Browsing by Author "del Rio, Rodrigo"

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    An electrochemical deposition route for obtaining alpha-Fe2O3 thin films - II. EQCM study and semiconductor properties
    (ELECTROCHEMICAL SOC INC, 2007) Schrebler, Ricardo; Llewelyn, Cynthia; Vera, Francisca; Cury, Paula; Munoz, Eduardo; del Rio, Rodrigo; Meier, Humberto Gomez; Cordova, Ricardo; Dalchiele, Enrique A.
    The electrochemical formation of hematite (alpha-Fe2O3) precursor thin films (oxyhydroxide iron compounds), onto gold substrates in an aqueous solution of Fe (III) + KF + H2O2 was investigated in situ using an electrochemical quartz crystal microbalance (EQCM) and voltammetric techniques. Nanostructured alpha-Fe2O3 obtained after annealing of oxyhydroxide iron compounds thin films have been prepared onto SnO2/F covered glass substrates through a potential cycling procedure in this electrolytic bath. Photoelectrochemical measurements, carried out in 0.1 M NaOH + 0.05 M KI electrolyte at pH 13, show an n-type behavior, a flatband potential of -1.08 V vs saturated mercury/mercury sulfate reference electrode, and an apparent donor density of 1.26 X 10(19) cm(-3) at 1 kHz. (C) 2007 The Electrochemical Society.
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    CdS amorphous thin films photochemical synthesis and optical characterization
    (2008) Tejos, Marisol; Rolon, Barbara G.; del Rio, Rodrigo; Cabello, Gerardo
    Thin amorphous nanostructured CdS films were photochemically obtained via direct UV radiation (lambda = 254 nm) of complex Cd[(CH3)(2)CHCH2CH2OCS2](2) on Si(100) and ITO-covered glass substrate by spin coating. Thin cadmium xanthate complex films' UV photolysis results in loss of all ligands from the coordination sphere. X-ray photoelectron spectra for as-deposited US thin films show the most representative signals of Cd 3d(5/2) located at 405eV, Cd 3d(3/2) located at 412eV and a small signal S 2p located at 162 eV. The surface morphology of the films was examined via atomic force microscopy. This can be described as a fibrous-type surface without structural order, which is characteristic of an amorphous deposit. The optical band gap value was 2.85 and 3.15 +/- 0.1 eV. (C) 2009 Elsevier Ltd. All rights reserved.
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    Comparison of Different Synthetic Routes of Hybrid Hematite-TiO2 Nanotubes-Based Electrodes
    (2021) Fornazari, Ana Luiza; Castillo-Rodriguez, Judith; Correa-Encalada, Daniel; Dalchiele, Enrique A.; Hevia, Samuel A.; del Rio, Rodrigo
    Nowadays, green hydrogen is an important niche of interest in which the search for a suitable composite material is indispensable. In this sense, titanium oxide nanotubes (TiO2 nanotube, TNTs) were prepared from double anodic oxidation of Ti foil in ethylene glycol electrolyte. The morphology of the nanotubes was characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). Once characterized, nanotubes were used as templates for the deposition of hematite. The use of three synthetic procedures was assayed: Chemical Vapor Deposition (CVD), Successive Ionic Layer Adsorption and Reaction (SILAR), and electrochemical synthesis. In the first case, CVD, the deposition of hematite onto TiO2 yielded an uncovered substrate with the oxide and a negative shift of the flat band potential. On the other hand, the SILAR method yielded a considerable amount of hematite on the surface of nanotubes, leading to an obstruction of the tubes in most cases. Finally, with the electrochemical synthesis, the composite material obtained showed great control of the deposition, including the inner surface of the TNT. In addition, the impedance characterization showed a negative shift, indicating the changes of the interface electrode-electrolyte due to the modification with hematite. Finally, the screening of the methods showed the electrochemical synthesis as the best protocol for the desired material.
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    Corrosion inhibition of copper in chloride media by 1,5-bis(4-dithiocarboxylate-1-dodecyl-5-hydroxy-3-methylpyrazolyl)pentane
    (PERGAMON-ELSEVIER SCIENCE LTD, 2008) Vera, Rosa; Bastidas, Francisco; Villarroel, Maria; Oliva, Alfonso; Molinari, Aurora; Ramirez, Daniel; del Rio, Rodrigo
    The efficiency of 1,5-bis(4-dithiocarboxylate-1-dodecyl-5-hydroxy-3-methyl-pyrazolyl)pentane (BDTCPP) as copper corrosion inhibitor in 3.5% NaCl solutions was studied by electrochemical polarization methods (Tafel extrapolation and polarization resistance method), electrochemical impedance spectroscopy and immersion assays. Results obtained in this study reveal that BDTCPP is a good inhibitor and the potentiodynamic polarization studies clearly show that BDTCPP is a mixed-type inhibitor for copper in chloride solutions. It decreases the anodic reaction rate more strongly than the cathodic reaction rate and it renders the open circuit potential of copper more positive in 3.5% NaCl solutions. The UV analysis of the protective layer of BDTCPP after corrosion experiments shows that the inhibitor prevents copper corrosion by physisorption on the metal surface, followed by chemisorption of a protective Cu(II)-complex. This Cu(II) is generated by oxidation of the Cu(I) ion formed at the beginning of the corrosion process in the aerated solution of NaCl. (C) 2007 Elsevier Ltd. All rights reserved.
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    CsPbBr3-based photoanode prepared by single-step Chemical vapor deposition of tunable thickness perovskite films
    (2024) Sosa-Acosta, J. R.; Fernandez-Izquierdo, L.; del Rio, Rodrigo; Navarrete-Astorga, Elena; Leinen, Dietmar; Hevia, Samuel A.
    Cesium Lead Bromide (CsPbBr3) perovskite films have gained significant attention in photoelectrochemistry due to their promising properties. However, their widespread application necessitates scalable processing methods to produce high-quality films. Current techniques often involve post-synthesis steps to achieve desirable crystalline films or surface coverage for optimal performance. This research performed a single-step Chemical Vapor Deposition (CVD) approach to grow high-quality CsPbBr3 films. This methodology offers precise control over film thickness and grain orientation, crucial for optimizing photoelectrochemical response. The procedure simplifies fabrication by bypassing annealing or toxic solvent excess and growing films directly from CsPbBr3 crystals. Film thickness was controlled by adjusting growth time and precursor mass parameters to examine the photoelectrochemical performance across thicknesses ranging from 0.6 mu m to 2.5 mu m. Optimal results were achieved with dense, compact films 1.5 mu m thick, which exhibited oriented grains along the (121) plane. Optical, structural, and morphological analyses confirmed a predominantly pure orthorhombic phase, although slight impurities were noted in thinner films. The 1.5 mu m films showed a four-hour stable photocurrent of 6.2 mA/cm2 at 1.23 V versus reversible hydrogen electrode (RHE) under simulated solar conditions, underscoring their potential in advancing perovskite-based electrodes for efficient photoelectrochemical solar fuel generation.
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    CVD Growth of Hematite Thin Films for Photoelectrochemical Water Splitting: Effect of Precursor-Substrate Distance on Their Final Properties
    (2023) Fernandez-Izquierdo, Leunam; Spera, Enzo Luigi; Duran, Boris; Marotti, Ricardo Enrique; Dalchiele, Enrique Ariel; del Rio, Rodrigo; Hevia, Samuel A.
    The development of photoelectrode materials for efficient water splitting using solar energy is a crucial research topic for green hydrogen production. These materials need to be abundant, fabricated on a large scale, and at low cost. In this context, hematite is a promising material that has been widely studied. However, it is a huge challenge to achieve high-efficiency performance as a photoelectrode in water splitting. This paper reports a study of chemical vapor deposition (CVD) growth of hematite nanocrystalline thin films on fluorine-doped tin oxide as a photoanode for photoelectrochemical water splitting, with a particular focus on the effect of the precursor-substrate distance in the CVD system. A full morphological, structural, and optical characterization of hematite nanocrystalline thin films was performed, revealing that no change occurred in the structure of the films as a function of the previously mentioned distance. However, it was found that the thickness of the hematite film, which is a critical parameter in the photoelectrochemical performance, linearly depends on the precursor-substrate distance; however, the electrochemical response exhibits a nonmonotonic behavior. A maximum photocurrent value close to 2.5 mA/cm(2) was obtained for a film with a thickness of around 220 nm under solar irradiation.
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    Effect of fertilization on Pinus pinea cone to seed and kernel yields
    (2023) Loewe-Munoz, Veronica; del Rio, Rodrigo; Delard, Claudia; Balzarini, Monica
    Stone pine (Pinus pinea L.) is a species of economic interest mainly due to its pine nuts, the most expensive nut in the world. Despite the high value of pine nuts, cones are mainly harvested from unmanaged forests. Therefore, research and its applications are needed to develop nutritional management techniques among other cultivation practices intened to boost production. This study evaluated the effect of fertilization on cone production and quality (cone weight and size, number of seeds and kernels, and health status), which in turn may affect cone to seed and cone to kernel yields. Fertilization consisted of two applications of macro and micronutrients in two adult plantations twice in the growing season (in spring and fall). Morphometric variables, cone production per tree and cone health were evaluated during two years after fertilization. Fertilization effect on cone production was positive and significant in both years, with variations between years. Most of the morphometric variables were positively impacted by fertilization, including cone diameter (3.5% increase), kernel weight and length (7.7% and 2.7% increase, respectively), and total seed and kernel weight per cone (20.9% and 18.6% increase, respectively). Fertilized stone pine trees increased production and quality of cones, seeds and kernels, but did not increase cone to seed or kernel yields. However, fertilization increased type II seed damage by 45.4% and 18.9% in 2020 and 2021, respectively. The results obtained in this research may help producers adopt cultural practices to boost pine nut production.
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    Effect of the Dispersing Agent on the Electrochemical Response of Glassy Carbon Electrodes Modified with Dispersions of Carbon Nanotubes
    (WILEY-V C H VERLAG GMBH, 2012) Gonzalez Segura, Karina; Canete Rosales, Paulina; del Rio, Rodrigo; Yanez, Claudia; Ferreyra, Nancy F.; Rivas, Gustavo A.; Bollo, Soledad
    The electrochemical response of a glassy carbon electrode modified with carbon nanotubes (CNT) dispersed in two solvents, water and DMF, and two polymers, chitosan and Nafion is reported. The films were homogeneous when the dispersing agent was water or DMF. In the case of polymers, the surfaces present areas with different density of CNTs. A more sensitive electrochemical response was obtained when CNTs are dispersed in the solvents. In the case of CNT dispersed with polymers, the nature of the polymer demonstrated to be a critical parameter not only for dispersing the nanotubes but also for the electrochemical activity of the resulting electrodes.
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    Effects of Tuber borchii inoculation on Pinus pinea 3 years after establishment along a latitudinal gradient in the Southern Hemisphere
    (2024) Loewe-Munoz, Veronica; Delard, Claudia; del Rio, Rodrigo; Gregori, Gianluigi; Balzarini, Monica
    Stone pine (Pinus pinea) produces a highly demanded dried fruit, the pine nuts; Tuber borchii produces a well-known commercialized truffle. Thus, the co-culture of P. pinea and T. borchii may represents an interesting productive option. This work evaluated the effect of T. borchii inoculation on stone pine tree growth, survival, health, entry into cone production, and mycorrhization level during the first 3 years after establishment along a 2000 km gradient in Chile. We tested two treatments (inoculation and non-inoculation) in a multi-environment trial (MET) involving seven sites along Chile. Plantations were repeatedly measured during 3 years after establishment. In all environments, inoculation enhanced tree height, root collar diameter (RCD) and crown diameter (6.9, 10 and 8.3% higher for inoculated than for non-inoculated plants). Vigor was also favored (14.1% more vigorous trees). Stone pine performance was enhanced in all sites, but mainly in those with extreme environmental conditions. T. borchii mycorrhizae were abundant (over 60% of mycorrhized root apexes) 3 years after establishment. The truffle-host plant combination was not previously evaluated in Chile. The results showed high root colonization levels and the persistence of mycorrhization 3 years after establishment, and an enhanced effect of mycorrhization on tree growth and vigor under different soil and climate conditions, confirming the high plasticity of both species.
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    Effects of climate and soil properties on growth of Pinus pinea young plantations
    (2024) Loewe-Munoz, Veronica; Bonomelli, Claudia; del Rio, Rodrigo; Delard, Claudia; Balzarini, Monica
    Background and aims Growth of Pinus pinea forests and plantations in native countries is known to be affected by soil and climate characteristics. However, edaphoclimatic drivers of growth and fruiting have been scarcely studied outside the species' native range; in addition, the role of soil nutrients, particularly in juvenile trees' development, has been poorly explored. Methods Relationships between edaphoclimatic variables and the performance of 54 young plantations were studied in Chile. Vegetative growth and fruiting were measured in 100 randomly selected trees per plantation. Composite soil samples were taken from each site to analyze soil chemical characteristics and texture. A principal component analysis was performed including climatic, soil data, and growth and fruiting variables. Results Annual growth was 1.3 cm year(-1) for stem diameter, 28.3 cm year(-1) for crown diameter, and 38.9 cm year(-1) for height; cone production per crown area was 0.07 cones m(-2). Negative correlation of height growth, crown growth and cone production with EC, Na, and pH were found, along with positive correlations with OM, PP and the index PP x AT. Stem diameter growth was favored by less acidic soils with high sand content, and showed no correlation with cone production. Furthermore, vegetative growth was positively correlated with N, P, Mg and clay content. In young plantations, vegetative growth was higher than in the species' native habitat. Conclusion Soil properties, in particular low EC and Na were identified as favorable for growth of young stone pine trees, along with high content of soil N, P and Mg, and PP.
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    Electrochemical Conversion of Carbon Dioxide into CHO-Containing Compounds on Multimetallic Porphyrins
    (2017) Calfuman, K.; Honores Sotelo, Jessica Scarlet; Guzmán Ángel, Daniela; Ohlbaum, M.; Armijo Mancilla, Juan Francisco; del Rio, Rodrigo; Isaacs Casanova, Mauricio
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    Lithium Iron Phosphate/Carbon (LFP/C) Composite Using Nanocellulose as a Reducing Agent and Carbon Source
    (2023) Kroff, Macarena; Hevia, Samuel A. A.; O'Shea, James N. N.; de Muro, Izaskun Gil; Palomares, Veronica; Rojo, Teofilo; del Rio, Rodrigo
    Lithium iron phosphate (LiFePO4, LFP) is the most promising cathode material for use in safe electric vehicles (EVs), due to its long cycle stability, low cost, and low toxicity, but it suffers from low conductivity and ion diffusion. In this work, we present a simple method to obtain LFP/carbon (LFP/C) composites with different types of NC: cellulose nanocrystal (CNC) and cellulose nanofiber (CNF). Microwave-assisted hydrothermal synthesis was used to obtain LFP with nanocellulose inside the vessel, and the final LFP/C composite was achieved by heating the mixture under a N-2 atmosphere. The resulting LFP/C indicated that the NC in the reaction medium not only acts as the reducing agent that aqueous iron solutions need (avoiding the use of other chemicals), but also as a stabiliser of the nanoparticles produced in the hydrothermal synthesis, obtaining fewer agglomerated particles compared to synthesis without NC. The sample with the best coating-and, therefore, the best electrochemical response-was the sample with 12.6% carbon derived from CNF in the composite instead of CNC, due to its homogeneous coating. The utilisation of CNF in the reaction medium could be a promising method to obtain LFP/C in a simple, rapid, and low-cost way, avoiding the waste of unnecessary chemicals.
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    Mixed Castanea sativa plantations including arboreal companion species enhance chestnut growth and high-quality timber production
    (2023) Loewe-Munoz, Veronica; Delard, Claudia; del Rio, Rodrigo; Barrales, Luis; Balzarini, Monica
    Context: Chestnut (Castanea sativa Mill.) is an important tree species for its timber, which is widely used for multiple purposes, including the veneer industry. The species has an interesting productive potential in Chile and requires specific management strategies to produce valuable, high-quality logs. Although mixed plantations including companion species usually enhance timber quality of several trees, the performance of chestnut under different associations is not well known. Aims: The objective of this study was to assess growth, survival, health, and timber quality of chestnut trees in several plantation types, including monoculture and mixtures with other companion trees and/or shrub. Methods: Growth and survival measurements were taken periodically in pure chestnut and mixed plantations established in southern Chile for a 20-year period after planting. The mixed plantations tested were: a main forest species mixture (Castanea sativa Mill., Quercus rubra L., Quercus robur L. and Prunus avium L.); three mixtures including main forest species plus one arboreal companion species (Alnus glutinosa L., Gevuina avellana Mol. or Embothrium coccineum J.R. Forst. & G. Forst.); one including main forest species plus one shrub nurse species (Fabiana imbricata Ruiz & Pav.); and three mixtures including one of the arboreal companion species and the shrub. Timber quality variables were assessed at age 20, and health status was recorded at ages 7 and 20 in all plantations. Growth variables were analyzed using linear mixed models to assess plantation effect over time. Kaplan-Meier survival analysis and Log Rank Test were used to compare chestnut tree survival among plantation types. Quality timber variables were analyzed with a chi 2 test. Results: Chestnut trees associated with arboreal main species (P. avium, Q. rubra, Q. robur) (Mix1) showed the best performance, with 10.1 % and 8.3 % higher height than average values of the other mixtures and the monoculture, respectively, and 19.1 % and 12.8 % higher diameter growth than across plantation types and monoculture average values, respectively. Mix1 had the highest average volume per tree (0.34 m(-3)), at least 30 % higher than the average volume of pure and other mixed plantations. This mixture including only main species also exhibited the highest percentage of trees with high trunk length values of all plantation types. No pest or diseases were recorded on chestnut trees, and survival was high in all plantation types. Conclusion: The impact of mixed plantations on growth and timber quality was evidenced at age 20. In particular, the association including arboreal companion species enhanced chestnut tree performance.
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    Nickel Nanopillar Arrays Electrodeposited on Silicon Substrates Using Porous Alumina Templates
    (2020) Bejide, Matias; Contreras, Patricio; Homm, Pia; Duran, Boris; Garcia-Merino, Jose Antonio; Rosenkranz, Andreas; Denardin, Juliano C.; del Rio, Rodrigo; Hevia, Samuel A.
    Nickel nanopillar arrays were electrodeposited onto silicon substrates using porous alumina membranes as a template. The characterization of the samples was done by scanning electron microscopy, X-ray diffraction, and alternating force gradient magnetometry. Ni nanostructures were directly grown on Si by galvanostatic and potentiostatic electrodeposition techniques in three remarkable charge transfer configurations. Differences in the growth mechanisms of the nanopillars were observed, depending on the deposition method. A high correlation between the height of the nanopillars and the charge synthesis was observed irrespective of the electrochemical technique. The magnetization measurements demonstrated a main dependence with the height of the nanopillars. The synthesis of Ni nanosystems with a controllable aspect ratio provides an effective way to produce well-ordered networks for wide scientific applications.
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    Recommendations for increasing yield of the edible Pinus pinea L. pine nuts
    (2024) Loewe-Munoz, Veronica; Delard, Claudia; del Rio, Rodrigo; Balzarini, Monica
    In Pinus pinea, cone to pine nut yield (total pine nut weight expressed as percentage of cone weight), an important crop trait, is decreasing worldwide. This phenomenon is of great concern, since the nuts of this species are highly demanded. Cone weight, seed and pine nut morphometry, and pine nut yield were monitored in a non-native area in Chile for 10 years. For this purpose, 560 cones, and the seeds and pine nuts contained in them, were counted, measured and weighed in a multi-environment study involving seven plantations. Seed and pine nut damage was evaluated. Two contrasting categories of cone weight (heavy/light) were defined. Cone to pine nut yield (PY) and other traits were calculated and compared between categories using a mixed linear model. Regression trees were used to explain PY variability. Cone weight was higher than in the species' native range (474 g vs 300 g on average). Pine nut number per cone and PY were significantly higher in the heavy cone category than in the light cone category (125 vs 89 units, and 4.05 vs 3.62%, respectively), The percentage of damaged seeds was lower in heavy than in light cones (9.0% vs 15.9%). Thus, PY depended on seed and pine nut morphometry as well as on seed health. Management practices, such as fertilization and irrigation, could be used to boost production of heavy cones and consequently increase PY.
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    Understanding the loss of electrochemical activity of nanosized limn2o4 particles: a combined experimental and ab initio DFT study
    (2018) Velasquez, Ever A.; Silva, Daiane P. B.; Falqueto, Juliana B.; Mejía López, José Félix; Bocchi, Nerilso; del Rio, Rodrigo; Mazo-Zuluaga, Johan; Rocha-Filho, Romeu C.; Biaggio, Sonia R.
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    α-Fe2O3/, Co3O4/, and CoFe2O4/MWCNTs/Ionic Liquid Nanocomposites as High-Performance Electrocatalysts for the Electrocatalytic Hydrogen Evolution Reaction in a Neutral Medium
    (2024) Ibarra, Jose; Aguirre, Maria Jesus; del Rio, Rodrigo; Henriquez, Rodrigo; Faccio, Ricardo; Dalchiele, Enrique A.; Arce, Roxana; Ramirez, Galo
    Transition metal oxides are a great alternative to less expensive hydrogen evolution reaction (HER) catalysts. However, the lack of conductivity of these materials requires a conductor material to support them and improve the activity toward HER. On the other hand, carbon paste electrodes result in a versatile and cheap electrode with good activity and conductivity in electrocatalytic hydrogen production, especially when the carbonaceous material is agglomerated with ionic liquids. In the present work, an electrode composed of multi-walled carbon nanotubes (MWCNTs) and cobalt ferrite oxide (CoFe2O4) was prepared. These compounds were included on an electrode agglomerated with the ionic liquid N-octylpyridinium hexafluorophosphate (IL) to obtain the modified CoFe2O4/MWCNTs/IL nanocomposite electrode. To evaluate the behavior of each metal of the bimetallic oxide, this compound was compared to the behavior of MWCNTs/IL where a single monometallic iron or cobalt oxides were included (i.e., alpha-Fe2O3/MWCNTs/IL and Co3O4/MWCNTs/IL). The synthesis of the oxides has been characterized by X-ray diffraction (XRD), RAMAN spectroscopy, and field emission scanning electronic microscopy (FE-SEM), corroborating the nanometric character and the structure of the compounds. The CoFe2O4/MWCNTs/IL nanocomposite system presents excellent electrocatalytic activity toward HER with an onset potential of -270 mV vs. RHE, evidencing an increase in activity compared to monometallic oxides and exhibiting onset potentials of -530 mV and -540 mV for alpha-Fe2O3/MWCNTs/IL and Co3O4/MWCNTs/IL, respectively. Finally, the system studied presents excellent stability during the 5 h of electrolysis, producing 132 mu mol cm(-2) h(-1) of hydrogen gas.