Papers by Raúl Procaccini
Surface and Coatings Technology, 2011
... Development of silver nanoparticles in coatings, as a function of pyridine/silver ratio and t... more ... Development of silver nanoparticles in coatings, as a function of pyridine/silver ratio and thermal treatment, was analyzed through Small Angle X-ray Scattering (SAXS) using the beam lines SAXS1 and SAXS2 of the National Laboratory of Synchrotron Light (LNLS, Campinas ...
Journal of Applied Electrochemistry, 2006
Surface oxides grown on copper and copper–nickel alloys (UNS 72000 and UNS 70600) in aerated bora... more Surface oxides grown on copper and copper–nickel alloys (UNS 72000 and UNS 70600) in aerated borax-borate buffer solution of pH 7.7 were characterized using various experimental techniques. Their influence on the mechanism of oxygen reduction was also investigated. The composition of the passive films formed in situ on the different materials was studied using differential reflectance spectroscopy. Electrochemical techniques such as voltammetry and potentiodynamic reductions, as well as hydrodynamic tools such as the rotating disk electrode were used to characterize the kinetic parameters of the oxygen reduction reaction. The results show that the addition of Ni to Cu to form copper–nickel alloys changes the composition of the surface film. As the amount of Ni in the alloy increases, the proportion of Cu(I) compounds decreases, and Ni(II) compounds are incorporated into the film structure. The films anodically grown at 0.5 V on Cu70Ni30 tend to be thinner but more resistive. This is supported by results from reflectance and impedance spectroscopy. The kinetics of oxygen reduction follows a four-electron path on surface-free films, independently of the Ni-content in the alloy.
Journal of Applied Electrochemistry, 2008
ABSTRACT The reduction of oxygen on brass type Cu77Zn21Al2 in contact with 0.1molL−1 borax at pH ... more ABSTRACT The reduction of oxygen on brass type Cu77Zn21Al2 in contact with 0.1molL−1 borax at pH 9.2 with and without chlorides was investigated and compared with the results on spectroscopic Cu. The surface film was characterized in situ by means of reflectance spectroscopy and by electrochemical impedance in the potential range negative to the open circuit potential. The main parameters associated to the kinetics of the oxygen reduction reaction were analyzed with a rotating disc electrode. The results show that within the potentials studied, a porous film was formed on brass while no significant spectral features were observed, except at −1.2V where zinc oxo-hydroxides grow in chloride-free solutions and dissolve when chlorides are present in the system. The number of electrons exchanged for brass was close to 4 in both solutions, showing that oxygen is predominantly reduced to hydroxyl ions, with a reaction order equal to one. The residual presence of oxides on the surface results in Koutecky–Levich plots with slopes dependent on the applied potential and interfere with the calculation of the Tafel slope.
Electrochimica Acta, 2009
Surface oxide films were grown on 99.99% copper and brass (copper-zinc alloy, Cu77Zn21Al2) in 0.1... more Surface oxide films were grown on 99.99% copper and brass (copper-zinc alloy, Cu77Zn21Al2) in 0.1 mol L −1 borax solution at open circuit potential and were characterized using various experimental techniques. The composition of the passive films formed in situ on the different materials was studied using differential reflectance spectroscopy. The thickness of the oxide layers on copper and brass was compared by chronopotentiometric curves and potentiodynamic reductions. The electrical properties of each oxide were analyzed by means of electrochemical impedance spectroscopy. Their influence on the oxygen reduction reaction was also investigated using voltammetry hydrodynamic tools such as the rotating disk electrode. The results show that the incorporation of Zn to Cu in brass changes the composition and the thickness of the surface film. The films grown on brass tend to be thicker but less resistive and Zn compounds incorporate to the film. This is supported by results from reflectance and impedance spectroscopy. The kinetics of oxygen reduction is strongly inhibited on oxidized electrodes, particularly in the case of brass. The global number of exchanged electrons remains close to four and seems to be independent of the presence of surface oxides.
Applied Surface Science, 2013
The corrosion resistance of Cu-Zn alloys strongly depends on the quality of the protective passiv... more The corrosion resistance of Cu-Zn alloys strongly depends on the quality of the protective passive film. This study focuses on the influence of Zn on the composition of oxide films on copper and brass (Cu77Zn21Al2) in borax 0.1 mol L −1 (pH 9.2) solution, where the solubility of copper oxides is minimal. The effect of the presence of chloride ions at low concentration (0.01 mol L −1) in the electrolyte was also evaluated. Both conditions were studied using a set of different electrochemical, optical and surface techniques such as cyclic voltammetry, differential reflectance, X-ray photoelectron spectroscopy and Raman spectroscopy. A duplex Cu 2 O/CuO layer forms on copper at potentials positive to the open circuit potential (OCP), while in the case of brass, zinc compounds are also incorporated to the surface film. It also became evident that a surface film can be formed on these materials even at potentials negative to the OCP. Zn(II) species are the main constituents of the films growing on brass, while copper oxides are incorporated to the surface film when approaching the OCP. The presence of chloride ions at low concentrations contributes to the dissolution of the oxo-hydroxides formed during the early stages of the aging process at open circuit potential. Also, copper chloro-compounds are formed, as shown by Raman spectroscopy for both copper and brass electrodes.
Surface and Coatings Technology, 2014
In this work, the effect of silver doping on the organic-inorganic hybrid structure of sol-gel co... more In this work, the effect of silver doping on the organic-inorganic hybrid structure of sol-gel coatings and its performance as bactericidal materials was analyzed. Coatings were synthesized through the hydrolytic condensation of tetraethoxysilane (TEOS) and methyltriethoxysilane (MTES); silver nitrate was used as a source of Ag + ions. The structural analysis, performed through Small Angle X-ray Scattering (SAXS) with synchrotron light, Fourier Transformed Infrared (FTIR) and UV-visible spectroscopies, revealed the complex scenario developed as the network crosslinking rises during the thermal treatment. The matrix structure works as a size-selective membrane where only the smaller silver clusters and ions are released to the surface while the higher nanoparticles remain trapped inside. Finally, bacteriologic analysis, performed with E.coli cultures, confirmed a tight correlation between silver lixiviation and the inhibition halos observed in agar diffusion tests.
Surface and Coatings Technology, 2022
Journal of Environmental Management, 2020
In this study, we prepared Ti 4 O 7 porous electrodes with continuous layered structures characte... more In this study, we prepared Ti 4 O 7 porous electrodes with continuous layered structures characterized by different layer-to-layer distance (from 2 to 10 μm) but the same total void fraction (88-90%), to modulate the electrodes' permeability and the volumetric electrochemical surface area (from 90 to 840 cm 2 cm À 3). These platforms were evaluated as anodes in the electro-oxidation (EO) of bentazon in a three-electrode cell under galvanostatic conditions, operated both in traditional batch (TB) or batch recycle flow-through (BRFT) modes. The performance was significantly enhanced when the liquid was recirculated through the lamellar structure of the electrodes. In BRFT mode, the electrode interlayer gap was found to be a key factor to control the bentazon and total organic carbon (TOC) conversions. For the best conditions evaluated (BRFT, 10 μm-interlayered Ti 4 O 7 electrodes with a volumetric surface area of 90 cm 2 cm À 3), the effect of the applied current (1 or 3 mA) and liquid flow rate (10, 12 or 14 mL. min À 1) was investigated. Specific energy consumption (SEC) values were estimated to reveal the performance of each of the EO treatments from an energetic point of view. The use of 10 μm-interlayered Ti 4 O 7 electrodes at 1 mA in BRFT mode at a flow rate of 14 mL min À 1 showed the best results, yielding 85% bentazon removal, 57% mineralization and SEC values of 0.006 kWh.g TOC À 1 after 6 h of treatment. This contribution highlights the use of layered Ti 4 O 7 electrodes as a promising strategy for intensifying EO processes, pointing to a trade-off between the accessibility to the internal electrode structure and the volumetric electrode surface area to enhance the contact between the target molecules and the hydroxyl radicals physisorbed on the electrode surface, while minimizing simultaneously the energy requirements.
Clinical Oral Investigations, 2019
Objectives It is widely accepted that current tooth whitening treatment effect is based on the ox... more Objectives It is widely accepted that current tooth whitening treatment effect is based on the oxidizing action of peroxides, even if the mechanism of action remains still unclear. Treatments are claimed to be safe, but several secondary effects have been described, since long application times and high concentrations are needed. A faster whitening ingredient which permits the use of lower concentrations and shorter application times could potentially overcome this problem. In this work, a different approach based on a reducing agent, sodium metabisulfite (MBS), is explored. Materials and methods The reaction between tannic acid (TA) with carbamide peroxide (CP), MBS, and potassium persulfate (PS), as an oxidizing agent, was monitored for 48 hours by measuring its absorbance, comparing their different whitening effects. The reduction process between TA and MBS was confirmed by cyclic voltammetry. An in vitro test was used to observe if MBS whitens also stained teeth. Results It is shown that MBS bleaching effect is faster and higher than CP's effect over time. PS produced a darkening effect after the 3rd hour because of the strong absorbance of the oxidation metabolite. Cyclic voltammetry showed a progressive increase in the intensity of the TA anodic peak when MBS was present, demonstrating that a reduction is taking place. In vitro, MBS showed a faster whitening performance than CP, using lower concentrations. Conclusions Using a TA solution as a staining model, it was possible to show that MBS has a visible bleaching effect through a reduction reaction, faster than CP, both in solution and in vitro. Low concentrations of MBS are effective in whitening. Clinical significance This work shows MBS as a promising candidate to develop novel whitening treatments, which is acting by reducing mechanism instead of oxidation.
Natural Product Communications, 2012
The electrochemical properties of gadusol, a metabolite extracted from fish roes, were determined... more The electrochemical properties of gadusol, a metabolite extracted from fish roes, were determined for the first time by cyclic- and square-wave voltammetries on a glassy carbon electrode in buffered aqueous solutions. The aims of the work were characterization of the redox behavior and assessment of the mechanism underlying the antioxidant capacity of the compound. Anodic waves with peak potentials of 710 ± 5 mV and 601 ± 9 mV vs. Ag/AgCl were obtained for gadusol and its anion gadusolate, respectively. The voltammograms point to the irreversible nature of the oxidation process and reveal better antioxidant properties for the compound under physiological pH, with a moderate reductive power, but improved stability under atmospheric oxidation in comparison with other natural antioxidants such as ascorbic acid. The presence of direct ionic micelles prepared with sodium dodecyl-sulfate or cetyl-trimethyl-ammonium chloride yielded no significant differences regarding homogeneous medium i...
Organic Electronics, 2014
Recently, unusual charge transfer properties of two triarylamines bridged through an aliphatic br... more Recently, unusual charge transfer properties of two triarylamines bridged through an aliphatic bridge (Tröger base) have been reported. The donor/acceptor couple was shown to have an important electronic coupling between its centers for the hole transfer, although in the absence of a π linker. In contrast, we here show, by combining first principles calculations with experimental studies, that the bridge has a practically null role in coupling the electron transfer. This sharp contrast might present an interesting potential in the design of molecular devices.Fil: Ramirez, Cristina Lujan. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales. Departamento de Química; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Procaccini, Raul Ariel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; ArgentinaFil: Chesta, Carlos Alberto. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas Fisicoquímicas y Naturales. Departamento de Química; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Parise, Alejandro Ruben. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales. Departamento de Química; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Vera, Domingo Mariano Adolfo. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales. Departamento de Química; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin
Journal of Sol-Gel Science and Technology, 2018
A synthetic exfoliated nanoclay smectite type, Laponite® S482, was incorporated as a functionaliz... more A synthetic exfoliated nanoclay smectite type, Laponite® S482, was incorporated as a functionalized load in a silica hybrid matrix synthesized by the sol-gel route. The previous functionalization was carried out through a "grafting" reaction with (3glycidoxypropyl)trimethoxysilane (GPTMS) assisted by ultrasonic dispersion. The precursor sols were synthesized by acid-catalyzed hydrolytic condensation between tetraethoxysilane (TEOS) and functionalized GPTMS, a silver ions source was added in order to obtain a coating material with controlled silver releasing properties. Coatings were obtained by "dip-coating" on different substrates. Structural characterization of the coatings was conducted by SAXS and SEM-EDS, the results revealed a complex silica matrix with intercalated nanoclays, an organic fraction and a homogeneous content of Ag+. The electrochemical characterization was realized by EIS tests on stainless steel coated substrates AISI 316L type; the results showed good barriers properties and a high integrity of the coatings loaded with nanoclay. The evolution of the release of Ag+ ions was studied by XRF, through exposing the coatings to a leaching process at steady state and determining the residual content of Ag within the coat at different immersion times. It was found that the addition of 1.5 wt. % of clay, in respect to condensed silica, decreased the initial diffusion rate of Ag+ ions at near the half part, allowing its potential use in the development of antibacterial coatings with longer terms of life. Response to Reviewers: COMMENTS FOR THE AUTHOR: Reviewer #1: A silver-laponite hybrid was synthesized and the silver release from such porous structure was studied. The subject is potentially interesting. But there are some points which should be addressed in the manuscript before any consideration. I suggest major revision of the manuscript based on the following comments: 1.The SEM image of silver samples shown in Figure 5a presents some surface cubic
Colloids and Surfaces A: Physicochemical and Engineering Aspects
This article shows how pine sawdust residues can be used to adsorb nickel ions from synthetic sol... more This article shows how pine sawdust residues can be used to adsorb nickel ions from synthetic solutions and then to produce porous bricks for civil construction using a mixture of natural clay and biomass containing the adsorbed metals. The adsorption tests were performed by mixing NiCl2 solutions with pine sawdust during a fixed stirring period of 24 h. The set was filtered and the filtrate was analysed. Highest efficiency adsorbate/adsorbent ratio was 1 mol L-1 of NiCl2 solution and 20 g L-1 of pine sawdust. This was the contaminated biomass sample used in the manufacture of the bricks. This paper analyses the properties of the bricks achieved and compares them with bricks without added biomass, porous bricks containing zinc and commercial bricks. The obtained values of apD: bulk density, aspW: apparent specific weight, apP: apparent porosity, H2O Abs: water absorption, apV: apparent volume, LOI: weight loss on ignition, σstr: compression fracture stress, MOR: flexural modulus o...
Journal of Solid State Electrochemistry
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Papers by Raúl Procaccini