4 research outputs found

    Influence of Dispersion Interactions on the Thermal Desorption of Nonplanar Polycyclic Aromatic Hydrocarbons on HOPG

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    A combination of low energy ion beam deposition and mass resolved thermal desorption spectroscopy is applied to analyze the binding behavior of two nonplanar polycyclic aromatic hydrocarbons (PAHs) to highly oriented pyrolytic graphite (HOPG) surfaces—also concerning their lateral dispersion interactions. In particular, the fullerene precursor C60H30 (FPC) and rubrene C42H28 are studied. Due to their smaller contact areas, both molecules exhibit significantly weaker binding energies to the HOPG surface compared to planar PAHs of similar size: C60H30 is bound to the surface by 3.04 eV, which is 0.6 eV lower than for a fully planar homologue. For rubrene, an isolated molecule–substrate binding energy of 1.59 eV is found, which is about 1 eV less than that of the corresponding planar homologue hexabenzocoronene C42H18. In contrast to FPC, rubrene shows a significant (intermolecular) lateral dispersion contribution to the binding energy as the submonolayer coverage increases

    Influence of Dispersion Interactions on the Thermal Desorption of Nonplanar Polycyclic Aromatic Hydrocarbons on HOPG

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    A combination of low energy ion beam deposition and mass resolved thermal desorption spectroscopy is applied to analyze the binding behavior of two nonplanar polycyclic aromatic hydrocarbons (PAHs) to highly oriented pyrolytic graphite (HOPG) surfaces—also concerning their lateral dispersion interactions. In particular, the fullerene precursor C60H30 (FPC) and rubrene C42H28 are studied. Due to their smaller contact areas, both molecules exhibit significantly weaker binding energies to the HOPG surface compared to planar PAHs of similar size: C60H30 is bound to the surface by 3.04 eV, which is 0.6 eV lower than for a fully planar homologue. For rubrene, an isolated molecule–substrate binding energy of 1.59 eV is found, which is about 1 eV less than that of the corresponding planar homologue hexabenzocoronene C42H18. In contrast to FPC, rubrene shows a significant (intermolecular) lateral dispersion contribution to the binding energy as the submonolayer coverage increases

    Antioxidant activity and phenolic profiles of wild currant Ribes magellanicum from Chilean and Argentinian Patagonia

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    The Patagonian currant Ribes magellanicum is highly valued due to its pleasantflavor and sweet taste. The aim of this study was to characterize its constituentsand to assess their antioxidant and cytoprotective properties. For the fruitphenolic-enrichedextract (PEE), total phenolics (TP), total flavonoids (TF), andantioxidant activity (DPPH, Ferric reducing antioxidant power (FRAP), andTrolox equivalent antioxidant activity (TEAC)) were determined. Argentineansamples presented better activity in the DPPH and FRAP assays. Best cytoprotectionagainst oxidative stress induced by H2O2 in AGS cells was found in oneArgentinean sample at 500 μg mL−1 (65.7%). HPLC MS/MS analysis allowedthe tentative identification of 59 constituents, including eight anthocyanins, 11conjugates of caffeic-,ferulic-,and coumaric acid, and 38 flavonoids, most ofthem quercetin and kaempferol derivatives. Argentinean samples showed a morecomplex pattern of anthocyanins, hydroxycinnamic acids (HCA), and flavonoids.Cyanidin rhamnoside hexoside and cyanidin hexoside were the main anthocyanins,accounting for 35 and 55% for the Argentinean and 60 and 27% for theripe Chilean fruits. HCA content was about three times higher in Argentineansamples. The phenolic profiles of Chilean and Argentinean Ribes magellanicumshow remarkable differences in chemical composition with higher HCA andflavonoid content in Argentinean samples.Fil: Jimenez Aspee, Felipe. Universidad de Talca; ChileFil: Tomas Valdez, Samanta. Universidad de Talca; ChileFil: Schulz, Ayla. Universidad de Talca; ChileFil: Ladio, Ana Haydee. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Patagonia Norte. Instituto de Investigación En Biodiversidad y Medioambiente; Argentina. Universidad Nacional del Comahue; ArgentinaFil: Theoduloz, Cristina. Universidad de Talca; ChileFil: Schmeda Hirschmann, Guillermo. Universidad de Talca; Chil
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