Browsing by Author "Focarete, Maria Letizia"

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    Nanocomposites based on poly(caprolactone)-chitosan electrospun nanofibers and metallic oxide nanoparticles. Their potential use to adsorption and photocatalytic degradation of organic contaminants
    (2023) Córdoba Manrique, Alexander; Leiva Campusano, Ángel; Focarete, Maria Letizia; Pontificia Universidad Católica de Chile. Escuela de Química
    La contaminación de los cuerpos de agua es uno de los problemas medioambientales más comunes en la actualidad. Los contaminantes orgánicos son uno de los compuestos perjudiciales más importantes, entre los que destacan los colorantes de larga vida, los productos farmacéuticos y los pesticidas. Esta investigación tiene como objetivo la obtención de nanocompositos basados en nanofibras (NFs) electrohiladas de policaprolactona-quitosano (PCL-CS) con nanopartículas de TiO2 (TiO2NPs) para la adsorción y degradación fotocatalítica de contaminantes orgánicos, utilizando como modelo la rodamina B. Los materiales híbridos fabricados se caracterizaron por FT-IR, TGA, DSC, SEM, TEM, propiedades de tracción y ángulo de contacto de gotas de agua. La fotoactividad de las NFs se investigó utilizando un sistema tipo “batch” seguida por espectroscopia UV-Vis y microscopia de fluorescencia. Para este propósito, se incorporaron ex-situ las TiO2NPs a la matriz polimérica mostrando buenas propiedades mecánicas y una mayor hidrofilicidad del material. Los resultados mostraron que la presencia de CS en las NFs aumentaba la absorción y degradación de RhB por las TiO2NPs. El CS atrae las moléculas contaminantes a los sitios activos como las TiO2NPs, favoreciendo la adsorción y degradación. En otras palabras, se evidenció un efecto anzuelo-y-destrucción (bait-hook-and-estroy effect). También se demostró que la sensibilización del TiO2 mediante colorantes orgánicos (por ejemplo, un derivado del perileno) mejora considerablemente la actividad fotocatalítica bajo radiación visible, permitiendo el uso de bajas cantidades de TiO2. (≈0,05 g/1 g de fibra). Por lo tanto, se espera que el presente estudio contribuya con una solución alternativa ecológica y respetuosa con el medio ambiente.
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    Nanofibers of chitosan-polycaprolactone blends as active support for photocatalytic nanoparticles: Outstanding role of chitosan in the degradation of an organic dye in water
    (2023) Cordoba, Alexander; Guernelli, Moreno; Montalti, Marco; Saldias, Cesar; Focarete, Maria Letizia; Leiva, Angel
    Hybrid nanofibers of a chitosan-polycaprolactone blend containing titanium dioxide nanoparticles TiO2NPs, were prepared through electrospinning to study their adsorption and photocatalytic degradation capabilities of the model organic water pollutants, rhodamine B, RhB. To obtain uniform and bead-free nanofibers, an optimization of the electrospinning parameters was performed. The optimization was carried out by systematically adjusting the solution conditions (solvent, concentration, and polymer ratio) and instrumental parameters (voltage, needle tip-collector distance, and flow). The obtained materials were characterized by FT-IR, TGA, DSC, SEM, TEM, mechanical tensile test, and water contact angle. The photoactivity was investigated using a batchtype system by following UV-Vis absorbance and fluorescence of RhB.TiO2NPs were incorporated ex-situ into the polymer matrix, contributing to good mechanical properties and higher hydrophilicity of the material. The results showed that the presence of chitosan in the nanofibers significantly increased the adsorption of RhB and its photocatalytic degradation by TiO2NPs (5, 55 and 80 % of RhB degradation with NFs of PCL, TiO2/PCL and TiO2/CS-PCL, after 30 h of light irradiation, respectively), evidencing a synergistic effect between them. The results are attributed to an attraction of RhB by chitosan to the vicinity of TiO2NPs, favouring initial adsorption and degradation, phenomenon known as "bait-and-hook-anddestruct" effect.
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    On the Versatile Role of Electrospun Polymer Nanofibers as Photocatalytic Hybrid Materials Applied to Contaminated Water Remediation: A Brief Review
    (2022) Cordoba, Alexander; Saldias, Cesar; Urzua, Marcela; Montalti, Marco; Guernelli, Moreno; Focarete, Maria Letizia; Leiva, Angel
    A wide variety of materials, strategies, and methods have been proposed to face the challenge of wastewater pollution. The most innovative and promising approaches include the hybrid materials made of polymeric nanofibers and photocatalytic nanoparticles. Electrospun nanofibers with unique properties, such as nanosized diameter, large specific surface area, and high aspect ratio, represent promising materials to support and stabilize photocatalytic nanosized semiconductors. Additionally, the role performed by polymer nanofibers can be extended even further since they can act as an active medium for the in situ synthesis of photocatalytic metal nanoparticles or contribute to pollutant adsorption, facilitating their approach to the photocatalytic sites and their subsequent photodegradation. In this paper, we review the state of the art of electrospun polymer/semiconductor hybrid nanofibers possessing photocatalytic activity and used for the remediation of polluted water by light-driven processes (i.e., based on photocatalytic activity). The crucial role of polymer nanofibers and their versatility in these types of procedures are emphasized.