V. Montiel

University of Alicante, Alicante, Valencia, Spain

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Publications (119)365.52 Total impact

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    ABSTRACT: l-lactate is an essential metabolite present in embryonic cell culture. Changes of this important metabolite during the growth of human embryo reflect the quality and viability of the embryo. In this study, we report a sensitive, stable, and easily manufactured electrochemical biosensor for the detection of lactate within embryonic cell cultures media. Screen-printed disposable electrodes are used as electrochemical sensing platforms for the miniaturization of the lactate biosensor. Chitosan/multi walled carbon nanotubes composite have been employed for the enzymatic immobilization of the lactate oxidase enzyme. This novel electrochemical lactate biosensor analytical efficacy is explored towards the sensing of lactate in model (buffer) solutions and is found to exhibit a linear response towards lactate over the concentration range of 30.4 and 243.9µM in phosphate buffer solution, with a corresponding limit of detection (based on 3-sigma) of 22.6µM and exhibits a sensitivity of 3417±131µAM(-1) according to the reproducibility study. These novel electrochemical lactate biosensors exhibit a high reproducibility, with a relative standard deviation of less than 3.8% and an enzymatic response over 82% after 5 months stored at 4°C. Furthermore, high performance liquid chromatography technique has been utilized to independently validate the electrochemical lactate biosensor for the determination of lactate in a commercial embryonic cell culture medium providing excellent agreement between the two analytical protocols.
    No preview · Article · Nov 2015 · Biosensors & Bioelectronics
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    ABSTRACT: The development of electrochemical processes for the conversion of CO2 into value-added products allows innovative carbon capture & utilization (CCU) instead of carbon capture & storage (CCS). In addition, coupling this conversion with renewable energy sources would make it possible to chemically store electricity from these intermittent renewable sources. The electroreduction of CO2 to formate in aqueous solution has been performed using Sn particles deposited over a carbon support. The effect of the particle size and Sn metal loading has been evaluated using cyclic voltammetry and chronoamperometry. The selected electrode has been tested on an experimental filter-press type cell system for continuous and single pass CO2 electroreduction to obtain formate as main product at ambient pressure and temperature. Experimental results show that using electrodes with 0.75mgSncm-2, 150nmSn particles, and working at a current density of 90mAcm-2, it is possible to achieve rates of formate production over 3.2mmolm-2s-1 and faradaic efficiencies around 70% for 90min of continuous operation. These experimental conditions allow formate concentrations of about 1.5gL-1 to be obtained on a continuous mode and with a single pass of catholyte through the cell.
    No preview · Article · Nov 2015 · Applied Energy
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    ABSTRACT: Mixed matrix membranes (MMM) are prepared from equivalent blends of poly (vinyl alcohol) (PVA) and chitosan (CS) polymers doped with organic ionomers 4VP and AS4, or inorganic layered titanosilicate AM-4 and stannosilicate UZAR-S3, by solution casting to improve the mechanical and thermal properties, hydroxide conductivity and alcohol barrier effect to reduce the crossover. The structural properties, thermal stability, hydrolytic stability, transport and ionic properties of the prepared composite membranes were investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD), thermo-gravimetric analysis (TGA), water uptake, water content, alcohol permeability, thickness, ion exchange capacity (IEC) and OH- conductivity measurements. The addition of both organic and inorganic fillers in a CS:PVA blend polymer enhances the thermal and ionic properties. All the membranes are homogenous, as revealed by the SEM and XRD studies, except when stannosilicate UZAR-S3 is used as filler, which leads to a dual layer structure, a top layer of UZAR-S3 lamellar particles bound together by the polymer matrix and a bottom layer composed mostly of polymer blend. The loss of crystallinity was especially remarkable in 4VP/CS:PVA membrane. Thus, the 4VP/CS:PVA membrane exhibits the best ionic conductivity, whereas the UZAR-S3/CS:PVA membrane the best reduced alcohol crossover. Finally, the performance of the CS:PVA-based membranes were tested in a Polymer Electrolyte Membrane Electrochemical Reactor. (PEMER) for the feasibility use of alkaline anionic exchange membranes in electrosynthesis under alkaline conditions, showing the 4VP/CS:PVA and UZAR-S3/CS:PVA membranes the best performances in PEMER.
    Full-text · Article · Sep 2015 · Journal of Membrane Science
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    ABSTRACT: The direct CO2 electrochemical reduction on model platinum single crystal electrodes Pt(hkl) is studied in [C2mim+][NTf2-], a suitable room temperature ionic liquid (RTIL) medium due to its moderate viscosity, high CO2 solubility and conductivity. Single crystal electrodes represent the most convenient type of surface structured electrodes for studying the impact of RTIL ions adsorption in relevant electrocatalytic reactions, such as surface sensitive electrochemical CO2 reduction. We propose here based on cyclic voltammetry and in-situ electrolysis measurements, for the first time, the formation of a stable adduct [C2mimH-CO2-] by a radical-radical coupling after the simultaneous reduction of CO2 and [C2mim+]. It means between the CO2 radical anion and the radical formed from the reduction of the cation [C2mim+] before forming the corresponding electrogenerated carbene. This is confirmed by the voltammetric study of a model imidazolium-2- carboxylate compound formed following the carbene pathway. The formation of that stable adduct [C2mimH-CO2-] blocks CO2 reduction after a single electron transfer and inhibits CO2 and imidazolium dimerization reactions. However, the electrochemical reduction of CO2 under those conditions provokes the electrochemical cathodic degradation of the imidazolium based RTIL. This important limitation in CO2 recycling by direct electrochemical reduction is overcome by adding a strong acid, [H+][NTf2-], in solution. Then, protons become preferentially adsorbed on the electrode surface by displacing the imidazolium cations and inhibiting their electrochemical reduction. This fact allows the surface sensitive electro-synthesis of HCOOH from CO2 reduction in [C2mim+][NTf2-], being Pt(110) the most active electrode studied.
    No preview · Article · Aug 2015 · Physical Chemistry Chemical Physics
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    ABSTRACT: The influence of the metal loading (i.e. interparticle distance) of shape-controlled Pt nanoparticles on their electrocatalytic properties is evaluated for the first time. For this purpose, carbon-supported cubic Pt nanoparticles (~17 nm) with different metal loadings were prepared, characterized and electrochemically tested. To avoid differences in particle size and shape/surface structure of the Pt nanoparticles between samples, all samples used in this work were prepared from a single batch. The surface structure of the Pt nanoparticles was evaluated through the so-called hydrogen region and showed a preferential (100) orientation. Interestingly, the electroactive surface area of the samples, estimated both from the H or CO stripping processes, was directly proportional to the total Pt mass, independently of the metal loading. The CO stripping profile was also found to be unaffected by the metal loading. However, for ammonia and formic acid electrooxidation, the activity obtained was dependent on the metal loading. For ammonia oxidation, the optimal loading was found to be about 20–30 wt%. Nevertheless, this trend may be altered by different factors including (i) active surface area, (ii) metal loading and (ii) thickness of the catalytic layer. For formic acid electrooxidation, the results obtained showed a clear decrease of the activity for increasing metal loadings which is explained in terms of formic acid consumption on the top layers of the catalyst.
    No preview · Article · Jul 2015 · Journal of Solid State Electrochemistry
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    ABSTRACT: In this study, we examine the performance of Cu 2 O and Cu 2 O/ZnO surfaces in a filter-press electro-chemical cell for the continuous electroreduction of CO 2 into methanol. The electrodes are prepared by airbrushing the metal particles onto a porous carbon paper and then are electrochemically characterized by cyclic voltammetry analyses. Particular emphasis is placed on evaluating and comparing the methanol production and Faradaic efficiencies at different loadings of Cu 2 O particles (0.5, 1 and 1.8 mg cm −2), Cu 2 O/ZnO weight ratios (1:0.5, 1:1 and 1:2) and electrolyte flow rates (1, 2 and 3 ml min −1 cm −2). The electrodes including ZnO in their catalytic surface were stable after 5 h, in contrast with Cu 2 O-deposited carbon papers that present strong deactivation with time. The maximum methanol formation rate and Faradaic efficiency for Cu 2 O/ZnO (1:1)-based electrodes, at an applied potential of −1.3 V vs. Ag/AgCl, were r = 3.17 × 10 −5 mol m −2 s −1 and FE = 17.7 %, respectively. Consequently, the use of Cu 2 O–ZnO mixtures may be of application for the continuous electrochemical formation of methanol, although further research is still required in order to develop highly active, selective and stable catalysts the electroreduction of CO 2 to methanol.
    Full-text · Article · May 2015 · Applied Catalysis B Environmental
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    ABSTRACT: In this work, electrodialysis has been proved to be a suitable technique for decreasing the conductivity of a real wastewater from an almond industry, which has been previously treated by electrocoagulation (EC) and electrooxidation (EO). A seven-cell electrodialyzer, with total active membrane area of 1400 cm2, was employed and several parameters, as the limiting current density, were determined. A method for measuring voltage across the membranes was developed, in order to control membrane fouling. The method consisted of capillaries inserted into the solution compartments and connected to a high impedance voltmeter. A study of the reuse of the concentrate solution was made, and it was stated that it can be concentrated 10 times. The treatment of the wastewater was performed at different voltages (7-16 V) to reach values of conductivity of the diluate of 0.5 mS cm−1. After that, the scaling up to a pre-industrial scale was performed by using a 70-cell electrodialyzer, with total active membrane area of 3.5 m2. The process was performed by applying voltages of 20-70 V and a final conductivity of the diluate of 0.5 mS cm−1 was achieved. The electric energy consumption was calculated in every case.
    No preview · Article · Feb 2015 · Journal of Membrane Science
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    ABSTRACT: In this study, we examine the performance of Cu2O and Cu2O/ZnO surfaces in a filter-press electrochemical cell for the continuous electroreduction of CO2 into methanol. The electrodes are prepared by airbrushing the metal particles onto a porous carbon paper and then are electrochemically characterized by cyclic voltammetry analyses. Particular emphasis is placed on evaluating and comparing the methanol production and Faradaic efficiencies at different loadings of Cu2O particles (0.5, 1 and 1.8mgcm−2), Cu2O/ZnO weight ratios (1:0.5, 1:1 and 1:2) and electrolyte flow rates (1, 2 and 3ml min−1 cm−2). The electrodes including ZnO in their catalytic surface were stable after 5 h, in contrast with Cu2O-deposited carbon papers that present strong deactivation with time. The maximum methanol formation rate and Faradaic efficiency forCu2O/ZnO (1:1)-based electrodes, at an applied potential of−1.3Vvs. Ag/AgCl, were r = 3.17×10−5 molm−2 s−1 and FE = 17.7 %, respectively. Consequently, the use ofCu2O–ZnOmixturesmay be of application for the continuous electrochemical formation of methanol, although further research is still required in order to develop highly active, selective and stable catalysts the electroreduction of CO2 to methanol.
    Full-text · Article · Jan 2015 · Applied Catalysis B Environmental
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    ABSTRACT: Abstracts: * Aiche meeting abstract- Del Castillo.docx (15.4KB) - Uploading Abstracts
    No preview · Conference Paper · Nov 2014
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    ABSTRACT: Oxidative stress has recently became one of the most important and negative factors that affect favourable human reproduction and therefore plays a crucial role in the successful outcome rates on artificial reproduction techniques (ARTs). The effects of oxidative stress are strengthened in an ART setting since there are more sources of reactive oxygen and nitrogen species (ROS/RNS) generation and a more vulnerable physiological defence mechanism. Culture media, for this reason, have improved in their composition and are becoming more complex, above everything, in their antioxidant power to face ROS/RNS generation. In this work, we suggest the use of electrochemical (bio)sensors to evaluate the presence and evolution of nitric oxide (NO) and superoxide anion (O-2(-)), in a commercial culture medium compared to conventional phosphate buffer solution. The electrochemical monitoring of NO was followed by the real-time NO-release from a commercially available NO donor (diazeniumdiolate) under aerobic conditions in a surface-modified screen-printed linear platinum array electrode. Concurrently, superoxide anion detection was evaluated at a surface-modified screen-printed linear gold electrode by the real-time and in situ generation of O-2(-). The performances of both arrayed sensors were compared to-those obtained at single modified ultramicroelectrodes. We deepen the study of the intrinsic and external interferents for the application of these electrochemical (bio)sensors in order to provide an oxidative stress index during embryo development. (C) 2014 Published by Elsevier Ltd.
    No preview · Article · Sep 2014 · Electrochimica Acta
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    ABSTRACT: Herein, we explore the immobilization of nickel on various carbon supports and their application as electrocatalysts for the oxidation of propargyl alcohol in alkaline medium. In comparison with massive and nanoparticulated nickel electrode systems, Ni-doped nanoporous carbons provided similar propargyl alcohol conversions for very low metallic contents. Nanoparticulated Ni on various carbon supports gave rise to the highest electrocatalytic activity in terms of product selectivity, with a clear dependence on Ni content. The results point to the importance of controlling the dispersion of the Ni phase within the carbon matrix for a full exploitation of the electroactive area of the metal. Additionally, a change in the mechanism of the propargyl alcohol electrooxidation was noted, which seems to be related to the physicochemical properties of the carbon support as well. Thus, the stereoselectivity of the electrooxidative reaction can be controlled by the active nickel content immobilized on the anode, with a preferential oxidation to (Z)-3-(2-propynoxy)-2-propenoic acid with high Ni-loading, and to propiolic acid with low loading of active Ni sites. Moreover, the formation of (E)-3-(2-propynoxy)-2-propenoic acid was discriminatory irrespective of the experimental conditions and Ni loadings on the carbon matrixes.
    Full-text · Article · Jul 2014 · Carbon

  • No preview · Conference Paper · May 2014
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    ABSTRACT: IntroductionOne of the typical problems addressed in electrochemical textbooks is how to define the theoretical kinetic law of an electrochemical reaction and how to propose a plausible mechanism for this reaction from its kinetic parameters, usually the Tafel slope and reaction orders.Most electrochemical reactions consist of at least two electron transfers, and it is usually accepted that their probability of being multiple simultaneous electron transfers is low, i.e., only single-electron transfer reactions are possible (although it seems that a simultaneous two-electron transfer can occur in certain cases). Thus, for an n-electron transfer reaction such as ...
    Full-text · Article · Mar 2014
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    ABSTRACT: The direct electron transfer of cytochrome c has been studied at screen-printed graphite macroelectrodes without recourse to mediators or the need for any electrode pre-treatment as is commonly employed within the literature. A wide range of pH values from 2.0 to 11.0 have been explored upon the electrochemical response of cytochrome c and different voltammetric signatures have been observed. The direct electron transfer of the alkaline transition of cytochrome c was found impeded within alkaline media leading to either an irreversible redox process or even no voltammetric responses. In acidic aqueous media the electrochemical process is observed to undergo a mixed diffusion and adsorption controlled process rather than a purely diffusional process of the native conformation as observed at pH 7.0. Interestingly, at pH 3.5 a new conformational state is revealed in cooperation with the native conformation. The immobilization of the protein was satisfactorily obtained using a simple method by cycling the protein at specific solution pH values allowing amperometric responses to be obtained and gives rise to useful pseudo-peroxidase activity for sensing H2O2. Apparent Michaelis-Menten constant values (Km) were calculated via the Lineweaver-Burk method with deduced values of 25 ± 4, 98 ± 12 and 230 ± 30 mM, respectively for pH values of 2.0, 3.0 and 7.0. Such work is important for those utilising cytochrome c in bio-electrochemical and related applications.
    Full-text · Article · Feb 2014 · The Analyst
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    ABSTRACT: Food industries such as almond industry generate large volumes of wastewater in their processes and common techniques are not always efficient for treating this kind of effluents. In this work, the feasibility of a treatment for pollutants removal of a real industrial wastewater by electrochemical oxidations studied at laboratory scale and then scaled-up to pre-industrial scale. The first stage of the work was performed at laboratory scale, using a 63 cm2 cell, where different anodes (Ti/Pt, and DSA anodes (Ti/RuO2 and Ti/IrO2)) and the optimal experimental conditions (pH, current density, temperature and [Cl−]) were studied and established. By using a DSA-Cl2 anode (Ti/RuO2), pH 9, j = 50 mA cm−2, [Cl−] = 2000 mg L−1 and room temperature, chemical oxygen demand (COD) was removed up to 75% and results show that electrooxidation can remove organic pollutants. In the second stage the scaling-up of the process from laboratory to pre-industrial scale was performed, by using a 3300 cm2 cell. The electrochemical reactor was finally powered by a photovoltaic generator directly connected, in order to operate by using a renewable energy and a COD elimination of 80% was achieved.
    Full-text · Article · Feb 2014 · Separation and Purification Technology
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    ABSTRACT: The pre-pilot scale synthesis of 1-phenylethanol was carried out by the cathodic hydrogenation of acetophenone in a 100 cm2 (geometric area) Polymer Electrolyte Membrane Electrochemical Reactor. The cathode was a Pd/C electrode. Hydrogen oxidation on a gas diffusion electrode was chosen as anodic reaction in order to take advantage of the hydrogen evolved during the reduction. This hydrogen oxidation provides the protons needed for the synthesis. The synthesis performed with only a solid polymer electrolyte, spe, has lower fractional conversion although a higher selectivity than that carried out using a support-electrolyte-solvent together with a spe. However, the difference between these two cases is rather small and since the work-up and purification of the final product are much easier when only a spe is used, this last process was chosen for the pre-pilot electrochemical synthesis of 1-phenylethanol.
    No preview · Article · Sep 2013 · Electrochemistry Communications
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    ABSTRACT: Arylated anthraquinone derivatives of different sizes and different π-basicities have been prepared, and the electrochemical behaviour of these substances has been studied on screen printed graphite electrodes in the three room temperature ionic liquids (RTILs), 1-butyl-3-methylimidazolium hexafluorophosphate ([C4MIM][PF6]), 1-hexyl-3-methylimidazolium hexafluorophosphate ([C6MIM][PF6]) and 1-octyl-3-methylimidazolium hexafluorophosphate ([C8MIM][PF6]). Half redox potentials for the first and second one electron reduction waves were identified, and the diffusion coefficient values were estimated from cyclic voltammetry measurements. The influence of the nature of the RTIL and of the substitution pattern of the anthraquinone on the solvodynamic radii were studied. A correlation of the reductive potentials with the corresponding Hammett constants of the substituents was tested. Copyright © 2013 John Wiley & Sons, Ltd.
    No preview · Article · Apr 2013 · Journal of Physical Organic Chemistry
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    ABSTRACT: The use of a solid polymeric electrolyte, spe, is not commonly found in organic electrosynthesis despite its inherent advantages such as the possible elimination of the electrolyte entailing simpler purification processes, a smaller sized reactor and lower energetic costs. In order to test if it were possible to use a spe in industrial organic electrosynthesis, we studied the synthesis of 1-phenylethanol through the electrochemical hydrogenation of acetophenone using Pd/C 30 wt% with different loadings as cathode and a hydrogen gas diffusion anode. A Polymer Electrolyte Membrane Electrochemical Reactor, PEMER, with a fuel cell structure was chosen to carry out electrochemical reduction with a view to simplifying an industrial scale-up of the electrochemical process. We studied the influence of current density and cathode catalyst loading on this electroorganic synthesis. Selectivity for 1-phenylethanol was around 90% with only ethylbenzene and hydrogen detected as by-products.
    No preview · Article · Feb 2013 · Electrochimica Acta
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    ABSTRACT: In this work carbon supported Pd nanoparticles were prepared and used as electrocatalysts for formic acid electrooxidation fuel cells. The influence of some relevant parameters such as the nominal Pt loading, the Nafion/total solids ratio as well as the Pd loading towards formic acid electrooxidation was evaluated using gold supported catalytic layer electrodes which were prepared using a similar methodology to that employed in the preparation of conventional catalyst coated membranes (CCM). The results obtained show that, for constant Pd loading, the nominal Pd loading and the Nafion percentage on the catalytic layer do not play an important role on the resulting electrocatalytic properties. The main parameter affecting the electrocatalytic activity of the electrodes seems to be the Pd loading, although the resulting activity is not directly proportional to the increased Pd loading. Thus, whereas the Pd loading is multiplied by a factor of 10, the activity is only twice which evidences an important decrease in the Pd utilization. In fact, the results obtained suggest the active layer is the outer one being clearly independent of the catalytic layer thickness. Finally, catalyst coated membranes with Pd catalyst loadings of 0.1, 0.5 and 1.2 mg cm-2 were also tested in a breathing direct formic acid fuel cell.
    No preview · Article · Jan 2013 · International journal of electrochemical science
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    ABSTRACT: We have summarized the state-of-the-art of some important aspects in the electrocatalysis at nanoparticles such as the effect of low-coordination surface sites on their electrocatalytic properties. Moreover, we have extensively summarized most of the contributions already published studying electrocatalysis at single nanoparticles. In the first section of this review, we have analyzed two main types of nanoparticles, those containing high-index facets and those enclosed by low-index planes, but whose electrocatalytic properties are strongly affected by the presence of defect sites, such as steps, kinks and edges. In the case of nanoparticles containing high-index facets, a remarkable increase of their electrocatalytic activity for different reactions of interest has been shown, evidencing its enormous potential as a way to improve the electrocatalysis at nanoparticles. On the other hand, in the case of nanoparticles enclosed by low-index facets, the presence of low-coordination surface sites such as steps, kinks, edges, and defects has been shown to affect and, even in some cases determine (not always), their electrocatalytic properties. Finally, reports of electrocatalysis at single nanoparticles included here mainly cover experiments of single nanoparticles attached to nanoelectrodes and experiments of electrocatalytic amplification by single nanoparticle collision events.
    No preview · Article · Jan 2013

Publication Stats

2k Citations
365.52 Total Impact Points

Institutions

  • 1984-2015
    • University of Alicante
      • • Departamento de Química Física
      • • Facultad de Ciencias
      Alicante, Valencia, Spain