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See detailOptimizing support properties of heterogeneous catalysts for the coupling of carbon dioxide with epoxides
Léonard, Géraldine L.-M.; Pirard, Sophie ULiege; Belet, Artium ULiege et al

in Chemical Engineering Journal (2019), 371

The study deals with the catalytic cyclocarbonation of epoxides to produce monomers used in the synthesis of polyurethane. A benchmark study of the textural properties of silica-based, doped or not ... [more ▼]

The study deals with the catalytic cyclocarbonation of epoxides to produce monomers used in the synthesis of polyurethane. A benchmark study of the textural properties of silica-based, doped or not, supports enabling the identification and optimization of the key parameters affecting the catalytic activity is reported. The results reveal that ammonium catalysts immobilized onto mesostructured supports with high surface area and low aggregation show better catalytic performances than analogue catalysts grafted onto microstuctured ones. While a high external surface area favours the grafting of ammonium salt, pore size must be large enough to enhance the accessibility of both carbon dioxide and epoxides to the catalytic sites. The activity of heterogeneous cat- alysts was evaluated for a model coupling reaction between carbon dioxide and propylene glycol diglycidylether. Using appropriated supports, cyclocarbonation yields are found to be higher in the presence of the hetero- geneous catalyst in comparison with the homogeneous one. These results allow to confirm the beneficial effect of the presence of residual OH silanol groups at the surface of the support, which activate epoxide through forming of hydrogen bonds. [less ▲]

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See detailHeterogenization of a cyclocarbonation catalyst: optimization and kinetic study
Léonard, Géraldine L.-M.; Belet, Artium ULiege; Grignard, Bruno ULiege et al

in Catalysis Today (2019), 334

Different types of heterogeneous catalysts designed for a cyclocarbonation reaction between an epoxidized source and CO2 under supercritical conditions have been synthesized. The process implied a ... [more ▼]

Different types of heterogeneous catalysts designed for a cyclocarbonation reaction between an epoxidized source and CO2 under supercritical conditions have been synthesized. The process implied a quaternization step where a (haloalkyl)trimethoxysilane reacted with tributylamine leading to a tributyl(trimethoxysilylalkyl)ammonium halide, with iodine and bromine as halogens. Then, a grafting step onto commercial fumed silica through condensation reaction between the silane part and Si-OH surficial groups provided the immobilized catalyst. The efficiency of grafting has been validated by liquid 1H NMR, solid 29Si NMR and TG-DSC-MS analyzes. The benchmark cyclocarbonation reaction of polyethylene glycol diglycidylether at 80 °C and 100 bar during 4 h showed that the best immobilized catalyst was tributylpropylammonium iodide (IC3Q-EH5). It has also been shown that immobilization provided -surprisingly !- better conversions than the corresponding homogeneous catalyst’s: this phenomenon has been explained through an epoxide-ring-opening activating effect thanks to Si-OH surficial groups. Furthermore, kinetic studies performed by in situ Raman spectroscopy on IC3Q-EH5 showed that temperature had a strong influence on the yield of the reaction while CO2 pressure had only a small effect. Recycling of the catalyst has also been considered, but no precise conclusions could be conducted because of the high catalyst dispersion. Finally, the addition of a fluorinated alcohol co-catalyst allowed obtaining a similar yield but at 80 °C and 55 bar during only 2,5 h with the best candidate. [less ▲]

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See detailTailored-made biodegradable polymers for drug delivery and tissue engineering
Grandfils, Christian ULiege; Regibeau, Nicolas ULiege; Tilkin, Rémi ULiege et al

Scientific conference (2019, June 06)

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See detailWet method for the production of thin films (1)
Liquet, Dimitri ULiege; Calberg, Cédric ULiege; Eskenazi, David et al

Patent (2019)

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See detailHeterogeneous singlet oxygen generation: in-operando visible light EPR spectroscopy
Mendoza Gallego, Carlos ULiege; Désert, Anthony; Khrouz, Lhoussain et al

in Environmental Science and Pollution Research (2019)

The use of photosensitizers immobilized on mesoporous materials to produce singlet oxygen (1O2) has opened a new way to synthetic and environmental applications due to the fast development of flow ... [more ▼]

The use of photosensitizers immobilized on mesoporous materials to produce singlet oxygen (1O2) has opened a new way to synthetic and environmental applications due to the fast development of flow photochemistry and continuous-flow microreactors. 1O2-based photosensitized processes can be employed for the degradation of organic pollutants in aqueous medium and the photosensitizer can be covalently attached to the support and separated from the effluent reducing the environmental impact. The aim of the present paper is to evaluate the 1O2 generation of Rose Bengal (RB) in homogeneous and heterogeneous systems using in-operando evaluation. Mesoporous SiO2 nanoparticles (MSNs) were successfully conjugated with RB (MSN-RB) and Electron Paramagnetic Resonance (EPR) spectroscopy in combination with the spin trap TEMP was employed to obtain paramagnetic TEMPO via generated 1O2 when RB or MSN-RB are exposed to visible light. Additionally, EPR/DMPO was used to exclude the possible generation of other reactive oxygen species (ROS) by the functionalized nanoparticles. We found that in situ 1O2 generation was enhanced when the same amount of RB is immobilized inside of mesoporous SiO2. [less ▲]

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See detailPorphyrin-based hybrid silica-titania as a visible-light photocatalyst
Mahy, Julien ULiege; Pàez Martinez, Carlos ULiege; Carcel, Carole et al

in Journal of Photochemistry and Photobiology A: Chemistry (2019), 373

A silylated porphyrin derivative is co-hydrolyzed with Ti(OiPr)4 to produce a hybrid TiO2 photocatalyst, and three different ratios between porphyrin and TiO2 are made. In this way, the porphyrin ... [more ▼]

A silylated porphyrin derivative is co-hydrolyzed with Ti(OiPr)4 to produce a hybrid TiO2 photocatalyst, and three different ratios between porphyrin and TiO2 are made. In this way, the porphyrin fragments are held in the resulting matrix through strong Si-O-Ti covalent bonds to limit porphyrin leaching. Thanks to its photoactive character the porphyrin fragment can act as an actuator for the TiO2 to degrade organic pollutants using light from ultra-violet to the visible range. The photocatalysts are synthesized using an easy aqueous route allowing “green conditions” for synthesis. For comparative purposes, the corresponding pure TiO2 and a grafted catalyst are also synthesized and studied. For all samples, a mixture of anatase/brookite TiO2 is obtained, resulting in crystalline materials with low temperature synthesis. The three porphyrin-doped samples prepared in water prove to be efficient photocatalysts for the degradation of p-nitrophenol (PNP) under visible light, and an improvement in photoactivity is observed when the amount of porphyrin increases. The photocatalyst activity is very stable over time as the PNP degradation remains nearly constant after 264 h of testing, showing no leaching of porphyrin. In recycling tests, the grafted sample presents bond breaking between POR-Si and TiO2 and a decrease in photoactivity towards pure TiO2 sample activity. A comparison with the commercial Evonik P25 catalyst shows that the porphyrin-doped TiO2 is nearly 6 times more photoactive under visible light for PNP degradation. [less ▲]

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See detailThe XIX International Sol-Gel Conference, Liège (Belgium) Sept 3-8, 2017, KEYNOTE, INVITED, AWARD and BEST ORAL AND POSTER PRESENTATIONS
Heinrichs, Benoît ULiege; Job, Nathalie ULiege; Lambert, Stéphanie ULiege et al

Book published by Journal of Sol-Gel Science and Technology (2019)

SOL-GEL 2017, the 19th International Sol-Gel Conference, has been organized from September 3rd to 8th, 2017, in Liège, Belgium and has gathered 430 participants from 40 countries. The great success of the ... [more ▼]

SOL-GEL 2017, the 19th International Sol-Gel Conference, has been organized from September 3rd to 8th, 2017, in Liège, Belgium and has gathered 430 participants from 40 countries. The great success of the Sol-Gel Conference series over the past 35 years attests that sol-gel science and technology is an extraordinarily multidisciplinary research area. This biennial conference, which gathers the most relevant and innovative advances in the field from the point of view of scientific research and industrial developments, has been organized previously in Padova (Italy, 1981), Würzburg (Germany, 1983), Montpellier (France, 1985), Kyoto (Japan, 1987), Rio de Janeiro (Brazil, 1989), Sevilla (Spain, 1991), Paris (France, 1993), Faro (Portugal, 1995), Sheffield (UK, 1997), Yokohama (Japan, 1999), Padova (Italy, 2001), Sydney (Australia, 2003), Los Angeles (CA, USA, 2005), Montpellier (France, 2007), Porto de Galinhas (Brazil, 2009), Hangzhou (China, 2011), Madrid (Spain, 2013) and Kyoto (Japan, 2015). Sol-Gel process is a tunable tool for the design of materials with precise morphologies, properties and shapes. Its high versatility allows to obtain materials with high performances for applications in many different fields. The following 16 topics of the 19th edition in Liège, are an attempt to cover both the fundamental and applied aspects of the research area: • Chemistry and fundamentals of the sol-gel process and non-conventional synthesis methods • Functional organic-inorganic hybrid materials • Nano- and micro-structured materials: particles, colloids, fibers, self-assembly, composites • Porous materials (aerogels, xerogels, cryogels, template-based) and hierarchical structured materials • Biomaterials, biohybrids and bioinspired materials • Carbon and hybrid carbon-based gels • Protective and functional coatings and thin films • Characterization and modelling techniques for sol-gel materials • Sol-Gel materials for (photo-)catalysis and membranes • Sol-Gel materials for energy and environmental applications • Sol-Gel materials for health and medical applications (including controlled drug release) • Sol-Gel materials for electronic, magnetic and ferroelectric applications • Sol-Gel materials for sensors, optic, photonic and optoelectronic applications • Sol-Gel materials for insulation • Industrialization of sol-gel science and technology • Sol-Gel as alternative to PVD and other conventional industrial processes Through papers related to keynote, invited and award lectures and to a selection of oral communications and posters, the present special issue covers many of these topics. Thus, it can be viewed as a representative sample of the today’s research variety in sol-gel science and technology. [less ▲]

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See detailEasy-cleaning and photocatalytic materials
Mahy, Julien ULiege; léonard, Géraldine; Zubiaur, Anthony ULiege et al

Conference (2018, November 20)

Dans ce travail, un procédé sol-gel en phase aqueuse a été développé pour produire à grande échelle un photocatalyseur à base de TiO2 présentant des propriétés hydrophiles et une activité photocatalytique ... [more ▼]

Dans ce travail, un procédé sol-gel en phase aqueuse a été développé pour produire à grande échelle un photocatalyseur à base de TiO2 présentant des propriétés hydrophiles et une activité photocatalytique élevée pour la dépollution de l'eau et de l'air. La première étape consistait à développer une synthèse sol-gel en phase aqueuse de TiO2 pur à l'échelle du laboratoire. Le protocole de synthèse a été simplifié pour réduire le temps de synthèse, la température et le nombre d’étapes comme les étapes de lavage. Les propriétés physico-chimiques et photocatalytiques du matériau obtenu ont été caractérisées pour évaluer la production d'un revêtement hydrophile sur acier inoxydable et la formation d'un photocatalyseur efficace sur la dégradation de trois polluants (bleu de méthylène, p-nitrophénol ou acétaldéhyde) sous différentes formes (film ou poudre) et dans différentes phases (liquide ou gazeuse). Dans la deuxième partie, la synthèse aqueuse a été adaptée pour produire des catalyseurs de TiO2 dopés avec des ions Fe3+, Ag+, Cu2+, Zn2+, Cr3+, Al3+, Mn2+ et Co2+ et des nanoparticules métalliques de Pt afin d'améliorer leur activité. Certains dopants ont montré une photoactivité accrue et certains mécanismes ont été proposés pour expliquer ces modifications de l'activité avec le dopage. En outre, la comparaison des coûts à l'échelle du laboratoire a montré que le dopage au Zn2+ pouvait être envisagé pour des applications industrielles. En utilisant cette méthode, un photocatalyseur de TiO2 dopé au Zn a été synthétisé à grande échelle et a montré des propriétés homologues au produit à l'échelle du laboratoire. La troisième étape consistait à étudier la propriété de redispersion des colloïdes de TiO2 nanocristallins. En effet, les poudres obtenues par séchage sous air de ces colloïdes peuvent être redispersées dans l'eau pour produire des colloïdes qui sont comparés à ceux obtenus initialement. Cinq cycles de séchage-redispersion ont été réalisés sur des colloïdes sélectionnés. Un mécanisme a été proposé pour expliquer cette propriété intéressante, l'acide présent dans la synthèse semble être le facteur principal. Cela peut être très utile pour une application industrielle de cette synthèse permettant de réduire le volume et le poids pour le transport et le stockage. [less ▲]

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See detailAqueous N-Doped TiO2 Catalysts for Visible Light Photocatalytic Applications
Mahy, Julien ULiege; Cerfontaine, Vincent; Poelman, Dirk et al

Poster (2018, November)

In this work, TiO2 prepared with an aqueous sol-gel synthesis by peptization process is doped with nitrogen precursor to extend its activity towards the visible region. Three N-precursors are used: urea ... [more ▼]

In this work, TiO2 prepared with an aqueous sol-gel synthesis by peptization process is doped with nitrogen precursor to extend its activity towards the visible region. Three N-precursors are used: urea, ethylenediamine and triethylamine. Different molar N/Ti ratios are tested and the synthesis is adapted for each dopant. For urea- and trimethylamine-doped samples, anatase-brookite TiO2 nanoparticles of 6–8 nm are formed, with a specific surface area between 200 and 275 m2 g−1. In ethylenediamine-doped samples, the formation of rutile phase is observed, and TiO2 nanoparticles of 6–8 nm with a specific surface area between 185 and 240 m2 g−1 are obtained. X-ray photoelectron spectroscopy (XPS) and diffuse reflectance measurements show the incorporation of nitrogen in TiO2 materials through Ti–O–N bonds allowing light absorption in the visible region. Photocatalytic tests on the remediation of water polluted with p-nitrophenol show a marked improvement for all doped catalysts under visible light. The optimum doping, taking into account cost, activity and ease of synthesis, is up-scaled to a volume of 5 L and compared to commercial Degussa P25 material. This up-scaled sample shows similar properties compared to the lab-scale sample, i.e., a photoactivity 4 times higher than commercial P25. [less ▲]

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See detailImproving Continuous Flow Singlet Oxygen Photooxygenations with Functionalized Mesoporous Silica Nanoparticles
Mendoza Gallego, Carlos ULiege; Emmanuel, Noémie ULiege; Pàez Martinez, Carlos ULiege et al

in ChemPhotoChem (2018)

Continuous flow photochemistry relying on photosensitizers faces two main challenges: the photodegradation (bleaching) and the downstream removal of the photosensitizer. Rose Bengal (RB) is a common ... [more ▼]

Continuous flow photochemistry relying on photosensitizers faces two main challenges: the photodegradation (bleaching) and the downstream removal of the photosensitizer. Rose Bengal (RB) is a common photosensitizer utilized for photooxygenations with singlet oxygen (1O2), but is notoriously sensitive to photobleaching and difficult to remove from reactor effluents. The heterogenization of photosensitizers on mesoporous silica nanoparticles (MSNs) is arguably a viable option for such applications. Herein, we report on the use of RB covalently incorporated into MSNs (RB@MSNs) for photooxygenations under continuous flow conditions. RB@MSNs enable the 1O2 photooxygenation of various organic substrates upon irradiation with 540 nm LEDs. A series of organic substrates were evaluated including methionine, α‐terpinene, 2‐furoic acid, triphenylphosphine, citronellol and cyclopentadiene. These results emphasize an improved resistance to photobleaching, and the possibility to use RB@MSNs as easily recoverable catalyst, which could be removed from the reactor effluent either (a) by centrifugation or (b) in‐line membrane filtration. [less ▲]

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See detailAu bipyramids/mSiO2 core-shell nanoparticles and their metal-enhanced generation of singlet oxygen – Application in photooxygenations
Mendoza Gallego, Carlos ULiege; Château, Denis; Désert, Anthony et al

Conference (2018, July 24)

Gold nanomaterials display interesting nanoplasmonic features with potential application in various fields depending on the size and shape of the metal nanoparticle (NP). Au bipyramids (AuBPs) exhibit ... [more ▼]

Gold nanomaterials display interesting nanoplasmonic features with potential application in various fields depending on the size and shape of the metal nanoparticle (NP). Au bipyramids (AuBPs) exhibit intense and well-defined plasmon resonance, easily tunable with the aspect ratio and synergy between Au NPs and chromophores can enhance the photophysical properties of nearby molecules. In Rose Bengal-NPs systems for the production of singlet oxygen (1O2), it is now well established that the control of the dye-to-NP distance ranging from 10 to 20 nm is crucial to achieve the proper coupling between plasmon resonance and the dye1. We have developed AuBPs@mesoporous SiO2 core-shell nanostructures to control the distance between metallic surface and photosensitizers in order to increase the production of 1O2 through metal-enhanced fluorescence (MEF). An enhancement of 1O2 generation has been shown with the obtained anisotropic AuBPs and AuBPs@mSiO2 in presence of RB using different methods of 1O2 quantification. They are of interest to the application in photooxygenation reactions e.g. α –terpinene to ascaridole. [less ▲]

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See detailFrom well-defined plasmonic nanoparticles to hybrid materials for photonic and catalytic applications
Mendoza Gallego, Carlos ULiege; Heinrichs, Benoît ULiege; Désert, Anthony et al

Conference (2018, July 19)

Our team develops research on hybrid materials devoted to optical applications, especially in the fields of optical protection, bioimaging, photocatalysis. In particular the expertise lies in the design ... [more ▼]

Our team develops research on hybrid materials devoted to optical applications, especially in the fields of optical protection, bioimaging, photocatalysis. In particular the expertise lies in the design of original molecular systems, coupled with inorganic materials like plasmonic nanostructures and the characterization of optical interactions and responses (absorption, emission, nonlinear responses…). In this context and through various studies, we will see the benefits and the way to use gold nanoparticles, from their well-controlled synthesis, and also their functionalization and incorporation in hybrid materials, to their impact on the optical and catalytic properties. Among numerous classes of nanoparticles like spheres, hollow spheres or nanorods, we have particularly investigated gold nano-bipyramids (AuBPs) for several years. Indeed, these AuBPs exhibit intense and well-defined plasmon resonance, easily tunable with the aspect ratio, and also strong localized electromagnetic field in the vicinity of the tips. Currently, our optimized synthesis method leads to well-designed AuBPs in high yield and in high concentration, with a sharp plasmon band tunable from 650 nm up to 2000 nm. We have recently developed an easy and general gold surface modification by a functional thiolated silicon polymer. In addition to be an alternative to the use of surfactants or long-chain polymers in order to provide efficient colloidal stabilization in a wide range of solvent, this surface modification allows us to prepare homogeneous hybrid materials like gold-doped sol-gel silica presenting clear plasmon band. Association with various photoactive compounds have been explored and positive impact such as enhancement have been shown for photocatalytic properties of SiO2/TiO2 films, or for non-linear optical absorption of dye-doped glasses. Finally, we will present in particular our current efforts to synthetize core-shell AuBP@SiO2 NPs combining with rose Bengal for catalysis based on singlet oxygen generation. [less ▲]

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See detailRB@Au/mSiO2 core-shell nanobipyramids for the enhanced-production of singlet oxygen
Mendoza Gallego, Carlos ULiege; Désert, Anthony; Château, Denis et al

Conference (2018, July 16)

Gold nanomaterials display interesting nanoplasmonic features with potential application in various fields depending on the size and shape of the metal nanoparticle. The size and geometry of Au NPs can be ... [more ▼]

Gold nanomaterials display interesting nanoplasmonic features with potential application in various fields depending on the size and shape of the metal nanoparticle. The size and geometry of Au NPs can be tuned by simply changing the experimental parameters in order to obtain different shapes tuning the wavelength where the maximum plasmon is located. Au bipyramids exhibit intense and well-defined plasmon resonance, easily tunable with the aspect ratio, and also strong localized electromagnetic field in the vicinity of the tips. Currently, our synthesis method leads to well-designed AuBPs in high yield and in high concentration, with a plasmon band located at 650 nm. Combining the ability to modulate the optical response of these NPs and to functionalize their surface with photosensitizers opens the way to new families of luminescent organic-inorganic materials. Synergy between Au NPs and chromophores has become a feasible way to control and modify optical effects. This control and understanding of PS-NP interactions have attracted many scientists and a wide range of publications report the fluorescence quenching or enhancement of the photophysical properties of nearby molecules. The presence of a dye in the vicinity of a metallic surface can lead to the limitation in the dye photobleaching. Rose Bengal (RB) is a metal-free, non-toxic, and popular PS that shows intense absorption bands in the green region of the visible spectrum (480-550 nm), and is renowned for its high quantum yield (ϕΔ = 0.76) for the generation of 1O2. In RB-NPs systems, it is now well established that the control of the dye-to-nanoparticle distance at the surface of the NPs is crucial to achieve the proper coupling between the plasmon resonance and the dye. RB needs to be located in a suitable distance ranging from 10 to 20 nm to achieve optimum emission enhancement according to literature. We have developed an easy method to control the distance between metallic surface and the photosensitizer with the SiO2 thickness in order to increase the production of singlet oxygen. An enhancement has been shown for the obtained anisotropic RB@Au/mSiO2 during photooxygenation model reactions in comparison with previous works. [less ▲]

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See detailHETEROGENIZATION OF A CYCLOCARBONATION CATALYST
Léonard, Géraldine; Belet, Artium ULiege; Grignard, Bruno ULiege et al

Poster (2018, July 09)

Nowadays, in order to limit the global warming, CO2 emissions have to be drastically reduced. A first way is to use CO2 as a renewable C1 feedstock that could be industrially valorized to produce added ... [more ▼]

Nowadays, in order to limit the global warming, CO2 emissions have to be drastically reduced. A first way is to use CO2 as a renewable C1 feedstock that could be industrially valorized to produce added value chemicals such as urea, methanol, salicylic acid and cyclic carbonates. Among those compounds, cyclic carbonates are used in a wide range of applications: electrolytes for Li-ion batteries, solvent, intermediates in pharmaceutical and cosmetic industries and also monomers of non-isocyanates polyurethanes (niPU). A second approach, in order to reduce the household energetic consumption and save energy, is insulating using polyurethane (PU) materials. In fact, in comparison with glass wool, rock wool, wood and hemp, PU is one of the most efficient materials for thermal insulation as it exhibits very low thermal conductivity values. But because of the high toxicity of the isocyanate monomer, a new alternative routine using the copolymerization of cyclic carbonates with diamines to produce niPU is a promising solution. In this work, different types of heterogeneous catalysts have been synthesized toward a cyclocarbonation reaction between CO2 in a supercritical state (scCO2) and an epoxidized source (polyethylene glycol diglycidylether (PEG-500), for 4h at 80°C and 100 bar of pressure). First, optimal organic salt-based catalysts were chosen for this reaction: tetrabutylammonium iodide (TBAI) and tetrabutylammonium bromide (TBABr). These catalysts were immobilized onto a silica-based support by condensation reaction between silane and surficial silanol groups (R2). The best support was identified being EH-5 fumed silica (from CAB-O-SIL) because of its large specific area and its higher mesoporous to microporous volume ratio. Afterwards, it has been demonstrated that better grafting percentages as well as a better conversions could be obtained if the quaternization (R1) step is performed before the grafting step (R2). Then, it has been shown that - surprisingly ! - the best candidate (FIGURE 1 : IC3Q-EH-5) gives better conversions than the corresponding homogeneous catalyst ! This phenomenon has been explained through an epoxy-ring-opening activator effect thanks to the surficial silanol groups. Finally, the up-scaling of the IC3Q-EH-5 from 5g to 60g was successfully performed, as well as the use of a fluorinated alcohol co-catalyst, which allows reducing the operation conditions from 100 bar to 55 bar and from 240 min. to 150 min. Characterizations were made by liquid 1H NMR for cyclocarbonation yield, by solid 29Si NMR for organic-to-inorganic bonds description, by TG-DSC-MS for grafting efficiency and catalyst description and by nitrogen adsorption/desorption for support description. Kinetic studies of cyclocarbonation with or without a co-catalyst were further performed by in situ Raman spectroscopy. [less ▲]

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See detailFunctionalization of mesoporous silica nanoparticles with Rose Bengal for heterogeneous photooxygenation reactions in microfluidic systems
Mendoza Gallego, Carlos ULiege; Emmanuel, Noémie ULiege; Pàez Martinez, Carlos ULiege et al

Poster (2018, July 09)

Singlet oxygen-based photocatalytic oxygenation reactions have emerged as an efficient technology to synthesize value-added organic molecules[1]. There are various methodologies for the production of ... [more ▼]

Singlet oxygen-based photocatalytic oxygenation reactions have emerged as an efficient technology to synthesize value-added organic molecules[1]. There are various methodologies for the production of singlet oxygen, among which the most popular involves a photoinduced electronic energy transfer from an excited state of a catalytic photosensitizer (PS) to triplet oxygen (3O2)[2]. The amino acids tyrosine, tryptophan, methionine, histidine and cysteine constitute one of the most relevant families among the photooxidizable biological substrates due to their areas of high electron density because of double bonds or sulfur moieties. Of particular interest is the photooxidation of methionine (Met) to methionine sulfoxide (MetO). In general, sulfoxides are frequently used in organic synthesis, pharmaceutical science, biochemistry and material science. However, the classical methods to oxidize sulfides to sulfoxides present a high risk of overoxidation to sulfones. In particular, MetO is a particularly valuable synthetic intermediate with applications ranging from peptide sciences, material sciences, to organic synthesis. PSs are commonly organic dyes bearing a (hetero)aromatic core such as Rose Bengal, Methylene Blue, Erythrosin B, porphyrins, phtalocyanines, and related tetrapyrroles. Rose Bengal (RB) is a popular photosensitizer that has been widely utilized for the production of 1O2 upon visible light aerobic irradiation[3]. The functionalization of mesoporous silica nanoparticles (MSNs) with PSs has attracted great research attention during last years to design efficient nanoplatforms to be used in nanomedicine as drug delivery systems or in targeted photodynamic cancer therapy (PDT) owing to their biocompatibility, high RB loading capacity and ease of surface functionalization, but its use as catalyst support in photooxygenation reactions is still a challenge. Regarding the use of RB under continuous-flow photocatalytic conditions and the configuration of the flow setup, three main strategies emerge from the literature based on the use of (a) homogeneous PSs, (b) packed-bed photoreactors with heterogeneous PSs embedded on the packing material and (c) heterogeneous PSs concomitantly fed with the substrate. Although each strategy comes with assets and drawbacks, the use of free flowing heterogeneous PSs is supposedly the most interesting option, as far as, besides their efficiency, (a) they (a) are readily prepared, (b) do not accumulate within the micro/mesoreactor channels or cause clogging and (c) are easily removed downstream. RB can be protected from photobleaching during important light exposures by a mesoporous SiO2 structure[4]. Synthesis of MSNs was made following well-known methods and the immobilization of RB at the surface of SiO2 by a covalent bond was carried out by two coupling agents: 1-Ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC) and (1-[Bis(dimethylamino)methylene]-1H-1,2,3-triazolo[4,5-b]pyridinium 3-oxide hexafluorophosphate) (HATU). A complete characterization of RB@MSNs was made by BET, Tg-MS, UV-Vis and TEM. Finally, the influence of key parameters like RB concentration and the liquid flow were studied as a function of the coupling agent used in a microfluidic system. The efficiency of methionine photooxygenation as well as the photobleaching of the dye was followed by Proton Nuclear Magnetic Resonance (1H NMR). This work converts MSNs in interesting support for new and clean heterogeneous continuous-flow photooxygenations. Taken together, our results show that heterogenization of PS for 1O2 production in microreactors is possible by grafting RB into MSNs by a covalent bond. This attachment is able to avoid the photobleaching of the dye and allows separating the solid support with the PS from the reactor effluent and reutilizing the PS. The potential of these NPs to be used as heterogeneous catalyst for photooxygenation of methionine has been demonstrated. [less ▲]

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See detailSurface functionalization of silica for the optimization of polymer/silica nanocomposites
Regibeau, Nicolas ULiege; Tilkin, Rémi ULiege; Heinrichs, Benoît ULiege et al

Conference given outside the academic context (2018)

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See detailSilica-based thin film solid-state electrolytes for Lithium-ion microbatteries
Hartmann, Korina ULiege; Calberg, Cédric ULiege; Liquet, Dimitri ULiege et al

Scientific conference (2018, June 19)

The emerging market of the Internet of Things, smart objects, wearables and others increases the demand for micro energy sources. Rechargeable lithium-ion batteries are a well-known technology for energy ... [more ▼]

The emerging market of the Internet of Things, smart objects, wearables and others increases the demand for micro energy sources. Rechargeable lithium-ion batteries are a well-known technology for energy storage. However, safety issues and high production costs constrain progress. Electrolyte solutions based on ionic liquids (ILs) with dissolved lithium salts can be confined into inorganic porous networks forming so-called ionogels, which are investigated as solid electrolytes [1]. Ionogels combine low hazard and good ionic conductivity. However, the growth of lithium dendrites may be observed during cycling, which reduce battery lifetime. In this project, we try to prepare a silica-ionogel to prevent dendritic growth by mechanical hindrance. The ionogel composition was studied to obtain a fast gelation and the correlation between the physical properties of the silica matrix and the electrochemical performances of the ionogel was evaluated. [less ▲]

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See detailRose Bengal@MSNs as heterogeneous photocatalysts in photooxygenation reactions
Mendoza Gallego, Carlos ULiege; Emmanuel, Noémie ULiege; Pàez Martinez, Carlos ULiege et al

Conference (2018, June 19)

The functionalization of mesoporous silica nanoparticles (MSNs) with photosensitizers e.g. Rose Bengal (RB) has attracted great research attention during last years to design efficient nanoplatforms to be ... [more ▼]

The functionalization of mesoporous silica nanoparticles (MSNs) with photosensitizers e.g. Rose Bengal (RB) has attracted great research attention during last years to design efficient nanoplatforms to be used in nanomedicine as drug delivery systems or in targeted photodynamic cancer therapy (PDT) owing to their biocompatibility, high loading capacity and ease of surface functionalization. Additionally, its use as catalyst support in photooxygenation reactions via singlet oxygen (1O2) can produce high-value added organic molecules in continuous-flow microreactors decreasing the environmental impact due to the possibility to recover the solid catalyst from the reactor effluent and reutilize the photosensitizer. Various model organic substrates were tested as previously reported for homogeneous photooxygenation reactions including bio-sourced methionine [1] and α-terpinene as well as 2-furoic acid, triphenylphosphine, citronellol and cyclopentadiene. The immobilization of the dye inside mesoporous silica nanoparticles plays a strategic role in preserving the chemical integrity of the photosensitizer as demonstrated by UV-Vis spectroscopy. The mechanism of photooxygenation by 1O2 could be influenced by the state of the dye, avoiding the ground state complexation between the amino acid and the photosensitizer as occurs in homogeneous systems. Moreover, heterogeneous photooxygenation of several substrates in order to obtain high-value added organic molecules. High conversions were achieved with methionine, α-terpinene in 72 s and triphenylphosphine in 300 s. However, the heterogeneous 1O2 photooxygenation of cyclopentadiene into cis-2-cyclopentadiene-1,4-diol provided a complete conversion in 51 s of residence time. Our results show that heterogenization of PS for 1O2 production in microreactors is possible by grafting RB into MSNs by a covalent bond. This attachment is able to avoid the photobleaching of the dye and allows separating the solid support with the PS from the reactor effluent and reutilizing the PS in different cycles. The potential of these NPs to be used as heterogeneous catalyst for photooxygenation of several organic substrates has been demonstrated. [less ▲]

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See detailDevelopment of a sensor for monitoring nitrate in groundwater
Damala, Polyxeni ULiege; Heinrichs, Benoît ULiege; Brouyère, Serge ULiege et al

Poster (2018, June 12)

The main objective of the present research is the development of a method for the continuous measurement of nitrate in water, thus enabling the detection of nitrate emitting sources and the prevention of ... [more ▼]

The main objective of the present research is the development of a method for the continuous measurement of nitrate in water, thus enabling the detection of nitrate emitting sources and the prevention of extended contamination in groundwater. In this study we examine a class of compounds, called ionophores, which have unique capabilities and can enhance the selectivity and performance of nitrate sensors with respect to the available ones. The research presented is focused on nitrate monitoring via optical sensing. The sensing mechanism used is based on the combination of a suitable ionophore and a chromoionophore, incorporated into a polymer matrix. [less ▲]

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