Browsing by Author "Castillo, Sebastian"

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    Marrying plasmonic earth-abundant metals with catalytic metals for visible-light-promoted hydrogen generation on biobased materials
    (2023) Ramirez, Oscar; Castillo, Sebastian; Bonardd, Sebastian; Saldias, Cesar; O'Shea, James N.; Clive, Christopher Philip; Diaz, David Diaz; Leiva, Angel
    Bimetallic CuPt alloyed nanoparticles were conveniently synthesized on biohydrogels and were capable of carrying out hydrogen release from ammonium borane hydrolysis. The biohydrogel consisted of bead-shaped alginate chains crosslinked by calcium ions, which were used as support material to synthesize and stabilize the bimetallic nanoparticles, employing adsorption and coreduction strategy steps. The as-prepared nanoparticles exhibited light absorption in the visible range (580 nm) resulting from the surface plasmon resonance (SPR) phenomenon ascribed to the presence of copper in the alloyed system. On the other hand, the presence of platinum atoms in these nanoalloys endows them with a notable catalytic performance toward ammonia borane hydrolysis as a hydrogen release reaction, reaching kr values from 0.32 x 10-4 to 2.23 x 10-4 mol L-1 min-1 as the Pt content increases. Finally, by taking advantage of the SPR light absorption shown by CuPt 1:1, it was demonstrated that these entities could be successfully employed as photocatalysts for the hydrogen generation reaction, boosting its activity by almost 2.06 times compared to its performance in dark conditions. This catalytic enhancement was mainly ascribed to the light-harvesting properties promoted by plasmonic effects and the specimen's metallic composition.
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    Poly(ionic liquid)-Based Hydrogel for Emerging Pollutant Removal and Controlled Drug Delivery
    (2024) Ramirez, Oscar; Castillo, Sebastian; Bonardd, Sebastian; Saldias, Cesar; Diaz, David Diaz; Leiva, Angel
    In this study, we report the synthesis and characterization of a set of poly(ionic liquid) (PIL)-based gel membranes formed by the reaction of poly(4-vinylpyridine) (P4VPy) with a terminal dibrominated poly(ethylene glycol) (PEG), which led to the formation of quaternized pyridines as cross-linking joints. First, for hydrogel synthesis, PEG terminal hydroxyls were brominated and subsequently reacted with P4VPy, resulting in the formation of ionic liquid (IL)-like moieties within the hydrogel network. Modified PEG and PIL-based membranes were characterized by Nuclear Magnetic Resonance (NMR), Fourier-Transform Infrared (FT-IR), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC), as well as their swelling and adsorption properties. FT-IR spectroscopy confirmed the quaternization of the pyridine pendant groups of P4VPy by the appearance of a band at 1639 cm-1 due to the presence of pyridinium units. Thermal characterization revealed a decrease in the thermal stability of the membranes with respect to the starting materials, probably ascribed to the presence of charged species inside the cross-linked matrix. Furthermore, DSC characterization revealed that the P4VPy:PEG ratio and degree of cross-linking strongly affected the amount of non-freezable water. Swelling experiments of the hydrogels revealed a swelling ratio value (% SW) near 297% after 2 h of hydration, showing remarkable recyclability over multiple hydration and drying cycles. Finally, sodium diclofenac (DCl) and methyl orange (MO) adsorption experiments revealed the remarkable ability of the hydrogels to remove pollutants from water, with q max values of 166.7 and 218.8 mg/g, respectively. Finally, a hydrogel loaded with DCl was used as a model system for drug release experiments, in which the hydrogel was able to release almost 70% of DCl to the medium within 1 day of exposure. This process is controlled mainly by a polymer relaxation mechanism and influenced by the temperature of the experiment, showing great potential for reuse in further experiments and also as an interesting platform for controlled drug release.