Laboratoire de Photochimie et d'Ingénierie Macromoléculaire

Crystalline microporous solids are an important class of inorganic materials with uses in different areas impacting our everyday lives, namely as catalysts, adsorbents, and ion exchangers. Advancements in synthesis have been invaluable in expanding the classical aluminosilicate zeolites to new unique framework types and compositions, motivating innovative developments. However, the inexhaustible post-synthetic options to tailor zeolite properties have been and will continue to be indispensable to realize emerging and to improve conventional applications. Starting from the routine drying and template removal processes that every zeolite must experience prior to use, a wide spectrum of treatments exists to alter individual or collective characteristics of these materials for optimal performance. This review documents the toolbox of post-synthetic strategies available to tune the properties of zeolitic materials for specific functions. The categorisation is based on the scale at which the alteration is aimed at, including the atomic structure (e.g. the introduction, dislodgment, or replacement of framework atoms), the micropore level (e.g. template removal and functionalisation by inorganic and organic species), and the crystal and particle levels (e.g. the introduction of auxiliary porosity). Through examples in the recent literature, it is shown that the combination of post-synthetic methods enables rational zeolite design, extending the characteristics of these materials way beyond those imposed by the synthesis conditions.

Abstract— The fluorescence excitation spectrum and the excitation polarization spectrum of indole in propylene glycol were measured at — 58°C, after selecting by optical filters the emission originating from the 1 L a electronic level. From the analysis of these spectra, the excitation spectrum was resolved into the 1 L a and 1 L a excitation bands. A similar resolution of the excitation spectrum of tryptophan is given. This method can also be applied to the resolution of the emission spectrum in cases of dual emission.

OBJECTIVE: To determine the effects over one year of contacting patients by telephone one month or three months after being discharged from an emergency department for deliberate self poisoning compared with usual treatment. DESIGN: Multicentre, randomised controlled trial. SETTING: 13 emergency departments in the north of France. PARTICIPANTS: 605 people discharged from an emergency department after attempted suicide by deliberate self poisoning. INTERVENTION: The intervention consisted of contacting patients by telephone at one month or three months after discharge from an emergency department for attempted suicide to evaluate the success of recommended treatment or to adjust treatment. Control patients received treatment as usual, in most cases referral back to their general practitioner. MAIN OUTCOME MEASURES: The primary outcome measures were proportion of participants who reattempted suicide, number of deaths by suicide, and losses to follow-up at 13 months' follow-up. Secondary outcome measures were types and number of contacts with health care. RESULTS: On an intention to treat basis, the three groups did not differ significantly for further suicide attempts, deaths by suicide, or losses to follow-up: contact at one month (intervention 23% (34/147) v controls 30% (93/312), difference 7%, 95% confidence interval - 2% to 15%), three months (25% (36/146) v 30%, difference 5%, - 4% to 14%). Participants contacted at one month were less likely at follow-up to report having reattempted suicide (12% v 22% in control group, difference 10%, 2% to 18%). CONCLUSION: Contacting people by telephone one month after being discharged from an emergency department for deliberate self poisoning may help reduce the number of reattempted suicides over one year.

Abstract The mechanical properties of polymers are strongly influenced not only by the structure of the material but by the magnitude of the molecular orientation. Thus a great deal of interest exists in information about the molecular orientation in samples introduced by drawing or other forming processes. Several techniques of evaluation of this orientation exist such as birefringence, x-ray diffraction, sonic modulus, and fluorescence measurements [l, 2]. Vibrational analysis of oriented polymers provides a method of determining independently the molecular orientation both in the crystalline and amorphous phases of polymers. By using vibrational techniques, a number of macromolecules have been studied in the solid state for a variety of different processes. It is the purpose of this review to summarize the recent theoretical and experimental results which have occurred since the review of Zbinden [3]. Infrared and Raman measurements will be reported since they are complementary to each other in their applications and results.

Abstract The photoinitiated cationic polymerization of di‐epoxy monomers has been studied using real‐time infrared (RTIR) spectroscopy. The polymerization rate and the amount of unreacted monomer were determined directly from the conversion vs. time curves recorded. The cure speed was greatly increased by using a Kr + laser (337.4 nm) as radiation source. A 0.25 s exposure proved sufficient to make react more than 60% of the epoxy groups. The overall polymerization quantum yield was evaluated to be 200 mol photon ‐1 . Dark polymerization was shown to develop extensively after the UV exposure for about 30 min and may represent up to 80% of the total process. The hardening of the UV‐cured tack‐free coating was found to occur mainly in the dark, leading after 1 h to a very hard and glassy material. A bimolecular chain termination process is postulated to account for the decay profile of the reactive species observed after UV exposure.

We have developed a tomographic diffractive microscope, equipped with a fluorescence confocal scanner. We measure experimentally the lateral resolution using an edge method and by comparing tomographic images of the same samples with wide-field and laser scanning confocal microscopy images; a scanning electron microscope image serves as a reference. The experimental resolution is shown to be to about 130 nm, or lambda/(3.5 NA). This instrument also permits one to measure 3D, complex index of refraction distributions, a quantity that is not accessible to conventional microscopes, and we show how this feature may be used to observe KCl crystals, absorption of which is very weak.

The highly virulent Escherichia coli O104:H4 that caused the large 2011 outbreak of diarrhoea and haemolytic uraemic syndrome secretes blended virulence factors of enterohaemorrhagic and enteroaggregative E. coli, but their secretion pathways are unknown. We demonstrate that the outbreak strain releases a cocktail of virulence factors via outer membrane vesicles (OMVs) shed during growth. The OMVs contain Shiga toxin (Stx) 2a, the major virulence factor of the strain, Shigella enterotoxin 1, H4 flagellin, and O104 lipopolysaccharide. The OMVs bind to and are internalised by human intestinal epithelial cells via dynamin-dependent and Stx2a-independent endocytosis, deliver the OMV-associated virulence factors intracellularly and induce caspase-9-mediated apoptosis and interleukin-8 secretion. Stx2a is the key OMV component responsible for the cytotoxicity, whereas flagellin and lipopolysaccharide are the major interleukin-8 inducers. The OMVs represent novel ways for the E. coli O104:H4 outbreak strain to deliver pathogenic cargoes and injure host cells.

Abstract. This paper presents an inverse method for inferring trace gas fluxes at high temporal (daily) and spatial (model grid) resolution from continuous atmospheric concentration measurements. The method is designed for regional applications and for use in intensive campaigns. We apply the method to a one month inversion of fluxes over Europe. We show that the information added by the measurements depends critically on the smoothness constraint assumed among the source components. We show that the initial condition affects the inversion for 20 days, provided one has enough observing sites to constrain regional fluxes. We show that the impact of the far-field fluxes grows throughout the inversion and hence a reasonable global flux field is a prerequisite for a regional inversion.

DNA solutions subjected to an electric field exhibit an instability that leads to DNA segregation in aggregates tilted with regard to the field. With the use of epifluorescence videomicroscopy, the evolution of DNA patterns in capillaries as a function of DNA concentration, DNA size, field strength, and field frequency was studied. The field threshold for segregation was decreased when the frequency was lowered or when the DNA molecular weight or concentration was increased. Aggregation is attributed to an electrohydrodynamic instability triggered by the dipole-dipole interaction. This phenomenon explains the failure of earlier attempts to separate large DNA in capillaries.

This work reports the synthesis and characterization of HDPE vitrimers obtained <italic>via</italic> reactive extrusion in the presence of bis-nitroxide dioxaborolanes.

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The photoredox catalysis approach is used to initiate the free radical promoted cationic photopolymerization of N-vinylcarbazole (NVK) under very soft irradiation conditions (halogen lamp, blue or green LED bulbs) using visible-light harvesting photocatalysts (mainly Ir(III) complexes) in iodonium salt and silane containing photoinitiating systems. The reactions were shown to proceed via an oxidative catalytic cycle where the generated free radicals are oxidized into cations. The effect of NVK on this catalytic cycle is discussed. Epoxy/NVK matrixes can also be polymerized. The luminescent properties of the synthesized polymers are presented.

The abilities of two naphthalimide derivatives with a methacryloyl group to initiate, when incorporated in multi-component systems, a ring-opening polymerization of epoxides and a radical polymerization of acrylates under different irradiation sources (e.g. very soft halogen lamp irradiation, laser diode at 457 nm, laser diode at 405 nm and blue LED bulb at 462 nm) have been investigated. One of them is particularly efficient for the cationic and radical photopolymerization of an epoxide/acrylate blend in a one-step hybrid cure and leads to the formation of an interpenetrated polymer network IPN (30 s for getting tack free coatings). The migration stability of one of these naphthalimide derivatives is found to be excellent in the cured polyacrylates and IPNs. The photochemical mechanisms are studied by steady state photolysis, fluorescence, cyclic voltammetry, electron spin resonance spin trapping and laser flash photolysis techniques.

Abstract Triplet state formation (Φ isc ) and properties (ε T‐T , τ T ) of phthalocyanine (HPC) and zinc phthalocyanine (ZnPC) have been characterized in homogeneous solutions (1‐chloronaphthalene, 1‐propanol) and in microemulsion by investigating the variation of the transient optical density as a function of the intensity of the exciting laser. Experimental results follow the theoretically predicted dependence only for very low intensities of the exciting pulse. At higher intensities, a more complicated scheme of primary reactions has to be taken into account, implicating qualitative restrictions in the application of saturation experiments. The observed transients at high‐intensity excitation are interpreted as being perturbed by aggregational phenomena.

Present study explains the detailed synthesis, structural characterization, antibacterial and antiviral studies on Titanium dioxide nano-colloids (TiO2-NCs). Titanium dioxide (TiO2) nano-colloids were synthesized by a simple sonochemical method. The structural studies were carried out by x-ray Diffraction (XRD), and the size of particle was found to be 8 nm with tetragonal structure. Surface morphological results by scanning electron microscopy (SEM), showed spherical nature of (TiO2) nano-colloids with almost uniform morphology. Energy Dispersive x-ray Diffraction (EDX) confirmed the chemical composition and presence of (TiO2) nanoparticles in sample. Dynamic light scattering was used to confirm the colloidal stability and hydrodynamic size of nano-colloids. Antibacterial assays were performed against several gram positive and negative pathogenic bacteria. TiO2-NCs showed maximum bacterial inhibition (67.3 ± 2.5%) at 150 μg ml− dose against Pseudomonas aeruginosa. Minimum inhibitory concentrations (MICs) against all tested pathogenic strains ranged from 2.24–21.21 μg ml−, indicating efficient therapeutic potential of (TiO2) nano-colloids. Antiviral activity of (TiO2) nano-colloids was also performed against Newcastle virus (NDV) which showed antiviral activity at a minimum dose of 6.25 ug ml−1. Possible mechanism of action include damage to the lipids found in viral envelop. The obtained results suggest potential application of TiO2-NCs in poultry to treat NDV infections after detailed mechanism studies.

The degradation of diuron photoinduced by iron(III) in aqueous solution has been investigated with different iron(III) species (monomeric species Fe(OH)2+, dimeric species Fe2(OH)24+ and water-soluble oligomeric species) under monochromatic excitation at 365 nm and under sunlight. The rate of degradation depends on the concentration in Fe(OH)2+, the most reactive species in terms of •OH radical formation. The major photoproduct is 3-(3,4-dichlorophenyl)-1-formyl-1-methylurea which represents more than 60% of diuron disappearance. The mechanism only involves the attack by •OH radicals arising from iron(III) excited species. The half-lives of diuron when submitted to such a process in the environment were estimated to be 1–2 h and a few days according to the concentration of Fe(OH)2+ (respectively 70% and <10% of total iron(III) concentration).

Abstract Real time infrared (RTIR) spectroscopy was used to study the kinetics of the polymerization of acrylic monomers exposed to the 337,4 nm continuous emission of a Kr + laser. Conversion versus time curves were directly recorded in the millisecond timescale, thus allowing a precise evaluation of the polymerization rate and of the induction period due to O 2 inhibition. The influence of the type and concentration of photoinitiator and of the laser beam intensity on the polymerization profile was examined for a 20 μm thick polyurethane‐acrylate (Actilane 20) coating. The growth of the radical concentration and its dependence on the initiation rate was determined from the kinetics of the dark polymerization which develops just after the laser exposure. Pulsed laser irradiation proved to be very effective in initiating the polymerization, the overall quantum yield reaching values up to 2500 mol · photon −1 .

Turning over a new leaf: Leaves of Equisetum Arvense can be successfully treated to yield zeolite-type structures which, after calcination, are transformed into a micro-/mesoporous material which keeps all of the morphological features of the vegetal template (see SEM image). Faithful zeolitization of the plant structure is induced by the highly reactive biomorphic silica deposited in the epidermal surface of the plant. The performance of bulk materials often depends on the size and habit of the primary particles, and their ordering into hierarchical structures. In the area of catalysis and separation processes, ordered materials with well-defined periodic structures and controlled sizes are highly desired. Hierarchical porous structures combine the benefits of each pore-size regime and are expected to lead to higher efficiency and new applications in catalytic and separation processes, biomolecular separations, and chromatographic supports.1 The most commonly used approach for the fabrication of such materials is the application of sacrificial templates, which after the synthesis of the inorganic framework are dissolved or volatilized by heating. The template approach, first employed for the preparation of zeolite-type materials, where small organic molecules are used for directing the microporosity,2 was extended to the formation of mesoporous3 and macroporous4 structures. By employing dual templates, hierarchical porous materials with combinations of micro-/mesopores,5 meso-/macropores,6 micro-/macropores7 and micro-/meso-/macropores8 were synthesized. Thus, a high level of control was achieved and materials with up to three different pore sizes were synthesized, however, the morphology of these hierarchical structures is far from being controlled. Nature provides many examples of biological specimens with complicated morphologies and hierarchically built anatomies that are completely petrified, and in which the organic structures are substituted by minerals. Laboratory simulation of this process may provide materials where complex anatomy is combined with specific macromorphology. Recently, laboratory zeolitization of silica cells from diatoms (single-celled algae) providing a micro-/macroporous material was reported.9, 10 Crystallization of the zeolite was induced from seeds, since the reactivity of the fossilized biogenic silica seems to be very low, which does not allow direct crystallization of the zeolite. In addition, by the adsorption of zeolite nanocrystals followed by a hydrothermal treatment, wood cellular structures were transformed into micro-/macroporous zeolite structures.11 Aggregation of silicalite-1 nanocrystals on biological macrotemplates was used for the preparation of micro-/macroporous fibers12 and spongelike monoliths.13 Previous studies have shown that the utilization of biological templates requires the application of zeolite seeds. On the other hand, the most perfect replication of biogenic materials in nature is by silica that is transported in solution and deposited in an amorphous form.14 Although zeolites are silicates and water transport is an important stage in their formation, successful laboratory zeolitization of biological templates without the use of seeds has not been reported. Thus, the application of zeolite seeds appeared to be indispensable for the synthesis of zeolites on biological macrotemplates. Herein, we report the in situ zeolitization of a vegetal macrotemplate, induced by the biogenic silica of a fresh plant. The content of silica in dry Equisetum arvense used for the present study was about 13 wt %, and is deposited in discrete knobs and rosettes at the epidermal surface.15 The 29Si NMR spectrum of the freeze-dried plant is typical of amorphous silica.16 Thus, Equisetum arvense offers a perfect surface for zeolitization where easily accessible, highly reactive amorphous silica is exposed. Leaves of the plant were subjected to hydrothermal treatment with a precursor solution that yielded silicalite-1 (MFI-type structure) crystals.17 The crystallization of silicalite-1 was accomplished after 24 h treatment. A series of experiments that varied the duration of the hydrothermal treatment from 4–24 h was performed. Analysis of the biological macrotemplate and the mother liquor showed that zeolite formation at the surface of Equisetum arvense overtook that observed in solution. The first trace of silicalite-1 on the surface of the plant was detected after 6 h hydrothermal treatment, followed by a rapid increase of the zeolite content. In contrast, silicalite-1 crystallization in the mother liquor took place over the 12–24 h period, which is in good agreement with literature data.18 The enhanced nucleation on Equisetum arvense, in comparison with that in the solution, clearly showed that the epidermal surface of the plant was not a simple support for nucleation and subsequent zeolite formation. The high rate of zeolite formation on the epidermal surface of the plant results from the interaction of the highly reactive initial mixture with biogenic silica, which induces a fast and uniform nucleation. Figure 1 shows the effect of one- and two-step hydrothermal treatments on the amount of crystallized zeolite. The halo emanating from the organic part of the composite decreased after the second crystallization procedure. Only pure, highly crystalline silicalite-1 was observed in the calcined material (600 °C for 5 h). X-ray diffraction patterns of silicalite-1/Equisetum arvense composites obtained by one- (a) and two-step (b) synthetic procedures, and the pure silicalite-1 replica (c) of the plant obtained after calcination of the two-step material. The amounts of silicalite-1 deposited after one and two synthesis steps were determined by thermogravimetric analysis (TGA). After one step, a weight loss of 50.1 wt % was recorded, of which 6.02 wt % was attributed to the loss of water, and the remaining 44 wt % results from thermal degradation of the plant tissues and the tetrapropylammonium (TPA) template. After two hydrothermal steps the total weight loss was about 36.9 wt %, where the weight loss through water was only 0.7 wt %, while that resulting from the decomposition of TPA and the biological macrotemplate was about 36 wt %. It is difficult, however, to evaluate the content of each of the templates because of the overlapping of the corresponding peaks. Figure 2 shows the zeolitized Equisetum arvense leaves, viewed at various magnifications by scanning electron microscopy (SEM), after the hydrothermal treatment and calcination procedure. The morphology of the leaves is maintained after combustion of the organic tissue (Figure 2 a,b2). It can be seen that the silicalite-1 replica (Figure 2 c) retains much of the detail observed in the original plant structure (Figure 2 d). Also of note are the extremely small silicalite-1 crystallites that grow on the surface, the size of which is approximately at the resolution limit of the SEM instrument; according to dynamic light scattering (DLS) measurements, the size of the silicalite-1 crystals formed in the solution is approximately 90 nm. An investigation by transmission electron microscopy (TEM) showed that crystallites grown at the epidermal surface of Equisetum arvense are much smaller, and range from 20 to 40 nm (Figure 2 e,f2). The TEM images reveal that the crystals are fairly uniform in size (Figure 2 e). These results prove that the reactive biomineral silica promotes zeolite nucleation at the epidermal surface. Thus, a very homogeneous fine silicalite-1 film is formed, and even the nanometer-scale morphological details of the plant are replicated. Low-(a) and higher (b) magnification views of the silicalite-1 replica of a leaf of Equisetum arvense. The silicalite-1 replica of a stomata structure (c) is compared with the original plant structure (d), where fine filaments covering the leaf can be seen; e,f) TEM images at two magnifications show the lattice fringes of the silicalite-1 nanocrystals within the homogeneous zeolite layer. Initially, the leaves showed a relatively high Brunnauer–Emmet–Teller (BET) surface area (3.9 m2 g−1) for a dense centimeter-sized material, which is probably a result of the nanosized silica particles exposed throughout the epidermal membrane. After a single-step hydrothermal synthesis, the BET surface area of the as-synthesized product increased to 58 m2 g−1. This value is indicative of the very small nanocrystallites formed on the biological template. After calcination, the sample showed a BET surface area of 217 m2 g−1, which is two orders of magnitude higher than natural Equisetum arvense leaves. This value, however, is lower than that of a highly crystalline MFI-type material, which reveals that after the one-step synthesis, a dense material with low specific surface area is still present. The second synthesis step substantially reduces the amount of non-zeolite material, and the calcined sample showed a BET surface area of 383 m2 g−1, which is in accordance with a highly crystalline MFI-type material. However, a total single-point pore volume of 0.92 cm3 g−1 was measured for the two-step material (of which the micro- and mesopores contribute 0.13 and 0.79 cm3 g−1, respectively), which does not correspond to that of a microporous MFI-type material. The value corresponding to the micropore volume is somewhat below that of a highly crystalline sample of silicalite-1 (about 0.18 cm3 g−1), which reveals the presence of some non-zeolitic material after the second hydrothermal synthesis. The type I adsorption/desorption isotherms of the calcined samples synthesized by one- and two-step hydrothermal treatments show the microporous character of the materials (Figure 3 a and b3). A steep rise in the gas uptake at low relative pressures corresponds to the filling of micropores with N2. In contrast to pure microporous materials, the steep uptake at low relative pressures is not followed by a flat curve. Instead, an inclination of the curve with an increase of the pressure can be observed. At high relative pressure the upward turn with a hysteresis loop is indicative of the generation of intercrystalline mesoporosity. Thus, the zeolitization of Equisetum arvense yields a material with combined micro- and mesoporosity. Adsorption/desorption isotherms of the calcined samples prepared by one- (a) and two-step (b) synthetic procedures. Results of small-angle X-ray scattering (SAXS) analysis are in good agreement with the TEM observations and the N2 adsorption measurements, that is, uniform nanoparticles and a secondary porosity were detected. SAXS data obtained for dried Equisetum arvense leaves do not show fractal behavior nor microporosity features (Figure 4 a). In contrast, SAXS data obtained after hydrothermal treatment of the fibers exhibits three Q-vector domains in the ranges Q<5×10−3 Å−1, 5×10−3<Q<2×10−2 Å−1, and 2×10−2 Å−1<Q (Figure 4 b). These Q-vector domains correspond to scattering from mesopores (or small macropores), micropores, and the surface of the crystallites, respectively. The slope deviation observed in the log–log plot of the SAXS curves at 5×10−3 Å−1 indicates a mean nanocrystallite size of about 30 nm. The power law behavior of the scattering intensities (that is, a linear increase with decreasing Q with a slope equal to −4) for Q>2×10−2 Å−1 suggests that these particles possess a smooth surface. SAXS profiles of Equisetum arvense leaves before (a) and after (b) hydrothermal treatment. Although no special tests were performed, the difference in the strength of the silicalite-1 replicas prepared by one- and two-step synthesis procedures is easily distinguishable. The one-step synthesized material retained the macromorphological features of the plant leaves. However, the fibrous structure easily disintegrates when a simple laboratory operation is performed. In contrast, the replicas obtained by the two-step synthesis are stable, rigid, and can be destroyed only under applied pressure; no destruction was observed during the laboratory manipulations performed with this material. Further increase of the strength of Equisetum arvense silicalite-1 replicas might be achieved either by an additional synthetic step, or by a hydrothermal treatment with a precursor gel that does not contain an organic structure-directing agent. In the latter case, subsequent calcination to open the zeolite microporosity is not necessary, and thus flexible fibrous zeolite/Equisetum arvense composites might be prepared. In conclusion, highly reactive silica in plants can promote zeolite crystallization. The large amount of silica found in the epidermal surface of Equisetum arvense facilitates zeolite nucleation providing homogeneously and densely distributed zeolite nuclei. Thus a micro-/mesoporous material which retains all of the morphological features of the plant was obtained. This study opens up routes for the zeolitization of silica-containing plants and the preparation of materials with controlled porosity and specific macromorphological features. The large variety of microporous aluminosilicates and numerous silica-containing plants present tremendous possibilities for tailoring such materials. The reactivity of biomorphous silica can most probably be used to promote the nucleation of other silicate materials that crystallize under soft hydrothermal conditions.

Supramolecular functional materials able to respond to external stimuli have several advantages over their classical covalent counterparts. The preparation of soft actuators with the ability to respond to external stimuli in a spatiotemporal fashion, to self-repair, and to show directional motion, is currently one of the most challenging research goals. Herein, we report a series of metallopolymers based on zinc(II)-terpyridine coordination nodes and bearing photoisomerizable diazobenzene units and/or solubilizing luminescent phenylene-ethynylene moieties. These supramolecular polymers act as powerful gelating agents at low critical gelation concentrations. The resulting multiresponsive organogels display light-triggered mechanical actuation and luminescent properties. Furthermore, owing to the presence of dynamic coordinating bonds, they show self-healing abilities.

The tackiness of model soft adhesive layers based on styrene-isoprene-styrene block copolymers and a tackifying resin were investigated with a flat-ended cylindrical steel probe. The contact between the probe and the adhesive was maintained for 1 s at a nominal pressure of 1 MPa before being detached at a constant velocity. The effect of resin content, probe velocity during debonding and temperature were systematically investigated. Failure was initiated by two main mechanisms: an interfacial cavitation at low debonding rates, giving relatively low adhesion energies, and a bulk cavitation process at higher debonding rates, which gave much higher adhesion energies. In both cases failure occurred at the end by interfacial detachment of fibrils. The characteristic probe velocity where the transition between these two mechanisms took place was controlled primarily by the linear viscoelastic properties of the adhesives. However, the important quantitative parameters obtained from a tack test, i.e., the maximum debonding stress and the adhesion energy, could not be predicted by the linear viscoelastic properties of these adhesives alone.