Browsing by Author "Barrientos, Lorena"
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- ItemCatalytic 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
- ItemControlled Ag-tio2 heterojunction obtained by combining physical vapor deposition and bifunctional surface modifiers(2018) Barrientos, Lorena; Allende, Patricio; Angel Laguna-Bercero, Miguel; Pastrian, Juan; Rodriguez-Becerra, Jorge; Caceres-Jensen, Lizethly
- ItemDegradation of dairy wastewater using sustainable nanotechnology composed of a-Fe2O3/TiO2 rod-shaped material and photocatalytic process: a complementary treatment approach for industrial wastewater(2024) Espinoza-Villalobos, Nicole; Rojas, Susana; Barrientos, Lorena; Salazar-Gonzalez, Ricardo; Luna, Damari; Flores, Caetano; Escalona, NestorBACKGROUND: High water consumption and the toxic pollutants found in industrial wastewater are key challenges in achieving a more sustainable development. In this sense, it is crucial to develop sustainable ways to reduce the organic pollutants found in wastewater and to promote its reuse.
- ItemFormation of Copper Nanoparticles Supported onto Inclusion Compounds of alpha-cyclodextrin: A New Route to Obtain Copper Nanoparticles(2010) Silva, Nataly; Moris, Silvana; Herrera Pisani, Bárbara Andrea; Diaz, Maximiliano; Kogan, Marcelo J.; Barrientos, Lorena; Yutronic, Nicolas; Jara, Paul
- ItemIdentification of potential trypanothione reductase inhibitors among commercially available beta-carboline derivatives using chemical space, lead-like and drug-like filters, pharmacophore models and molecular docking(2017) Rodriguez, J.; Caceres, L.; Hernandez, J.; Barrientos, Lorena
- ItemInclusion compounds of alpha-cyclodextrin with alkylthiols(2008) Jara, Paul; Barrientos, Lorena; Herrera Pisani, Bárbara Andrea; Sobrados, Isabel
- ItemInsights of the formation mechanism of nanostructured titanium oxide polymorphs from different macromolecular metal-complex precursors(2021) Allende, Patricio; Orera, Alodia; Laguna-Bercero, Miguel A.; Luisa Valenzuela, Maria; Diaz, Carlos; Barrientos, LorenaThe insight into the mechanism of the unprecedented formation of pure anatase TiO2 from the macromolecular (Chitosan)center dot(TiOSO4)(n) precursor has been investigated using micro Raman spectroscopy, Scanning Electron Microscopy (SEM) and thermogravimetric/differential thermal analysis (TGA/DTA). The formation of a graphitic film was observed upon annealing of the macromolecular precursor, reaching a maximum at about 500 degrees C due to decomposition of the polymeric chain of the Chitosan and (PS-co-4-PVP) polymers. The proposed mechanism is the nucleation and growth of TiO2 nanoparticles over this graphitic substrate. SEM and Raman measurements confirm the formation of TiO2 anatase around 400 degrees C. The observation of an exothermic peak around 260 degrees C in the TGA/DTA measurements confirms the decomposition of carbon chains to form graphite. Another exothermic peak around 560 degrees C corresponds to the loss of additional carbonaceous residues.
- ItemPalmitic 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, LorenaA 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.
- ItemPedagogical Content Knowledge of Chemical Kinetics: Experiment Selection Criteria To Address Students’ Intuitive Conceptions(2018) Marzabal Blancafort, Ainoa; Delgado Chang, Virginia; Moreira Seguel, Patricia Magdalena; Barrientos, Lorena; Moreno Cortes, Jeannette del Pilar
- ItemRole 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, LorenaThe 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.
- ItemSelective 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, LorenaValorization 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.
- ItemSilver /Silver oxide nanoparticles as potential sensitizers in dye-sensitized solar cells(2010) Barrientos, Lorena; Loeb Luschow, Bárbara
- ItemSolid state tuning of TiO2 morphology, crystal phase, and size through metal macromolecular complexes and its significance in the photocatalytic response(2018) Allende-Gonzalez, P.; Laguna Bercero, M.A.; Barrientos, Lorena; Valenzuela, M.L.; Diaz, C.
- ItemSolvent-less method for efficient photocatalytic alpha-Fe2O3 nanoparticles using macromolecular polymeric precursors(2016) Diaz, Carlos; Barrientos, Lorena; Carrillo, Daniel; Valdebenito, Javier; Valenzuela, María L.; Allende, Patricio; Geaney, Hugh; O'Dwyer, Colm
- ItemStudy of Sorption Kinetics and Sorption-Desorption Models to Assess the Transport Mechanisms of 2,4-Dichlorophenoxyacetic Acid on Volcanic Soils(2021) Caceres-Jensen, Lizethly; Rodriguez-Becerra, Jorge; Garrido, Carlos; Escudey, Mauricio; Barrientos, Lorena; Parra-Rivero, Jocelyn; Dominguez-Vera, Valentina; Loch-Arellano, BrunoThe sorption behavior of 2,4-dichlorophenoxyacetic acid (2,4-D) in the abundant agricultural volcanic ash-derived soils (VADS) is not well understood despite being widely used throughout the world, causing effects to the environment and human health. The environmental behavior and risk assessment of groundwater pollution by pesticides can be evaluated through kinetic models. This study evaluated the sorption kinetics and 2,4-D sorption-desorption in ten VADS through batch sorption experiments. Differences in the sorption extent for the fast and slow phases was observed through the IPD model where 2,4-D sorption kinetics was controlled by external mass transfer and intra organic matter diffusion in Andisols (C1 not equal 0). We confirmed from the spectroscopic analysis that the carboxylate group directly drives the interaction of 2,4-D on Andisol soil. The MLR model showed that IEP, FeDCB, and pHxSilt are important soil descriptors in the 2,4-D sorption in VADS. The Freundlich model accurately represented sorption equilibrium data in all cases (Kf values between 1.1 and 24.1 mu g(1-1/n) mL(1/n)g(-1)) with comparatively higher sorption capacity on Andisols, where the highest hysteresis was observed in soils that presented the highest and lowest OC content (H close to 0).
- ItemSynthesis, spectroscopic and electrochemical characterization of copper(I) complexes with functionalized pyrazino[2,3-f]-1,10-phenanthroline(2008) Barrientos, Lorena; Araneda, Carmen; Loeb Luschow, Bárbara; Crivelli, Irma G.
- ItemTiO2/SiO2 Composite for Efficient Protection of UVA and UVB Rays Through of a Solvent-Less Synthesis(2019) Allende, P.; Barrientos, Lorena; Orera, A.; Laguna Bercero, M. A.; Salazar, N.; Valenzuela, M. L.; Díaz, C.
- ItemTuning amphiphilic properties of Ni/Carbon nanotubes functionalized catalysts and their effect as emulsion stabilizer for biomass-derived furfural upgrading(2020) Herrera, C.; Barrientos, Lorena; Rosenkranz, Andreas; Sepulveda, C.; Garcia-Fierro, J. L.; Laguna-Bercero, M. A.; Escalona, Néstor
- ItemValorization of biomass derivatives through the conversion of phenol over silica-supported Mo-Re oxide catalysts(2020) Herrera Hernández, Carla Pía; Ghampson, IT; Cruces, K; Sepulveda, C; Barrientos, Lorena; Laurenti, D; Geantet, C; Serpell Carriquiry, Ricardo Javier; Contreras, D; Melin, V; Escalona, N