded in Na2SO4 (0.1 M) electrolyte exhibits a linear behavior, characteristic of n-type conductivity and confirmed by chronoamperometry. The flat band potential (−0.63 VSCE) is close to the photocurrent onset potential (Eon= −0.64 VSCE) and a donor density of 3.54 × 1016 cm−3 was determined. The electrochemical impedance spectroscopy measured in the range (10−2 − 5 × 104 Hz) showed two semicircles assigned to a faradic charge transfer (Rct = 2.46 kΩ cm2) and grain boundaries contribution (Rgb= 13.69 kΩ cm2). The conduction band, located at −4.02 eV below vacuum, is made up of Sn4+: 5p while the valence band (−6.28 eV) derives mainly from S2−: 3p. As an application, Rhodamine B was successfully oxidized by photocatalysis on SnS2, 93.67% of the initial concentration (10 mg L−1) disappeared after 3 h of exposure to solar light (90 mW cm−2).

Controlling adsorption of proteins onto medical devices is a key issue for implant-related infections. As self-assembled monolayers (SAMs) on titanium oxide represent a good model to study the surface-protein interactions, TiO 2 surface properties were modified by grafting bisphosphonate molecules terminated with hydrophilic poly(ethylene glycol) groups and hydrophobic perfluoropolyether ones, respectively. Characterisation of the surface chemistry and surface topography of the modified surfaces was performed using XPS and atomic force microscopy (AFM). Quartz-crystal microbalance with dissipation (QCM-D) was used to determine the mass of adsorbed proteins as well as its kinetics. Poly(ethylene glycol)-terminated SAMs were the most effective surfaces to limit the adsorption of both BSA and fibrinogen in comparison to perfluorinated-terminated SAMs and non-modified TiO 2 surfaces, as expected. The adsorption was not reversible in the case of BSA, while a partial reversibility was observed with Fg, most probably due to multilayers of proteins. The grafted surfaces adsorbed about the same quantity of proteins in terms of molecules per surface area, most probably in monolayer or island-like groups of adsorbed proteins. The adsorption on pristine TiO 2 reveals a more important, non-specific adsorption of proteins.

Conducting polymer composite films based on different aliphatic polyamides (PA) (PA-6, PA-11 and PA-12) have been synthesized by in situ aniline polymerization inside a surface layer of the PA host matrix. Dielectric permittivity and dielectric loss of these films are explained in terms of the interfacial polarization. The real part of permittivity is found to be higher in the PA/polyaniline (PANI) composite films than in the virgin PA polymer matrix. Such behaviour is attributed to the interaction between PA and PANI molecular chains and to the conductivity increase after the aniline polymerization. The performed confocal Raman spectrometry and X-ray diffraction studies also confirmed the presence of interactions between PA and PANI molecular chains.

Composite polyurethane/polyaniline and polyamide-6/polyaniline films were chemically prepared by oxidative in situ polymerization of aniline inside the previously swelled matrix film. Swelling kinetic studies had shown that for polyurethane and polyamide-6 films the swelling degree of aniline was 25 wt.% and 15 wt.%, respectively. The dielectric and electrical properties of the composite films were established using dielectric relaxation spectroscopy and four-probe method. Dielectric measurements as a function of temperature and frequency revealed the presence of relaxation processes influenced by the nature of the polymer matrix, i.e. one relaxation process for the polyurethane based composite film and two relaxation processes for polyamide-6 based composite film. These relaxations were explained in terms of interfacial polarization caused by the polyaniline organisation as it was revealed by atomic force microscopy. Activation energy values obtained by dielectric and electrical measurements are close and this result confirms the conducting character of the polyaniline containing layer.

The adhesion of the biocompatible hydrophilic polymer, poly (vinyl alcohol) to a model substrate, silicon, was investigated. Contact angle measurements were used to reveal the effect of various substrate cleaning procedures including sonication and UV–ozone treatment prior to casting a 35 μm coating. Raman microspectrometry and X-ray reflectometry were used to characterise the composition and the thickness of PVA thin films. The use of mechanical abrasion of the substrate followed by a 131 nm primer layer of PVA in combination with vacuum treatment at temperatures higher than the glass transition temperature ( T g = 80 °C) provided the best resistance to delamination as demonstrated by visual observation during prolonged immersion of the coatings in water.

International audience; The homogeneity of the oxygen content of TSMTG-YBa2Cu3O7 − δ/Y2BaCuO5 composites has been investigated by micro-Raman spectrometry. The Y123 compound has been found to be very sensitive to the laser power, but a laser power of 0.04 mW has been shown to not to be harmful for the samples, even after 2 h of irradiation. Raman spectra have shown that the oxygen content of YBa2Cu3O7 − δ/Y2BaCuO5 ceramics is not homogeneous at the micrometer scale. In addition, no monotonic decrease of the oxygen content is observed from the periphery to the core of the sample, confirming that the oxygen uptake is not strictly controlled by a diffusion process.

International audience; This paper discusses a method to measure the thickness of thin layers deposited on a reflective substrate. An interferometer with three wavelengths produces color interferences. A color sensor records the tint that is produced. The color interferences are approximated by a model based on the measurement of the laser intensities obtained with the reference mirror only. An iterative process leads to unambiguous algorithmic convergence and high accuracy thickness measurement. This method is simple, robust, compact, and single shot. The method does not need angular scanning over the field of measurement (about 75 mm2). The measurement on the surface yields a histogram of the thickness distribution and there is no requirement for any reference points (e.g., no need to make a groove or a walk on the layer). A thickness measurement performance of 50 nm was demonstrated for homogeneous polymer films deposited on a silicon wafer. The setup and digital image processing are discussed.

Optically transparent and highly ordered mesoporous organosilica thin films functionalized with two different organic groups in various proportions were synthesized by templated-directed co-condensation of tetraethylorthosilicate (TEOS) and a mixture of two distinct and functional organotriethoxysilanes [NC(CH 2 ) 3 Si(OEt) 3 and O=P(OEt) 2 (CH 2 )3Si(OEt)3]. The mesostructured films obtained by evaporation induced self-assembly (EISA) approach were deposited on glass or silicon substrates by dip-coating. They were characterized by Grazing Incidence Small Angle X-ray Scattering (GISAXS) and X-ray reflectivity. We showed that whatever the proportion in organic groups, only 2D hexagonal phase having p6m symmetry was observed for all the materials indicating a good compatibility between the organic groups. The bi-functionalization of the internal pores surface by the organotriethoxysilanes groups was clearly evidenced by using micro-Raman spectroscopy.

The influence of controlled humidity on the phase transformation of CTAB templated silica thin films is studied by time-resolved in situ GISAXS measurements. It is shown that during a short period of time the silica matrix is flexible enough to follow the morphologic changes of the cylindrical micelles into spherical ones. During this time water can be uptaken and outtaken from the film. The evolution of the lattice parameters upon cycling dry and humid air is presented and discussed.

The dielectric properties of conducting polymer composite films based on polyaniline located in a thin layer in the vicinity of the surface of different insulating polymer matrices (polyamide and poly(ethylene terephthalate)) have been studied using dielectric relaxation spectroscopy in a wide temperature and frequency range. Several relaxation processes related to the film surface conductivity and influenced by the nature of the polymer matrix have been found in these composites. The nature of the polymer matrix is found to influence the rate of aniline polymerization, the distribution of polyaniline clusters and the depth of aniline penetration as shown, respectively, by Conducting Probe AFM and Raman spectroscopy. These features are correlated to the dielectric behavior of the composite films.

A self-assembled zirconia-based film, produced at the air–water interface using sodium dodecyl sulphate (SDS) as the template, has been characterised by energy-dispersive X-ray reflectometry, X-ray diffraction, and X-ray fluorescence analysis. Long-range order due to the lamellar liquid crystalline arrangement of the surfactant micelles was significant enough to produce Bragg diffraction. X-ray fluorescence from the specimens in the electron microscope indicates that the principal component of the film contains zirconium, oxygen and sulphate, -suggesting that the film contains zirconium polyoxo ions and surfactant. Raman spectroscopy indicates the presence of a zirconium hydroxide.

Raman scattering signals recorded by microscopy from organic self-assembled monolayers (thin nanometric films of calibrated thickness) on silica substrates were found to be much stronger than those obtained from identical films assembled on bulk silicon substrates. This effect, observed in the backscattering geometry, is shown to result from interferences between the direct and reflected beams (including both the excitation and scattered radiation) in front of a smooth reflecting surface. Strong dependence of the effect on the distance between the sampled monolayer and the bulk silicon substrate allows enhancement of the Raman signals of organic monolayer films on silicon by factors up to approximately 70 by using appropriate silica spacers. The dependence of the Raman signal intensity on film thickness was also studied for thicker nanometric films comprising a series of self-assembled organosilane multilayers on bulk silicon and fused silica substrates, and the predicted deviation from linearity in the case of the silicon substrate is experimentally confirmed.

A new route for the elaboration of the polypropylene surface directly modified by 4-amino-4‘-nitroazobenzene (Disperse Orange 3) was studied. The synthesis consists of a cold carbon dioxide-plasma treatment followed by a mixed anhydride reaction and Disperse Orange 3 fixation. The quantity of active acid introduced by the plasma treatment was estimated to be 0.7 groups/nm2 by fluorescence labeling with thionine acetate. The azo-modified surfaces were characterized by Fourier transform infrared, resonance Raman, and X-ray photoelectron spectroscopies. Confocal resonance Raman spectrometry has shown that Soxhlet extraction is effective to eliminate diffused molecules from the material. It was shown that the azo dye molecules are chemically fixed onto the polymer surface.

The structure of a series of alcohol-terminated bifunctional long-tail organosilane films with varying numbers of superimposed monolayers (between 1 and 11), prepared on smooth, hydrophilic silicon substrates by the layer-by-layer self-assembly approach, has been investigated with the purpose of elucidating details of the molecular organization and the intra- and interlayer modes of binding in such films. To this end, experimental results obtained by synchrotron X-ray scattering, micro-Raman, and Fourier transform infrared (FTIR) spectroscopic techniques have been combined and compared. A comprehensive analysis of all data demonstrates that the studied multilayer films consist of stacks of uncorrelated discrete monolayers, the inner molecular order of which is preserved with the growing total number of superimposed layers. Similar to self-assembled films of long-tail silanes with terminal −COOH groups,1 the intermolecular binding in the present films is characterized by partial intra- and interlayer coval...

A new 2-step growth process was developed, combining both the r.f. sputtering and the pyrosol techniques, in which nucleation and growth stages could be partially separated and controlled. Using this refined deposition method, d c ¢ -oriented LiNbO 3 thin films could be successfully grown on (111) silicon and (001) sapphire substrates. Thin film structures have been determined by X-ray diffraction and pole figure analyses. Depositions performed on Si (111) templates led to fiber textures, characteristic of oriented polycrystalline samples. Al 2 O 3 (001) substrates allowed the growth of in-plane oriented layers with two distinguishable variants in the interfacial plane, namely, an aligned variant d 110 ¢ LiNbO 3 //[110]Al 2 O 3 and a 60 °-rotated one.

Structural and magnetic properties of γ-Fe2O3 nanoparticles of 4 nm diameter, dispersed into silica SiO2 matrix with a wide range value of volume fraction (0.05 to 1), were investigated. Produced γ-Fe2O3@SiO2 nanocomposites consist of an assembly of very small single domain magnetic object (

The formation and properties of diamond-like carbon (DLC) films prepared on silicon substrates at room temperature, using C2H2–Ar plasma immersion ion processing, are investigated with respect to film deposition parameters. Decreases in the reactive gas-flow ratios of C2H2 to Ar(FC2H2/FAr) or the gas pressure were found to decrease the hydrogen content, increase the density and hardness, and improve the surface finish of the DLC films, all of which led to enhanced tribological properties. Decreasing the friction coefficient requires increasing the hardness of the film and smoothing its surface, whereas increasing the wear resistance correlates with reducing both the hydrogen content and residual stress in DLC films. High hardness and optimum tribological properties were reached as the growth of DLC films was subjected to low-energy ion impingement, which was induced by a −150 V pulsed bias from the C2H2–Ar plasma produced at low reactive gas pressures with low FC2H2/FAr ratios.

Engineering highly nonlinear optically (NLO) active assemblies can lead to thin films with potentially useful properties. For instance, materials with electron donor and acceptor groups bridged by a conjugated system have potential application as molecular wires, where electrons can tunnel or hop through the conjugated bridge. Phenothiazine and its derivatives are of widespread chemical interest. For example, they have useful pharmacological properties and can potentially be used in solar energy conversion. There is also interest in these systems as charge-transfer complexes with several acceptors due to their low ionization potentials. 4-(trans-4-(4-(10-phenothiazinyl)butyramido)styryl)pyridine (PBSP) has been synthesized and covalently bound to a coupling layer of (p-(chloromethyl)phenyl)trichlorosilane (CPTS) on a quartz substrate to produce a polar-ordered thin film. The addition of the PBSP molecules on the coupling layer was monitored by FTIR spectroscopy, UV--visible spectroscopy, AFM, and second harmonic generation (SHG). The observation of an amine band and strong methylene bands in the infrared spectra indicates the presence of the PBSP layer. The UV-visible spectrum shows a red shift in the charge-transfer band, consistent with the addition of the PBSP layer on the coupling layer. The nonlinear optical properties of the PBSP monolayers were measured by SHG. The second harmonic (SH) signal increasedmore » by 1 order of magnitude after the addition of the PBSP chromophore layer. The dependence of the SH intensity on incident angle and input polarization was modeled. The average molecular orientation angle of the chromophore was determined to be 55{degree}, and a value of {chi}{sub zzz}= {chi}{sub zxx} = 2.8 x 10 {sup {minus}8} esu was calculated.« less

Extracting characteristic dimensions from mounded surfaces such as grain size or intergrain lengths is usually made by statistical analysis. Different statistical functions are used in the literature to extract characteristic lengths. The main issue is that depending on the choice of the statistical function the results can be very different. In this paper, we demonstrate using a series of model mounded surfaces for which characteristic dimensions are known, that a method (namely, interfacial differential function, IDF) is the most effective method to determine the different characteristic lengths. The influence on the statistical treatment of the variation of the different characteristic lengths is then studied and confirms the ability of the IDF analysis. The IDF method was used to analyze the evolution of ultrathin gold film morphology as function of deposition temperature. This approach allows us to demonstrate that the roughness increase with deposition temperature is mainly due to a grain height increase and not to a grain coarsening phenomena as it was claimed before.

International audience; Ellipsometry is used as a technique to determine glass temperature transitions of isotactic Poly(methyl methacrylate) (iPMMA) ultra-thin films and isolated chains deposited on a silicon wafer surface. The importance of systematically probing the samples at different wavelengths is pointed out in this work since for a similar thin film, slope changes in delta are more or less pronounced according to the wavelength used. The technique performed on iPMMA thin films and isolated globular chains, deposited on Piranha treated surfaces, reveals the presence of multiple transitions, whereas films of comparable thicknesses deposited on HF treated silicon wafers show only one transition. The results confirm the assumptions of a layered structure yielding specific () which depends on depth location, which is in good agreement with recent theories of glass transitions in confined polymers, and emphasize the influence of polymer-substrate interactions and chain disentanglement.

International audience; Surface modification with functional polymers or molecules offers great promise for the development of smart materials and applications. Here, we describe a versatile and easy-to-use method of site-selective surface modification based on the ease of microcontact printing and the exquisite selectivity of enzymatic degradation. A micropatterned poly-L-lysine (PLL) layer on solid substrates was prepared by enzymatic degradation using trypsin enzyme immobilized on a prestructured poly(dimethlylsiloxane) (PDMS) stamp. After the enzymatic degradation of PLL and the removal of the degradation products, very well defined patterning was revealed over a large scale by fluorescence microscopy and atomic force microscopy (AFM). We investigate the advantage of our method by comparison with traditional microcontact printing and found that lateral diffusion was reduced, yielding a more accurate reproduction of the master. We also demonstrate that the stamp can be reused without reinking. The patterned surface was used for site-selective modification. The strategy was applied to two applications: the first is dedicated to the creation of amino-silane patterned surfaces, and the second illustrates the possibility of patterning polyelectrolyte multilayered thin films.

New TiO(2) films have been self-assembled on solid substrate by dip-coating using TiCl(4) as the titanium source and the partly fluorinated surfactant F(CF(2))(8)C(2)H(4)(OC(2)H(4))(9)OH as the liquid crystal template. By control over the dip-withdrawal speed, film thicknesses from a minimum of 43 nm were produced with rms roughnesses of 0.5-0.7 nm. The films were characterized by X-ray reflectivity, grazing incidence small-angle X-ray scattering, atomic force microscopy, contact angle measurements, and Raman spectroscopy. Their GI-SAXS patterns are characteristic of a 2-D hexagonal structure in which tubular rods of the fluorinated surfactant are packed hexagonally and aligned parallel to the substrate. Reflectivity and contact angle measurements of the as-prepared film indicate that a low-density hydrophilic TiO(2) surface presents to the air.

Bisphosphonates form self-assembled monolayers (SAMs) spontaneously on stainless steel, silicon, and titanium oxidized surfaces. We used contact angle measurements, atomic force microscopy, and X-ray reflectivity analysis to study the formation of SAMs on a model surface of ultraflat titanium (rms = 0.2 nm). The results were extended to standard materials (mechanically polished titanium, stainless steel, and silicon) and showed that water-soluble bisphosphonic perfluoropolyether can easily form SAMs, with 100% surface coverage and a layer thickness of less than 3 nm. Hydrophobic (water contact angle110 degrees on stainless steel or titanium) and lipophobic (methylene iodide contact angle105 degrees on titanium) properties are discussed in terms of industrial applications.

A simple method for elaborating mesoporous thin films with patterns normal to the substrate has been studied. The structured thin films were prepared by deposition of thin silica film templated by the so-called P123 (EO) 20 -(PO) 69 -(EO) 20 (poly-[ethyleneoxide-co-propyleneoxide-co-ethyleneoxide]) triblock copolymer on monolayers of n -octadecyltrichlorosilane (OTS) assembled onto a silicon wafer. Surface morphologies of films deposited onto silicon wafers modified by this hydrophobic monolayer or cleaned hydrophilic bare silicon wafer were characterized by using atomic force microscopy (AFM). We evidenced that, in the case of hydrophobic modified substrate, organic–inorganic hybrid thin films made of P123 species embedded in a silica matrix exhibit regularly-shaped craters in the direction normal to the surface. Our investigation has shown that the diameter of the craters agrees fairly well with the length of the fully extended organic chains of the triblock copolymer. The specific interfacial interactions between both the hydrophilic part of the shell of the surfactant, the native silicon oxide of the silicon wafer and the silanized surface are discussed.

A simple procedure to elaborate robust ultraflat gold surface without clean room facilities is presented. Self-assembled 3-mercaptopropytriethoxysilane (MPTMS) on silicon was used as a buffer layer on which gold was sputtered using a common sputter-coating apparatus. The optimization of the sample position into the chamber of the sputtering machine yielded the formation of a thin (approximately 8 nm) gold layer. The characterization of the resulting gold surface (i.e., AFM, X-ray reflectivity, and diffraction) has demonstrated its high smoothness (0.7 nm) over a large scale with a preferred (111) orientation. The robustness of the substrate toward organic solvents and thermal treatment was also tested. The ability of these surfaces to be used as substrates for high-resolution surface modification was confirmed by functionalizing the gold surface using the dip pen nanolithography process.

A compact monolayer containing azobenzene has been prepared on silicon substrates. The elaboration route consisted of covalent grafting of freshly synthesized azobenzene moieties onto an isocyanate-functionalized self-assembled monolayer (SAM). The highly packed and ordered isocyanate-functionalized SAM and the azobenzene-functionalized SAM were monitored and characterized by contact angle measurements and X-ray reflectivity (XR). Photoswitching of the wettability of the film induced by the reversible cis-trans isomerization of the azobenzene chromophores is experimentally shown from water and olive oil contact angle measurements.

International audience; The vibrational properties of silicon carbide nanoparticles (np-SiC) were investigated as function of the nanocrystal size (5-25 nm) and the features of their outermost surfaces. Raman experiments and numerical methods were conjugated to characterize the signatures from the active SiC normal modes and the vibrational density of states (VDOS). The Raman spectra of the nanopowders were marked by VDOS signals which correlate with the SiC amorphous fractions favoured by the high specific surfaces of the nanoparticles and their surface reconstruction. Quantitative interpretation of the experimental VDOS features, IR absorption and Raman scattering properties in nanosized SiC were carried out by means of numerical methods developed on SiC clusters with suitable structures and sizes.

International audience; In this work a systematic comparison of DC electrical conductivity and IR optical properties of thin films of (RxR'1-xNiO3), where R' = Nd and R = Sm or Eu, is performed. Independently of the nature of R, it is confirmed that the metal-insulator transition temperature (T-MI) in RxR'1-xNiO3 as well as in RNiO3 is driven by the mean lattice distortion quantified by the tolerance factor of the perovskite. The internal chemical pressure decrease due to substitution of Nd by another rare earth element with smaller cationic radius gives rise to an increasing resistivity in the metallic state together with a decrease of the screening effect in the IR reflectance. We suggest this is due to a modification of the free electron properties at the Fermi level and of the Fermi surface proper-ties consistent with photoemission literature data. On the other hand, similar transmittance spectra for various systems are reported in the insulating state. A systematic temperature independent drop of the transmittance above 0.6 eV is found for each system whatever the value of T-MI

The glass-transition temperature, Tg, of isotactic PMMA thin films has been measured for four thicknesses by enhanced Raman spectroscopy and ellipsometry. This was made possible by inserting a silica spacer layer between the film and the substrate. The use of such a spacer drastically improves the sensitivity of Raman scattering measurements. The improvement in the sensitivity allows us to study phenomena involving changes in molecular dynamics, such as the phase transition, and to probe the existence in very thin films of several thickness-dependent transition temperatures, Tg(h). This in turn is interpreted as the occurrence in the film of a layered structure. The influence of the polymer concentration on the conformation of the surface adsorbed polymer layer and therefore on Tg(h) is discussed.

symposium N " New materials and technologies in sensor applications ", session I " Materials and characterisations " [N-I.6]; International audience; A method to impregnate OPS by means of a suitable CR solution has been developed, taking into account properties of solvent (e.g. b.p. polarity, etc.) and environmental conditions (e.g. vacuum and heating) in order to enhance and optimise drying and filling of the pores of the material. Presence of CR in depth has been investigated by means of micro-Raman spectroscopy. A good transmittance of the porous layer, before impregnation, has been found by means of spectroscopic measurements in the visible spectral range, in Specular Reflectance mode. An absorption band, centred on about 490 nm, related to the presence of CR inside the pores, appears after impregnation by the dye, whereas that shifts to ~ 650 nm after exposition to acid vapours. The shift is reversible, that is the initial conditions are restored by exposition to basic vapours. This composite material is interesting for achievement of waveguides acting as chemical sensors optically monitored. By this way, bilayers of porous material have been performed for the realisation of planar waveguides. Several porosity values for the guiding layer have been attempted to define the bestconfiguration for the waveguides at 633 nm. After filling with CR, how the light is guided depending on the pH has been studied.

poster session 2 " Properties and Applications " [P2-28]; International audience; Mesoporous silicon layers, realised by electrochemical anodisation of p+ silicon substrates were completely oxidised and then impregnated by Disperse Red 1 (referred to as DR1) molecules dissolved in various solvents: butanol, propanol and THF. The formed composite materials were characterised by the "m-lines", micro-Raman spectrometry and optical reflectivity measurements. Raman investigations show that DR1 is uniformly distributed inside the porous layer and that the DR1 quantity is the highest when THF solvent is used. The refractive index evolution is in agreement with the DR1 quantities detected by Raman analysis.

Shifts in the main phase transition temperatures caused by a highly specific, protein-receptor interaction in a hybrid bilayer architecture are probed utilizing temperature programmed infrared vibrational spectroscopy. The specific case of cholera toxin attachment to glycolipid receptors embedded in a phospholipid outer layer at a hydrophobized silicon surface is investigated. Potential applications of the approach as a signal amplification method in biosensors will be discussed.