References of "Léonard, Géraldine"
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See detailInteractions between Zn2+ or ZnO with TiO2 to produce an efficient photocatalytic, superhydrophilic and aesthetic glass
Léonard, Géraldine ULiege; Pàez Martinez, Carlos ULiege; Ramirez, Alfonso et al

in Journal of Photochemistry and Photobiology A : Chemistry (2018), 350

Zinc was coupled with titanium dioxide using different methods. SiO2 and Zn-SiO2 doped TiO2 films, on the one hand, and Zn doped TiO2 on the other hand, have been produced using controlled sol-gel ... [more ▼]

Zinc was coupled with titanium dioxide using different methods. SiO2 and Zn-SiO2 doped TiO2 films, on the one hand, and Zn doped TiO2 on the other hand, have been produced using controlled sol-gel processes by alcoholic, cogelation and aqueous ways. From these syntheses, films were deposited on soda lime glass. These samples were compared to ZnO samples but also to bilayer samples constituting one layer of TiO2 and one layer of ZnO. The physico-chemical properties of the films were characterized by grazing-incidence X-ray diffraction, profilometry and UV-Vis absorption analyses. The photocatalytic activity has been evaluated from the degradation of methylene blue under UV-A light, from the degradation of p-nitrophenol under visible light and from the degradation of H2O2 under halogen light (UV-A + visible light). Superhydrophilicity was evaluated from contact angle measurement after UV exposition and also from hysteresis effects. Finally, a haze measurement was performed to evaluate the impact of the coating on the aesthetic property of the coated glass. Aqueous films have better photocatalytic activity and superhydrophilicity than samples from alcoholic synthesis. The crystallization of the sample appears to be one key factor: alcoholic films required calcination to ensure the crystallization of TiO2, but the alkali migration from the glass support prevents this crystallisation, while aqueous synthesis promotes crystallized particles at low temperatures without alkali interference. It appears that the relative activity from one sample to another depends on the nature of the illumination and on the nature of the molecule to be degraded. Nevertheless, the sample with ZnO layer deposited on first TiO2 layer (ZnO 500 Alc/TiO2 100 AQ) composite is found to be the best sample, maintaining a high hydrophilicity similar to TiO2 and a good activity. [less ▲]

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See detailDevelopment of functionalized materials through sol-gel route for applications in catalysis and surface protection
Léonard, Géraldine ULiege

Doctoral thesis (2017)

In this work, materials have been produced by sol-gel route. This synthesis way has been used for immobilization on a support of a function focused on green chemistry. The different functions are related ... [more ▼]

In this work, materials have been produced by sol-gel route. This synthesis way has been used for immobilization on a support of a function focused on green chemistry. The different functions are related with different applications that allow to illustrate the versatility and the flexibility of this sol-gel process. The two applications are: - Photocatalysis: Synthesis of material with photocatalytic property or with an additional property - Cyclocarbonation: Synthesis of an immobilized catalyst for polyurethane production through a green process The first application concerns the use of a photocatalyst that allows to degrade volatile organic compounds (VOC). The main photocatalyst is TiO2. It has been studied as a powder or as a film deposited on a support. A comparison of these two shapes has shown that an identical photocatalyst can have different performances depending on the final shape. A catalyst must be considered in its totality and with its environment rather than as a chemical composition only. To increase the photocatalyst performances, modifications have been added as the Zn doping to increase the photocatalytic activity and the superhydrophilicity. These new photocatalysts have been compared with pure ZnO and bilayer films composed of TiO2 and of ZnO. Different photocatalytic tests have been performed and depending on the test the best photocatalyst was different. Then, to increase the economic interest, some dopant have been used. In addition of the improvement of the photocatalytic activity and superhydrophilicity, theses dopants add a new property such as electrical conductivity and anticorrosion. First, metallic silver has been incorporated to add antistatic property and to increase the photocatalytic activity. The photocatalytic property has been improved, superhydrophilicity has been kept but no antistatic property was observed. Multiwall carbon nanotubes (MWCNTs) have been tested with TiO2 to increase the electrical conductivity. This doping is efficient because MWCNTs increase the conductivity, the photocatalytic activity and maintain the superhydrophilicity. In addition, anticorrosive property has been observed on stainless steel in a preliminary study with the MWCNTs incorporation. The second study is focused on the heterogeneous cyclocarbonation catalyst synthesis to produce, in fine, polyurethane. The catalyst was immobilized on different matrices that are inert from catalytic point of view but that have a potential activator effect. First, with the preselected catalyst, different supports have been investigated. The comparison between the supports has highlighted the activator effect and the texture influence (accessibility of the active sites) on cyclocarbonation yields. Then, with the optimal matrix, different catalysts from a same family have been grafted to choose the best catalyst. Therefore, it has been possible to define the best catalyst and the best support. With this combination, a kinetic study has been performed to determine the best experimental conditions to produce cyclocarbonates. [less ▲]

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See detailVisible-light TiO2 photocatalyst doped with silylated porphyrin
Mahy, Julien ULiege; Pàez Martinez, Carlos ULiege; Léonard, Géraldine ULiege et al

Conference (2017, August 15)

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See detailHighly efficient doped nanocristalline TiO2 for water Treatment
Mahy, Julien ULiege; Léonard, Géraldine ULiege; Zubiaur, Anthony ULiege et al

Conference (2017, July 13)

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See detailAqueous sol-gel synthesis and film deposition methods for the large-scale manufacture of coated steel with self-cleaning properties
Mahy, Julien ULiege; Léonard, Géraldine ULiege; Pirard, Sophie ULiege et al

in Journal of Sol-Gel Science and Technology (2017), 81(1), 27-35

A process has been developed to enable the large scale production of pure TiO2 films deposited on 316L stainless steel in order to get an easy-to-clean surface. This large scale process requires an easy ... [more ▼]

A process has been developed to enable the large scale production of pure TiO2 films deposited on 316L stainless steel in order to get an easy-to-clean surface. This large scale process requires an easy aqueous sol-gel procedure for the synthesis of the TiO2 sol. This synthesis has been simplified to facilitate the extrapolation towards an industrial scale. Results of TEM, photocatalytic properties, film hydrophilicity, and texture obtained with the simplified aqueous sol-gel synthesis (IsoP-TiO2 synthesis) show similar properties to those obtained with the standard aqueous sol-gel synthesis of TiO2 (HAc-TiO2 synthesis) developed previously. Only X-Ray Diffraction patterns showed differences, with the presence of anatase-brookite phases in IsoP-TiO2 synthesis while anatase phase only was observed in HAc-TiO2 synthesis. Both the aqueous sol-gel synthesis of pure TiO2 and the film deposition on steel by roll-coating have been successfully extrapolated to a larger scale. The photocatalytic activity and the hydrophilicity of the film were found to be unchanged when compared to films produced at a laboratory scale, thus validating the production of an efficient easy-to-clean material. Although some problems are still to be solved, this study is a hopeful first step in the development of a large scale process for self-cleaning steel production. [less ▲]

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See detailStudy of the photocatalytic activity of Fe3+, Cr3+, La3+ and Eu3+ single-doped and co-doped TiO2 catalysts produced by aqueous sol-gel processing
Malengreaux, Charline; Pirard, Sophie ULiege; Léonard, Géraldine ULiege et al

in Journal of Alloys and Compounds (2017), 691

An aqueous sol-gel process, previously developed for producing undoped and Cu2+, Ni2+, Zn2+ or Pb2+ doped TiO2 photocatalysts with remarkably high photocatalytic activity without requiring any calcination ... [more ▼]

An aqueous sol-gel process, previously developed for producing undoped and Cu2+, Ni2+, Zn2+ or Pb2+ doped TiO2 photocatalysts with remarkably high photocatalytic activity without requiring any calcination step, has been adapted to produce Fe3+, Cr3+, La3+ or Eu3+ single-doped TiO2 photocatalysts as well as La3+-Fe3+ and Eu3+-Fe3+ co-doped TiO2 catalysts. The physicochemical properties of the obtained catalysts have been characterized using a suite of complementary techniques, including ICP-AES, XRD, UV-Vis spectroscopy, nitrogen adsorption-desorption and Fe-57 Mössbauer. The active crystalline phase is obtained without requiring any calcination step and all the different catalysts are composed of nanocrystallites of anatase with a size of 6-7 nm and a high specific surface area varying from 181 to 298 m² g-1. In this study, the effect of the NO3:Ti(IV) mole ratio used to induce the peptisation reaction during the synthesis has been studied and the results revealed that this ratio can influence significantly the textural properties of the resulting catalyst. A screening of the photocatalytic activity of the undoped and Fe3+, Cr3+, La3+ or Eu3+ single-doped and co-doped photocatalysts has been performed by evaluating the degradation of 4-nitrophenol under UV-Visible light (330 nm < λ < 800 nm). This study suggests that the photocatalytic activity is significantly influenced by the dopant nature and content with an optimal dopant content being observed in the case of Fe3+ or La3+ single-doped as well as in the case of La3+-Fe3+ and Eu3+-Fe3+ co-doped catalysts. In the case of Cr3+ single-doped catalysts, a detrimental effect of the dopant on the photocatalytic degradation of 4-nitrophenol has been observed while no significant influence of the dopant has been detected in the case of Eu3+ single-doped catalysts. The role of the different dopants in modulating the photocatalytic activity is discussed. [less ▲]

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See detailTowards a large scale aqueous sol-gel synthesis of doped TiO2: Study of various metallic dopings for the photocatalytic degradation of p-nitrophenol
Mahy, Julien ULiege; Lambert, Stéphanie ULiege; Léonard, Géraldine ULiege et al

in Journal of Photochemistry and Photobiology A : Chemistry (2016), 329

In this paper, an easy aqueous sol-gel synthesis developed previously by Mahy et al. [J. Sol-Gel Sci. Technol. (2016)] is adapted to produce highly active TiO2 catalysts doped with Fe3+, Ag+, Cu2+, Zn2 ... [more ▼]

In this paper, an easy aqueous sol-gel synthesis developed previously by Mahy et al. [J. Sol-Gel Sci. Technol. (2016)] is adapted to produce highly active TiO2 catalysts doped with Fe3+, Ag+, Cu2+, Zn2+, Cr3+, Al3+, Mn2+, and Co2+ ions and Pt metallic nanoparticles. Samples are characterized by inductively coupled plasma–atomic emission spectroscopy (ICP-AES), X-ray diffraction (XRD), Mössbauer spectroscopy, transmission electron microscopy (TEM), nitrogen adsorption–desorption measurements and diffuse reflectance spectroscopy measurements. Results show that the samples are composed of anatase-brookite TiO2 nanoparticles with a spherical shape and mean diameter of around 5-8 nm and a surface area of between about 150 - 250 m2 g-1. In each doped sample, the dopant is present in the form added during the synthesis, given that the sample has not undergone any particular treatment. Photoactivity tests show improvement in catalyst activity for Fe3+, Ag+, Cu2+, Zn2+, and Al3+ ion and Pt metallic nanoparticle dopants, while a decrease of activity is obtained for Cr3+, Mn2+ and Co2+ ion dopants. For some dopants, the activity of TiO2 doped with metallic ions and synthesized from the aqueous sol-gel process is equal or superior to the activity of the commercial photocatalyst Degussa P25. Some mechanisms are proposed to explain these modifications of activity with doping. Furthermore, cost comparison at laboratory scale showed that Zn and Cu nitrate salt dopings are clearly less expensive for a halogen light (UV/visible) or low energy light enhanced catalyst and may be considered for industrial applications. Using this method, a large scale Zn-doped TiO2 photocatalyst is synthesized with properties homologous to the lab-scale product. Results show that the aqueous sol-gel synthesis developed previously can be easily adapted for doping in order to produce an up-scalable synthesis. [less ▲]

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See detailDevelopment of a large scale aqueous sol-gel synthesis of doped TiO2
Mahy, Julien ULiege; Lambert, Stéphanie ULiege; Léonard, Géraldine ULiege et al

Conference (2016, July 20)

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See detailDevelopment of an easy aqueous sol-gel synthesis for large-scale film deposition methods for the manufacture of coated steel with self-cleaning properties
Mahy, Julien ULiege; Léonard, Géraldine ULiege; Pirard, Sophie ULiege et al

Conference (2016, May 20)

In this work, a global process has been developed to produce at a large scale pure TiO2 films deposited on steel in order to get an easy-to-clean surface. This large scale process implies an easy aqueous ... [more ▼]

In this work, a global process has been developed to produce at a large scale pure TiO2 films deposited on steel in order to get an easy-to-clean surface. This large scale process implies an easy aqueous sol-gel process for the synthesis of the TiO2 sol. This synthesis [1] has been simplified to make easier the extrapolation towards an industrial scale. Results of TEM, photocatalytic properties, film hydrophilicity, and texture obtained with the simplified aqueous sol-gel synthesis (IsoP-TiO2 synthesis) show similar properties than those obtained with the standard aqueous sol-gel synthesis of TiO2 developed previously (HAc-TiO2 synthesis [2]). Only XRD patterns were slightly different with the presence of anatase-brookite phases in IsoP-TiO2 synthesis while anatase phase only was observed in HAc-TiO2 synthesis. Both the aqueous sol-gel synthesis of pure TiO2 and the film deposition on steel by roll-coating have been successfully extrapolated to a larger scale. Indeed, the deposition was done on a pilot line, the steel substrate is 25 cm width, and the band length is 800 m. The coating was deposited at line speed ranging from 30 to 120 m.min-1.The photocatalytic activity and the hydrophilicity of the film were found to be unchanged compared to the films produced at a laboratory scale, thus validating the production of an efficient easy-to-clean material. Even if some problems have still to be solved, this study is a hopeful first step in the development of a large scale process for self-cleaning steel production. [1] S. Mahshid, M. Askari, M.S. Ghamsari, J. Mater. Process. Technol. 189 (2007) 296–300 [2] C.M. Malengreaux, S. Douven, D. Poelman, B. Heinrichs, J.R. Bartlett, J. Sol-Gel Sci. Technol. 71 (2014) 557–570 [less ▲]

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See detailDoping TiO2 films with carbon nanotubes to simultaneously optimise antistatic, photocatalytic and superhydrophilic properties
Léonard, Géraldine ULiege; Remy, Simon; Heinrichs, Benoît ULiege

in Journal of Sol-Gel Science and Technology (2016)

Pure and multiwall carbon nanotube (MWCNT)- doped titanium dioxide (TiO2) films, synthesised from two sol–gel routes (alcoholic and aqueous) and deposited by dipcoating on glass, have been developed as ... [more ▼]

Pure and multiwall carbon nanotube (MWCNT)- doped titanium dioxide (TiO2) films, synthesised from two sol–gel routes (alcoholic and aqueous) and deposited by dipcoating on glass, have been developed as conductive, photocatalytic and superhydrophilic materials. While already crystallised in anatase structure at low temperature when synthesised in water, samples prepared in alcohol are amorphous. Their crystallisation in air has been studied at increasing temperatures. Effective incorporation of functionalised MWCNTs is confirmed in both aqueous and alcoholic samples with a closer interaction with TiO2 particles in the case of aqueous synthesis. In alcoholic samples, 400 C seems to be an optimised calcination temperature since 300 C does not allow crystallisation into anatase and 500 C removes MWCNTs through burning. The purpose of MWCNT doping is to obtain coatings that exhibit easy-toclean or self-cleaning properties. This can be achieved through an optimised combination of electrical conductivity (for antistatic property), photoactivity and superhydrophilicity. These three properties require the crystallisation of TiO2 into anatase. MWCNT doping dramatically increases both conductivity and photocatalytic activity, especially in alcoholic samples for the former and in aqueous samples for the latter. On the other hand, MWCNT introduction does not significantly affect the (super)hydrophilicity of films, which depends solely on the crystallinity of TiO2. [less ▲]

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See detailOverview of Superhydrophilic, Photocatalytic and Anticorrosive Properties of TiO2 Thin Films Doped with Multi-walled Carbon Nanotubes and Deposited on 316L Stainless Steel
Léonard, Géraldine ULiege; Remy, Simon; Heinrichs, Benoît ULiege

in Materials Today: Proceedings (2016, February), 3(2), 434-438

TiO2 films with MWCNTs are produced for anticorrosive applications to increase the lifetime of steel materials. TiO2 has two additional properties, photoactivity and superhydrophilicity. Two TiO2 samples ... [more ▼]

TiO2 films with MWCNTs are produced for anticorrosive applications to increase the lifetime of steel materials. TiO2 has two additional properties, photoactivity and superhydrophilicity. Two TiO2 samples, synthesized in aqueous or alcoholic media, have been doped with MWCNTs. The material which best combines anticorrosive, superhydrophilic and photocatalytic properties, is the one produced in aqueous medium (Aq-TiO2-CNT). Doping with MWCNTs increases the photodegradation of p-nitrophenol from 18% to 50%. MWCNTs allow to reduce the corrosion current and the corrosion potential. The good superhydrophilicity of TiO2 is kept on stainless steel with a contact angle after illumination around 5°. [less ▲]

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See detailDoped sol–gel films vs. powders TiO2: On the positive effect induced by the presence of a substrate
Léonard, Géraldine ULiege; Malengreaux, Charline; Melotte, Quentin et al

in Journal of Environmental Chemical Engineering (2016), 4

SiO2 and Ag–SiO2 doped TiO2 films and powders have been produced using a controlled sol–gel process. The dopant has been introduced using an alkoxysilane-functionalized ligand, with or without complexed ... [more ▼]

SiO2 and Ag–SiO2 doped TiO2 films and powders have been produced using a controlled sol–gel process. The dopant has been introduced using an alkoxysilane-functionalized ligand, with or without complexed silver ions. The influence of dopants on physico-chemical properties of the catalysts is studied by XRD, TEM–EDX, DRUV–vis analyses in the case of powders, while GIXRD, XPS, profilometry, UV–vis absorption analyses have been used for thin films. The photocatalytic activity has been evaluated from the degradation of methylene blue under UV-A light in the presence of the different catalysts over a period of 24 h. The detailed comparison between powders and films highlights a surprising positive effect in the case of films due to the presence of the substrate. In the case of photocatalytic powders, the presence of SiO2 or Ag–SiO2 into the TiO2 matrix has a detrimental effect on the photocatalytic activity while the opposite tendency is observed in the case of films, with best activities obtained with Ag–SiO2 doping. Different factors, in particular crystallinity modification between powders and films, have been studied to explain these opposite behaviors. In the case of powders, crystallization is hindered by SiO2 and Ag particles incorporation into the TiO2 matrix, leading to a decrease of the photocatalytic activity. In the case of thin films, probably because of the presence of a substrate, crystallization is not influenced by the presence of SiO2 and Ag particles. Therefore, the latter ones can fully play their role of electron traps leading to an enhanced photocatalytic activity. [less ▲]

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See detailModification of Conductivity, Superhydrophilicity and Photocatalytic Activity of TiO2 Thin Films Through Carbon Nanotubes Doping
Léonard, Géraldine ULiege; Remy, Simon; Malengreaux, Charline ULiege et al

Poster (2014, July 15)

In this work, a superhydrophilic and photocatalytic material allowing to reduce the accumulation of electrostatic charges is developed. The superhydrophilicity and photocatalytic activity of TiO2 films ... [more ▼]

In this work, a superhydrophilic and photocatalytic material allowing to reduce the accumulation of electrostatic charges is developed. The superhydrophilicity and photocatalytic activity of TiO2 films provide the “easy-to-clean” property. Indeed, superhydrophilicity induces a very low contact angle between TiO2 and water leading to the formation of a water film at the surface of the material. The photocatalytic activity, responsible for the pollutant decomposition, is explained by the excitation of the semiconductor under UV light leading to the formation of electron-hole pairs. The electrical conductivity of semiconductor TiO2 is very low leading to the accumulation of electrostatic charges and so the surface becomes a dust trap. Multi-walled carbon nanotubes (MWCNTs) are electrical conductors and their introduction in TiO2 could increase the conductivity. The incorporation of MWCNTs can modify the superhydrophilicity of TiO2. The photoactivity can be improved by reducing the electron-hole recombination rate. MWCNTs play a role in electron transfer and allow to decrease the recombination of electron-hole pairs. Two sol-gel syntheses were studied in alcohol and water respectively. In the alcoholic medium, monolayer films are obtained by dip-coating on alkaline free glass and calcined at 300, 400 or 500°C. The thermal treatment allows to crystallize TiO2 in the anatase form. In the aqueous synthesis, monolayer film are obtained by dip-coating on alkaline free glass. The TiO2 shows already the anatase structure. The characterizations of the samples have confirmed the nanotube presence in the aqueous synthesis, and in the alcoholic synthesis at 300°C and 400°C but not at 500°C. The highest conductivity is obtained from the syntheses in alcohol and the calcination at 300°C. That sample does not exhibit a high photoactivity because of its poor crystallinity. The films without MWCNTs are superhydrophilic but the contact angle increase with the incorporation of MWCNTs. The superhydrophilicity is lost with MWCNTs introduction. MWCNTs increase the roughness, the thickness and the electron transfer of the TiO2 matrix. This induces an enhancement of the photoactivity under UV. The comparison between the two syntheses shows that the alcoholic synthesis (400°C) is the best for pure film. When MWCNTs are introduced, the improvement is higher in the case of aqueous synthesis than in the case of alcoholic synthesis. The aqueous synthesis leads to more active photocatalysts than the alcoholic synthesis. [less ▲]

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