24 results on '"Pablo S. Fernández"'
Search Results
2. Versatile Spectroelectrochemical Cell for In Situ Experiments: Development, Applications, and Electrochemical Behavior**
- Author
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Pablo S. Fernández, Mariana da Rocha Corrêa Silva, José L. Bott-Neto, Ernesto C. Pereira, Santiago J. A. Figueroa, Junior C. Mauricio, Evaldo B. Carneiro-Neto, Marta V. F. Rodrigues, and Gabriel Wosiak
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In situ ,Materials science ,law ,Electrochemistry ,Nanotechnology ,In situ spectroscopy ,Catalysis ,Synchrotron ,law.invention - Published
- 2020
3. Impact of Heating Rates on Alicyclobacillus acidoterrestris Heat Resistance under Non-Isothermal Treatments and Use of Mathematical Modelling to Optimize Orange Juice Processing
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A. Esnoz, Asunción Iguaz, Arantxa Aznar, Pablo S. Fernández, María Ros-Chumillas, Juan-Pablo Huertas, Alfredo Palop, and Alberto Garre
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Health (social science) ,Materials science ,Thermal resistance ,Microorganism ,Food spoilage ,Pasteurization ,Heat resistance ,Plant Science ,TP1-1185 ,Health Professions (miscellaneous) ,Microbiology ,Alicyclobacillus acidoterrestris ,Levensmiddelenmicrobiologie ,Isothermal process ,Article ,Food safety ,law.invention ,03 medical and health sciences ,0404 agricultural biotechnology ,law ,predictive microbiology ,dynamic modeling ,Orange juice ,0303 health sciences ,pasteurization ,Predictive microbiology ,030306 microbiology ,Chemical technology ,fungi ,thermal resistance ,04 agricultural and veterinary sciences ,Pulp and paper industry ,040401 food science ,food safety ,Food Microbiology ,Dynamic modeling ,Food Science - Abstract
Alicyclobacillus acidoterrestris is a spoilage microorganism responsible for relevant product and economic losses in the beverage and juice industry. Spores of this microorganism can survive industrial heat treatments and cause spoilage during posterior storage. Therefore, an effective design of processing treatments requires an accurate understanding of the heat resistance of this microorganism. Considering that industrial treatments are dynamic, this understanding must include how the heat resistance of the microorganism is affected by the heating rate during the heating and cooling phases. The main objective of this study was to establish the effect of heating rates and complex thermal treatments on the inactivation kinetics of A. acidoterrestris. Isothermal experiments between 90 and 105 °C were carried out in a Mastia thermoresistometer, as well as four different dynamic treatments. Although most of the inactivation takes place during the holding phase, our results indicate the relevance of the heating phase for the effectiveness of the treatment. The thermal resistance of A. acidoterrestris is affected by the heating rate during the heating phase. Specifically, higher heating rates resulted in an increased microbial inactivation with respect to the one predicted based on isothermal experiments. These results provide novel information regarding the heat response of this microorganism, which can be valuable for the design of effective heat treatments to improve product safety and stability. Moreover, it highlights the need to incorporate experimental data based on dynamic treatments in process design, as heating rates can have a very significant effect on the thermal resistance of microorganisms.
- Published
- 2021
- Full Text
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4. Standard Underpotential Deposition Shift. A New Parameter to Characterize the UPD Phenomenon
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Gomes Hvn, Rafael A. Vicente, and Pablo S. Fernández
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symbols.namesake ,Materials science ,chemistry ,Field (physics) ,Chemical physics ,symbols ,chemistry.chemical_element ,Deposition (phase transition) ,Nernst equation ,Substrate (electronics) ,Underpotential deposition ,Copper ,Ion - Abstract
Underpotential deposition (UPD) is a phenomenon where atoms of an element M are deposited from ions Mn+ on a substrate S at potentials more positive than for the deposition of Mn+ on M. These systems have been studied for more than a century and are interesting from both the applied and the fundamental point of view. Despite the vast literature on the subject, there is no thermodynamic parameter so far able to characterize an UPD system. Even if the so-called “UPD shift” has been used for decades, the limitations of this parameter has been fully recognized in the field. Herein, using a simple Nernstian treatment and straightforward measurements, we show how to measure and calculate a new proposed fundamental thermodynamic parameter namely, the “Standard UPD potential”. We showed results for the deposition of Cu+2 on Au in acidic media, in solutions containing ClO4- or SO4-2 anions. We obtained Standard UPD potential= 0.65 ± 0.02 V, independently of the concentration of the acid and the nature of the anion.
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- 2021
5. Bragg Coherent Diffraction Imaging for In Situ Studies in Electrocatalysis
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I.T. Neckel, Subramanian K. R. S. Sankaranarayanan, José Solla-Gullón, Pablo S. Fernández, Rafael A. Vicente, Universidad de Alicante. Departamento de Química Física, Universidad de Alicante. Instituto Universitario de Electroquímica, and Electroquímica Aplicada y Electrocatálisis
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Materials science ,General Physics and Astronomy ,Fourth-generation synchrotron ,Nanotechnology ,02 engineering and technology ,Review ,010402 general chemistry ,Electrocatalyst ,01 natural sciences ,Strain ,strain ,In situ experiments ,computational experiments ,Sustainable economy ,fourth-generation synchrotron ,Electrochemistry ,Single-nanoparticle experiments ,electrocatalysis ,single-nanoparticle experiments ,General Materials Science ,Química Física ,Bragg coherent diffraction imaging ,in situ experiments ,General Engineering ,021001 nanoscience & nanotechnology ,Coherent diffraction imaging ,0104 chemical sciences ,X-ray diffraction ,electrochemistry ,0210 nano-technology ,Electrocatalysis ,Computational experiments - Abstract
Electrocatalysis is at the heart of a broad range of physicochemical applications that play an important role in the present and future of a sustainable economy. Among the myriad of different electrocatalysts used in this field, nanomaterials are of ubiquitous importance. An increased surface area/volume ratio compared to bulk makes nanoscale catalysts the preferred choice to perform electrocatalytic reactions. Bragg coherent diffraction imaging (BCDI) was introduced in 2006 and since has been applied to obtain 3D images of crystalline nanomaterials. BCDI provides information about the displacement field, which is directly related to strain. Lattice strain in the catalysts impacts their electronic configuration and, consequently, their binding energy with reaction intermediates. Even though there have been significant improvements since its birth, the fact that the experiments can only be performed at synchrotron facilities and its relatively low resolution to date (∼10 nm spatial resolution) have prevented the popularization of this technique. Herein, we will briefly describe the fundamentals of the technique, including the electrocatalysis relevant information that we can extract from it. Subsequently, we review some of the computational experiments that complement the BCDI data for enhanced information extraction and improved understanding of the underlying nanoscale electrocatalytic processes. We next highlight success stories of BCDI applied to different electrochemical systems and in heterogeneous catalysis to show how the technique can contribute to future studies in electrocatalysis. Finally, we outline current challenges in spatiotemporal resolution limits of BCDI and provide our perspectives on recent developments in synchrotron facilities as well as the role of machine learning and artificial intelligence in addressing them. Financial support from Brazilian agencies: P.S.F. thanks FAPESP (Grants 2017/11986-5, 2018/20952-0, and 2019/13888-6 (RAV fellowship)), CNPq (Grant136436/2019-6 (RAV fellowship)), Shell, and the strategic importance of the support given by ANP (Brazil’s National Oil, Natural Gas and Biofuels Agency) through the R&D levy regulation. Use of the Center for Nanoscale Materials, an Office of Science user facility, was supported by the U.S. Department of Energy (DOE), Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357. This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences Data, Artificial Intelligence and Machine Learning at DOE Scientific User Facilities program under Award No. 34532.
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- 2021
6. Electrooxidation of C-4 polyols on platinum single- crystals: a computational and electrochemical study
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Marc T. M. Koper, Pablo S. Fernández, Victor Y. Yukuhiro, Yuvraj Y. Birdja, José L. Bott-Neto, Cléo T. G. V. M. T. Pires, Carlos C. Lima, Cinthia R. Zanata, Miguel A. San-Miguel, and Gabriela Volpini Soffiati
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Carbon chain ,Chemical substance ,Materials science ,Biomass ,chemistry.chemical_element ,02 engineering and technology ,Reaction intermediate ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Electrochemistry ,01 natural sciences ,0104 chemical sciences ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,General Energy ,chemistry ,Chemical engineering ,Molecule ,Physical and Theoretical Chemistry ,0210 nano-technology ,Science, technology and society ,Platinum - Abstract
Many polyols are abundant and cheap molecules highly spread in the biomass. These molecules have an enormous potential to be used in electrochemical devices to generate energy and/or value-added molecules. The electrooxidation of polyols can produce different substances of interest in the chemical industry concomitantly to high purity hydrogen in electrolyzers. The cost in the production of all these chemicals depends, among other factors, on the develop of more active and selective catalysts. However, in order to search for these materials using computational experiments, it is mandatory to have a better understanding of the fundamental aspect of the reactions, which permit to base the search on the adsorption energies of one or more key reaction intermediates. To contribute to this task, we performed (spectro)-electrochemical and computational experiments to study the electrooxidation of C-4 polyols. We show that the electrooxidation of polyols does not depend on the relative orientation of their OH groups. Besides, using Pt single crystals, we demonstrate that the trend for the oxidation of the primary carbon (relative to the secondary) increases in the order Pt(111) < Pt(100) < Pt(110) and that this result can be extended to polyols with longer carbon chains. Finally, computational experiments permit us to rationalize these trends looking at the relative stability of double dehydrogenated intermediates on the Pt basal planes.
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- 2020
7. Hematite nanorods photoanodes decorated by cobalt hexacyanoferrate: the role of mixed oxidized states on the enhancement of photoelectrochemical performance
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Juliano Alves Bonacin, Ana Flávia Nogueira, Saulo A. Carminati, Bruno Leuzinger da Silva, Claudia Longo, Mauricio A. Melo, Miguel T. Galante, Pablo S. Fernández, and José L. Bott-Neto
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Materials science ,In situ infrared spectroscopy ,Energy Engineering and Power Technology ,Hematite ,Cobalt hexacyanoferrate ,Chemical engineering ,visual_art ,Materials Chemistry ,Electrochemistry ,visual_art.visual_art_medium ,Chemical Engineering (miscellaneous) ,Nanorod ,Electrical and Electronic Engineering ,PROPRIEDADES DOS MATERIAIS ,Science, technology and society - Abstract
In this work, we report on the incorporation of cobalt hexacyanoferrate (Co-NC-Fe) with different iron oxidation states (FeII and FeIII) on hematite (α-Fe2O3) nanorod photoanodes with a systematic ...
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- 2020
8. Mathematical quantification of the induced stress resistance of microbial populations during non-isothermal stresses
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Juan-Pablo Huertas, Arturo Esnoz, Pablo S. Fernández, Alberto Garre, Alfredo Palop, Gerardo A. González-Tejedor, and Jose A. Egea
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0301 basic medicine ,Materials science ,Acclimatization ,Thermal resistance ,030106 microbiology ,Colony Count, Microbial ,Thermodynamics ,Bacterial Physiological Phenomena ,Models, Biological ,Microbiology ,Isothermal process ,03 medical and health sciences ,0404 agricultural biotechnology ,Stress, Physiological ,Phase (matter) ,Escherichia coli ,Microbial Viability ,Estimation theory ,Diagram ,Temperature ,technology, industry, and agriculture ,04 agricultural and veterinary sciences ,General Medicine ,040401 food science ,Microbial inactivation ,Kinetics ,Induced stress ,Food Microbiology ,Constant (mathematics) ,Food Science - Abstract
This contribution presents a mathematical model to describe non-isothermal microbial inactivation processes taking into account the acclimation of the microbial cell to thermal stress. The model extends the log-linear inactivation model including a variable and model parameters quantifying the induced thermal resistance. The model has been tested on cells of Escherichia coli against two families of non-isothermal profiles with different constant heating rates. One of the families was composed of monophasic profiles, consisting of a non-isothermal heating stage from 35 to 70 °C; the other family was composed of biphasic profiles, consisting of a non-isothermal heating stage followed by a holding period at constant temperature of 57.5 °C. Lower heating rates resulted in a higher thermal resistance of the bacterial population. This was reflected in a higher D-value. The parameter estimation was performed in two steps. Firstly, the D and z-values were estimated from the isothermal experiments. Next, the parameters describing the acclimation were estimated using one of the biphasic profiles. This set of parameters was able to describe the remaining experimental data. Finally, a methodology for the construction of diagrams illustrating the magnitude of the induced thermal resistance is presented. The methodology has been illustrated by building it for a biphasic temperature profile with a linear heating phase and a holding phase. This diagram provides a visualization of how the shape of the temperature profile (heating rate and holding temperature) affects the acclimation of the cell to the thermal stress. This diagram can be used for the design of inactivation treatments by industry taking into account the acclimation of the cell to the thermal stress.
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- 2018
9. Probing the surface fine structure through electrochemical oscillations
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Hamilton Varela, Pablo S. Fernández, Germano Tremiliosi-Filho, and B. A. F. Previdello
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In situ ,Surface (mathematics) ,Materials science ,General Physics and Astronomy ,02 engineering and technology ,Low frequency ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Electrochemistry ,01 natural sciences ,0104 chemical sciences ,Catalysis ,Reaction rate ,Adsorption ,Chemical physics ,Electrode ,FÍSICO-QUÍMICA ,Physical and Theoretical Chemistry ,0210 nano-technology - Abstract
In the course of (electro)catalytic reactions, reversible and irreversible changes, namely the formation of adsorbed poisons, catalyst degradation, surface roughening, etc., take place at distinct time-scales. Reading the transformations on the catalyst surface from the measurement of the reaction rates is greatly desirable but generally not feasible. Herein, we study the effect of random surface defects on Pt(100) electrodes toward the electro-oxidation of methanol in acidic media. The surface defects are gently generated in situ and their relative magnitudes are reproducibly controlled. The system was characterized under conventional conditions and investigated under an oscillatory regime. Oscillatory patterns were selected according to the presence of surface defects, and a continuous transition from large amplitude/low frequency oscillations (type L) on smooth surfaces to small amplitude/high frequency oscillations (type S) on disordered surfaces was observed. Importantly, self-organized potential oscillations were found to be much more sensitive to the surface structure than conventional electrochemical signatures or even other in situ characterization methods. As a consequence, we proved the possibility of following the surface fine structure in situ and in a non-invasive manner by monitoring the temporal evolution of oscillatory patterns. From a mechanistic point of view, we describe the role played by surface defects and of the adsorbed and partially oxidized, dissolved species on the oscillations of type S and L.
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- 2018
10. A portable system for photoelectrochemical detection of lactate on TiO2 nanoparticles and [Ni(salen)] polymeric film
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Osvaldo N. Oliveira, Lorenzo A. Buscaglia, Sergio A.S. Machado, Patricia V.B. Santiago, José L. Bott-Neto, Thiago S. Martins, and Pablo S. Fernández
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Detection limit ,chemistry.chemical_classification ,Materials science ,ELETROQUÍMICA ,Inorganic chemistry ,Metals and Alloys ,Infrared spectroscopy ,Polymer ,engineering.material ,Condensed Matter Physics ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,Coating ,Linear range ,chemistry ,Electrode ,Materials Chemistry ,engineering ,Electrical and Electronic Engineering ,Fourier transform infrared spectroscopy ,Selectivity ,Instrumentation - Abstract
In this paper we present a portable photoelectrochemical system developed with screen-printed carbon electrodes (SPCEs) and a 3 W light-emitting diode (LED). The device with 3D printed structure was applied for detecting lactate on TiO2 nanoparticles modified with [Ni(salen)] polymer film (referred to as TiO2@poly[Ni(salen)]). Electrode coating with the polymer increased the sensitivity of the photoelectrochemical sensor, resulting in a linear range from 0.1 to 20 mmol L−1 with a limit of detection (LOD) of 88 μmol L−1. The sensing system exhibited excellent stability, reproducibility, and selectivity. We also demonstrated by in situ Fourier-transform infrared spectroscopy (FTIR) measurements that carbon dioxide (CO2) is the main product from photoelectrooxidation of lactate on TiO2@poly[Ni(salen)]. The portable system can be employed with any type of modified electrodes to function as photoelectroanalytical (bio)sensors, especially for point-of-care diagnostics.
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- 2021
11. Exponential improving in the activity of Pt/C nanoparticles towards glycerol electrooxidation by Sb ad-atoms deposition
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Pablo S. Fernández, Cinthia R. Zanata, Erico Teixeira-Neto, Cauê A. Martins, T.S. Almeida, Giuseppe A. Camara, and Gabriella L. Caneppele
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Materials science ,Process Chemistry and Technology ,Inorganic chemistry ,chemistry.chemical_element ,Nanoparticle ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Electrochemistry ,Platinum nanoparticles ,01 natural sciences ,Catalysis ,Nanomaterial-based catalyst ,0104 chemical sciences ,chemistry ,Antimony ,0210 nano-technology ,Selectivity ,Carbon ,General Environmental Science - Abstract
Tuning the chemical composition of heterogeneous nanocatalysts has emerged as an efficient strategy to improve their electroactivity and selectivity for electrolizers and fuel cells application. The stability of a catalyst is ascribed as the ability of the nanoparticles (NPs) in maintaining their chemical composition and physical structure during recycles of use. By an electrochemical procedure, here we decorated platinum nanoparticles supported on carbon with different coverage degrees of antimony ad-atom (θ Sb ) to investigate glycerol electrooxidation reaction (GEOR). The successful decoration of Pt/C with Sb was monitored by electrochemical and physicochemical characterizations. θ Sb is highly dependent on the upper potential applied. Sb atoms are rapidly leached from Pt surface in potentials greater than 0.7 V in acid solution while they remain stable during several cycles in potentials lower than that. We showed that the current density of GEOR exponentially increases with the increase of Sb coverage, reaching 109 times the pseudo stationary current density of Pt/C for high θ Sb . Furthermore, the ad-atom facilitates the reaction by shifting the onset potential towards lower potentials. We found an improvement of −320 mV in the onset for θ Sb = 0.81.
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- 2017
12. Rh-decorated PtIrO nanoparticles for glycerol electrooxidation: Searching for a stable and active catalyst
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Analía L. Soldati, Pablo S. Fernández, Cauê A. Martins, Richard Landers, Adriana Evaristo de Carvalho, Cinthia R. Zanata, Horacio Esteban Troiani, and Giuseppe A. Camara
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Materials science ,Process Chemistry and Technology ,Inorganic chemistry ,chemistry.chemical_element ,Nanoparticle ,02 engineering and technology ,Chronoamperometry ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Platinum nanoparticles ,01 natural sciences ,Catalysis ,0104 chemical sciences ,Rhodium ,chemistry ,Iridium ,Cyclic voltammetry ,0210 nano-technology ,Platinum ,General Environmental Science ,Nuclear chemistry - Abstract
We report a fast method of producing rhodium-decorated platinum nanoparticles (NPs) containing iridium oxides (IrOx) to be used in the glycerol electrooxidation reaction. We synthesize PtIrOx/C electrocatalysts of different atomic compositions dispersed on Carbon Vulcan XC-72R® by using the fast polyol method assisted by microwaves. Afterwards, PtIrOx/C was potentiodynamically decorated by Rh (Rh/PtIrOx/C). The NPs are characterized by energy dispersive X-ray analysis, X-ray diffraction, X-ray photoelectron spectroscopy and transmission electron microscopy. The electrooxidation of glycerol was investigated in acid medium by cyclic voltammetry and chronoamperometry. The electrochemical stability of Rh/PtIrOx/C NPs was evaluated by following a degradation test protocol, which consists in exhaustive cyclic voltammetries. Our results show that the presence of iridium oxides in the architecture of platinum enhances the electrochemical stability of the catalyst by avoiding agglomeration effects. Moreover, the presence of rhodium catalyzes the glycerol electrooxidation reaction. These results help understanding the role of Rh and IrOx in the glycerol electrooxidation and provide new insights for designing nanomaterials with improved stability and activity.
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- 2016
13. Front Cover: Versatile Spectroelectrochemical Cell for In Situ Experiments: Development, Applications, and Electrochemical Behavior (ChemElectroChem 21/2020)
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Mariana da Rocha Corrêa Silva, Evaldo B. Carneiro-Neto, Santiago J. A. Figueroa, Marta V. F. Rodrigues, Gabriel Wosiak, Ernesto C. Pereira, Junior C. Mauricio, Pablo S. Fernández, and José L. Bott-Neto
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In situ ,Materials science ,Front cover ,law ,Electrochemistry ,Nanotechnology ,In situ spectroscopy ,Catalysis ,Synchrotron ,law.invention - Published
- 2020
14. Adatom decorated shape-controlled metal nanoparticles: advanced electrocatalysts for energy conversion
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Pablo S. Fernández, José Solla-Gullón, Matheus Souza, Universidad de Alicante. Instituto Universitario de Electroquímica, and Electroquímica Aplicada y Electrocatálisis
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Materials science ,Metal nanoparticles ,Nanotechnology ,02 engineering and technology ,Shape-controlled ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Electrocatalyst ,01 natural sciences ,0104 chemical sciences ,Analytical Chemistry ,Adatoms ,Electrochemistry ,Energy transformation ,Química Física ,0210 nano-technology ,Electrocatalysis - Abstract
The use of adatom decorated shape-controlled metal nanoparticles in electrocatalysis, and particularly for energy conversion reactions, has made important contributions to the development of better electrocatalysts. In this short review, we highlight some of the most relevant findings and discuss about future challenges. J.S-G and P.S.F. acknowledges financial support from FAPESP (Process numbers 2017/09780-0 and 2016/01365-0). J.S-G. also acknowledges financial support from VITC (Vicerrectorado de Investigación y Transferencia de Conocimiento) of the University of Alicante (UATALENTO16-02). M.B.C.S acknowledges CAPES for his fellowship.
- Published
- 2018
15. The electrooxidation of glycerol on Ag nanoparticles decorated with ultra-low Pt quantities
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Pablo S. Fernández, Fernando Bonin Okasaki, Érico T.neto, Cléo T. G. V. M. T. Pires, and Carlos C. Lima
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chemistry.chemical_compound ,Materials science ,Chemical engineering ,chemistry ,Glycerol ,Ag nanoparticles - Published
- 2017
16. A Novel Technique for Sterilization Using a Power Self-Regulated Single-Mode Microwave Cavity
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Alejandro Díaz-Morcillo, Paula M. Periago, Pablo S. Fernández, Antonio Jose Lozano-Guerrero, J.L. Pedreno-Molina, Juan D. Reverte-Ors, and Ministerio de Economía y Competitividad
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Novel technique ,Materials science ,Microbiological food safety ,microbiological food safety ,Microwave oven ,animal by-products ,Organoleptic ,02 engineering and technology ,lcsh:Chemical technology ,Biochemistry ,Article ,Analytical Chemistry ,0404 agricultural biotechnology ,Power and temperature control ,biosensors ,microwave cavity ,power and temperature control ,sterilization ,0202 electrical engineering, electronic engineering, information engineering ,lcsh:TP1-1185 ,Electrical and Electronic Engineering ,Process engineering ,Instrumentation ,Microwave cavity ,Teoría de la Señal y las Comunicaciones ,Animal by-products ,3309.25 Esterilización de Alimentos ,business.industry ,Single-mode optical fiber ,Sterilization ,020206 networking & telecommunications ,04 agricultural and veterinary sciences ,Sterilization (microbiology) ,040401 food science ,Atomic and Molecular Physics, and Optics ,Biosensors ,business ,Microwave ,Biomedical engineering ,Power control - Abstract
In this paper, a novel technique to achieve precise temperatures in food sterilization has been proposed. An accurate temperature profile is needed in order to reach a commitment between the total removal of pathogens inside the product and the preservation of nutritional and organoleptic characteristics. The minimal variation of the target temperature in the sample by means of a monitoring and control software platform, allowing temperature stabilization over 100 °C, is the main goal of this work. A cylindrical microwave oven, under pressure conditions and continuous control of the microwave supply power as function of the final temperature inside the sample, has been designed and developed with conditions of single-mode resonance. The uniform heating in the product is achieved by means of sample movement and the self-regulated power control using the measured temperature. Finally, for testing the sterilization of food with this technology, specific biological validation based on Bacillus cereus as a biosensor of heat inactivation has been incorporated as a distribution along the sample in the experimental process to measure the colony-forming units (CFUs) for different food samples (laboratory medium, soup, or fish-based animal by-products). The obtained results allow the validation of this new technology for food sterilization with precise control of the microwave system to ensure the uniform elimination of pathogens using high temperatures. This work was supported by the Ministerio de Economía y Competitividad under the project with reference DPI2014-61857-EXP.
- Published
- 2017
17. Glycerol Electrooxidation on Platinum-Tin Electrodeposited Films: Inducing Changes in Surface Composition by Cyclic Voltammetry
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Giuseppe A. Camara, Pablo S. Fernández, María Elisa Martins, and Gisele A.B. Mello
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Materials science ,SURFACE COMPOSITION CHANGE ,Stripping (chemistry) ,Tunable composition ,Inorganic chemistry ,chemistry.chemical_element ,02 engineering and technology ,010402 general chemistry ,Electrochemistry ,Platinum-tin ,TUNABLE COMPOSITION ,01 natural sciences ,Catalysis ,chemistry.chemical_compound ,X-ray photoelectron spectroscopy ,ELECTRODEPOSITS ,Glycerol ,Electrodeposits ,Otras Ciencias Químicas ,Ciencias Químicas ,Química ,021001 nanoscience & nanotechnology ,PLATINUM-TIN ,0104 chemical sciences ,chemistry ,Surface composition change ,Glycerol electrooxidation ,GLYCEROL ELECTROOXIDATION ,Cyclic voltammetry ,0210 nano-technology ,Tin ,Platinum ,CIENCIAS NATURALES Y EXACTAS - Abstract
In this work, PtSn binary electrodeposits were prepared in three compositions and submitted to successive voltammetric cycles in presence of glycerol (1.0 mol L−1) in acidic media. Catalysts were characterized by energy dispersive X-ray analysis and X-ray photoelectron spectroscopy before and after the cycles being performed, in order to check eventual changes in their compositions during the process. Spectroscopic results show that surface compositions are sensibly richer in Sn than their bulk counterparts. Overall, PtSn catalysts show a poor initial catalytic activity toward glycerol electrooxidation. However, as the cycles succeed, the voltammetric responses increasingly resemble that of Pt, while the oxidation currents increase. Results are rationalized in terms of a continuous enrichment of the surface by Pt at the expenses of a loss of Sn. Moreover, when the electrochemical surface area (ECSA) is estimated by stripping of CO, it becomes evident that electrooxidation currents remain growing, even when the ECSA is decreased, which makes the gain in catalytic activity particularly relevant. Ultimately, from a broader perspective, our results suggest that catalytic surfaces with tunable features (such as surface composition and catalytic response) can be obtained by the application of easily executable electrochemical protocols., Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas
- Published
- 2017
18. Remarkable electrochemical stability of one-step synthesized Pd nanoparticles supported on graphene and multi-walled carbon nanotubes
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Horacio Esteban Troiani, Gilberto Maia, María Elisa Martins, Ana Arenillas, Pablo S. Fernández, Cauê A. Martins, Giuseppe A. Camara, and Fábio de Lima
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Nanotecnología ,Materials science ,Renewable Energy, Sustainability and the Environment ,Graphene ,graphene ,chemistry.chemical_element ,Nanotechnology ,Context (language use) ,INGENIERÍAS Y TECNOLOGÍAS ,Carbon black ,Carbon nanotube ,Nano-materiales ,Electrochemistry ,Catalysis ,law.invention ,chemistry.chemical_compound ,Pd nanoparticles ,chemistry ,law ,General Materials Science ,Electrical and Electronic Engineering ,C nanotubes ,Carbon ,Ethylene glycol ,potential cycling - Abstract
Anodes and cathodes of fuel cells are usually composed of metallic nanoparticles (NPs) dispersed on carbon, in order to increase their active area. Since the degradation of the catalyst affects the performance of the fuel cells, understanding the stability of its components is pivotal to make these systems more reliable. As such, graphene sheets and carbon nanotubes have been employed as alternative supports to improve the stability of anodes in fuel cells. In this context, we have used polyvinylpyrrolidone (PVP) combined with a one-step chemical reduction induced by ethylene glycol to synthesize Pd NPs dispersed on chemically converted graphene (CCG). We compared the electrochemical stability of Pd NPs supported on carbon black (C), multi-walled carbon nanotubes (MWCNTs) and CCG. MWCNTs and CCG make Pd NPs electrochemically more stable than carbon black. Pd/CCG catalysts are more stable than Pd/MWCNTs during the first potential cycles, while Pd/MWCNTs showed a higher long-term stability. These results allow us to consider a competition between agglomeration of NPs and degradation of the support, where the agglomeration seems to be limited by the available surface area of the support. Fil: Martins, Cauê A.. Universidade Federal do Mato Grosso do Sul; Brasil. Universidade Federal da Grande Dourados; Brasil Fil: Fernández, Pablo Sebastián. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas; Argentina Fil: De Lima, Fabio. Universidade Federal do Mato Grosso do Sul; Brasil Fil: Troiani, Horacio Esteban. Comisión Nacional de Energía Atómica. Gerencia del Area de Investigación y Aplicaciones No Nucleares. Gerencia de Física (Centro Atómico Bariloche); Argentina Fil: Martins, María Elisa. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas; Argentina Fil: Arenillas de la Puente, Ana. Instituto Nacional del Carbón; España. Consejo Superior de Investigaciones Científicas; España Fil: Gilberto, Maia. Universidade Federal do Mato Grosso do Sul; Brasil Fil: Camara, Giuseppe A.. Universidade Federal do Mato Grosso do Sul; Brasil
- Published
- 2014
19. Platinum nanoparticles produced by EG/PVP method: The effect of cleaning on the electro-oxidation of glycerol
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Pablo S. Fernández, Giuseppe A. Camara, Cauê A. Martins, Dênis S. Ferreira, Horacio Esteban Troiani, and María Elisa Martins
- Subjects
Materials science ,Físico-Química, Ciencia de los Polímeros, Electroquímica ,General Chemical Engineering ,GLYCEROL ELECTRO-OXIDATION REACTION ,Ciencias Químicas ,chemistry.chemical_element ,Nanotechnology ,Platinum nanoparticles ,Electrochemistry ,ETHYLENE GLYCOL SYNTHESIS ,Catalysis ,chemistry.chemical_compound ,chemistry ,Chemical engineering ,Pulmonary surfactant ,Impurity ,SURFACTANT REMOVAL ,Glycerol ,PLATINUM NANOPARTICLES ,Carbon ,Dissolution ,CIENCIAS NATURALES Y EXACTAS - Abstract
Carbon supported Pt nanoparticles (NPs) have been prepared through polyols method using PVP. As observed with a large number of surfactants employed in NPs synthesis, it is very difficult to attain an efficient NPs cleaning, which is a fundamental requirement in catalysis researches. The aim of this paper was to obtain clean NPs, beginning by using “soft” methods, in order to keep unaltered both the NPs size and shape; however, an important surfactant remnant was observed. Consequently, it was performed an electrochemical cleaning through PVP and glycolate electro-oxidation, being accompanied with important perturbations of NPs atoms and dissolution and re-deposition of Pt. Finally, the performance of the catalyst towards the glycerol electro-oxidation reaction (GER), before and after the cleaning process was studied. In addition, we demonstrate how the impurities bring about poor reproducibility in this kind of experiments due to the fact that the cleaning process is occurring at the same time that the GER and because cleaning extent along cycles varies for each independent experiment. Fil: Fernández, Pablo Sebastián. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico la Plata. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas; Argentina. Universidad Nacional de La Plata; Argentina Fil: Ferreira, Dênis S.. Universidade Federal Do Mato Grosso Do Sul; Brasil Fil: Martins, Cauê A.. Universidade Federal Do Mato Grosso Do Sul; Brasil Fil: Troiani, Horacio Esteban. Comisión Nacional de Energía Atómica. Gerencia del Area de Investigación y Aplicaciones No Nucleares. Gerencia de Física (Centro Atómico Bariloche); Argentina Fil: Câmara, Giuseppe A.. Universidade Federal Do Mato Grosso Do Sul; Brasil Fil: Martins, María Elisa. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico la Plata. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas; Argentina. Universidad Nacional de La Plata; Argentina
- Published
- 2013
20. Electrochemical study of glycerol oxidation on gold surfaces covered by metallic monolayers
- Author
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Cléo Thomás Gabriel Vilela Menegaz Teixeira Pires, Matheus De Morais Guide, Matheus Souza, and Pablo S. Fernández
- Subjects
Metal ,chemistry.chemical_compound ,Materials science ,chemistry ,visual_art ,Monolayer ,visual_art.visual_art_medium ,Glycerol ,Nanotechnology ,Electrochemistry - Published
- 2016
21. Electrochemical behavior and capacitance properties of carbon xerogel/multiwalled carbon nanotubes composites
- Author
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María Elisa Martins, Arnaldo Visintin, Élida Beatriz Castro, Angel J. Menéndez, E.G. Calvo, Ana Arenillas, Pablo S. Fernández, Silvia Real, and Emilio J. Juarez-Perez
- Subjects
Nanotube ,Materials science ,Carbon nanofiber ,chemistry.chemical_element ,Carbon nanotube ,Condensed Matter Physics ,law.invention ,Dielectric spectroscopy ,Potential applications of carbon nanotubes ,chemistry ,law ,Frit compression ,Electrochemistry ,General Materials Science ,Electrical and Electronic Engineering ,Cyclic voltammetry ,Composite material ,Carbon - Abstract
The electrochemical behavior of carbon xerogel/multiwalled carbon nanotubes composite in a 6 M KOH solution has been investigated. Three different mixtures of teflonized carbons with varying nanotube content were prepared. The electrodes containing multiwalled carbon nanotubes were found to provide enhanced capacities compared with those prepared with only carbon xerogel. Cyclic voltammetry and charge–discharge experiments reveal the presence of a strong resistive component, which decreases as the amount of nanotubes increases. Electrochemical impedance spectroscopy results analyzed in terms of an adequate physicochemical model of the porous electrode, show that an increasing amount of nanotubes enhances both the effective solid-phase conductivity and the effective liquid-phase conductivity, linked to the porosity of the electrodes.
- Published
- 2011
22. Single walled carbon nanotubes as supports for metal hydride electrodes
- Author
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E.B. Castro, María Elisa Martins, Pablo S. Fernández, S.G. Real, Arnaldo Visintin, and Alejandro N. Filippin
- Subjects
Materials science ,Hydrogen ,Renewable Energy, Sustainability and the Environment ,Hydride ,Energy Engineering and Power Technology ,chemistry.chemical_element ,Nanotechnology ,Carbon nanotube ,Condensed Matter Physics ,Electrochemistry ,law.invention ,Dielectric spectroscopy ,Hydrogen storage ,Fuel Technology ,chemistry ,Chemical engineering ,law ,Cyclic voltammetry ,Carbon - Abstract
The electrochemical generation and the storage of hydrogen employing metal hydrides has become a good alternative attending the requirement to search for new sources of clean energy. This work is devoted to study the hydrogen storage as hydrides in an AB 5 -type metal alloy (MmNi 4.1 Co 0.4 Mn 0.4 Al 0.5 ). The behaviour of the alloy containing electrode was evaluated employing several electrodes containing the alloy and diverse carbons. Carbons were prepared by using Single Walled Carbon Nanotubes (SWCNT) with different PTFE percentages (15%, 25% y 33%) and Carbon Vulcan XC72® with 33% of PTFE (VT). Several electrochemical techniques as Cyclic Voltammetry (CV), Charge–Discharge cycles and Electrochemical Impedance Spectroscopy (EIS) were used. Results demonstrate that at low discharge currents, electrodes containing SWCNT exhibit better hydrogen storage than Vulcan XC72® containing electrodes. Studies made with carbon supports only show that this little but not disregarded differences are related to different hydrogen sorption behaviour of SWCNT and Vulcan XC72®. From the kinetic point of view, Vulcan XC72® containing electrodes have a better behaviour than those prepared with SWCNT. On the other hand, the optimal percentage of PTFE for SWCNT was determined to be 25%.
- Published
- 2010
23. Obtaining Clean and Well-dispersed Pt NPs with a Microwave-assisted Method
- Author
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L. de Oliveira, Víctor Rolando Roberto Armendáriz, María Elisa Martins, Horacio Esteban Troiani, Pablo S. Fernández, Jusinei Meireles Stropa, Cauê A. Martins, and Giuseppe A. Camara
- Subjects
Nanotecnología ,Materials science ,CO probe ,agglomeration ,Active surface area ,Nanotechnology ,Química ,surface area ,INGENIERÍAS Y TECNOLOGÍAS ,Electrochemistry ,Platinum nanoparticles ,Nano-materiales ,Microwave assisted ,Catalysis ,Microwave-assisted synthesis ,Impurity ,Cleaning process ,Fuel cells ,Agglomeration of nanoparticles ,Dispersion (chemistry) ,platinum nanoparticles - Abstract
Carbon-supported platinum nanoparticles Pt/C (NPs) are used in many fields of science. These kinds of materials have been extensively studied in electrochemistry due to the fact that they are applied in fuel cell technology. Although there are a myriad of methods for Pt NP synthesis, the need for obtaining Pt/C NPs with a good dispersion (covering over the entire support), a narrow size distribution, and clean surface (among other parameters) is far to be overcome. On this sense herein we describe a very easy and quick method of synthesis of highly dispersed Pt NPs followed by a simple electrochemical cleaning step. The catalysts were electrochemically characterized by studying their behavior in 0.5 M H2SO4 and also by using CO as a probe during the CO electro-oxidation reaction (COEOR). This paper shows how to obtain highly dispersed and clean Pt/C NPs that produce very reproducible results. Besides, we demonstrate how the presence of impurities negatively affects the electrochemical reproducibility of Pt NPs with a clear impact on their catalytic activity., Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas
- Published
- 2014
24. Nonisothermal heat resistance determinations with the thermoresistometer Mastia
- Author
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Alfredo Palop, Raquel Conesa, S. Andreu, A. Esnoz, and Pablo S. Fernández
- Subjects
Orange juice ,Materials science ,Hot Temperature ,Alicyclobacillus ,technology, industry, and agriculture ,Food preservation ,Colony Count, Microbial ,Thermodynamics ,Sterilization ,Heat resistance ,General Medicine ,Sterilization (microbiology) ,Applied Microbiology and Biotechnology ,Alicyclobacillus acidoterrestris ,Adaptation, Physiological ,Isothermal process ,Microbiology ,Culture Media ,Slow heating ,Food Preservation ,Escherichia coli ,Food Microbiology ,Biotechnology - Abstract
Aims: To design and build a thermoresistometer, named Mastia, which could perform isothermal and nonisothermal experiments. Methods and Results: In order to evaluate the thermoresistometer, the heat resistance of Escherichia coli vegetative cells and Alicyclobacillus acidoterrestris spores was explored. Isothermal heat resistance of E. coli was characterized by D60� C =0 AE38 min and z= 4AE7� C in pH 7 buffer. When the vegetative cells were exposed to nonisothermal conditions, their heat resistance was largely increased at slow heating and fast cooling rates. Isothermal heat resistance of A. acidoterrestris was characterized by D95� C =7 AE4 min and z= 9AE5� C in orange juice. Under nonisothermal conditions, inactivation was reasonably well predicted from isothermal data. Conclusions: The thermoresistometer Mastia is a very suitable instrument to get heat resistance data of micro-organisms under isothermal and nonisothermal treatments. Significance and Impact of the Study: The thermoresistometer Mastia can be a helpful tool for food processors in order to estimate the level of safety of the treatments they apply.
- Published
- 2009
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