Browsing by Author "Benavente, Eglantina"

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    Photoinduced Paramagnetic Centers in Nanocomposites Formed by Titanium Dioxide and Myristic Acid
    (2021) Magon, Claudio Jose; Zarto, Harold Lozano; Donoso, Jose Pedro; Eckert, Hellmut; Devis, Sindy; Benavente, Eglantina; Villarroel, Roberto; Gonzalez, Guillermo
    An electron paramagnetic resonance (EPR) study has been carried out on the hybrid layered nanocomposite formed by TiO2 and myristic acid. The samples were characterized by means of X-ray diffraction (XRD), thermogravimetric analysis, solid-state NMR, scanning electron microscopy (SEM), spectral absorbance (UV-vis), and Raman and infrared spectroscopy (FTIR). X-band continuous wave (CW)-EPR was used to investigate the photo-induced paramagnetic species generated in the nanocomposite by UV irradiation at 365 nm in vacuum and in ambient atmosphere and characterized spectroscopically at 90 K. Various paramagnetic species were identified and characterized by their Hamiltonian parameters. They include disordered isolated Ti3+ centers, dimeric units producing S = 1 triplet species, and superoxide radicals, (ROO center dot), whose concentrations were monitored as a function of temperature and annealing times during the course of well-defined temperature cycling protocols.
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    Two-Dimensional Titanium Dioxide-Surfactant Photoactive Supramolecular Networks: Synthesis, Properties, and Applications for the Conversion of Light Energy
    (2022) Lozano, Harold; Devis, Sindy; Aliaga, Juan; Alegria, Matias; Guzman, Hernan; Villarroel, Roberto; Benavente, Eglantina; Gonzalez, Guillermo
    The desire to harness solar energy to address current global environmental problems led us to investigate two-dimensional (2D) core-shell hybrid photocatalysts in the form of a 2D-TiO2-surfactant, mainly composed of fatty acids. The bulk products, prepared by two slightly different methods, consist of stacked host-guest hybrid sheets held together by van der Waals forces between alkyl carboxylate moieties, favoring the synergistic conjugation of the photophysical properties of the core and the hydrophobicity of the self-assembled surfactant monolayer of the shell. X-ray diffraction and the vibrational characteristics of the products revealed the influence of synthesis strategies on two types of supramolecular aggregates that differ in the core chemical structure, guest conformers of alkyl surfactant tails and type, and the bilayer and monolayer of the structure of nanocomposites. The singular ability of the TiO2 core to anchor carboxylate leads to commensurate hybrids, in contrast to both layered clay and layered double-hydroxide-based ion exchangers which have been previously reported, making them potentially interesting for modeling the role of fatty acids and lipids in bio-systems. The optical properties and photocatalytic activity of the products, mainly in composites with smaller bandgap semiconductors, are qualitatively similar to those of nanostructured TiO2 but improve their photoresponse due to bandgap shifts and the extreme aspect-ratio characteristics of two-dimensional TiO2 confinement. These results could be seen as a proof-of-concept of the potential of these materials to create custom-designed 2D-TiO2-surfactant supramolecular photocatalysts.