Highly efficient Cu2O@CuxFeyO4 nanohybrid catalyst for the degradation of emerging pollutants
S. Fernandez-Velayos, FJ. Recio, FJ. Palomares, N. Menendez, P. Herrasti, E. Mazario,
J Water Process Eng 52, 103549 (2023).
Abstract
Cu2O@CuxFeyO4 nanohybrids (NHs) have been electrosynthesized by a simple and environmentally safe method to be used as catalysts for tetracycline degradation. NHs shown an average diameter of 14(5) nm and exhibit high crystallinity with spherical morphology. XPS results demonstrate a cuprite-enriched surface; meanwhile, the inner layer is composed by a nonstoichiometric copper spinel structure. The degradation has been monitored by UV-Visible spectroscopy, TOC analysis, and HPLC. The electrochemical characterization demonstrates the syn-ergetic effect of Fe3+/Fe2+ and Cu2+/Cu+ coupling to enhance the activation of persulfate. This effect results in a greater degradation efficiency of NHs than other catalysts, namely, CuxOy, Fe3O4, and a mixture of both and Cu2O. It has been found that a previous adsorption stage before degradation does not improve the elimination of the pollutant and its length in time, with a TOC reduction of 72.6 % in 2 h. Conversely, conducting the oxidative process in a direct step resulted in a more rapid and efficient process, 82.3 % of reduction in 1 h. Through this method, the catalyst reutilization resulting in a decrease of 50 % in TOC degradation from the third use, while the TCY concentration degraded remains almost constant. This reduced catalytic activity with use might be a consequence of 1) the absence of the single Cu-oxide layer due to the leaching of mainly Cu ions but also Fe ions during the degradation tests, and, 2) the passivation of the outermost layer, mainly covered by C-O species and OH groups, which hinders access to active catalyst sites.
Highly Sensitive Enzyme-free Sensor Based on a Carbon Paste Electrode Modified with Binary Zinc Oxide/Polyaniline Nanocomposites for Dopamine, Ascorbic Acid and Uric Acid Sensing
Y. Kadri, I. Bekri-Abbess, P. Herrasti,
Electroanal 35, (2023).
Abstract
Hybrid composites ZnO/PANI were facily synthesized by a sonication process at room temperature. This procedure is non-expensive, time/energy saving and environmentally safe. The as-prepared ZnO/PANI were characterized by FTIR, UV-vis spectroscopies and SEM in order to investigate the structure and morphology of the studied composites. The samples were used to modify carbon paste electrode (CPE) in order to develop electrochemical biosensors (ZnO/PANI/CPE). The sensing properties of the nanoparticles were evaluated for dopamine, ascorbic acid and uric acid non-enzymatic detection. The effect of percentage of polyaniline in the composites and the effect of calcination on the biosensor's response were also examined in the present study. It was revealed that the existence of PANI in ZnO/PANI/CPE largely enhanced the electroactive surface area and therefore the sensitivity for electrochemical sensing. A good electrochemical behavior was noted for ZnO/40 wt% PANI-cal/CPE modified electrode toward DA, AA and UA oxidation. The electroactive surface area of the previously mentioned modified electrode (0.235 cm(2)) was two times higher than that of the bare electrode (0.117 cm(2)). The liner relationships between current intensities and concentrations were found to be 0.01-1.4 mM, 0.1-1.3 mM and 0.01-0.12 mM, with detection limit of 0.029 mM, 0.063 mM and 0.007 mM, for DA, AA and UA respectively. In the mixtures of ascorbic acid (AA), dopamine (DA) uric acid (UA) and glucose (Glu) the sensor showed high selectivity of DA with low interference of ascorbic acid by a current change of 14 %. The as-prepared ZnO/PANI/CPE biosensor displayed a good reproducibility and stability.
Improved Suzuki-Miyaura reaction conversion efficiency using magnetic nanoparticles and inductive heating
A. Villacampa, L. Duque, O. Juanes, FJ. Palomares, P. Herrasti, N. Menendez,
J Mater Sci 57, 241 (2022).
Abstract
The use of magnetic nanoparticles in C-C coupling reactions enables the facile recovery of the catalyst under environmentally friendly conditions. Herein, the synthesis of Pd/Fe@Fe3O4 nanoparticles by the reduction of Pd2+ and oxidation of Fe on the surface of preformed Fe@Fe3O4 is reported. The nanoparticles were characterized using a variety of analytical techniques (transmission electron microscopy, Mossbauer spectroscopy, X-ray photoelectron spectroscopy, and X-ray diffraction) to determine their size, structure, and chemical composition. The catalytic efficiency of these nanoparticles in classical Suzuki-Miyaura coupling reactions was investigated. The nanoparticles achieved high catalytic activity with the application of local heating by an alternating magnetic field. An investigation was conducted at identical temperatures to compare global heating with the application of an external magnetic field; magnetic heating demonstrated excellent substrate conversion in lesser time and at a lower temperature. The catalyst could also be recycled and reused three times, with similar to 30% decrease in the substrate conversion, which is most likely due to the agglomeration of the Pd nanoparticles or poisoning of the Pd catalyst. This approach, which takes advantage of the catalytic activity and magnetic susceptibility of magnetic nanoparticles, can be applied to several organic transformations to improve their efficiency. [GRAPHICS]
Nanostructured Fe-N-C pyrolyzed catalyst for the H2O2 electrochemical sensing
Christian Candia-Onfray, Soledad Bollo, Claudia Yanez, Nestor Escalona, Jose F. Marco, Nieves Menendez, Ricardo Salazar, F. Javier Recio,
Electrochim Acta 387, 138468 (2021).
Abstract
Fe-N-C pyrolyzed materials have been proposed as substitutes of the noble-based catalyst for energy conversion reactions. However, their use as electrochemical sensors has not been deeply explored. In the present work, different Fe-N-C pyrolyzed catalysts were synthesized for the amperometric sensing of the H2O2 reduction in neutral media. The catalysts were characterized by BET, TEM, FESEM, XPS, Mossbauer spectroscopy, and cyclic voltammetry. The catalysts present an N-doped graphitic matrix with a macroporous structure and mesoporous contribution. Different amounts of N-pyridinic, N-pyrrolic, N-graphitic, N-oxides, and FeN4 sites have been detected on the catalysts. Among the different active sites present in the catalysts, the FeN4 structure is proposed as the most catalytic active site for the hydrogen peroxide reduction reaction (HPRR). Under optimal conditions (0.61 V vs. NHE, 0.00 V vs. Ag/AgCl), the materials show a lineal amperometric response in the range of 0.08 and 14 mu M, with a sensitivity of 31.3 mu A mu M-1 cm(-2), and a detection and quantification limits of 0.25 mu M and 0.75 mu M respectively. The amperometric results indicate that the best performance is reached when increasing the amount of FeN4 active sites, and the redox potential of the FeN4 species becomes more positive. The Fe-N-C catalyst stands out for the more positive working potential than other materials proposed in the literature. (C) 2021 Elsevier Ltd. All rights reserved.
Layered double hydroxides intercalated with methyl orange as a controlled-release corrosion inhibitor for iron in chloride media
N. Bakhtaoui, O. Benali, E. Mazario, Francisco J. Recio, P. Herrasti,
Nano Ex 2, 010017 (2021).
Abstract
In this study, the corrosion inhibition properties of nanocontainer-type layered double hydroxide (LDH) are evaluated on iron that is immersed in a 3.5% NaCl aqueous solution. LDH ZnAl-NO3 was synthesized via coprecipitation. The material presents satisfactory crystallinity with a Zn/Al ratio of 2:1. Methyl orange (MO) has been added into the synthesis process by exchange with nitrate ions and/or by adsorption of MO onto LDH surfaces (LDH-MO). Iron was immersed in solutions with various concentrations of LDH and LDH-MO ranged 1-6 gl(-1), and the corrosion inhibition properties were investigated using linear sweep votammetry, electrochemical impedance spectroscopy (EIS), and SEM. Based on pitting potential studies, LDH has demonstrated inhibition of the pitting corrosion process, and the optimal concentration was identified as 2 gl(-1). The presence of MO in LDH provides excellent anticorrosive properties with a mixed inhibition mechanism. The corrosion potential of LDH-MO presents more noble values and exchange current densities that are one order of magnitude less than those of the bare iron after 72 h of immersion in a 3.5% NaCl aqueous solution. EIS results corroborated that the corrosion resistance increased when 2 gl(-1) of LDH-MO was in solution. SEM images support the anticorrosive behaviour of the LDH-MO.
Evidence of cathodic peroxydisulfate activation via electrochemical reduction at Fe(II) sites of magnetite-decorated porous carbon: Application to dye degradation in water
S. Mirehbar, S. Fernandez-Velayos, E. Mazario, N. Menendez, P. Herrasti, FJ. Recio, I. Sires,
J Electroanal Chem 902, 115807 (2021).
Abstract
Peroxydisulfate (PDS, S2O82-)-based advanced oxidation processes have been developed as an alternative to those based on center dot OH, as PDS activation yields a much more stable radical like SO4 center dot(- )that can maintain the oxidation ability of water treatment systems for longer time. Here, the electrochemical PDS activation has been investigated using reticulated vitreous carbon (RVC) substrate modified with Fe3O4 nanoparticles (NPs) as cathode. The NPs were exhaustively characterized by different surface analysis techniques (TEM, SEM) and Mossbauer spectroscopy. Cyclic voltammetry and linear sweep voltammetry with a rotating disk electrode allowed concluding that the main electrocatalytic role in the cathodic PDS activation to SO4 center dot(-) corresponded to the Fe(II) active sites continuously promoted upon cathodic polarization. These sites were less catalytic for O-2 reduction reaction, although it was still feasible with n = 2.7 electrons as determined from Koutecky-Levich analysis. Both cathodic reactions followed an inner-sphere reaction mechanism. The Fe3O4 modified RVC cathodes were employed to electrolyze Methylene Blue aqueous solutions at pH 3.5, employing different current values and PDS concentrations. Dissolved O-2 was purged to impede the competitive cathodic H2O2 production and Fenton's reaction. The occurrence of dye adsorption/electrosorption on the cathode reduced the mass transport limitations, enhancing the reaction between SO4 center dot(-) and organic molecules. The best operation conditions to reach total and fast color removal at 18 min were 2 mM PDS and 10 mA, yielding > 80% TOC abatement at 45 min. Reproducible degradation profiles were found after 5 runs, thereby ensuring the stability of the Fe3O4-modified RVC, with no iron sludge production.
Understanding the structural and magnetic evolution of superparamagnetic Zn ferrites nanoparticles synthesized by an easy electrochemical process
M. Rivero, A. Serrano, J. A. Rodriguez-Velamazan, A. Munoz-Bonilla, J. Sanchez-Marcos,
J Alloy Compd 881, 160585 (2021).
Abstract
In the present work, a series of zinc ferrite nanoparticles of 11 nm on average size were synthesized following an electrochemical method in aqueous medium. The nanoparticles were structurally characterized by X-ray diffraction (XRD), inductively coupled plasma spectroscopy (ICP), transmission electron microscopy (TEM), X-ray absorption spectroscopy (XAS) and neutron diffraction (ND). The magnetic characterization was carried out by vibrating sample magnetometer (VSM) and superconducting quantum interference device (SQUID) measurements. The electrochemical synthetic methodology used in this paper yields zinc ferrite monocrystalline nanoparticles with a controlled size, shape and composition, in a reproducible manner. The control of such parameters enables obtaining ferrite nanoparticles with tuneable magnetic properties. The results show that the Zn2+ cations are situated in tetrahedral sites in the crystalline spinel structure, which causes a progressive decrease in the magnetic moments of the ferrites with Zn content due to the breakdown of the super-exchange interactions. (C) 2021 Elsevier B.V. All rights reserved.
Direct 3D printing of zero valent iron@polylactic acid catalyst for tetracycline degradation with magnetically inducing active persulfate.
S. Fernandez-Velayos, J. Sanchez-Marcos, A. Munoz-Bonilla, P. Herrasti, N. Menendez, E. Mazario,
Sci Total Environ , 150917 (2021).
Abstract
Catalyst stability has become a challenging issue for advanced oxidation processes (AOPs). Herein, we report an alternative method based on 3D printing technology to obtain zero-valent iron polylactic acid prototypes (ZVI@PLA) in a single step and without post etching treatment. ZVI@PLA was used to activate persulfate (PS) for the removal of Tetracycline (TC) in recirculating mode under two different heating methodologies, thermal bath and contactless heating promoted by magnetic induction (MIH). The effect of both heating methodologies was systematically analysed by comparing the kinetic constant of the degradation processes. It was demonstrated that the non-contact heating of ZVI by MIH reactivates the surface of the catalyst, renewing the surface iron content exposed to the pollutant solution, which makes the ZVI@PLA catalyst reusable up to 10cycles with no efficiency reduction. In contrast, by using a conventional thermal bath, the kinetic constant gradually decreases over the 10cycles, because of the superficial iron consumption, being the kinetic constant 5 times lower in the 10th run compared to MIH experiment. X-ray diffraction and Mossbauer spectroscopy confirmed the presence of metallic iron embedded in the ZVI@PLA prototype, whose crystalline structure remained unchanged for 10th cycles of MIH. Moreover, it was proven that with no contact heating technology at low magnetic fields (12.2 mT), the solution temperature does not increase, but only the surface of the catalyst does. Under these superficial heated conditions, kinetic rate is increased up to 0.016min-1 compared to the value of 0.0086min-1 obtained for conventional heating at 20°C. This increase is explained not only by PS activation by iron leaching but also by the contribution of ZVI in the heterogeneous activation of persulfate.
Tunneling the size of iron oxide NPs using different alcohols and proportions water-alcohol
FL. Rivera, J. Sanchez-Marcos, N. Menendez, P. Herrasti, E. Mazario,
Adv Nano Res 8, 95 (2020).
Abstract
In this work the properties of iron oxide magnetic nanoparticles (MNPs) synthesized by electrochemical method using different water-alcohol proportions and alcohols have been investigated. The syntheses were carried out using 99% iron foils acting electrodes in a 0.04 M NaCl solutions at room temperature applying 22 mAcm(-2) on the working electrode, mostly obtaining magnetite nanoparticles. The impact of the electrolyte in the size of the synthesized MNPs has been evaluated by transmission electron microscopy (TEM), X-ray diffraction (XRD), chronopotentiometric studies, and magnetic characterization. The results have shown that nanoparticles can be obtained in the range of 6 to 26 nm depending on the type of alcohol and the proportions in the mixture of water-alcohol. The same trend has been observed for all alcohols. As the proportion of these in the medium increases, the nanoparticles obtained are smaller in size. This trend is maintained until a certain proportion of alcohol: 50% for methanol, and 60% for the rest of alcohols, proportions where obtaining a single phase of magnetite is not favored.
Improved magnetosensor for the detection of hydrogen peroxide and glucose
P. Herrasti, E. Mazario, Francisco J. Recio,
J Solid State Electr , (2020).
Abstract
In this work, the use of neodymium electrodes as a basis for the immobilization of magnetite nanoparticles has been carried out. The sensitivity and detection limit to H2O2 are 2.4 x 10(4) mu A M-1 and 1.8 x 10(-5) M, respectively. The amount of peroxide in a contact lens liquid was also determined; there was a discrepancy between the manufacturer reported and the experimental measured values less than 2% of error. For the use of a biosensor in glucose detection, the sensitivity and detection limit are 938 mu A M-1 and 9 mM, respectively. In both cases, the most notable is the increase in reuse of the electrode of up to 10 times without loss of sensitivity and its excellent performance after 1-month aging.
New insights into the structural analysis of maghemite and (MFe2O4, M = Co, Zn) ferrite nanoparticles synthesized by a microwave-assisted polyol process
A. Gallo-Cordova, A. Espinosa, A. Serrano, L. Gutierrez, N. Menendez, MD. Morales, E. Mazario,
Improvement in Heavy Metal Removal from Wastewater Using an External Magnetic Inductor
Fernanda Lyzeth Rivera, Francisco Javier Palomares, Pilar Herrasti, Eva. Mazario,
Nanomaterials 9, 1508 (2019).
Abstract
Magnetite nanoparticles (Fe3O4) of 12 +/- 4 nm diameter are electrochemically synthesized for the adsorption and magnetic harvesting of Cr(VI) from contaminated simulated solutions. The removal of Cr(VI) from aqueous media follows pseudo-second-order kinetics. The adsorption efficiency is evaluated in three different scenarios. In standard conditions, i.e., at room temperature; in a thermal bath working at 60 degrees C, where the temperature could be considered homogeneous within the solution; and finally, under magnetic induction heating, while adjusting the frequency and magnetic field used to attain the same temperature as in the bath experiments. Two benefits of using a magnetic inductor are demonstrated. First, the removal efficiency is almost doubled in comparison to that of the room temperature experiments, and it is higher by 30% compared to that of the bath setup. At the same time as the adsorption occurs, a redox reaction occurs on the surface of the nanoparticles, and Cr(VI), the predominant species in the contaminated solution, is significantly reduced to Cr(III). Through X-ray photoelectron spectroscopy, it is shown that a greater reduction effect is achieved when working in induction conditions than at room temperature. This is the first time that this synergistic effect using magnetic induction heating has been demonstrated for heavy metal decontamination of wastewater.
Electrochemical Synthesis and Magnetic Properties of MFe2O4 (M = Fe, Mn, Co, Ni) Nanoparticles for Potential Biomedical Applications
J. G. Ovejero, A. Mayoral, M. Canete, M. Garcia, A. Hernando, P. Herrasti,
J Nanosci Nanotechno 19, 2008 (2019).
Abstract
In this study, we evaluate the magnetic properties and cytotoxic effect of magnetic nanoparticles (MNPs) based on magnetite and Mn, Co and Ni ferrites, obtained by electrochemical synthesis. These nanoparticles have almost spherical shape and an mode size of 9 +/- 1 nm. The electrochemical synthesis produces a single crystallographic phase with a spinel-like structure in all cases. Magnetization saturation at room temperature varies with the composition of the ferrites from M-S (Fe3O4) > M-S (MnFe2O4) > M-S (CoFe2O4) > M-S (NiFe2O4). Ferrite MNPs present low magnetic remanence indicating a superparamagnetic-like response at room temperature. However, the different values of magnetic anisotropy and size produce variations in the values of coercivity and susceptibility of the ferrite MNPs. The cytotoxicity of the different ferrites was evaluated by internalizing MNP in HeLa cancer cells. Although magnetite and Mn ferrite present low toxicity for all the concentrations studied, significant cytotoxic effect were observed when incubating the cells with high concentration of Co and Ni ferrites.
Toxicity and biodegradation of zinc ferrite nanoparticles in Xenopus laevis
M. Rivero, M. Marin-Barba, L. Gutierrez, E. Lozano-Velasco, GN. Wheeler, J. Sanchez-Marcos, A. Munoz-Bonilla, CJ. Morris, A. Ruiz,
J Nanopart Res 21, 181 (2019).
Abstract
Zn-doped Fe3O4 magnetic nanoparticles have been proposed as the ideal ferrite for some biomedical applications like magnetic hyperthermia or photothermal therapy because of the possibility to adjust their size and chemical composition in order to design tailored treatments. However, reliable approaches are needed to risk assess Zn ferrite nanoparticles before clinical development. In this work, the in vitro toxicity of the nanoparticles was evaluated in five cellular models (Caco-2, HepG2, MDCK, Calu-3 and Raw 264.7) representing different target organs/systems (gastrointestinal system, liver, kidney, respiratory system and immune system). For the first time, these nanoparticles were evaluated in an in vivo Xenopus laevis model to study whole organism toxicity and their impact on iron and zinc metabolic pathways. Short- and long-term in vivo exposure studies provided insights into the contrasting adverse effects between acute and chronic exposure. Quantitative PCR combined with elemental analysis and AC magnetic susceptibility measurements revealed that at short-term exposure (72 h), the nanoparticles' absorption process is predominant, with the consequent over-expression of metal transporters and metal response proteins. At long-term exposure (120 h), there is an upregulation of metal accumulation involved genes and the return to basal levels of both iron and zinc transporters, involved in the uptake of metals. This suggests that at this stage, the nanoparticles' absorption process is residual compared with the following steps in metabolism, distribution and/or excretion processes, indicated by the increase of iron accumulation proteins at both transcriptional and translational level. This testing approach based on a battery of cellular systems and the use of the Xenopus laevis model could be a viable strategy for studying the toxicity, degradability and ultimately the long-term fate of zinc ferrites in the organism.
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