María Jesús Aguirre

University of Santiago, Chile, CiudadSantiago, Santiago Metropolitan, Chile

Are you María Jesús Aguirre?

Claim your profile

Publications (56)95.08 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: Electro and photoelectrochemical reduction of nitrite in aqueous solution was studied using a multielectrocatalysts modified ITO electrode. ITO modification was carried out using the layer-by-layer (LBL) method, where sequential electrostatic assemblies were formed using a μ-(meso-5,10,15,10-tetra(pirydil)porphyrin)tetrakis {bis(bipyridine)chloride ruthenium (II)} [MTRP]n+, coordinated in its central cavity with Mn(III), Zn(II) or Ni(II) as a cationic layer, and polyoxotungstate [SiW12O40]4− as the anionic layer. Electrochemical measurements and UV–vis spectroscopy were used to monitor the modification process. Optimal results were obtained when three layers were deposited onto the ITO surface and were stable in aqueous solution. The order of the multilayer formation was explored by comparing a modified electrode where [Zn(II)TRP]4+ was the outermost layer with an electrode where [SiW12O40]4− was the outer layer. Results show that the best performing electrode is one with [SiW12O40]4− as the outer layer. Nitrite reduction on these electrode surfaces was studied in dark conditions and under light irradiation. Potential controlled electrolysis experiments were also performed, finding hydroxylamine, hydrazine and ammonia as the reduction products in dark conditions. Under light irradiation, only hydrazine and ammonia were found and, we observed an increase in the amount of obtained product. In this case, the electrolysis was carried out 150 mV less and half of time than in dark conditions. These results show that the combination of light and potential give rise to an improvement in the electrocatalytic properties of the modified electrodes. Continuous photolysis and IR spectroelectrochemical experiments were carried out to determinate the nature of this phenomena, evidencing the formation of an intermediary species between nitrite and [Mn(III)TRP]5+.
    No preview · Article · Jan 2016
  • Source
    Diego Quezada · Jessica Honores · María Jesús Aguirre · Mauricio Isaacs
    [Show abstract] [Hide abstract]
    ABSTRACT: Electrocatalytic reduction of carbon dioxide has been studied using modified electrodes with conducting polymers from tetra-amino-phenyl porphyrins containing transition metals (Zn(II) and Fe(III)), on an indium tin oxide electrode in BMImBF4, as solvent and supporting electrolyte. Electropolymerized Fe porphyrin is active toward the reaction under survey, while Zn derivative shows poor activity. Spectroelectrochemistry experiments on electropolymerized Fe porphyrin films have shown intermediary species like Fe–CO2 and Fe–CO at open-circuit potential. Potential-controlled bulk electrolysis carried out in ionic liquid shows that only carbon monoxide can be detected as reaction product in the gas phase and that Fe polymeric film shows a turnover number of 9.18, while the Zn film shows a value of 2.74, corroborating the poor activity observed in cyclic voltammetry.
    Full-text · Article · Dec 2014 · Journal of Coordination Chemistry
  • Source
    Roxana Arce · Julio Romero · María Jesús Aguirre
    [Show abstract] [Hide abstract]
    ABSTRACT: At basic pH values, the integrated system modified electrode / membrane absorber, it is possible to obtain a sensor of sulfite in actual red wine samples. This quantification method consumes small amounts of sample, it is fast and shows good linearity with r2 of 0.998 and good accuracy. This integrated approach can separate free sulfite red wine matrix with the absorption system of the membrane and, moreover, can be quantified using the electrochemical sensor using NiTSPc modified electrodes, obtaining a concentration of sulfite free 29.8 ± 0.2 mg·L-1.
    Full-text · Article · Dec 2014 · International journal of electrochemical science
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The antioxidant and/or prooxidant ability of extracts obtained from wine waste were analyzed using in vitro and in vivo assays. Cyclic voltammetry was used as the in vitro assay to determine the antioxidant and/or prooxidant properties and, the in vivo effect on mycelial growth of the fungus Botrytis cinerea was evaluated. In addition, the prooxidant activity was evaluated by intracellular oxidation of compound 2,7-dichlorodihydrofluorescein diacetate (DCFH-DA) in B. cinerea. The extracts used in this study were obtained from grape pomace of Cabernet Sauvignon, Carménère and Syrah varieties from the Misiones de Rengo Vineyard by simple extraction, using methanol/HCl 1% (v/v), ethanol 70% (v/v), or Soxhlet extraction. According to the results obtained, gallic acid was the most represented phenolic compound independent of grape variety and extraction method. In addition, vanillic acid; protocatechuic acid, syringic acid, quercetin and kaempferol were found in the extracts. From this study it was possible concluded that, depending of the method of extraction of the grape residues and the grape variety (Cabernet Sauvignon, Carménère and Syrah), the extracts showed antioxidant and/or prooxidant activity. However, no correlation can be established between the anodic oxidation potentials of the extracts and their effect on the fungus B. cinerea.
    Full-text · Article · Dec 2014 · Molecules
  • Source
    Roxana Arce · Julio Romero · María J. Aguirre
    [Show abstract] [Hide abstract]
    ABSTRACT: In this work, we present a comparison among three glassy carbon electrodes modified by Co-porphyrin, ortho-phenylenediamine, or both simultaneously. This comparison shows the differences among the electrochemical behavior, morphological characteristics and electrocatalytic behavior toward the sulfite oxidation of these electrodes. The electrode modified by Co-porphyrin, ortho-phenylenediamine and copolymer has been investigated in detail for the comparision of electrocatalytic activity towards the sulfite oxidation. In the case of the glassy carbon-modified electrodes, the presence of the copolymer enhances the electrocatalytic performance of the modified electrodes in spite of the non-catalytic response (compared to the bare glassy carbon) of both homopolymer-modified electrodes toward the oxidation of sulfite. Additionally, the oxidation of sulfite extracted from red wine is shown. The copolymer-modified electrode is capable of oxidizing the extracted free sulfite in a 0.02 M NaOH solution. Through the addition of standards method, a concentration of free sulfite in a Chilean red wine sample was determined to be 44 ppm.
    Full-text · Article · Dec 2014 · Journal of Applied Electrochemistry
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Multilayer electrostatic assemblies described as {[FeTPyP(Crphen2Cl)4]8+/SiW12O404−}ni and {[NiTPyP(Crphen2Cl)4]8+/SiW12O404−}ni, where TPyP = 5,10,15,20-tetra(4-pyridyl) porphyrin, phen = 1,10-phenanthroline, SiW12O404− = silicontungstate and ni = number of multilayers, wereassembledonto different electrodic surfaces. The modified electrodes were constructed using the layer by layer methodology. UV-Vis spectroscopy, scanning electron microscopy (SEM), and cyclic voltammetry were used for the electrodes characterization. The electrocatalytically reduction of oxygen in aqueous solution was driven with these electrodes. In the oxygen reduction, rotating ring-disk and cyclic voltammetry techniques revealed a synergic effect between the cationic porphyrin and SiW12O404−. The synergism is related to the number of multilayers, the porphyrin complex employed, inner electroactive process across assemblies and the overpotential applied in the electrochemical process.
    Full-text · Article · Sep 2014 · Electrochimica Acta
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: In this paper, we studied of photoelectric properties of multilayer organic photovoltaic cells (OPV cells). The active organic layers consisted of a planar heterojunction between a layer of (meso-tetrakis(5-bromo-2-thienyl)porphyrin), (TBrTP) as electron donor (ED) and a layer fullerene molecules. For the manufacture of photovoltaic devices we use a the technique of high vacuum by thermal sublimation that allows multilayer devices realization easily by successive depositions, and it does not require solvents, achieving purer films with reproducible characteristics. The TBrTP allows achieving OPVCs exhibiting promising efficiencies when the ABL is the MoO3/CuI DABL. The CuI improves the current in the organic layer by one order of magnitude, which allows decreasing the series resistance of the OPVCs and therefore improving the OPVCs.
    Full-text · Article · Jun 2014 · Journal of Porphyrins and Phthalocyanines
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Electrochemical and photoelectrochemical reduction of carbon dioxide was studied in aqueous solution, using an ITO/multilayer modified electrode. The multilayer formation was carried out by the Layer-by-Layer method (LBL), using a μ-(meso-5,10,15,20-tetra(pirydil)porphyrin)tetrakis {bis(bipyridine)chloride ruthenium(II)} coordinated with Mn(III), Zn(II) and Ni(II) in its central cavity and an anionic polyoxotungstate [SiW12O40]4−. The multilayer formation was corroborated by electrochemical methods and UV–visible spectroscopy. For this study, 3 multilayers were formed on the ITO surface. Carbon dioxide reduction was studied by linear sweep voltammetry at pseudo stationary state (5 mV s−1) in a 0.1 M NaClO4, CO2 saturated solution. Photoelectrochemical reduction of carbon dioxide was studied in the same conditions described above under light irradiation at 440 nm. In dark conditions, an enhancement in current is detected at −0.75 V indicating carbon dioxide reduction. Under light irradiation the reduction process shifts to −0.60 V. Chemical analysis after controlled potential electrolysis shows that in dark conditions, formic acid, carbon monoxide and methanol are the reduction products. Under light irradiation there is a change in the product distribution and for some metals; formaldehyde can be detected, evidencing a change in the reduction mechanism. These results support the fact that [MTRP]n+/[SiW12O40]4− multilayer modified electrodes act as electrocatalysts for carbon dioxide reduction and that this activity is enhanced by a combination of light and potential where light produces excited states sites on the multilayer, that are more reactive toward carbon dioxide reduction.
    Full-text · Article · Jan 2014 · Electrochimica Acta
  • Roxana Arce · María Jesús Aguirre · Julio Romero

    No preview · Article · Jan 2014 · ECS Transactions
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The aim of this work is to study the sulfite oxidation mediated by glassy carbon electrodes modified with copolymers formed by ortho-phenylenediamine (OPD) and Co(II)-tetrakis(para-aminophenyl)porphyrin (CoTAPP). The copolymer was obtained through continuous cycling of potential of a glassy carbon electrode in acid medium containing each respective homopolymer in 1:1 feeding volume, in which the ortho-phenylenediamine concentration was 110-1 M and the CoTAPP concentration was 110-4 M. The film obtained is thin, stable and contains a low amount of porphyrin in comparison to the amount in ortho-phenylenediamine. Its electrocatalytic activity was tested toward the sulfite oxidation. In this case, this film is more electrocatalytic than the modified electrode modified with the CoTAPP electropolymer, even though ortho-phenylenediamine is inactive in this reaction. In this work the electrocatalysis process, the morphology of the film, and the difference of electrocatalytic behavior between the ortho-phenylenediamine and cobalt porphyrin homopolymers and the ortho-phenylenediamine-porphyrin copolymer were studied. The morphologic studies were done using Au electrodes since the electrocatalytic activity on Au and on glassy carbon are quite similar.
    Full-text · Article · Dec 2013 · Journal of the Chilean Chemical Society
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The use of a glassy carbon electrode modified with polymeric meso–tetrakistetrabromothienyl porphyrin (TBrTP) to determine Pb(II) and Cd(II) is reported. TBrTP was prepared by electrochemical polymerization in acetonitrile. Using SWASV, variables like number of cycles on the electropolymerization, pH, time and accumulation potential (t acc , E acc) were optimized. Optimal analytical conditions were: pH 5.0 (acetate buffer); E acc –1.00 V vs. Ag/AgCl and t acc 60 s. The linear calibration curves ranged from 10.0 to 70.0 g L –1 for Pb(II) and from 10.0 to 100.0 g L –1 for Cd(II). The detection limits (3) were 0.03 and 0.02 g L –1 for Pb(II) and Cd(II) respectively. The relative standard deviation was 4.8 % and 6.3 % (n=6), respectively, for a solution containing 10.0 g L –1 of Pb(II) and Cd(II). The method was validated using TMDA 51.3 and SPS–WW1 certified reference materials and then applied to determination of Pb(II) and Cd(II) in spiked tap water.
    Full-text · Article · Sep 2013 · International journal of electrochemical science
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: a b s t r a c t This work describes the influence of n-octyl pyridinium cations based ionic liquids–carbon paste modified electrodes on the oxidation mechanism of dopamine. Ionic liquids formed by hexafluorophosphate anion and n-octyl pyridinium [R-OPy] + ; R = CH 3 , H, CF 3 , where ionic liquids containing CH 3 and CF 3 are new products, were synthesized and characterized. Modified carbon paste electrodes with these salts were characterized by electrochemical impedance spectroscopy and cyclic voltammetry. Electrochemical oxi-dation of dopamine was studied in PBS buffer solution at pH = 7.4. The influence of the ionic liquids in the oxidation of dopamine was studied by cyclic voltammetry and rotating disk electrode. The results show that typical carbon paste electrode presents an electrochemical/chemical mechanism; whereas [OPy]PF 6 and [CF 3 -OPy]PF 6 modified electrodes present an electrochemical/chemical/electrochemical mechanism. The experimental study is complemented with a theoretical analysis of substituent effects in terms of the molecular electrostatic potential, Mulliken population analysis and second order perturbation theory probed at the cation moiety of the IL. These indices consistently show an electron density accumulation at the ipso position of the pyridinium moiety of the IL that is in agreement with the electrochemical characterization.
    Full-text · Dataset · Aug 2013
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Sulfites $$({\hbox{ SO }}_{3}^{2-})$$ or sulfur dioxide (SO2) is a preservative widely used in fruits and fruit-derived products. This study aims to propose a membrane contactor process for the selective removal and recovery of SO2 from wines in order to obtain its reliable quantification. Currently, the aspiration and Ripper methods offer a difficult quantification of the sulfite content in red wines because they involve evaporation steps of diluted compounds and a colorimetric assay, respectively. Therefore, an inexpensive and accurate methodology is not currently available for continuous monitoring of SO2 in the liquids food industry. Red wine initially acidified at pH < 1 was treated by membrane extraction at 25 . This operation is based on a hydrophobic Hollow Fiber Contactor, which separates the acidified red wine in the shell side and a diluted aqueous sodium hydroxide solution as receiving solution into the lumenside in countercurrent. Sulfite and bisulfite in the acidified red wine become molecular SO2, which is evaporated through the membrane pores filled with gas. Thus, SO2 is trapped in a colorless solution and the membrane contactor controls its transfer, decreasing experimental error induced in classical methods. Experimental results using model solutions with known concentration values of $${\hbox{ SO }}_{3}^{2-}$$ show an average extraction percentage of 98.91 after 4 min. On the other hand, two types of Chilean Cabernet Sauvignon wines were analyzed with the same system to quantify the content of free and total sulfites. Results show a good agreement between these methods and the proposed technique, which shows a lower experimental variability.
    Full-text · Article · Jul 2013 · Food Science and Technology International
  • [Show abstract] [Hide abstract]
    ABSTRACT: At pH 3 and 7, a glassy carbon electrode modified by deposition of a physio-adsorbed Cu-10-(4-aminophenyl)-5,15-dimesitylcorrole reduces molecular oxygen to water through a 4-electron direct transference. In the case of a glassy carbon electrode modified by electropolymerizing the same corrole on the surface, the reduction occurs by two parallel ways giving peroxide and water simultaneously. However at pH 7 this electrode gives peroxide as the unique product. This indicates that the way of modifying the electrode affects the product of reduction of oxygen. At pH 12, both modified electrodes catalyze the reduction to peroxide. It is noticeable that a Cu-azamacrocycle reduces oxygen to water. At all the studied pH values, the modified electrodes are unstable and lose activity after a first cycle in the presence of oxygen.
    No preview · Article · May 2013 · International journal of electrochemical science
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The anthocyanin content of grape pomace from different Chilean grape varieties (Vitis vinifera var. Cabernet Sauvignon, Carménère and Syrah) from two vineyards (Misiones de Rengo and Miguel Torres) was determined by the differential pH method and the anthocyanin perfile was characterized by HPLC. In all chromatograms, a major peak corresponding to malvidin-3-O-glucoside was observed. Also, the in vitro antifungal activity of these extracts against mycelia growth of the phytopathogenic fungus Botrytis cinerea was evaluated. The anthocyanin containing extract from Cabernet Sauvignon grape pomace of Misiones de Rengo vineyard was the most active. The extract from the same variety form Miguel Torres vineyard did not inhibit mycelia growth of B. cinerea. In general, the other extracts were less active against the fungus.
    Full-text · Article · Dec 2012 · Journal of the Chilean Chemical Society
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: This work describes the formation of modified electrodes layer-by-layer assembly of a μ-{meso-5,10,15,20-tetra(pyridyl)porphyrin}tetrakis{bis(bipyridine)chloride ruthenium(II)} coordinated with Zn(II) and Mn(III) in its central cavity and an anionic polyoxotungstate [SiW12O40]4−. The bilayer formation was monitored using electrochemical and UV–vis techniques, following the oxidation process of the RuIII/II couple and the absorbance of the Soret band of porphyrin complexes respectively. It was possible to form 10 stable bilayers onto ITO surface. SEM studies were carried out finding that the morphology of the film depends on the metal center in the porphyrin. The thickness of these films was estimated as 0.603 μm for [Zn(II)TRP]4+/[SiW12O40]4− and 2.18 μm for [Mn(III)TRP]5+/[SiW12O40]4− modified electrodes respectively. Raman spectroscopy showed that new bands appeared for [Mn(III)TRP]5+/[SiW12O40]4− assembly confirming stronger interactions than only electrostatic forces. Kinetics parameters such as charge transfer coefficient, α, and heterogeneous electron transfer rate constant, ks were obtained for both electrodes. Using electrochemical and UV–vis data it was possible to estimate the energy levels involved in the charge transfer process through the films formed. Sensor properties of [Zn(II)TRP]4+/[SiW12O40]4− modified electrode toward chlorite oxidation was tested. The results show electrocatalytic activity, amperometric determination demonstrate a detection limit of 13.8 μM.
    Full-text · Article · Oct 2012 · Electrochimica Acta
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Glassy carbon electrodes modified with conducting polymers of Ni(II), Zn(II) and metal free tetraruthenated porphyrin were evaluated for reduction and oxidation processes of S(IV) oxoanions in Na2SO3/water-ethanol at pH 1.0 and 3.5, showing electrocatalytic activity. A Ni(II) film was able to reduce the S(IV) oxoanions selectively in presence of high concentration of gallic acid. The Ni(II) film was also used as an amperometric sensor toward S(IV) oxoanions reduction in white wine samples showing a detection and quantification limit of 1.40 mg L−1 and 4.68 mg L−1, respectively. These results are promising for the electrochemical determination of S(IV) using conducting polymers from these macrocycles.
    Full-text · Article · Jul 2012 · Electroanalysis
  • [Show abstract] [Hide abstract]
    ABSTRACT: The simultaneous electropolymerization of aniline and Fe-porphyrin in HCl by cycling the potential on glassy carbon (GC) and highly ordered pyrolytic graphite (HOPG) electrodes was studied by Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM) and electrochemical techniques. A conducting copolymer thin film was produced, which was stable and contained a low quantity of porphyrin compared to aniline. Its electrocatalytic activity was tested for the reduction of molecular oxygen and also for the oxidation of ascorbic acid and sulfite anion. This activity was higher than that of the poly-porphyrin and the poly-aniline modified electrodes for these reactions. Here we describe in detail the electropolymerization process and the film morphology. The electrocatalytic behavior of the aniline and porphyrin homopolymers is compared to that of the aniline-porphyrin copolymer.
    No preview · Article · Jan 2012 · International journal of electrochemical science
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The fungotoxicity against Botrytis cinerea of a flavonoid isolated from Pseudognaphalium robustum was analyzed. Two absorption column chromatographies and one semipreparative thin layer chromatography were used to purify the active flavonoid. It was determined, by 1 H-NMR spectroscopy and co-elution with standards in HPLC, that this compound was 5,7-dihydroxy-3,8-dimethoxyflavone (gnaphaliin A). To determine the fungitoxicity of the purified compound, the effect on in vitro mycelial growth and conidial germination was studied. The compound concentration that reduced mycelial growth by 50% was 45.5 μg/mL. This compound also partially affected conidial germination of B. cinerea, reduced oxygen consumption by germinating conidia and affected the integrity of plasma membrane. Finally, using cyclic voltammetry, it was shown that the purified flavone had a pro-oxidant effect.
    Full-text · Article · Dec 2011 · Molecules
  • [Show abstract] [Hide abstract]
    ABSTRACT: Anthocyanins in aged Cabernet Sauvignon red wines were studied by HPLC-MS. The major anthocyanin in 6, 7, and 8 year old red wine extracts was the dimer vitisin A produced by condensation of malvidin-3-O-glucoside mediated by pyruvic acid. In aged wine, the content of malvidin-3-O-glucoside decreased with age with a concomitant increase of vitisin A. The latter is accompanied by several condensation products with molecular weight up to 1500 m/z. Differential pulse voltammetry indicated that aged wines have lower antioxidant capacity than young wine (400 mV), but higher than malvidin-3-O-glucoside (483 mV). Tafel's plots showed that the electrochemical process occurring in aged wines is different from young wines. Six, seven and eight year old wines show similar behaviour with plots of 234, 177 and 188 mV/dec, respectively. These values are higher than the expected 120 mV/dec corresponding to a first electronic transfer but smaller compared to the 523 mV/dec corresponding to young wine.
    No preview · Article · Nov 2011 · Food Chemistry