Browsing by Author "Rojas de la Fuente, Susana Dennis"

Now showing 1 - 14 of 14
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    A simple method to generate spontaneous chemisorption of metallic particles mediated by carboxylate groups from silylated oligomeric poly(amide-imide)s
    (2017) González Enríquez, Carmen; Sarabia Vallejos, Mauricio; Terraza Inostroza, Claudio; Cabrera, Alejandro Leopoldo; Rojas de la Fuente, Susana Dennis; González Enríquez, Carmen; Sarabia Vallejos, Mauricio; Terraza Inostroza, Claudio; Cabrera, Alejandro Leopoldo; Rojas de la Fuente, Susana Dennis
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    Comparative study of the structural and optical properties of epitaxial CuFeO2 and CuFe(1-x)GaxO(2) delafossite thin films grown by pulsed laser deposition methods
    (2017) Wheatley, Robert Alastair; Rojas de la Fuente, Susana Dennis; Oppolzer, C.; Joshi, T.; Borisov, P.; Lederman, D.; Cabrera, Alejandro Leopoldo
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    EVAPORATION OF LOW-VAPOR PRESSURE METALS USING A CONVENTIONAL MINI ELECTRON BEAM EVAPORATOR
    (2014) Cabrera, Alejandro Leopoldo; Rojas de la Fuente, Susana Dennis; Díaz, Donovan; Ferrari Ramírez, Piero Antonio.
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    Gas adsorption properties of complex copper oxides
    (2017) Rojas de la Fuente, Susana Dennis; Cabrera, Alejandro Leopoldo; Pontificia Universidad Católica de Chile. Facultad de Física
    Highly epitaxial films of CuFeO2 and CuFe0.75Ga0.25O2 were grown by pulsed laserdeposition (PLD) from stoichiometric targets over Al2O3 (001) substrate undercontrolled partial pressure of oxygen as carrier gas. Resulting films were highly orientedin c-axis direction.Structural properties of samples were characterized by X-Ray Diffraction (XRD), Raman spectroscopy, X-Ray Photoelectron Spectroscopy (XPS), optical transmittance and diffuse reflectance. This characterization techniques confirmed the rhombohedral Delafossite crystal structure for both kind of samples and CuFe0.75Ga0.25O2 samples were formed by an alloy between CuFeO2 and CuGaO2 Delafossite materials. Using optical transmittance and diffuse reflectance, the optical transitions were estimated by using theTauc method. Direct optical transitions were measured at 1.28±0.02 eV and 2.20±0.05eV for pure CuFeO2 samples and for CuFe0.75Ga0.25O2 were measured at 1.50±0.04 eVand 2.30±0.09 eV, plots showed another higher transition near 3 eV but due to technical limitations this gap cannot be clearly determined. Adsorption of CO2 and H2O was studied via thermal programmed desorption technique. In both films Copper and Iron were present at the surface, and consequently formed part of the surface-gas interface. X-ray photoelectron data indicated that CO2 is adsorbed preferentially at copper sites forming a similar coordination to CuCO3. The energy for desorption of CO2 and H2O was estimated to be 1.0±0.8 eV/molecule for CuFeO2 and0.7±0.4 eV/molecule for CuFe0.75Ga0.25O2. Also, it was possible to correlate second order desorption with a CO2 reduction reaction. Copper Delafossite materials studied in this work showed some catalytic activity in good agreement with the literature. Future work in this field would involve synthesis of a wider variety of CuFe1-xGaxO2 samples in order to get a better idea of the influence ofiron substitution for gallium in the Delafossite structure. Also, for a better understanding of the relationship between adsorption properties and catalytic behavior some futurework regarding electrical and electrochemical properties is proposed
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    Germicidal effect of UV light on epiphytic fungi isolated from blueberry = Efecto germinicida de luz ultravioleta sobre hongos epifíticos aislados desde arándanos.
    (2012) Latorre G., Bernardo; Rojas de la Fuente, Susana Dennis; Díaz, Gonzalo A.; Chuaqui Kettlun, Hernán
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    Hydrogen Sorption of Porous Tungsten Oxide Nanomaterial and Effect of a Pd Coating on its Storage Capacity Under Hydrogenation Cycles
    (2018) Díaz Droguett, Donovan Enrique; Rojas de la Fuente, Susana Dennis; Roble Albeal, Martín Cristián
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    Hydrothermal improvement for 3R-CuFeO2 delafossite growth by control of mineralizer and reaction atmosphere
    (2019) Roble Albeal, Martín Cristián; Rojas de la Fuente, Susana Dennis; Wheatley, Robert Alastair; Wallentowitz, Sascha; Cabrera, Alejandro Leopoldo; Díaz Droguett, Donovan Enrique
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    Inhibition of hydrogen absorption in bulk Pd by the formation of Ru-Pd surface alloy
    (2014) Ferrari Ramírez, Piero Antonio.; Díaz, Donovan; Rojas de la Fuente, Susana Dennis; Cabrera, Alejandro Leopoldo
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    Optical detection of carbon dioxide adsorption on epitaxial CuFe1-xGaxO2 Delafossite film grown by pulse laser deposition
    (2016) Rojas de la Fuente, Susana Dennis; Joshi, T.; Wheatley, Robert Alastair; Sarabia Vallejos, Mauricio; Borisov, P.; Lederman, D.; Cabrera, Alejandro Leopoldo
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    Quantitative determination of hydrogen absorption by Pd cluster-assembled films using a quartz crystal microbalance
    (2012) El Far Manríquez, Rodrigo Andrés; Díaz Droguett, Donovan Enrique; Rojas de la Fuente, Susana Dennis; Ávila Osses, Jonathan Israel; Romero, C.P.; Lievens, P.; Cabrera, Alejandro Leopoldo
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    Rapid synthesis of carbon nanoparticles with an optimized combination of specific surface area and crystallinity by a plasma-assisted single-step process
    (2013) Aomoa, N.; Bhuyan, Heman; Cabrera, Alejandro Leopoldo; Favre Domínguez, Mario; Díaz Droguett, Donovan Enrique; Rojas de la Fuente, Susana Dennis; Ferrari, P.; Srivastava, D.; Kakati, M.
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    Role of Nb2O5 Crystal Phases on the Photocatalytic Conversion of Lignin Model Molecules and Selectivity for Value‐Added Products
    (2024) Rojas de la Fuente, Susana Dennis; Rafaela, Gabriela; Espinoza Villalobos, Nicole Margarita; Díaz, Donovan; Salazar, Ricardo; Cáceres Jensen, Lizethly; Escalona, Néstor; Barrientos, Lorena
    The photocatalytic conversion in aqueous media of phenol and guaiacol as a lignin model compound using Nb2O5 with different crystal phases was studied. Nb2O5 particles were synthesized using hydrothermal methods, where it was observed that changes in the solvent control their morphology and crystal phase. Different photocatalytic behavior of Nb2O5 was observed with the selected model compounds, indicating that its selection directly impacts the resulting conversion and selectivity rates as well as the reaction pathway, highlighting the relevance of model molecule selection. Photocatalytic conversion of phenol showed conversion rate (C%) up to 25 % after 2 h irradiation and high selectivity (S%) to pyrogallol (up to 50 %). Orthorhombic Nb2O5 spheres favored conversion through free hydroxyl radicals while monoclinic rods did not convert phenol. Guaiacol photocatalytic oxidation showed high conversion rate but lower selectivity. Orthorhombic and monoclinic Nb2O5 favored the formation of resorcinol with S % ~0.43 % (C % ~33 %) and ~13 % (C % ~27 %) respectively. The mixture of both phases enhanced the guaiacol conversion rate to ~55 % with ~17 % of selectivity to salicylaldehyde. The use of radical scavengers provided information to elucidate the reaction pathway for these model compounds, showing that different reaction pathways may be obtained for the same photocatalyst if the model compound is changed.
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    Selective photocatalytic conversion of guaiacol using g-C3N4 metal free nanosheets photocatalyst to add-value products
    (ELSEVIER SCIENCE SA, 2021) Rojas de la Fuente, Susana Dennis; Espinoza Villalobos, Nicole Margarita; Salazar, R.; Escalona, Néstor; Contreras, D.; Melin, V; Laguna Bercero, M. A.; Sanchez Arenillas, M.; Vergara, E.; Caceres Jensen, L.; Rodríguez Becerra, J.; Barrientos, Lorena
    Valorization of lignin into high valuable chemical is a critical challenge. Its availability is a key factor for the development of viable lignocellulosic processes to replace fossil derived compounds. In this work, new insights on the high photocatalytic conversion of guaiacol (82%) as a lignin model compound was achieved, also, high selectivity to p-benzoquinone (59%), catechol (27%), and pyrogallol (6%) was obtained using metal-free pyrolyzed g-C3N4 under visible light irradiation. To highlight the new insights, experimental parameters were modified to control the reaction mechanism to increase selectivity and photo-conversion. g-C3N4 photocatalyst was synthesized through urea calcination at 550 degrees C and the photocatalytic performance was assessed in terms of pyrolysis time, where higher time resulted in better photocatalytic activity. This effect was attributed to smaller structures and therefore better quantum confinement of the charges. The oxidation was promoted by OH radicals, which were detected through EPR operando mode and the addition of radical scavengers. A reaction pathway was proposed, in which the OH attacks guaiacol through a methoxy group. The photocatalytic reaction can be tuned using external oxidant agents such as O-2 and/or H2O2 to promote certain radical formation, enhancing conversion rates and promoting selectivity for a specific product, where yield shifting from p-benzoquinone to pyrogallol was experimentally observed.
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    Wetting properties of hydrothermally synthesized crystalline CuFeO2 delafossite porous surfaces
    (2019) Wheatley, Robert Alastair; Roble Albeal, Martín Cristián; Molina, S.; Díaz Droguett, Donovan Enrique; Rojas de la Fuente, Susana Dennis; Seifert, Birger; Wallentowitz, Sascha; Díaz Droguett, D. E.; Volkmann, Ulrich