[en] We have studied cadmium stearate Langmuir-Blodgett (LB) films by spectroscopic ellipsometry (SE) and we have compared the results with those obtained by using X-ray reflectivity and atomic force microscopy. The measurements on cadmium stearate LB films deposited on silicon wafers capped by a native oxide layer provide sound results for films formed by 1-25 molecular layers. The experimental data are well fitted by a Cauchy-type model over the whole examined wavelength range (245-725 nm). The model, which takes into account the anisotropy of the film, uses the film thickness of several mono- and multi-layers films, together with the in-plane and the out-of-plane components of the refraction index as free parameters. The obtained mean thickness of the monolayer (ML), 2.50±0.02 nm, very well agrees with X-rays reflectivity measurements and with literature data

[en] We have studied the effect of physiological amounts of myelin basic protein (MBP) on pure dimyristoyl L-α-phosphatidic acid (DMPA) oriented membranes. The investigation has been carried out using several complementary experimental methods to provide a detailed characterization of the proteo-lipid complexes. In particular, taking advantage of the power of the quasi-elastic neutron scattering (QENS) technique as optimal probe in biology, a significant effect is suggested to be induced by MBP on the anisotropy of lipid dynamics across the liquid-gel phase transition. Thus, the enhancement of the spatially restricted, vertical translation motion of DMPA is suggested to be the main responsible for the increased contribution of the out of plane lipid dynamics observed at 340 K

[en] Tapping mode atomic force microscopy (AFM) was employed to study the surface structure of spin-coated and solvent-cast films of the newly synthesized electroluminescent copolymer TT9 and its fractions A and B. Fraction A is well soluble in chloroform while fraction B forms aggregates of high molecular weight in the same solvent. TT9 and fraction A are photoluminescent; fraction B is not. TT9 spin-coated and solvent-cast films show similar morphologies characterized by wormlike structures. Solvent-cast films formed by fraction A have a large density of defects. Fraction B forms larger structures, giving rise to more corrugated surfaces. These structures are formed by grains of rather uniform size, likely to be related to the aggregates already present in solution. For all the examined films, the surface roughness scales in the same way with the linear dimension of the surface, suggesting similar growth mechanisms

[en] We have performed an incoherent neutron scattering investigation of the modification of dynamical properties of model membrane induced by the addition of the myelin basic proteins. Elastic (ENS) and quasi-elastic (QENS) neutron scattering experiments revealed that the addition of physiological amounts of MBP induces a change in the average proton membrane dynamics across the lipid gel to liquid-crystalline phase transition. In particular, the appearance of anisotropic motion has been observed at two different time scales (accessible with IN13 and IN16 high-energy resolution backscattering spectrometers at ILL, Grenoble)

[en] High-T_c thick films of YBa₂Cu₃O_7-δ (YBCO) were grown on Ag substrates by a cryoelectrophoretic technique, i.e. deposited by electrophoresis in a cryogenic environment. The orienting effect is provided by the application of an external magnetic field of small intensity (120 G). After sintering, these films exhibited a superconducting transition at 92 K in the electrical resistivity. Oriented films show significantly enhanced critical current densities. A detailed study of the structural and morphological properties of the film surfaces was undertaken using scanning electron microscopy, x-ray diffraction and scanning force microscopy (SFM). All microscopies revealed different types of film growth induced by the application of an external magnetic field during the cryogenic deposition showing an increasing degree of order with the field intensity (0-120 G). Observations of surface topography as studied by SFM are also discussed. (author)

[en] We report recent results showing the evidence of the effect induced by physiological amounts of myelin basic protein (MBP) on the dynamics of dimyristoyl L-a-phosphatidic acid (DMPA) membranes. Incoherent elastic neutron scattering scans, performed over a wide temperature range, have shown that the anisotropy of motions in oriented membranes is significantly enhanced by the presence of MBP. (orig.)

[en] The morphological and mechanical properties of encapsulated yeast cells (Saccharomyces cerevisiae) have been investigated by atomic force microscopy (AFM). Single living cells have been coated through the alternate deposition of oppositely charged polyelectrolyte (PE) layers. The properties of cells coated by different numbers of PE layers and from PE solutions of different ionic strength have been investigated. AFM imaging indicates an increase in PE coating stability when decreasing the solution ionic strength. The Young's moduli of the different examined systems have been evaluated through a quantitative analysis of force-distance curves by using the Hertz-Sneddon model. The analysis indicates an increase in hybrid system stiffness when lowering the ionic strength of the PE solution. An evaluation of the viability of encapsulated cells was obtained by confocal laser scanning microscopy (CLSM) measurements. CLSM analysis indicates that cells preserve their subcellular structure and duplication capability after encapsulation. By coupling AFM and CLSM data, a correlation between local stiffness and duplication rate was obtained

[en] L-cysteine self-assembled monolayers (SAMs) have been deposited on gold from the liquid and vapour phase. Synchrotron based high resolution x-ray photoemission spectroscopy has been used to characterize the sulfur chemical states at the SAM/gold interface. Results obtained from pristine and x-ray irradiated samples, prepared with both as-received and purified L-cysteine, are reported. Pristine samples prepared with purified cysteine are characterized by an intense, largely dominant S 2p state at a binding energy around 162 eV (2p_3/2 level) assigned to thiolates. A second doublet around 161 eV develops during irradiation. By comparison with the literature, this doublet is assigned to atomic sulfur present either as impurity or generated by S-C bond scission. Comparative measurements performed, under similar experimental conditions, on pristine 3-mercaptopropionic acid [HS(CH₂)₂COOH] layers deposited from the liquid phase are also presented and discussed

[en] We report on the preparation and characterization of self-assembled monolayers (SAMs) of a novel diacetylene monomer, the 14-N-carbazolyltetradeca-10,12-diyndisulfide. The SAM/gold interface was investigated by means of spectroscopic ellipsometry (SE), X-ray photoelectron spectroscopy (XPS) and scanning tunnelling microscopy (STM). SE data indicate a layer thickness compatible with the formation of a monomolecular layer. The occurrence of molecular chemisorption is confirmed by XPS measurements which indicate the formation of a thiolate species. This result is confirmed by STM imaging which shows the formation of small pits, one gold layer deep, a typical feature of self-assembled organosulfur monolayers on gold