Jean-Marc Janot

PHOTOPHYSICAL PROPERTIES OF THREE METHANOFULLERENE DERIVATIVES

The three [6,6]-ring bridged methanofullerenes 1, 2, and 3 were synthesized; their ground-state absorption spectra in toluene and cyclohexane solutions are presented and possible assignments discussed. Although these three molecules are very different, they have very similar triplet–triplet spectra and near-unity values for the quantum yield for O2(1Δg) production by energy transfer from the triplet states, implying that the quantum yield of triplet production is approximately 1.

Optical limiting and nonlinear optical absorption properties of C60–polystyrene star polymer films: C60 concentration dependence

The optical limiting behavior and the nonlinear optical properties of pure C60–(polystyrenex)y (C60–(PSx)y) star polymer, and C60–(PSx)y incorporated in a polystyrene matrix, are reported. Two, four and six polystyrene arms of controllable length were grafted directly on the C60 cage, preventing aggregation of the fullerene molecule, and consequently permitting achievement of high C60 concentrations. The optical limiting behavior of these films was measured below the damage threshold, and the nonlinear absorption coefficient β was determined by the Z-scan technique, using nanosecond 532 nm and sub-picosecond 497 nm laser radiation. In some of the samples, the high concentration of C60 gives rise to intermolecular interactions, which diminish the average molecular nonlinear optical properties of the film. However, the observed dependence of the nonlinear optical properties as a function of laser pulse duration and C60 concentration may be relevant to applications of these compounds in solid state devices.

Photophysical properties of three hydrofullerenes

Abstract The ground state and lowest triplet state properties of three hydrofullerenes, C60H2, C60H4 and [1-methylsuccinate-4-methyl-cyclohexadiene-2,3]buckminsterfullerene, have been investigated in toluene at room temperature. Their visible ground state absorption spectra are compared to those of methanofullerenes and methanolfulleroids. The triplet properties, including the absorption spectrum between 300 and 800 nm, molar absorption coefficient, quantum yield of formation and quantum yield for the photosensitized production of O 2 ( 1 Δ g ) , are compared to those of other C60 derivatives.

New bioinspired membrane made of a biological ion channel confined into the cylindrical nanopore of a solid-state polymer.

A hybrid nanoporous membrane made of a solid-state polymeric thin film in which an ion channel is confined is realized. The primary and extremely encouraging results obtained by confocal fluorescence spectroscopy and ion diffusion measurement demonstrate respectively that (i) the considered ion channel, that is, Gramicidin-A, can be confined selectively inside the nanopores and (ii) the ionic permeability of the membrane is enhanced. Atomistic molecular simulations are also reported and fruitfully compared to the experimental findings.

A new Multi-charged C60 Derivative: Synthesis and Biological Properties

A new water-soluble multi-charged monoadduct fullero[60]pyrrolidine derivative with three ethylene glycol chains and three ammonium groups has been synthesized by means of two alternative synthetic pathways. Increasing the concentration of this C60 derivative did not show a significant modification of concentration of superoxide anion radical O2·−, generated by the xanthine/xanthine oxidase system. Moreover, this C60 derivative was ineffective for neuroprotection in quantitative assessment of a neuronal injury considered to occur via radicals. (© Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)

Structure, Orientation and Stability of Lysozyme Confined in layered Materials

The confinement of lysozyme in 3 layered materials based on montmorillonite and lamellar double hydroxides exhibiting different surface charges was studied. The protein structure and orientation in these materials were determined by X-ray diffraction, time resolved fluorescence and fluorescence anisotropy. For montmorillonite exchanged with sodium and modified with a non-ionic surfactant (tri-ethylene glycol mono n-decyl ether), the lysozyme was found to be located in the interlayer space with the “end-on” and “side-on” orientations, respectively. Conversely, no lysozyme intercalation was observed with a lamellar double hydroxide modified with an anionic surfactant (sodium octylsulfate), since the protein was adsorbed on the surface of the particles. Fourier transformed infrared spectroscopy analysis shows that lysozyme confinement in the interlayer space preserves its structure after dehydration, whereas some structural changes were observed for lysozyme adsorbed on the particle surface.

PHOTOINDUCED ELECTRON TRANSFER PROPERTIES OF POROUS POLYMER MEMBRANES DOPED WITH THE FULLERENE C60 ASSOCIATED WITH PHOSPHOLIPIDS

Abstract The vast range of possible applications for fullerenes makes them interesting compounds, either as materials or as substances able to confer on other materials their physicochemical properties. Porous polymer membranes were modified by the incorporation of C60 concomitantly with amphipathic molecules (phospholipids). These membranes had the same photoconducting properties, by electron transfer, as those already described for bilayer lipid membranes incorporating C60. They present the advantage of an uncomparably greater mechanical stability in comparison with their ultrathin homologues.

Adsorption of Alexa-Labeled Bt Toxin on Mica, Glass, and Hydrophobized Glass: Study by Normal Scanning Confocal Fluorescence

We studied the kinetics of adsorption of alexa-labeled Bt toxin Cry1Aa, in monomer and oligomer states, on muscovite mica, acid-treated hydrophilic glass, and hydrophobized glass, in the configuration of laminar flow of solution in a slit. Normal confocal fluorescence through the liquid volume allows the visualization of the concentration in solution over the time of adsorption, in addition to the signal due to the adsorbed molecules at the interface. The solution signal is used as calibration for estimation of interfacial concentration. We found low adsorption of the monomer compared to oligomers on the three types of surface. The kinetic adsorption barrier for oligomers increases in the order hydrophobized glass, muscovite mica, acid-treated hydrophilic glass. This suggests enhanced immobilization in soil if toxin is under oligomer state.

Involvement of C60 fullerene monomers and aggregates in the photoconductivity of ultrathin bilayer lipid membranes

Abstract Due to its hydrophobic character, the hydrocarbon core of ultrathin phospholipid bilayer membranes lends itself to the insertion of fullerenes. When doped with C 60 these membranes are photoconducting, the photoconductivity being affected by the presence of quenchers of the excited triplet state such as oxygen. The photoconductivity involves trans-membrane electron transfer; its dependence on C 60 concentration and on the excitation wavelength suggests the participation of small aggregates in the membrane. As derived from time-resolved triplet absorption and fluorescence quenching measurements, the suggested mechanism makes more precise (i) the role of the aggregates which might act as a collecting antenna for the benefit of the monomers, and (ii) the role of the monomers which have a much higher yield of photoinduced triplet state formation than the aggregates.

Optical limiting behaviour of the water-soluble C60/γ-cyclodextrin complex

Abstract The third-order nonlinear optical response of the water-soluble inclusion complex consisting of C 60 incorporated in γ-cyclodextrin was examined employing the z -scan technique. Using 532 nm, 10 ns laser pulses, significant optical limiting action was observed, the effect being slightly lower than that of pure C 60 diluted in toluene. Ageing of the C 60 /γ-cyclodextrin–water solution results in the formation of aggregates that enhance the optical limiting action by a factor of almost two.