Browsing by Author "Alves, Tiago Vinicius"

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    Molecular 5,8-π-extended quinoxaline derivatives as chromophores for photoluminescence applications.
    (2019) Aguiar, Leonardo de Oliveira; Lima Junior, Adalberto Santana; Bechtold, Ivan Helmuth; Curcio, Sergio Fernando; Cazati, Thiago; Alves, Tiago Vinicius; Vieira, André Alexandre
    The 5,8-π-extended quinoxaline derivatives are widely studied due to their wellknown photophysical and electrochemical properties. In order to investigate the structure-property relationship, a novel series of fluorescent calamitic liquid crystals based on the quinoxaline heterocycle was successfully synthesized and characterized. The final molecules presented calamitic mesomorphism with nematic and smectic phases. These compounds displayed intense green photoluminescence under UV light excitation in solution and in the solid state. In chloroform solution, the fluorescence quantum yields (ΦFL= 0.54–0.62) of the quinoxaline-based derivatives were significantly higher than those previously described for similar benzothiadiazoles. The maximum emission peaks were between 511-520 nm with singlet excited-state lifetimes in the nanosecond timescale. The solvatochromism studies showed a significant dependence of the emission on the polarity of the solvent. Doping of the quinoxalines with fullerene C60 suggests a charge transfer process, this being dependent on the π-conjugate core. The energy band gaps predicted with DFT calculations are in excellent agreement with the experimental data.
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    Synergistic effect between CeO2 nanowires and gold NPs over the activity and selectivity in the oxidation of thioanisole.
    (2021) Rosado, Taíssa F.; Teixeira, Moisés Paulo; Moraes, Leonardo César de; Silva, Leonardo A. da; Silva, Augusto V. Pontes; Taylor, Jason Guy; Freitas, Isabel Cristina de; Oliveira, Daniela Coelho de; Gardener, Jules; Solorzano, Guilhermo; Alves, Tiago Vinicius; Venancio, Mateus Fernandes; Silva, Maria Isabel Pais da; Brocchi, Eduardo de Albuquerque; Fajardo, Humberto Vieira; Silva, Anderson Gabriel Marques da
    Gold nanoparticles incorporated on ceria nanowires have been employed as efficient nanocatalysts for the se lective oxidation of thioanisole. The control of both physical and chemical parameters as well as metal–support interactions are important factors that determine their performances. Considering their one-dimensional morphology with large surface area, thin diameters, high concentration of oxygen vacancies, and small Au NPs uniformly on the entire CeO2 surface with a high fraction of oxidized gold species, these characteristics make them favorable nanocatalysts for oxidation transformations. The CeO2-Au nanowires displayed improved per formances towards the oxidation of thioanisole when compared to the pure CeO2 nanowires and commercial CeO2-Au catalysts. The CeO2-Au nanowires catalyzed the selective synthesis of methyl phenyl sulfoxide with up to 100 % of selectivity and high conversion. The impact of solvent and temperature during the catalytic reaction was also experimentally and theoretically investigated by DFT calculations, indicating a key role in the observed activities.