Browsing by Author "Florez, Jiress"

Now showing 1 - 2 of 2
  • Thumbnail Image
    Item
    Furanyl chalcone derivatives as efficient singlet oxygen quenchers. An experimental and DFT/MRCI study
    (PERGAMON-ELSEVIER SCIENCE LTD, 2020) Diaz Uribe, Carlos; Vallejo, William; Florez, Jiress; Trilleras, Jorge; Gutierrez, Margarita; Rodriguez Serrano, Angela; Schott, Eduardo; Zarate, Ximena
    This study reports the antioxidant activity against singlet oxygen (O-1(2)) of five newly synthesized furanyl chalcones (FCs) (E)-3 (5-(4 chlorophenyl)furan-2-yl)-1-arylprop-2-en-1-ones (3a-e). Their structural difference is based on the aryl substituent as follows (Ar): 3a = -C6H4-OCH3, 3b = -C6H3-(1,2-OCH3), 3c = -C6H4OC6H4, 3d = - C10H6-(OCH3) and 3e = -C4H3O. We used a Claisen-Schmidt condensation involving a 5-(4-chlorophenyl)furan-2-carbaldehyde and the corresponding ketones under ultrasonic irradiation. Their property to O-1(2) quenching was analyzed in terms of the rate constant for the process (k(Q) at 25 degrees C) determined by the Stern-Volmer model in ethanol. For the compounds 3c, 3d and 3e, the k(Q) values are slightly larger respect to 3a and 3b. The FCs 3c behaves as the best quencher (k(Q )of 8.44 (+/- 0.09) x 10(7) M-1 s(-1)). Geometry analysis and electronic structure calculations have been performed in the framework of Density Functional Theory (DFT) and DFT/Multi-Reference Configuration Interaction (DFT/MRCI) methods. According to DFT/MRCI, a physical quenching of O-1(2) from the ground states of the FCs may not likely induce a spontaneous energy transfer processes but a chemical quenching mechanism may dominate the kinetics. (C) 2020 Elsevier Ltd. All rights reserved.
  • Thumbnail Image
    Item
    Removal and photocatalytic degradation of methylene blue on ZrO2 thin films modified with Anderson-Polioxometalates (Cr3+, Co3+, Cu2+): An experimental and theoretical study
    (2024) Díaz-Uribe, Carlos; Florez, Jiress; Vallejo, William; Duran, Freider; Puello, Esneyder; Roa, Vanesa; Schott, Eduardo; Zarate, Ximena
    In this work, several ZrO2 thin films modified with Anderson-type polyoxomolybdates (POMs) with general formula (NH4)6-n[XMo6O24H6]-6+n where X = Co3+, Cr3+ and, Cu2+ were prepared. Thin films were characterized through SEM and EDX assay, UV–Vis diffuse reflectance and Fourier Transform Infrared (FTIR) assay. The optical bandgap of ZrO2 thin films was determined to be 3.25 eV, while the modified thin films showed a red shift in the optical activity compared with bare ZrO2 thin films. Methylene Blue (MB) adsorption studies showed that Freundlich isotherm describes properly the experimental data for modified-ZrO2 thin films. Besides, the kinetic results showed the MB adsorption of modified-ZrO2 thin films was superior to bare ZrO2 thin film. The adsorption rate values (K2) of the pseudo-second order model follow these trend ZrO2/CrPOM > ZrO2/CoPOM > ZrO2/CuPOM > ZrO2. The photocatalytic activity of the thin films for MB decomposition under UV and Visible irradiation was studied. Among all the catalysts, the ZrO2 thin films showed the lowest photocatalytic degradation rate kap value (kap = 1.5 × 10−3 min−1), while the best result was obtained for ZrO2/CrPOM thin films (kap = 5.7 × 10−3 min−1) under UV irradiation. Besides, this was the only catalyst efficiently active in MB degradation under visible irradiation, these materials reach 10.4 % after 100 min under visible irradiation. Finally, chemical calculations supported the observed results, by means of TDDFT, EDA analysis, Fukui function and periodic DFT calculations.