References of "Páez Martínez, Carlos"
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See detailPhotocatalytic decomposition of hydrogen peroxide over nanoparticles of TiO2 and Ni(II)-porphyrin doped TiO2: a relationship between activity and porphyrin anchoring mode
Tasseroul, Ludivine ULg; Pàez Martinez, Carlos ULg; Lambert, Stéphanie ULg et al

in Applied Catalysis B : Environmental (2016), 182

The nickel tetra(4-carboxyphenyl)porphyrin (TCPPNi) was chimisorbed on Degussa P25 TiO2 at different concentrations. Diffuse reflectance spectroscopy in the UV/vis region, Fourier transform infrared ... [more ▼]

The nickel tetra(4-carboxyphenyl)porphyrin (TCPPNi) was chimisorbed on Degussa P25 TiO2 at different concentrations. Diffuse reflectance spectroscopy in the UV/vis region, Fourier transform infrared spectroscopy and thermal gravimetry combined with differential scanning calorimetry measurements allowed the determination of the TCPPNi anchoring mode. At low TCPPNi concentrations, this anchoring on Degussa P25 TiO2 took place through all four carboxylic groups, while at higher concentrations the anchoring occurred through one or two carboxylic groups. For the firsttime,the effect of UV/vis light irradiation on the H2O2-degradation activity of TiO2 and TCPPNi-doped TiO2 was studied using the method of following the production of O2 by gas pressure monitoring. The activity of seven different catalysts was related to the TCPPNi anchoring mode and the percentage of TiO2 Degussa P25 coverage. An optimum degradation of H2O2 was observed for 0.0115 mol TCPPNi × g−1 P25. In that case, the TCPPNi was anchored through the four carboxylic groups, corresponding to a strong interaction with Degussa P25 TiO2. Moreover, the TCPPNi did not cover the surface completely, therefore allowing the light to reach and activate the TiO2. [less ▲]

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See detailDegradation of p-nitrophenol and bacteria with TiO2 xerogels sensitized in situ with tetra(4-carboxyphenyl)porphyrins
Tasseroul, Ludivine ULg; Lambert, Stéphanie ULg; Eskenazi, David et al

Poster (2015, September 10)

Heterogeneous photocatalysis is widely studied for environmental applications as oxidative processes can completely destroy organic pollutants such as alkanes, pesticides, dyes, etc. and microorganisms ... [more ▼]

Heterogeneous photocatalysis is widely studied for environmental applications as oxidative processes can completely destroy organic pollutants such as alkanes, pesticides, dyes, etc. and microorganisms. The most used photocatalyst is the commercial TiO2 Degussa P25, which is composed of 80% anatase and 20% rutile and which is active when TiO2 is exposed to UV light ( < 380 nm). Recently, several studies have been performed to extend the light absorption range of TiO2 towards the visible range. In this study, TiO2-based materials doped with porphyrins, a widely used dye for the photosensibilization of TiO2, have been prepared using a sol-gel process. To stabilize the TiO2-dye interactions, free metal tetra(4-carboxyphenyl)porphyrin and nickel tetra(4-carboxyphenyl)porphyrin were introduced in situ into the TiO2 matrix during the sol-gel process rather than by grafting. Samples were thoroughly characterized by TEM, X-ray diffraction, FT-IR, DR-UV/Vis and their texture has been examined by nitrogen adsorption–desorption at 77 K. The photocatalytic activity for the degradation of p-nitrophenol and Escherichia coli and Lactobacillus rhamnosus bacteria cells in aqueous medium, under halogen lamp light have been evaluated in relation with the physico-chemical modifications induced by the doping. The low temperature vacuum drying protocol (150°C) used in the present study enabled to obtain porphyrin doped TiO2 xerogels with a high specific surface area, and containing nanoparticles composed of amorphous- and anatase-TiO2. Diffuse reflectance spectroscopy attest the presence of TCPPH2 and TCPPNi within the TiO2 matrix. In a first step, the photoactivity of the xerogels is tested for p-nitrophenol degradation. Results show that crystallinity and nature and concentration of porphyrin introduced in situ have major impact on the degradation performances. In a second step, the best xerogel for p-nitrophenol degradation has been used to degrade bacteria. This xerogel degrades E. coli and L. rhamnosus bacteria cells in less than 48 and 24 h respectively. The photocatalytic degradation of a pollutant is thus correlated to the degradation of bacteria since a xerogel doped with the TCPPNi degrades both p-nitrophenol, E. coli and L. rhamnosus. [less ▲]

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See detailWet method for the production of thin films (2)
Liquet, Dimitri ULg; Calberg, Cédric ULg; Eskenazi, David et al

Patent (2015)

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

Patent (2015)

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See detailA one-step short-time synthesis of Ag@SiO2 core-shell nanoparticles
Lismont, Marjorie ULg; Pàez Martinez, Carlos ULg; Dreesen, Laurent ULg

in Journal of Colloid & Interface Science (2015)

A performance of shell-thickness precise control in silver-silica coating core-shell nanoparticles is presented. 60 nm sized citrate-stabilized silver nanoparticles are directly silica coated using a ... [more ▼]

A performance of shell-thickness precise control in silver-silica coating core-shell nanoparticles is presented. 60 nm sized citrate-stabilized silver nanoparticles are directly silica coated using a modified Stöber process. Tetraethyl orthosilicate is used as a silica precursor and ammonium hydroxide as catalyst in an alcoholic solvent to promote the seeded silica growth. By simply varying the synthesis reaction time from 4 to 60 minutes, the silica shell thickness is increased from 5.1 nm to 76.4 nm. This well-controlled synthesis is then transposed to 40, 80 and 100 nm sized silver cores in order to show the independence of the silica shell growth on the nanoparticle core size. Optical properties, i.e. localized surface plasmon resonance, of the produced silver-silica core-shell are also investigated. [less ▲]

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See detailCore-shell AgSiO2-Protoporphyrin IX nanoparticle: Effect of the Ag core on reactive oxygen species generation
Lismont, Marjorie ULg; Pàez Martinez, Carlos ULg; Dreesen, Laurent ULg

in SPIE proceeding - Colloidal Nanoparticles for Biomedical Applications X (2015, February)

Photodynamic therapy (PDT) for cancer is based on the use of a light sensitive molecule to produce, under specific irradiation, toxic reactive oxygen species (ROS). A way to improve the therapy efficiency ... [more ▼]

Photodynamic therapy (PDT) for cancer is based on the use of a light sensitive molecule to produce, under specific irradiation, toxic reactive oxygen species (ROS). A way to improve the therapy efficiency is to increase the amount of produced ROS near cancer cells. This aim can be achieved by using a metal enhanced process arising when an optically active molecule is located near a metallic nanoparticle (NP). Here, the coupling effect between silver (Ag) NPs and protoporphyrin IX (PpIX) molecules, a clinically approved photosensitizer, is studied compared first, to PpIX fluorescence yield and second, to ROS production efficiency. By applying a modified Stöber process, PpIX was encapsulated into a silica (SiO2) shell, surrounding a 60 nm sized Ag core. We showed that, compared to SiO2-PpIX NPs, Ag coated SiO2-PpIX NPs dramatically decreased PpIX fluorescence together with singlet oxygen production efficiency. However, after incubation time in the dark, the amount of superoxide anions generated by the Ag doped sample was higher than the control sample one. [less ▲]

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See detailThe range of validity of sorption kinetic models
Douven, Sigrid ULg; Pàez Martinez, Carlos ULg; Gommes, Cédric ULg

in Journal of Colloid & Interface Science (2015), 448

Several hundred papers are published yearly reporting liquid-phase adsorption kinetics data. In general the data is analyzed using a variety of standard models such as the pseudo first- and second-order ... [more ▼]

Several hundred papers are published yearly reporting liquid-phase adsorption kinetics data. In general the data is analyzed using a variety of standard models such as the pseudo first- and second-order models and the Intraparticle-Diffusion model. The validity of these models is often assessed empirically via their ability to fit the data, independently of their physicochemical soundness. The aim of the present paper is to rationalize the analysis of liquid-phase adsorption kinetics data, and to investigate experimental factors that influence the adsorption kinetics, in addition to the characteristics of the adsorbent material itself. For that purpose we use a simple Langmuir adsorption–diffusion model, which enables us to identify three dimensionless numbers that characterize the working regime of any batch adsorption experiment: an adsorption Thiele modulus, a saturation modulus, and a loading modulus. The standard models are found to be particular cases of the general adsorption–diffusion model for specific values of the dimensionless numbers. This provides sound physicochemical criteria for the validity of the models. Based on our modeling, we also propose a general yet simple data analysis procedure to practically estimate the diffusion coefficient in adsorbent pellets starting from adsorption halftimes. [less ▲]

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See detailPhotocatalytic degradation of water pollutants with visible light-sensitized TiO2 xerogels
Tasseroul, Ludivine ULg; Pirard, Sophie ULg; Lambert, Stéphanie ULg et al

in Récents Progrès en Génie des Procédés (2014), 106

To extend its photocatalytic activity to visible light, TiO2 has been doped in situ through the cogelation sol-gel proces with two dyes : free metal tetra(4-carboxyphenyl)porphyrin and nickel tetra(4 ... [more ▼]

To extend its photocatalytic activity to visible light, TiO2 has been doped in situ through the cogelation sol-gel proces with two dyes : free metal tetra(4-carboxyphenyl)porphyrin and nickel tetra(4-carboxyphenyl)porphyrin. DR and FT-IR spectroscopies have been performed to determine the interaction between porphyrins and TiO2. Cristallinity and specific surface area have been measured by XRD and N2 adsorption. The photoactivity of the doped TiO2 xerogels has been evaluated for p-nitrophenol (a model water pollutant) degradation under visible light and a kinetic study has been performed. The samples allow the degradation of 40% of p-nitrophenol in 6 h which makes them very promising for water decontamination under natural light. A kinetic study of p-nitrophenol degradation with the Ni-doped catalyst has shown that the best kinetic model involves one type of active site corresponding to the hole h+ of electron-hole pairs created at the TiO2 surface by light. The rate determining step consists of the surface reaction between adsorbed p-nitrophenol and adsorbed OH• radicals. [less ▲]

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See detailSol-gel preparation and characterisation of SnO2 powders employed as catalyst for phenol photodegradation
Benhebal, Hadj; Chaib, Messaoud; Léonard, Angélique ULg et al

in Scientia Iranica (2013), 20(6), 1891-1898

Crystallized pure SnO2 powders were prepared by the sol-gel process and were used as photocatalyst for the degradation of phenol under UV light at pH 6.5 and a temperature of 20°C. The physical properties ... [more ▼]

Crystallized pure SnO2 powders were prepared by the sol-gel process and were used as photocatalyst for the degradation of phenol under UV light at pH 6.5 and a temperature of 20°C. The physical properties of photocatalyst were characterized by X-ray diffraction, Scanning Electron Microscopy, nitrogen adsorption-desorption and Ultraviolet-visible diffuse reflectance spectroscopy. The influences of different operating variables such as the pH, the photocatalyst loading, the initial concentration of phenol, were studied to improve the efficiency of phenol degradation. [less ▲]

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See detailAdsorption du bleu de méthylène sur des xérogels de carbone activés
Páez Martínez, Carlos ULg; Contreras, Soledad; Léonard, Angélique ULg et al

Poster (2012, October)

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See detailEffect of CO2 activation of carbon xerogels on the adsorption of methylene blue
Páez Martínez, Carlos ULg; Contreras, M. S.; Léonard, Angélique ULg et al

in Adsorption (2012), 18(3-4), 199-211

The effect of physical activation with CO2 of carbon xerogels, synthesized by pyrolysis of a resorcinolformaldehyde aqueous gel, on the adsorption capacities of Methylene Blue (MB) was studied. The ... [more ▼]

The effect of physical activation with CO2 of carbon xerogels, synthesized by pyrolysis of a resorcinolformaldehyde aqueous gel, on the adsorption capacities of Methylene Blue (MB) was studied. The activation with CO2 lead to carbon materials with micropore volumes ranging from 0.28 to 0.98 cm³/g -1 C. MB-adsorption isotherm studies showed that the increase of micropore volume and corresponding surface area led to: (i) a significant improvement in the capacity of MB-adsorption at monolayer coverage, from 212 to 714 mgg -1 C, and (ii) an increase of the binding energy related to Langmuir isotherm constant up to 45 times greater than those of commercial microporous activated carbons used as reference (NORIT R2030, CALGON BPL and CALGON NC35). It is proposed that the increase of the binding energy results from chemical cleaning of the O-groups onto carbon surface as a consequence of CO2-activation, increasing the π-π interaction between MB and graphene layers of the carbon xerogels. Finally, a series of batch kinetics were performed to investigate the effect of CO2-activation conditions on the mechanism of MB-adsorption. Experimental data were fitted using pseudo-first-order, pseudo-second-order and intraparticle diffusion kinetic models. From pseudo-second-order kinetic model, one observes an increase in the initial rate of MB-adsorption from 0.019 to 0.0565 min -1, by increasing the specific surface area from 630 to 2180 m²/g -1 C via CO2-activation. Depending on the activation degree of the carbons, two different mechanisms control the MB-adsorption rate: (i) at low activation degree, the intraparticle diffusion is the rate-limiting phenomenon, whereas (ii) at high activation degree, the reactions occurring at the solid/liquid interface are the rate-limiting steps. © 2012 Springer Science+Business Media, LLC. [less ▲]

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See detailKinetic study of p-nitrophenol photodegradation with modified TiO2 xerogels
Tasseroul, Ludivine ULg; Pirard, Sophie ULg; Lambert, Stéphanie ULg et al

in Chemical Engineering Journal (2012), 191

TiO2 xerogels were sensitized in one step by the in situ introduction of nickel (II) tetra(4-carboxyphenyl)porphyrin (TCPPNi) into the TiO2 matrix during sol–gel synthesis. Crystalline photoactive phase ... [more ▼]

TiO2 xerogels were sensitized in one step by the in situ introduction of nickel (II) tetra(4-carboxyphenyl)porphyrin (TCPPNi) into the TiO2 matrix during sol–gel synthesis. Crystalline photoactive phase TiO2-anatase was obtained without high thermal treatments and was determined by X-ray diffraction. The presence of TCPPNi in TiO2 xerogels was established by DR-UV/Vis and FT-IR spectroscopy. The introduction of porphyrin led to a diminution of the specific surface area of TiO2 xerogels, and this diminution was analyzed by nitrogen adsorption–desorption. The particle size was estimated by SEM. The xerogel surface charge state, which influences the interactions between pollutant and TiO2, was determined by measurement of the point of zero charge. The photoactivity of xerogels was evaluated for p-nitrophenol degradation in aqueous medium at 20 ◦C. Results showed that porphyrin doped TiO2 degraded more than 40% of the p-nitrophenol whereas non doped TiO2 xerogel degraded only 10% of the compound. Moreover, porphyrin was found to improve the photoactivity of TiO2 xerogels in a similar way to UV-A pretreatment. A kinetic study of p-nitrophenol degradation was then performed. Results showed that one type of active site corresponding to the hole of electron–hole pairs was created at the TiO2 surface by light and that the rate determining step was the reaction between the adsorbed p-nitrophenol molecule and the adsorbed OH• radical. The apparent activation energy was found to be equal to 12 kJ mol−1. [less ▲]

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See detailAdsorption of methylene blue on activated carbon xerogels
Páez Martínez, Carlos ULg; Contreras, Maria Soledad; Léonard, Angélique ULg et al

Poster (2011, November 30)

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See detailSynthesis by the sol-gel process of visible light sensitive-TiO2 for the degradation of pollutants and microorganisms
Tasseroul, Ludivine ULg; Lambert, Stéphanie ULg; Páez Martínez, Carlos ULg et al

in Récents Progrès en Génie des Procédés, Lavoisier Technique et Documentation, Volume 101, 6 p. (CD-ROM) (2011, November 29)

To stabilize the TiO2-dye interaction, free metal tetra(4-carboxyphenyl)porphyrin and nickel tetra(4-carboxyphenyl)porphyrin were introduced into the TiO2 matrix by cogelation rather than by grafting. DR ... [more ▼]

To stabilize the TiO2-dye interaction, free metal tetra(4-carboxyphenyl)porphyrin and nickel tetra(4-carboxyphenyl)porphyrin were introduced into the TiO2 matrix by cogelation rather than by grafting. DR and FT-IR spectroscopies were performed to establish the interaction between porphyrins and TiO2. Cristallinity and specific surface area were performed by XRD and nitrogen adsorption-desorption measurements. The photoactivity of doped-TiO2 xerogels was evaluated for p-nitrophenol and Escherichia coli degradation. Under visible light, the samples allowed the degradation of 40% of p-nitrophenol in 6 h and the elimination of 108 CFU/mL of E. coli in 48 h. [less ▲]

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