Bioenergetics of cancer results in an increased oxidation state and toxic by-products such as rea... more Bioenergetics of cancer results in an increased oxidation state and toxic by-products such as reactive oxygen species (ROS). ROS-mediated thiol oxidation of specific sensory proteins triggers the antioxidant response in order to decrease ROS levels and to trigger apoptosis when the oxidative stress cannot be overcome. This metabolic reprogramming has been implicated in refractory and relapsed disease and shaping of the microenvironment in solid cancers. Two redundant antioxidant pathways counteract ROS-mediated oxidation: the Glutathione (GSH)- and Thioredoxin (Trx)-dependent pathways. An effective way to treat tumors is to irreversibly block both pathways simultaneously. Experimental and therapeutic experience has shown that blocking only one is insufficient because one active pathway is enough for tumor survival, a reason why inhibitors of these pathways have shown limited success in the clinic. The TMC Ag5 irreversibly blocks both the GSH and Trx-dependent pathways, making it a h...
In this work, the removal efficiency of U(VI) from water using commercial nanoparticles of zerova... more In this work, the removal efficiency of U(VI) from water using commercial nanoparticles of zerovalent iron (nZVI) (NANOFER 25, NANO IRON s.r.o.) and magnetite (nM) (NanoFe®, Nanotek SA) was evaluated. Batch experiments were carried out in a jacketed reactor with a vertical paddle stirrer, using UO2(NO3)2 solutions([U(VI)]0 = 0.25 mM = 59.5 mg L-1) at pH 5.3. The nanoparticles (initially suspended in water) were added tothe U(VI) solution to achieve different Fe:U(VI) molar ratios (MR) in the range of 1 to 100. U(VI) removal with nZVI and nM at MR 4 and dissolved oxygen (DO) levels higher than 0.1 mg L-1 were rather efficient, reaching in both cases a final removal of 65 %. Under these conditions, uranium removal strongly depends on thepresence of DO, decreasing with increasing DO. When 40 and 100 MR were used, a complete U(VI) removal in the first 15 min of treatment was observed, and oxygen was consumed reaching negligible DO levels (below0.1 mg L-1). With MR = 4 and DO levels belo...
Mesoporous hybrid materials containing inorganic and organic functional groups are relevant for a... more Mesoporous hybrid materials containing inorganic and organic functional groups are relevant for advanced applications in separation, sorption or heterogeneous catalysis. The possibility of combining materials with high surface area and tailorable mesopore size with a mixed oxide framework and organic functions open the gate to imitating complex biosystems such as enzyme active sites. One of the critical aspects towards a multiscale control of these complex materials is the understanding of the actual framework structure and the interplay of the framework ions and the organic functions, and how these features are related to the sol-gel preparation conditions. In this work, mesoporous hybrid organic-inorganic thin films (MHTF) based on a mixed silica-titania matrix containing 20% aminopropyl functions were prepared and thoroughly studied by X-ray absorption spectroscopy at both the Ti and Si K-edges, and by O1s and N1s X-ray photoelectron spectroscopy. This approach permitted us to simultaneously probe the changes in Si and Ti coordination, the linkages between the inorganic centers, and the availability of the amino functions along samples with varying Si:Ti ratio. We find substantial differences between the local structure of pure inorganic oxides and the hybrid materials. In the oxides, increasing the %Ti leads to an increase in octahedral Si sites and Ti-oxo clusters with shorter Ti-O bonds. In the hybrid materials, higher Ti coordination with longer bonds are observed, along with a prevalence of Si centers with distorted tetrahedral coordination. These findings suggest that aminopropyl building blocks act as a compatibilizer between Ti(IV) and Si(IV) centers, leading to a hybrid mixed phase with large silica-titania interface. This intermixing also influences the exposition of amino groups at the pore surface. These aspects are of importance in the design of high surface area adsorbents, permselective membranes or heterogeneous catalysts. The structure of highly organized mesoporous thin films with aminopropyl groups and Si-Ti framework can be precisely determined by combining XANES and XPS. Functionality can be controlled from synthesis. The structure of highly organized mesoporous thin films with aminopropyl groups and Si-Ti framework can be precisely determined by combining XANES and XPS. Functionality can be controlled from synthesis. Highly organized mesoporous thin films with aminopropyl groups and Si-Ti framework are synthesized from a one-pot, low-temperature method. We present an exhaustive spectroscopic study of these materials by combining XANES and XPS. Ti and Si K-Edge XANES permit to assess the changes in bonding and coordination of both cations in mixed oxide and hybrid matrices. XPS measurements permit to understand the formation of Si-O-Ti interfaces and the availability of the amino groups. This study permits to link sol-gel processing conditions to the structure of complex hybrid mesoporous materials. Highly organized mesoporous thin films with aminopropyl groups and Si-Ti framework are synthesized from a one-pot, low-temperature method. We present an exhaustive spectroscopic study of these materials by combining XANES and XPS. Ti and Si K-Edge XANES permit to assess the changes in bonding and coordination of both cations in mixed oxide and hybrid matrices. XPS measurements permit to understand the formation of Si-O-Ti interfaces and the availability of the amino groups. This study permits to link sol-gel processing conditions to the structure of complex hybrid mesoporous materials.
It has been suggested that enhanced anion concentrations at the liquid/vapor interface of airborn... more It has been suggested that enhanced anion concentrations at the liquid/vapor interface of airborne saline droplets are important to aerosol reactions in the atmosphere. We report ionic concentrations in the surface of such solutions. Using x-ray photoelectron spectroscopy operating at near ambient pressure, we have measured the composition of the liquid/vapor interface for deliquesced samples of potassium bromide and potassium iodide. In both cases, the surface composition of the saturated solution is enhanced in the halide anion compared with the bulk of the solution. The enhancement of anion concentration is more dramatic for the larger, more polarizable iodide anion. By varying photoelectron kinetic energies, we have obtained depth profiles of the liquid/vapor interface. Our results are in good qualitative agreement with classical molecular dynamics simulations. Quantitative comparison between the experiments and the simulations indicates that the experimental results exhibit mor...
En este trabajo se presenta la sintesis controlada de peliculas delgadas de oxido de grafeno (GO)... more En este trabajo se presenta la sintesis controlada de peliculas delgadas de oxido de grafeno (GO) mediante la tecnica Langmuir-Blodgett (LB) y su posterior reduccion por diferentes vias para obtener peliculas de oxido de grafeno reducido (rGO). Este metodo de produccion tiene gran potencial debido a que abre la posibilidad de sintetizar de forma controlada desde monocapas hasta multicapas de materiales del tipo de los grafenos, con propiedades de transporte controladas como potencial plataforma para diversas aplicaciones en el area de nanotecnologia. En particular se presenta la obtencion de un nanocompuesto, incorporando sobre la pelicula de rGO nanohilos de plata (Ag), los cuales ya han mostrado capacidad como biosensore.
Bioenergetics of cancer results in an increased oxidation state and toxic by-products such as rea... more Bioenergetics of cancer results in an increased oxidation state and toxic by-products such as reactive oxygen species (ROS). ROS-mediated thiol oxidation of specific sensory proteins triggers the antioxidant response in order to decrease ROS levels and to trigger apoptosis when the oxidative stress cannot be overcome. This metabolic reprogramming has been implicated in refractory and relapsed disease and shaping of the microenvironment in solid cancers. Two redundant antioxidant pathways counteract ROS-mediated oxidation: the Glutathione (GSH)- and Thioredoxin (Trx)-dependent pathways. An effective way to treat tumors is to irreversibly block both pathways simultaneously. Experimental and therapeutic experience has shown that blocking only one is insufficient because one active pathway is enough for tumor survival, a reason why inhibitors of these pathways have shown limited success in the clinic. The TMC Ag5 irreversibly blocks both the GSH and Trx-dependent pathways, making it a h...
In this work, the removal efficiency of U(VI) from water using commercial nanoparticles of zerova... more In this work, the removal efficiency of U(VI) from water using commercial nanoparticles of zerovalent iron (nZVI) (NANOFER 25, NANO IRON s.r.o.) and magnetite (nM) (NanoFe®, Nanotek SA) was evaluated. Batch experiments were carried out in a jacketed reactor with a vertical paddle stirrer, using UO2(NO3)2 solutions([U(VI)]0 = 0.25 mM = 59.5 mg L-1) at pH 5.3. The nanoparticles (initially suspended in water) were added tothe U(VI) solution to achieve different Fe:U(VI) molar ratios (MR) in the range of 1 to 100. U(VI) removal with nZVI and nM at MR 4 and dissolved oxygen (DO) levels higher than 0.1 mg L-1 were rather efficient, reaching in both cases a final removal of 65 %. Under these conditions, uranium removal strongly depends on thepresence of DO, decreasing with increasing DO. When 40 and 100 MR were used, a complete U(VI) removal in the first 15 min of treatment was observed, and oxygen was consumed reaching negligible DO levels (below0.1 mg L-1). With MR = 4 and DO levels belo...
Mesoporous hybrid materials containing inorganic and organic functional groups are relevant for a... more Mesoporous hybrid materials containing inorganic and organic functional groups are relevant for advanced applications in separation, sorption or heterogeneous catalysis. The possibility of combining materials with high surface area and tailorable mesopore size with a mixed oxide framework and organic functions open the gate to imitating complex biosystems such as enzyme active sites. One of the critical aspects towards a multiscale control of these complex materials is the understanding of the actual framework structure and the interplay of the framework ions and the organic functions, and how these features are related to the sol-gel preparation conditions. In this work, mesoporous hybrid organic-inorganic thin films (MHTF) based on a mixed silica-titania matrix containing 20% aminopropyl functions were prepared and thoroughly studied by X-ray absorption spectroscopy at both the Ti and Si K-edges, and by O1s and N1s X-ray photoelectron spectroscopy. This approach permitted us to simultaneously probe the changes in Si and Ti coordination, the linkages between the inorganic centers, and the availability of the amino functions along samples with varying Si:Ti ratio. We find substantial differences between the local structure of pure inorganic oxides and the hybrid materials. In the oxides, increasing the %Ti leads to an increase in octahedral Si sites and Ti-oxo clusters with shorter Ti-O bonds. In the hybrid materials, higher Ti coordination with longer bonds are observed, along with a prevalence of Si centers with distorted tetrahedral coordination. These findings suggest that aminopropyl building blocks act as a compatibilizer between Ti(IV) and Si(IV) centers, leading to a hybrid mixed phase with large silica-titania interface. This intermixing also influences the exposition of amino groups at the pore surface. These aspects are of importance in the design of high surface area adsorbents, permselective membranes or heterogeneous catalysts. The structure of highly organized mesoporous thin films with aminopropyl groups and Si-Ti framework can be precisely determined by combining XANES and XPS. Functionality can be controlled from synthesis. The structure of highly organized mesoporous thin films with aminopropyl groups and Si-Ti framework can be precisely determined by combining XANES and XPS. Functionality can be controlled from synthesis. Highly organized mesoporous thin films with aminopropyl groups and Si-Ti framework are synthesized from a one-pot, low-temperature method. We present an exhaustive spectroscopic study of these materials by combining XANES and XPS. Ti and Si K-Edge XANES permit to assess the changes in bonding and coordination of both cations in mixed oxide and hybrid matrices. XPS measurements permit to understand the formation of Si-O-Ti interfaces and the availability of the amino groups. This study permits to link sol-gel processing conditions to the structure of complex hybrid mesoporous materials. Highly organized mesoporous thin films with aminopropyl groups and Si-Ti framework are synthesized from a one-pot, low-temperature method. We present an exhaustive spectroscopic study of these materials by combining XANES and XPS. Ti and Si K-Edge XANES permit to assess the changes in bonding and coordination of both cations in mixed oxide and hybrid matrices. XPS measurements permit to understand the formation of Si-O-Ti interfaces and the availability of the amino groups. This study permits to link sol-gel processing conditions to the structure of complex hybrid mesoporous materials.
It has been suggested that enhanced anion concentrations at the liquid/vapor interface of airborn... more It has been suggested that enhanced anion concentrations at the liquid/vapor interface of airborne saline droplets are important to aerosol reactions in the atmosphere. We report ionic concentrations in the surface of such solutions. Using x-ray photoelectron spectroscopy operating at near ambient pressure, we have measured the composition of the liquid/vapor interface for deliquesced samples of potassium bromide and potassium iodide. In both cases, the surface composition of the saturated solution is enhanced in the halide anion compared with the bulk of the solution. The enhancement of anion concentration is more dramatic for the larger, more polarizable iodide anion. By varying photoelectron kinetic energies, we have obtained depth profiles of the liquid/vapor interface. Our results are in good qualitative agreement with classical molecular dynamics simulations. Quantitative comparison between the experiments and the simulations indicates that the experimental results exhibit mor...
En este trabajo se presenta la sintesis controlada de peliculas delgadas de oxido de grafeno (GO)... more En este trabajo se presenta la sintesis controlada de peliculas delgadas de oxido de grafeno (GO) mediante la tecnica Langmuir-Blodgett (LB) y su posterior reduccion por diferentes vias para obtener peliculas de oxido de grafeno reducido (rGO). Este metodo de produccion tiene gran potencial debido a que abre la posibilidad de sintetizar de forma controlada desde monocapas hasta multicapas de materiales del tipo de los grafenos, con propiedades de transporte controladas como potencial plataforma para diversas aplicaciones en el area de nanotecnologia. En particular se presenta la obtencion de un nanocompuesto, incorporando sobre la pelicula de rGO nanohilos de plata (Ag), los cuales ya han mostrado capacidad como biosensore.
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Papers by Felix Requejo