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5. Thermo-temporal physisorption in metal–organic frameworks probed by cyclic thermoellipsometry.

Author

Amyar, Hajar, Avci, Civan, Boissière, Cédric, Cattoni, Andrea, Besbes, Mondher, and Faustini, Marco

Subjects
METAL-organic frameworks, PHYSISORPTION, POROUS materials, SORPTION
Abstract

Temperature-induced sorption in porous materials is a well-known process. What is more challenging is to determine how the rate at which temperature is varied affects these processes. To address this question, we introduce a methodology called ‘‘cyclic thermo-ellipsometry’’ to explore the thermo-kinetics of vapor physisorption in metal–organic framework films. [ABSTRACT FROM AUTHOR]

Published
2024
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8. In Situ Infrared and UV–Vis Ellipsometries to Probe The Varnish Ageing and Swelling of G. Bellini "Transfiguration".

Author

Pasco, Hélène, Lesaine, Arnaud, Cerasuolo, Angela, Boissière, Cédric, Walter, Philippe, Sanchez, Clément, de Viguerie, Laurence, and Faustini, Marco

Subjects
ART conservation & restoration, VARNISH & varnishing, OPTICAL coatings, DETERIORATION of materials, WATER vapor
Abstract

Varnish layers are optical coatings that act as physico‐chemical barrier between the historical paint layers and the environment. Understanding how varnish materials protect historical paintings over time and in the presence of humidity or organic vapors is of central importance for art preservation. However, probing the behavior of varnish after aging in real conditions remains a challenge. Here the question is addressed by "reshaping" the varnish material from the masterpiece of G. Bellini, the "Transfiguration", into an optical layer; coupling in situ Ultraviolet‐Visible (UV–vis) and Infrared (IR) ellipsometries, the chemical state is correlated, optical properties and swelling of the varnish in presence of water and organic vapors. It shows that the varnish material aged since the 1950s still exhibits effective water repellence. The methodology may be applied to other relevant historical systems beyond paintings and may help in establishing more efficient preservation strategies for historical artworks. [ABSTRACT FROM AUTHOR]

Published
2024
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12. Revealing the Dependency of Dye Adsorption and Photocatalytic Activity of ZnO Nanoparticles on Their Morphology and Defect States.

Author

Hendrix, Yuri, Rauwel, Erwan, Nagpal, Keshav, Haddad, Ryma, Estephan, Elias, Boissière, Cédric, and Rauwel, Protima

Subjects
PHOTOCATALYSTS, ORGANIC dyes, DYES & dyeing, ZINC oxide, METHYLENE blue, TRANSMISSION electron microscopy, NANOPARTICLES
Abstract

ZnO is an effective photocatalyst applied to the degradation of organic dyes in aqueous media. In this study, the UV-light and sunlight-driven photocatalytic activities of ZnO nanoparticles are evaluated. A handheld Lovibond photometer was purposefully calibrated in order to monitor the dye removal in outdoor conditions. The effect of ZnO defect states, i.e., the presence of zinc and oxygen defects on the photocatalytic activity was probed for two types of dyes: fuchsin and methylene blue. Three morphologies of ZnO nanoparticles were deliberately selected, i.e., spherical, facetted and a mix of spherical and facetted, ascertained via transmission electron microscopy. Aqueous and non-aqueous sol-gel routes were applied to their synthesis in order to tailor their size, morphology and defect states. Raman spectroscopy demonstrated that the spherical nanoparticles contained a high amount of oxygen vacancies and zinc interstitials. Photoluminescence spectroscopy revealed that the facetted nanoparticles harbored zinc vacancies in addition to oxygen vacancies. A mechanism for dye degradation based on the possible surface defects in facetted nanoparticles is proposed in this work. The reusability of these nanoparticles for five cycles of dye degradation was also analyzed. More specifically, facetted ZnO nanoparticles tend to exhibit higher efficiencies and reusability than spherical nanoparticles. [ABSTRACT FROM AUTHOR]

Published
2023
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14. Gold–silica quantum rattles for multimodal imaging and therapy

Author

Hembury, Mathew, Chiappini, Ciro, Bertazzo, Sergio, Kalber, Tammy L., Drisko, Glenna L., Ogunlade, Olumide, Walker-Samuel, Simon, Krishna, Katla Sai, Jumeaux, Coline, Beard, Paul, Kumar, Challa S. S. R., Porter, Alexandra E., Lythgoe, Mark F., Boissière, Cédric, Sanchez, Clément, and Stevens, Molly M.

Published
2015

40. Catalytic hollow spheres loaded with Cross-Linked Enzyme Aggregates for the green chemo-enzymatic production of epoxides

Author

Smeets, Valentin, Boissière, Cédric, Baaziz, Walid, Ersen, Ovidiu, Gaigneaux, Eric M., Sanchez, Clément, Debecker, Damien P., International Symposium on Relations between Homogeneous and Heterogeneous Catalysis (ISHHC18), and UCL - SST/IMCN/MOST - Molecules, Solids and Reactivity

Abstract

Here, we propose a new strategy for the preparation of a hybrid catalyst that allows us to combine all the features of TS-1 with a high loading of GOx. The method is based on the aerosol-assisted self-assembly of TS-1 nanocrystals to form hollow spheres with tailored texture and good epoxidation activity. The latter spheres are subsequently loaded with the enzymes which are then cross-linked to secure their entrapment. Upon optimization of the working conditions for these new hybrid structures, we show that it is possible to reach much higher epoxide productivity.

Published
2018

41. Bio-inorganic hybrid catalyst combining enzyme aggregates and catalytic hollow spheres for the green epoxidation of olefins

Author

Smeets, Valentin, Boissière, Cédric, Baaziz, Walid, Ersen, Ovidiu, Gaigneaux, Eric M., Sanchez, Clément, Debecker, Damien P., 7th EuCheMS Chemistry Congress, and UCL - SST/IMCN/MOST - Molecules, Solids and Reactivity

Abstract

In line with green chemistry principles, Vennestrom et al. proposed the chemoenzymatic epoxidation of olefins by sequential catalysis using glucose oxidase (GOx) - for in situ production of H2O2 - and microporous titanosilicalite-1 (TS-1). The direct immobilization of GOx on the catalyst was also proposed but the epoxide production was notably limited by the low enzyme loading. Here, we propose a new strategy for the preparation of a hybrid catalyst that combines all the features of TS-1 with a high loading of GOx. The method is based on the aerosol-assisted self-assembly of TS-1 nanocrystals to form hollow spheres with tailored texture and good epoxidation activity. These spheres are subsequently loaded with the enzymes which are then cross-linked to secure their entrapment. Upon optimization of the working conditions, we show that it is possible to reach much higher epoxide productivity.

Published
2018

45. Stability and degradation of PEO20PPO70PEO20 triblock copolymers in mesostructured silica.

Author

Dragoi, Brindusa, Laurent, Guillaume, Casale, Sandra, Benamor, Taissire, Lebeau, Bénédicte, Boissière, Cédric, Ribot, François, Selmane, Mohamed, Schmidt, Patrick, Kreher, David, and Davidson, Anne

Abstract

Organic−inorganic hybrid mesostructured silicas are prepared, without stirring (at pH = 0.0) and with stirring (at pH = 0.6) to obtain isolated and gyroidal-like attached silica grains with incorporated triblock P123 poly (ethylene oxide)-poly (propylene oxide)–poly (ethylene oxide) copolymers. Selected hybrids are submitted to various thermal and aging treatments for studying hydrolysis and oxidation of PEO and PPO chains. Two complementary spectroscopic techniques are used: near-infrared (NIR) with measurements performed in diffuse reflectance, as well as 1H and 13C liquid- and solid-state nuclear magnetic resonance (NMR) to study the mobility and stability of PEO and PPO chains. With precipitated fresh hybrids, the ratio of PEO over (PEO + PPO) units is lower (30% ± 5%) than in theory. This ratio also decreases depending on temperature when a hydrothermal treatment is applied. An acidic hydrolysis involving both PEO and PPO chains, with generated fragments eliminated by washing with water and/or synthesis liquor, is then demonstrated. For comparison, another hybrid obtained by spray drying via evaporation-induced self assembly mechanism is also studied. Its NMR signals are much more stable than those of the samples prepared by precipitation. Depending on aging time, thermal history, and materials processing, the textural properties and template decomposition inside mesostructured silica are found significantly different. The influence of the hydrolysis and oxidation of the template onto final materials texture is likely to be as important as the processing conditions. Highlights: Mesostructured "hybrids" containing silica and P123 triblock copolymers obtained by precipitation (in acidic HCl solution) and spray drying are compared. A copolymer acidic hydrolysis is observed for all samples having been heated during synthesis (that is, hydrothermal treatment for synthesis by precipitation, or drying temperature for spray drying experiments). 1,2-ethanediol and peroxide traces associated with the copolymer oxidative decomposition are identified by NMR. The temperature of the heat treatment applied for HT is directly correlated with the remaining EO/(EO + PO) weight %. The NMR study of polymer chains mobility confirms the dehydration and retraction of hydrated PEO chains from silica walls upon temperature increase. We proved for the first time that this effect, now well known for precipitated SBA-15 materials, also occur for spray-dried samples. [ABSTRACT FROM AUTHOR]

Published
2019
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46. 'SiAl(HIPE)': An acidic macro-mesocellular aluminosilicate foam monolith showing high ethanol dehydration activity

Author

Debecker, Damien P., Boissière, Cédric, Laurent, Guillaume, Huet, Stéphanie, Eliaers, Philippe, Sanchez, Clément, Backov, Rénal, and UCL - SST/IMCN/MOST - Molecules, Solids and Reactivity

Abstract

The new alkaline sol-gel route presented here allows preparing meso-macrocellular self-standing aluminosilicate monoliths that are easy to cast and manipulate and that exhibit open and interconnected macroporosity, high surface area and strong acidic properties. Strong acidity is brought about by the formation of a true mixed oxide. Effectiveness of these catalysts is demonstrated here in the case of bioethanol dehydration, and good performance can be expected in other processes like cracking, isomerization, alkylation reactions, etc.

Published
2016

50. Bimodal mesoporous titanium dioxide anatase films templated by a block polymer and an ionic liquid: influence of the porosity on the permeability

Author

Sallard, Sébastien, Schröder, Michael, Boissière, Cédric, Dunkel, Christian, Etienne, Mathieu, Walcarius, Alain, Oekermann, Torsten, Wark, Michael, Smarsly, Bernd M., and Justus Liebig University Giessen

Subjects
ddc:540
Abstract

In the present paper, we report the synthesis of bimodal mesoporous anatase TiO2 films by the EISA (Evaporation-Induced Self-Assembly) method using sol-gel chemistry combining two porogen agents, a low molecular weight ionic template and a neutral block copolymer. The surfactant template (C(16)mimCl) generates non-oriented worm-like pores (8 to 10 nm) which connect the regularly packed ellipsoidal mesopores (15 to 20 nm diameter) formed by an amphiphilic block copolymer of the type poly(isobutylene)-b-poly(ethylene oxide) (PIB-PEO). The surfactant template can also significantly influence the size and packing of the ellipsoidal mesopores. The mesostructural organization and mesoporosity of the films are studied by Environmental Ellipsometry-Porosimetry (EEP), Grazing-Incidence Small-Angle X-ray Scattering (GISAXS) and electron microscopy techniques. Electrochemical characterization is performed to study the permeability of the films to liquid solutions, using two types of probe moieties (K3FeIII(CN)(6) and Ru(bpy)(3)(2+)) by the wall-jet technique. An optimum ratio of C(16)mimCl/PIB-PEO provides anatase films with a continuous bimodal mesopore structure, possessing a permeability up to two times higher than that of the mesoporous films templated by PIB-PEO only (with partially isolated mesopores). When C(16)mimCl is used in large quantities, up to 20% weight vs. PIB-PEO, large overall porous volume and surface area are obtained, but the mesostructure is increasingly disrupted, leading to a severe loss of permeability of the bimodal films. A dye-sensitized solar cell set-up is used with anatase films as the photoelectrode. The photosensitizer loading and the total energy conversion efficiency of the solar cells using the mesoporous films templated by an optimal ratio of the two porogen agents C(16)mimCl and PIB-PEO can be substantially increased in comparison with the solar cells using mesoporous films templated by PIB-PEO only.

Published
2013
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