Dr. Valdes-Morales, Hector

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Nombre de publicaciĂ³n
Dr. Valdes-Morales, Hector
Nombre completo
Valdes Morales, Hector
Facultad
Email
hvaldes@ucsc.cl
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2020 - 20212
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Author: Kandasamy, M. Ă—

Research Outputs

Now showing 1 - 2 of 2
  • No Thumbnail Available
    Publication
    Fluorine-free synthesis of reduced graphene oxide modified anatase TiO2 nanoflowers photoanode with highly exposed {0 0 1} facets for high performance dye-sensitized solar cell
    (Elsevier, 2020)
    Dr. Valdes-Morales, Hector 
    ;
    Pugazhenthiran, Nalandhiran
    ;
    Mangalaraja, R.
    ;
    Vijaya, S.
    ;
    Suresh, S.
    ;
    Kandasamy, M.
    ;
    Sathishkumar, P.
    ;
    Gracia-Pinilla, M.
    ;
    Murugesan, S.
    ;
    Anandan, S.
    A facile, fluorine-free and non-toxic one-pot solvothermal technique was adopted to synthesis TiO2 nanoflowers with anatase phase having 98% highly exposed {001} facets (TiO2 {001} NFs). The morphology, grain size and crystallinity of pure TiO2 {001} NFs and reduced graphene oxide (RGO) sheets modified TiO2 {001} NFs (RGOTiO2 {001} NFs) were inspected by diffuse reflectance spectroscopy (DRS), X-ray diffractometry (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). TEM images showed the development of anatase TiO2 {001} NFs with high crystallinity and uniform shape. The influence of RGO on the performance of the TiO2 {001} NFs as a photoanode material in dye-sensitized solar cell (DSSC) was examined. High energy conversion efficiency (ɳ) was observed for the DSSC based on a photoanode made of RGO-TiO2 {001} NFs when compared to DSSCs based on photoanodes fabricated using pure TiO2 {001} NFs and commercial Degussa P25 TiO2, which exhibited η of 6.78, 4.59 and 2.71%, respectively. The improved performance of the DSSC based on a photoanode composed of RGOTiO2 {001} NFs was due to its good crystallinity, high dye intake and enhanced light-harvesting properties. Moreover, the presence of RGO greatly hindered the recombination of photogenerated electrons and increased their lifespan. This work discloses a novel efficient photoanode design for improving performance of the DSSCs.
  • No Thumbnail Available
    Publication
    Biocidal activity of citrus limetta peel extract mediated green synthesized silver quantum dots against MCF-7 cancer cells and pathogenic bacteria
    (Elsevier, 2021)
    Pugazhenthiran, N.
    ;
    Murugesan, S.
    ;
    Muneeswaran, T.
    ;
    Suresh, S.
    ;
    Kandasamy, M.
    ;
    Valdes-Morales, Hector 
    ;
    Selvaraj, M.
    ;
    Savariraj, A. Dennyson
    ;
    Mangalaraja, R. V.
    Monodispersed silver quantum dots (Ag QDs) of sub 5 nm range are prepared through a facile and size-controllable green synthesis route using sweet lime (Citrus limetta) peel (SLP) extract. Powder X-ray diffraction studies confirm the formation of face-centered-cubic structured Ag QDs which is corroborated by selected area electron diffraction. The Ag QDs show an absorption maximum at ~415 nm due to characteristic surface plasmon resonance. The Ag QDs prepared at 80 °C exhibit high photoluminescence quenching, indicating low recombination rate and high lifetime of photoexcited electrons. The examination of SLP extract by Fourier-transform infrared spectroscopy, LC-MS and NMR spectroscopy reveals the presence of citrate and carbohydrate biomolecules that could be responsible for the formation of small and stable Ag QDs. The cytotoxic studies indicate that the synthesized Ag QDs are able to effect 71% cancer cells death at 100 µg/mL concentration. Moreover, Ag QDs exhibit minimum inhibitory concentration (MIC) value of 50 μg/mL against all the selected pathogenic bacteria. Present findings suggest that Ag QDs obtained by SLP extract mediated green synthesis can be employed as a low-cost and eco-friendly biocidal agent.