DSpace Angular :: Browsing by Author "Saldias, Cesar"

Browsing by Author "Saldias, Cesar"

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Bimetallic NiPt nanoparticles-enhanced catalyst supported on alginate-based biohydrogels for sustainable hydrogen production
(2023) Ramirez, Oscar; Bonardd, Sebastian; Saldias, Cesar; Kroff, Macarena; O'Shea, James N.; Diaz, David Diaz; Leiva, Angel
Alginate hydrogel beads were loaded with bimetallic NiPt nanoparticles by in situ reduction of the respective polymer matrix containing precursor metallic ions using a NaBH4 aqueous solution. The alginate hydrogel beads loaded with NiPt nanoparticles were characterized by TEM, AAS, FT-IR, TGA, XPS, and oscillatory rheometry. The prepared hybrid hydrogels were proven to be effective as catalytic materials for the hydrolysis of ammonia borane (AB) for quantitative hydrogen generation using catalytic loadings of 0.1 mol%. In addition, the reaction mechanism of the hydrolytic reaction using NiPt loaded alginate hydrogel beads was determined by Langmuir-Hinshelwood model. The experimental results showed that the reaction mechanism consisted of an initial fast adsorption of reactants at the surface of the nanoparticles, followed by a rate-limiting surface reaction. The NiPt nanoalloys exhibited an enhanced behavior for hydrogen generation with a maximum TOF of 84.1 min-1, almost 71 % higher compared to monometallic platinum atoms, and likely related to a synergistic interaction between both metals. Finally, the hydrogel matrix enabled the material to be easily recovered from the reaction medium and reused in further catalytic cycles without desorption of active nanoparticles from the material.
Biocomposites with increased dielectric constant based on chitosan and nitrile-modified cellulose nanocrystals
(2018) Bonardd Salvador, Sebastián Ignacio; Robles, Eduardo; Barandiaran, Irati; Saldias, Cesar; Leiva Campusano, Ángel; Kortaberria, Galder
Biohydrogel Based on Dynamic Covalent Bonds for Wound Healing Applications
(2021) Agubata, Chukwuma O.; Mbaoji, Cynthia C.; Nzekwe, Ifeanyi T.; Saldias, Cesar; Diaz Diaz, David
In this work, a biohydrogel based on alginate and dynamic covalent B-O bonds, and derived composites, has been evaluated for wound healing applications. In particular, a phenylboronic acid-alginate (PBA-Alg) complex was synthesized by coupling 3-aminophenylboronic acid onto alginate, and used to prepare varied concentrations of hydrogels and silicate-based nanocomposites in PBS. The resulting hydrogels were characterized in terms of interfacial tension, moisture uptake and loss, interaction with fresh acid-soluble collagen, self-healing ability, effects on blood clotting and wound healing. The interfacial tension between the hydrogels and biorelevant fluids was low and moisture loss of 55-60% was evident without uptake from the environment. The components of the hydrogels and their mixtures with collagen were found to be compatible. These hydrogels showed efficient self-healing and thixotropic behavior, and the animals in the treatment groups displayed blood clotting times between 9.1 min and 10.7 min. In contrast, the composites showed much longer or shorter clotting times depending on the silicate content. A significant improvement in wound healing was observed in 3% w/v PBA-Alg formulations. Overall, the PBA-Alg hydrogels exhibit self-healing dynamic covalent interactions and may be useful in dressings for incision wounds.
Chromophoric Dendrimer-Based Materials: An Overview of Holistic-Integrated Molecular Systems for Fluorescence Resonance Energy Transfer (FRET) Phenomenon
(2021) Bonardd, Sebastian; Diaz Diaz, David; Leiva, Angel; Saldias, Cesar
Dendrimers (from the Greek dendros -> tree; meros -> part) are macromolecules with well-defined three-dimensional and tree-like structures. Remarkably, this hyperbranched architecture is one of the most ubiquitous, prolific, and recognizable natural patterns observed in nature. The rational design and the synthesis of highly functionalized architectures have been motivated by the need to mimic synthetic and natural-light-induced energy processes. Dendrimers offer an attractive material scaffold to generate innovative, technological, and functional materials because they provide a high amount of peripherally functional groups and void nanoreservoirs. Therefore, dendrimers emerge as excellent candidates since they can play a highly relevant role as unimolecular reactors at the nanoscale, acting as versatile and sophisticated entities. In particular, they can play a key role in the properties of light-energy harvesting and non-radiative energy transfer, allowing them to function as a whole unit. Remarkably, it is possible to promote the occurrence of the FRET phenomenon to concentrate the absorbed energy in photoactive centers. Finally, we think an in-depth understanding of this mechanism allows for diverse and prolific technological applications, such as imaging, biomedical therapy, and the conversion and storage of light energy, among others.
CuAu bimetallic plasmonic-enhanced catalysts supported on alginate biohydrogels
(2022) Ramirez, Oscar; Bonardd, Sebastian; Saldias, Cesar; Zambrano, Yadira; Diaz Diaz, David; Leiva, Angel
We describe the synthesis, characterization and catalytic properties of a series of hybrid materials composed of inorganic plasmonic mono-and bimetallic nanoparticles supported on organic bio-based hydrogel beads. The bimetallic materials showed a localized surface plasmon resonance in the visible region, with a maximum light absorption correlated to the metal composition of the alloyed systems. Thermogravimetric analysis revealed a total water content near to 90 % w/w, which was in good agreement with the free-volume calculated from mu CT scan reconstruction of lyophilized samples. Catalytic essays for the reduction of 4-nitrophenol demonstrated that alginate beads loaded with bimetallic nanoparticles exhibit a 5.4-fold higher apparent kinetic constant (k(app)) than its monometallic counterparts. Additionally, taking advantage of the plasmonic properties given by the nanoparticles is that the materials were tested as photocatalysts. The activity of the catalysts was enhanced by near 2.2 times higher in comparison with its performance in dark conditions.
Effects of the Solvent Vapor Exposure on the Optical Properties and Photocatalytic Behavior of Cellulose Acetate/Perylene Free-Standing Films
(2023) Coderch, Gustavo; Cordoba, Alexander; Ramirez, Oscar; Bonardd, Sebastian; Leiva, Angel; Haering, Marleen; Diaz, David Diaz; Saldias, Cesar
The search to deliver added value to industrialized biobased materials, such as cellulose derivatives, is a relevant aspect in the scientific, technological and innovation fields at present. To address these aspects, films of cellulose acetate (CA) and a perylene derivative (Pr) were fabricated using a solution-casting method with two different compositions. Consequently, these samples were exposed to dimethylformamide (DMF) solvent vapors so that its influence on the optical, wettability, and topographical properties of the films could be examined. The results demonstrated that solvent vapor could induce the apparent total or partial preferential orientation/migration of Pr toward the polymer-air interface. In addition, photocatalytic activities of the non-exposed and DMF vapor-exposed films against the degradation of methylene blue (MB) in an aqueous medium using light-emitting diode visible light irradiation were comparatively investigated. Apparently, the observed improvement in the performance of these materials in the MB photodegradation process is closely linked to the treatment with solvent vapor. Results from this study have allowed us to propose the fabrication and use of the improved photoactivity "all-organic" materials for potential applications in dye photodegradation in aqueous media.
Evaluation of electro-synthesized oligothiophenes as donor materials in vacuum-processed organic photovoltaic devices
(2023) Camarada, Maria Belen; Saldias, Cesar; Castro-Castillo, Carmen; Angel, Felipe A.
2,2 ':5 ',2 ''-terthiophene (3Th) was utilized as a precursor in the electro-synthesis of oligothiophenes and their further evaluation as donor materials in the active layer of vacuum-processed organic photovoltaic (OPV) devices. Electro-polymerization conditions were optimized to obtain a controlled fraction of polydisperse oligomers, as demonstrated by size exclusion chromatography (SEC). The polydispersity of the material was further decreased during thermal evaporation, where a reduced fraction of the oligomer was deposited, as observed by SEC, absorption spectroscopy, and the characterization of the fabricated devices. Our results demonstrate for the first time the potential of the electro-synthesis of oligothiophenes as active materials for their application in bulk heterojunction for OPV devices.
Fed-Batch mcl- Polyhydroxyalkanoates Production in Pseudomonas putida KT2440 and ΔphaZ Mutant on Biodiesel-Derived Crude Glycerol
(2021) Borrero-de Acuna, Jose Manuel; Rohde, Manfred; Saldias, Cesar; Poblete-Castro, Ignacio
Crude glycerol has emerged as a suitable feedstock for the biotechnological production of various industrial chemicals given its high surplus catalyzed by the biodiesel industry. Pseudomonas bacteria metabolize the polyol into several biopolymers, including alginate and medium-chain-length poly(3-hydroxyalkanoates) (mcl-PHAs). Although P. putida is a suited platform to derive these polyoxoesters from crude glycerol, the attained concentrations in batch and fed-batch cultures are still low. In this study, we employed P. putida KT2440 and the hyper-PHA producer Delta phaZ mutant in two different fed-batch modes to synthesize mcl-PHAs from raw glycerol. Initially, the cells grew in a batch phase (mu(max) 0.21 h(-1)) for 22 h followed by a carbon-limiting exponential feeding, where the specific growth rate was set at 0.1 (h(-1)), resulting in a cell dry weight (CDW) of nearly 50 (g L-1) at 40 h cultivation. During the PHA production stage, we supplied the substrate at a constant rate of 50 (g h(-1)), where the KT2440 and the Delta phaZ produced 9.7 and 12.7 gPHA L-1, respectively, after 60 h cultivation. We next evaluated the PHA production ability of the P. putida strains using a DO-stat approach under nitrogen depletion. Citric acid was the main by-product secreted by the cells, accumulating in the culture broth up to 48 (g L-1) under nitrogen limitation. The mutant Delta phaZ amassed 38.9% of the CDW as mcl-PHA and exhibited a specific PHA volumetric productivity of 0.34 (g L-1 h(-1)), 48% higher than the parental KT2440 under the same growth conditions. The biosynthesized mcl-PHAs had average molecular weights ranging from 460 to 505 KDa and a polydispersity index (PDI) of 2.4-2.6. Here, we demonstrated that the DO-stat feeding approach in high cell density cultures enables the high yield production of mcl-PHA in P. putida strains using the industrial crude glycerol, where the fed-batch process selection is essential to exploit the superior biopolymer production hallmarks of engineered bacterial strains.
Highly efficient and reusable CuAu nanoparticles supported on crosslinked chitosan hydrogels as a plasmonic catalyst for nitroarene reduction
(2024) Ramirez, Oscar; Bonardd, Sebastian; Saldias, Cesar; Leiva, Angel; Diaz, David Diaz
The synthesis of CuAu-based monometallic (MNPs) and bimetallic nanoparticles (BNPs) supported on chitosanbased hydrogels for their application as catalysts is presented. The hydrogels consisted of chitosan chains crosslinked with tripolyphosphate (TPP) in the form of beads with an approximate average diameter of 1.81 mm. The MNPs and BNPs were obtained by the adsorption of metallic ions and their subsequent reduction with hydrazine, achieving a metallic loading of 0.297 mmol per gram of dry sample, with average nanoparticle sizes that were found between 2.6 and 4.4 nm. Both processes, metal adsorption and the stabilization of the nanoparticles, are mainly attributed to the participation of chitosan hydroxyl, amine and amide functional groups. The materials revealed important absorption bands in the visible region of the light spectra, specifically between 520 and 590 nm, mainly attributed to LSPR given the nature of the MNPs and BNPs inside the hydrogels. Subsequently, the hydrogels were evaluated as catalysts against the reduction of 4-nitrophenol (4NP) into 4-aminophenol (4AP), followed by UV-visible spectroscopy. The kinetic advance of the reaction revealed important improvements in the catalytic activity of the materials by synergistic effect of BNPs and plasmonic enhancement under visible light irradiation, given the combination of metals and the light harvesting properties of the nanocomposites. Finally, the catalytic performance of hydrogels containing BNPs CuAu 3:1 showed an important selectivity, recyclability and reusability performance, due to the relevant interaction of the BNPs with the chitosan matrix, highlighting the potential of this nanocomposite as an effective catalyst, with a potential environmental application.
Hydrogel composites based on chitosan and CuAuTiO₂ photocatalysts for hydrogen production under simulated sunlight irradiation
(2024) Ramirez, Oscar; Lopez-Frances, Anton; Baldovi, Herme G.; Saldias, Cesar; Navalon, Sergio; Leiva, Angel; Diaz, David Diaz
This study explored the photocatalytic hydrogen evolution reaction (HER) using novel biohydrogel composites comprising chitosan, and a photocatalyst consisting in TiO2 P25 decorated with Au and/or Cu mono- and bimetallic nanoparticles (NPs) to boost its optical and catalytic properties. Low loads of Cu and Au (1 mol%) were incorporated onto TiO2 via a green photodeposition methodology. Characterization techniques confirmed the incorporation of decoration metals as well as improvements in the light absorption properties in the visible light interval (lambda > 390 nm) and electron transfer capability of the semiconductors. Thereafter, Au and/or Cu NP- supported TiO2 were incorporated into chitosan-based physically crosslinked hydrogels revealing significant interactions between chitosan functional groups (hydroxyls, amines and amides) with the NPs to ensure its encapsulation. These materials were evaluated as photocatalysts for the HER using water and methanol mixtures under simulated sunlight and visible light irradiation. Sample CuAuTiO2/ChTPP exhibited a maximum hydrogen generation of 1790 mu mol g(-1) h(-1) under simulated sunlight irradiation, almost 12-folds higher compared with TiO2/ChTPP. Also, the nanocomposites revealed a similar tendency under visible light with a maximum hydrogen production of 590 mu mol g(-1) h(-1) . These results agree with the efficiency of photoinduced charge separation revealed by transient photocurrent and EIS.
In Situ Synthesis of CuO/Cu₂O Nanoparticle-Coating Nanoporous Alumina Membranes with Photocatalytic Activity under Visible Light Radiation
(2023) Duran, Boris; Saldias, Cesar; Villarroel, Roberto; Hevia, Samuel A. A.
We report the synthesis and characterization of CuO/Cu2O film supported on nanoporous alumina membranes (NAMs) and the photocatalytic properties in the removal of the organic pollutant methyl orange (MO). For this purpose, transparent nanostructured membranes were fabricated and sequentially modified with APTS ((3-aminopropyl)-trimethoxysilane) and EDTAD (ethylenediaminetetraacetic dianhydride) to form a highly functionalized surface with high density of carboxyl groups, which easily complex with copper cations. The Cu2+-modified membranes were annealed in a chemical vapor deposition (CVD) furnace to form a well-ordered nanostructured coating of CuO/Cu2O with photocatalytic properties. These modifications were followed by characterization with FT-IR and UV-visible spectra, X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (FE-SEM), and energy dispersive X-ray spectroscopy (EDS). Finally, the photocatalytic performance of the NAM-CuO/Cu2O nanostructured membranes was tested in the aqueous removal of MO dye as a model reaction system. Our results revealed 50% photocatalytic removal of MO under continuous light irradiation for 2 h. The procedure presented in this work provides an adequate approach for the fabrication of nanostructured devices with photocatalytic properties for the degradation of organic compounds.
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.
Molecular Weight Enables Fine-Tuning the Thermal and Dielectric Properties of Polymethacrylates Bearing Sulfonyl and Nitrile Groups as Dipolar Entities
(2021) Bonardd, Sebastian; Saldias, Cesar; Leiva, Angel; Diaz Diaz, David; Kortaberria, Galder
In this work, polymethacrylates containing sulfonyl and nitrile functional groups were successfully prepared by conventional radical polymerization and reversible addition-fragmentation chain-transfer polymerization (RAFT). The thermal and dielectric properties were evaluated, for the first time, considering differences in their molecular weights and dispersity values. Variations of the aforementioned properties do not seem to substantially affect the polarized state of these materials, defined in terms of the parameters epsilon'(r), epsilon"(r) and tan (delta). However, the earlier appearance of dissipative phenomena on the temperature scale for materials with lower molecular weights or broader molecular weight distributions, narrows the range of working temperatures in which they exhibit high dielectric constants along with low loss factors. Notwithstanding the above, as all polymers showed, at room temperature, epsilon'(r) values above 9 and loss factors below 0.02, presenting higher dielectric performance when compared to conventional polymer materials, they could be considered as good candidates for energy storage applications.
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.
New Benzotriazole and Benzodithiophene-Based Conjugated Terpolymer Bearing a Fluorescein Derivative as Side-Group: In-Ternal Forster Resonance Energy Transfer to Improve Organic Solar Cells
(MDPI, 2022) Jessop, Ignacio A.; Cutipa, Josefa; Perez, Yasmin; Saldias, Cesar; Fuentealba, Denis; Tundidor-Camba, Alain; Terraza, Claudio A.; Camarada, Maria B.; Angel, Felipe A.
A new benzodithiophene and benzotriazole-based terpolymer bearing a fluorescein derivative as a side group was synthesized and studied for organic solar cell (OSC) applications. This side group was covalently bounded to the backbone through an n-hexyl chain to induce the intramolecular Forster Resonance Energy Transfer (FRET) process and thus improve the photovoltaic performance of the polymeric material. The polymer exhibited good solubility in common organic chlorinated solvents as well as thermal stability (TDT10% > 360 degrees C). Photophysical measurements demonstrated the occurrence of the FRET phenomenon between the lateral group and the terpolymer. The terpolymer exhibited an absorption band centered at 501 nm, an optical bandgap of 2.02 eV, and HOMO and LUMO energy levels of -5.30 eV and -3.28 eV, respectively. A preliminary study on terpolymer-based OSC devices showed a low power-conversion efficiency (PCE) but a higher performance than devices based on an analogous polymer without the fluorescein derivative. These results mean that the design presented here is a promising strategy to improve the performance of polymers used in OSCs.
New Hybrid Copper Nanoparticles/Conjugated Polyelectrolyte Composite with Antibacterial Activity
(2021) Jessop, Ignacio A.; Perez, Yasmin P.; Jachura, Andrea; Nunez, Hipolito; Saldias, Cesar; Isaacs, Mauricio; Tundidor-Camba, Alain; Terraza, Claudio A.; Araya-Duran, Ingrid; Camarada, Maria B.; Carcamo-Vega, Jose J.
In the search for new materials to fight against antibiotic-resistant bacteria, a hybrid composite from metallic copper nanoparticles (CuNPs) and a novel cationic pi-conjugated polyelectrolyte (CPE) were designed, synthesized, and characterized. The CuNPs were prepared by chemical reduction in the presence of CPE, which acts as a stabilizing agent. Spectroscopic analysis and electron microscopy showed the distinctive band of the metallic CuNP surface plasmon and their random distribution on the CPE laminar surface, respectively. Theoretical calculations on CuNP/CPE deposits suggest that the interaction between both materials occurs through polyelectrolyte side chains, with a small contribution of its backbone electron density. The CuNP/CPE composite showed antibacterial activity against Gram-positive (Staphylococcus aureus and Enterococcus faecalis) and Gram-negative (Escherichia coli and Salmonella enteritidis) bacteria, mainly attributed to the CuNPs' effect and, to a lesser extent, to the cationic CPE.
New Hybrid Nanocomposites with Catalytic Properties Obtained by In Situ Preparation of Gold Nanoparticles on Poly (Ionic Liquid)/Poly (4-Vinylpyridine) Nanofibers
(2022) Ramirez, Oscar; Leal, Matias; Briones, Ximena; Urzua, Marcela; Bonardd, Sebastian; Saldias, Cesar; Leiva, Angel
In this work, we report the obtaining of new hybrid nanocomposites with catalytic activity formed by nanofibers of polymer blends and gold nanoparticles. The nanofibers were obtained by electrospinning blends of a poly (ionic liquid) (PIL) and its precursor polymer, poly (4-vinyl pyridine) (P4VPy). The characteristics of the nanofibers obtained proved to be dependent on the proportion of polymer in the blends. The nanofibers obtained were used to synthesize, in situ, gold nanoparticles on their surface by two-step procedure. Firstly, the adsorption of precursor ions on the nanofibers and then their reduction with sodium borohydride to generate gold nanoparticles. The results indicated a significant improvement in the performance of PIL-containing nanofibers over pure P4VPy NFs during ion adsorption, reaching a 20% increase in the amount of adsorbed ions and a 6-fold increase in the respective adsorption constant. The catalytic performance of the obtained hybrid systems in the reduction reaction of 4-nitrophenol to 4-aminophenol was studied. Higher catalytic conversions were obtained using the hybrid nanofibers containing PIL and gold nanoparticles achieving a maximum conversion rate of 98%. Remarkably, the highest value of kinetic constant was obtained for the nanofibers with the highest PIL content.
Novel N-benzoylimidazolium ionic liquids derived from benzoic and hydroxybenzoic acids as therapeutic alternative against Biofilm-forming bacteria in skin and soft-tissue infections
(2022) Forero-Doria, Oscar; Parra-Cid, Cristobal; Venturini, Whitney; Espinoza, Carolina; Araya-Maturana, Ramiro; Valenzuela-Riffo, Felipe; Saldias, Cesar; Leiva, Angel; Duarte, Yorley; Echeverria, Javier; Guzman, Luis
The skin and soft tissue infections (SSTIs) -producing pathogens have acquired resistance to a wide range of antimicrobials, thus it is highly relevant to have new treatment alternatives. In this study, we report the synthesis, characterization, and antibacterial activity of three novel series of ionic liquids (ILs) derived from benzoic and hydroxybenzoic acids, with different lengths of the alkyl chain. The minimum inhibitory concentration (MIC) were tested in Gram positive: Pseudomonas aeruginosa, Staphylococcus aureus, Staphylococcus epidermidis, and Streptococcus pyogenes, and Gram negative: Acinetobacter baumannii and Escherichia coli, showing a MIC range of 0.01562 2.0 mM, with the activity varying according to the aromatic ring functionalization and the length of the alkyl chains. Regarding the antibiofilm activity, different efficacy was observed among the different ILs, some of them presenting antibiofilm activities close to 80% as in the case of those derived from syringic acid with an alkyl chain of six carbon atoms against Pseudomonas aeruginosa. Furthermore, the cell viability in HaCaT cells was determined, showing a half maximal effective concentration (EC50) values higher than the MIC values. The antimicrobial and antibiofilm results, along with not producing cellular toxicity at the MIC values shows that these ILs could be a promising alternative against SSTIs.
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.
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.

Browsing by Author "Saldias, Cesar"

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