Examinando por Autor "Segura, Rodrigo"

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    Ítem
    Enhanced photoconversion efficiency of hybrid TiO2/nox-MWCNT/Si photoanode for water splitting in neutral medium
    (Elsevier, 2021) Olivares, Fernanda; Segura, Rodrigo; Reyes, Javier; Peón, Francisco; Henríquez, Ricardo; Hevia, Samuel A.; Durán, Boris; Villalonga, Reynaldo
    Hybrid films composed by TiO2 and functionalized MWCNTs were synthesized and used as photoanodes to perform the water splitting process under neutral and free of sacrificial agents medium. The results show that introducing a sublayer of MWCNTs functionalized with –NO2 and –COOH groups leads to structural modifications on TiO2 that decrease the band gap and reduce the recombination phenomenon. Those groups anchored to nanotubes also play an important role in their dispersibility and provide an additional electron withdrawing effect to the pristine nanotubes. These conditions significantly improve the photoconversion efficiency of the hybrid system until 15-fold regarding pristine TiO2 prepared under the same conditions.
  • Miniatura
    Ítem
    Phytostimulant properties of highly stable silver nanoparticles obtained with saponin extract from Chenopodium quinoa
    (Society of Chemical Industry, 2020) Segura, Rodrigo; Vásquez, Gustavo; Colson, Emmanuel; Gerbaux, Pascal; Frischmon, Caroline; Nesic, Aleksandra; García, Danni E; Cabrera-Barjas, Gustavo
    BACKGROUND: Quinoa (Chenopodium quinoa Willd) is an Andean original pseudocereal with high nutritional value. During quinoa processing, large amounts of saponin-rich husks byproducts are obtained. Quinoa saponins, which are biologically active, could be used for various agriculture purposes. Silver nanoparticles have increasingly attracted attention for the management of crop diseases in agriculture. In this work, silver nanoparticles are synthesized by a sustainable and green method, using quinoa husk saponin extract (QE) to evaluate their potential for application in agriculture as biostimulants. RESULTS: Quinoa extract was obtained and characterized by liquid chromatography with tandem mass spectrometry (LC–MS/ MS). Sixteen saponin congeners were successfully identified and quantified. The QE obtained was used as a reducing agent for silver ions to synthesize silver nanoparticles (QEAgNPs) under mild conditions. The morphology, particle size, and stability of Ag nanoparticles were investigated by transmission electron microscopy (TEM), ultraviolet–visible spectroscopy (UV-visible), energy-dispersive X-ray (EDS), zeta potential, and Fourier transform infrared spectroscopy with attenuated total reflection (FTIR-ATR). Ultraviolet–visible spectroscopy measurements confirmed the formation of silver nanoparticles in the presence of QE, with estimated particle sizes in a range between 5 and 50 nm. According to the zeta potential values, highly stable nanoparticles were formed. The QE and QEAgNPs (200–1000 ∼g/mL) were also tested in radish seed bioassay to evaluate their phytotoxicity. The seed germination assays revealed that QEAgNPs possessed a phytostimulant effect on radish seeds in a dosedependent manner, and no phytotoxicity was observed for both QE and QEAgNPs. CONCLUSION: Silver nanoparticles obtained by a so-called ‘green’ method could be considered as good candidates for application in the agricultural sector for seed treatment, or as foliar sprays and plant-growth-promoters.