Examinando por Autor "Pereira, Reinaldo"

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An in situ approach to entrap ultra-small iron oxide nanoparticles inside hydrophilic electrospun nanofibers with high arsenic adsorption
(Elsevier (Países Bajos), 2023) Torasso, Nicolás; Vergara-Rubio, Alicia; Pereira, Reinaldo; Martinez-Sabando, Javier; Jose-Roberto, Vega-Baudrit; Cerveny, Silvina; Goyanes, Silvia
Abstract. The problem of arsenic contamination in water demands sustainable, scalable, and easy-to-implement solutions. Various nano-adsorbents flourished in the last decade, but their use alone requires additional filtering processes to avoid environmental contamination. This work presents a simple, efficient, green approach to overcome this inconvenience while maximizing adsorption capacity. We show for the first time a novel approach to synthesizing ultra-small nanoparticles (IONPs) within electrospun hydrophilic poly(vinyl alcohol) (PVA) nanofibers, avoiding NPs release into the environment when submerged in water. The in-situ synthesis favor enhanced arsenic adsorption capacity due to the excellent dispersion, tiny size, and surface availability of IONPs, reaching 3.5 mg/g at 10 μg/L. We show that IONPs alter the polymeric matrix properties, such as the glass transition temperature and crystallinity, by preventing the formation of strong hydrogen bond inter/intramolecular interactions of PVA. Insolubility and swelling capacity are essential characteristics of this membrane, which allow solution interchange for arsenic adsorption onto IONPs. Isotherm studies show that the increase from 1 wt% to 3 wt% of IONPs content decreases the active sites for adsorption per mass of IONPs. Still, it does not alter the reusability of the membrane, which reaches at least 3 adsorption cycles with 80 % efficiency. We discuss the adsorption mechanisms and show that phosphate anions partially inhibit As(V) adsorption and that the membranes are also highly capable of removing Cr(VI), independently of the presence of Ni(II).
Biogenic silica-based microparticles obtained as a sub-product of the nanocellulose extraction process from pineapple peels
(Nature Publishing Group, 2018-07-10) Corrales-Ureña, Yendry R.; Villalobos-Bermúdez, Carlos; Pereira, Reinaldo; Camacho, Melisa; Estrada, Eugenia; Argüello-Miranda, Orlando; Vega-Baudrit, Jose R.
Silica in plant tissues has been suggested as a component for enhancing mechanical properties, and as a physical barrier. Pineapples present in their shell and bracts rosette-like microparticles that could be associated to biogenic silica. In this study, we show for the first time that silica-based microparticles are co-purified during the extraction process of nanocellulose from pineapple (Ananas comosus). This shows that vegetable biomass could be an underappreciated source, not only for nanocellulose, but also for a highly valuable sub-product, like 10 µm biogenic rosette-like silica-based microparticles. The recovery yield obtained was 7.2 wt.%; based on the dried initial solid. Due to their size and morphology, the microparticles have potential applications as reinforcement in adhesives, polymer composites, in the biomedical field, and even as a source of silica for fertilizers.
Encapsulated salts in velvet worm slime drive its hardening
(Springer Nature (Alemania), 2022) Corrales, Yendry; Schwab, Fabienne; Ochoa‑Martínez, Efraín; Benavides-Acevedo, Miguel; Jose-Roberto, Vega-Baudrit; Pereira, Reinaldo; Rischka, Klaus; Noeske, Paul-Ludwig Michael; Gogos, Alexander; Vanhecke, Dimitri; Rothen-Rutishauser, Barbara; Fink, Alke
Abstract. Slime expelled by velvet worms entraps prey insects within seconds in a hardened biopolymer network that matches the mechanical strength of industrial polymers. While the mechanic stimuliresponsive nature and building blocks of the polymerization are known, it is still unclear how the velvet worms’ slime hardens so fast. Here, we investigated the slime for the first time, not only after, but also before expulsion. Further, we investigated the slime’s micro- and nanostructures in-depth. Besides the previously reported protein nanoglobules, carbohydrates, and lipids, we discovered abundant encapsulated phosphate and carbonate salts. We also detected CO2 bubbles during the hardening of the slime. These findings, along with further observations, suggest that the encapsulated salts in expelled slime rapidly dissolve and neutralize in a baking-powder-like reaction, which seems to accelerate the drying of the slime. The proteins’ conformation and aggregation are thus influenced by shear stress and the salts’ neutralization reaction, increasing the slime’s pH and ionic strength. These insights into the drying process of the velvet worm’s slime demonstrate how naturally evolved polymerizations can unwind in seconds, and could inspire new polymers that are stimuli-responsive or fast-drying under ambient conditions.
Generation of potential bactericidal surfaces from aluminum via anodization
(Laboratorio Nacional de Nanotecnología (LANOTEC) (Costa Rica), 2019) Paniagua, Sergio; Rojas-Gatjens, Esteban; Villalobos, Javier; Montes de Oca-Vásquez, Gabriela; Pereira, Reinaldo; Murillo, Luis Carlos; Jose-Roberto, Vega-Baudrit
Bactericidal nanostructured surfaces are found in nature, developed through millions of years of evolution. Gecko skin, dragonfly wings and cicada wings possess nanoscale spikes or pillars that are able to have bactericidal action through non-chemical bactericidal methods, via impalement2 or mechanical stress3 (Fig. 1). These mechanisms offer the advantage of being more difficult for bacteria to develop resistance compared to pharmaceutical alternatives.1 An important strategy to control the spread of disease is to maintain surfaces clean to prevent secondary infection. Many high touch areas in operating rooms, factories, kitchens, and bathrooms are made of aluminum (trays, door handles, poles, tables, etc.). An aluminum surface engineered to have nanopillars could be bactericidal by mechanical means, thereby helping with prevention of spread of diseases.