Browsing by Author "Mendizabal, Fernando"

Now showing 1 - 11 of 11
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    Catalytic activity of iron phthalocyanine for the oxidation of thiocyanate and L-cysteine anchored on Au(111) clusters
    (2019) Castro Latorre, Pablo; Miranda Rojas, Sebastián; Barrientos, Lorena; Mendizabal, Fernando
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    Improvement of photovoltaic performance by substituent effect of donor and acceptor structure of TPA-based dye-sensitized solar cells
    (2016) Inostroza, Natalia; Mendizabal, Fernando; Arratia Perez, Ramiro; Orellana, Carlos; Linares Flores, Cristian
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    Interaction of LD14 and TiO2 in dye-sensitized solar-cells (DSSC) : A density functional theory study
    (2015) Mendizabal, Fernando; Lopéz, Alfredo; Arratia Pérez, Ramiro; Zapata-Torres, Gerald
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    Interaction of YD2 and TiO2 in dye-sensitized solar cells (DSSCs) : a density functional theory study
    (2015) Mendizabal, Fernando; Lopéz, Alfredo; Arratia Pérez, Ramiro; Inostroza, Natalia; Linares-Flores, Cristian
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    Palmitic acid and hexadecylamine molecules assdsorbed on titania surface in hybrid composites. Effect of surfactants using density functional theory
    (2017) Orellana, Carlos; Mendizabal, Fernando; Gonzalez, Guillermo; Miranda-Rojas, Sebastian; Barrientos, Lorena
    A complete theoretical characterization of the factors involved in the stabilization of hybrid laminar composites is reported, with the purpose of understanding the main interactions involved in the formation of these types of systems. The models were built using two different surfactants: hexadecylamine (HDA) and palmitic acid (PAc), on a cluster of titania (TiO2) which represents its anatase crystalline phase. We explored the relevance of the titania-surfactant and surfactant-surfactant interactions, and of the protonation state of the palmitic acid in the stabilization of the hybrid laminar composites. The results were rationalized using energy decomposition analysis (EDA) and the non-covalent interaction index (NIC). The interaction energies between HDA and the TiO2 surface without the contribution of the dispersion forces were -25 kcal/mol and -29 kcal/mol for the (1 0 0) and (1 01) surfaces, respectively. These results suggest the formation of a donor-acceptor bond between HDA-TiO2 allowing its stabilization. On the other hand, the interaction energy between PAc and the TiO2 (1 0 1) surface was about -45 kcal/mol without the dispersion term. Thus, the PAc-TiO2 model has a higher covalent character than the HDA-TiO2 interaction, as confirmed by the energy decomposition analyses. The results suggest new hybrid laminar composites which are better when carboxylic acid was used instead of amines. Therefore, the use of surfactants with the carboxyl functional group yielded more stable TiO2 hybrid composites. The interaction energy between surfactant chains was about -13 kcal/mol, confirming the importance of dispersion forces in the stabilization of these types of systems. The study of systems with palmitic acid was complemented by building some anionic models to show the importance of acid protons in those systems. However, when the acidic hydrogens were removed, the interaction energy between the PAc molecules considering the dispersion correction increased to 45 kcal/mol, with a highly repulsive character. These results suggest that the acid hydrogens of the PAc surfactants play a fundamental role in terms of correctly representing the carboxylic acid-TiO2 interface and the stabilization of the laminar hybrid composites. (C) 2017 Elsevier B.V. All rights reserved.
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    Role of β-CD Macromolecule Anchored to α-Fe2O3/TiO2 on the Selectivity and Partial Oxidation of Guaiacol to Add-Value Products
    (2021) Espinoza-Villalobos, Nicole ; Rojas, Susana ; Salazar, Ricardo Andrés ; Contreras, David ; Escalona, Nestor ; Vergara, Elizabeth ; Laguna-Bercero, Miguel Angel ; Mendizabal, Fernando ; Barrientos, Lorena
    Biomass is a naturally abundant, sustainable, and clean resource, which has the potential to replace fossil feedstock for sustainable production of high add-value chemicals. However, an efficient conversion process is still difficult to achieve due to the difficult reaction conditions. In this study as a novel and versatile concept, we introduced the use of beta-cyclodextrin (beta-CD) macromolecule to enhance the photocatalytic behavior of a alpha-Fe2O3/TiO2 heterojunction. The selective conversion of guaiacol was evaluated using 0.2, 1.0, and 2.0 molar ratios of beta-CD anchored on 0.7 wt % alpha-Fe2O3/TiO2 under mild reaction conditions. 1.0 molar ratio of beta-CD promoted photo-oxidation of guaiacol to mainly produce p-benzoquinone with similar to 68% selectivity at similar to 10% conversion. To understand this effect, Electron Paramagnetic Resonance Spectroscopy (EPR) in operando mode and Diffuse Reflectance Spectroscopy (DRS) experiments were performed. The results showed that the 1.0 molar ratio of beta-CD decreases the bandgap from 3.06 to 2.76 eV and controls the center dot OH radical concentration due to the formation of a covalent bond between beta-CD and semiconductors. The improved guaiacol adsorption capacity on the photocatalyst resulted in the enhancement of the photochemical activity and selectivity. Additionally, a possible pathway of guaiacol transformation was proposed through the oxidation intermediates. Furthermore, the photocatalyst beta-CD/alpha-Fe2O3/TiO2 can be recycled efficiently and reused three times, without loss in reactivity.
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    Substituents role in zinc phthalocyanine derivatives used as dye-sensitized solar cells. A theoretical study using Density Functional Theory
    (2015) Linares Flores, Cristián; Mendizabal, Fernando; Arratia Pérez, Ramiro; Inostroza, Natalia; Orellana, Carlos
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    Tailoring electroactive surfaces by non-template molecular assembly. Towards electrooxidation of L-cysteine
    (2017) Santander Nelli, Mireya; Silva, Carlos P.; Espinoza Vergara, Javier; Silva, Juan F.; Olguín, Camila F.; Cortés Arriagada, Diego; Zagal Moya, José Heráclito; Mendizabal, Fernando; Díez Pérez, Ismael; Pavez, Jorge
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    Theoretical insights into the adsorption of neutral, radical and anionic thiophenols on gold(111)
    (2013) Miranda-Rojas, S.; Munoz-Castro, Alvaro; Arratia-Perez, Ramiro; Mendizabal, Fernando
    The interaction of thiol and thiolate containing molecules with gold (S-Au) has gained increasing interest because of its applications in molecular electronic devices and catalysis. In this context, the enhanced conductivity of thiophenol compared to alkanethiol represents an opportunity to develop more sensitive and selective gold-based devices by incorporating molecules with the aryl-thiol moiety into their structures. As has been proposed earlier, the thiol moiety is deprotonated after binding to gold, hence, we present here a comparative study of the S-Au bond strength between several neutral and deprotonated aromatic-sulfur systems in their anionic and radical forms with a detailed description of the nature of this interaction. The study was performed by means of computational chemistry methods, using a cluster of 42 Au atoms as a model of the Au(111) surface that allowed us to provide new chemical insights to control the S-Au interface interaction strength. Our results revealed that the thiophenols-gold interaction is mainly dispersive where the interaction energies range between 31 and 43 kcal mol(-1). The radical and anionic thiophenolates-gold interaction increases due to a strong charge transfer character, depicting interaction energies in the range of 50 to 55 kcal mol(-1) and 62 to 92 kcal mol(-1), respectively. These results suggest that for the anionic thiophenolate the binding strength can be tailored according to the electron-donor capabilities of the ligand which in turn can be finely tuned by several substituents. Our results are of possible impact for the design of new devices.
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    Unraveling the Nature of the Catalytic Power of Fluoroacetate Dehalogenase
    (2018) Miranda-Rojas, Sebastian; Fernandez, Israel; Kaestner, Johannes; Toro Labbé, Alejandro; Mendizabal, Fernando