Diseño de nanopartículas magnéticas para aplicaciones en biomedicina y bioingeniería

ABSTRACT: In the present study the one-step coprecipitation method is used to obtain magnetic nanoparticles at controlled pH of 10 and 12, and surfactant concentration of 1% and 3%(m/m). The surfactant is sodium polyacrylate(PS), biocompatible and biodegradable, necessary attributes for biological applications. The magnetic nanoparticles have a magnetite core, and a shell of maghemite surrounded by a shell of polymer. The maghemite layer is smaller for large surfactant concentration(3%) and pH 10. The TEM images confirm the particle size distribution in the average range of 5-10 nm. Mössbauer results at 80 K showed line shapes dominated by magnetic relaxation effects with sextets and combinations of sextets and doublets for pH 12. The doublet features dominated the samples obtained at pH 10. The interactions of the surfactant with the nanoparticle surface, mainly with the Fe3+, is strong showing at least two surfactant layers, one layer directly over the nanoparticle surface and another layer resting over the inner layer. FTIR confirmed the attachment of the surfactant to the magnetic nanoparticle surface. The nanoparticles showed superparamagnetic behavior at room temperature and ferromagnetic properties at 5 K. The saturation magnetization presented lower values than reported bulk systems due to the presence of a large layer of maghemite. The very close particle size for all samples gave indication that the particle growth was dominated by the surface properties of the nanoparticles and that the pH and surfactant concentration did not affect importantly the growth process.RESUMEN: Se usó el método de coprecipitación en un solo paso controlando el pH a 10 y 12 y en concentraciones de poliacrilato(PS) de 1% y 3%(m/m). El surfactante es biocompatible y biodegradable, atributos necesarios para su uso en aplicaciones biológicas. Las nanopartículas magnéticas están formadas por una coraza interna de magnetita, una capa de maghemita y una capa externa del polímero. La capa de maghemita es pequeña para la concentración de 3% y pH 10. Las imágenes de TEM confirman la distribución de tamaños de partícula en el rango promedio de 5-10 nm. Los resultados Mössbauer a 80 K mostraron formas de línea dominadas por efectos de relajación magnética en forma de sextetos y combinanciones de sextetos y dobletes; estos dominaron a pH 10. Las interacciones del polímero con la superficie de las nanopartículas, principalmente con el Fe3+, es fuerte mostrando al menos dos capas del polímero sobre ellas. Las medidas magnéticas muestran un comportamiento superparamagnético a temperatura ambiente y ferrimagnético a 5 k. La magnetización de saturación presentó valores menores que las repotadas para volúmenes grandes debido a la caapa de maghemita presente. El tamaño de partícula obtenido para todas las muestras es muy cercano entre si indicando que el crecimiento de las partículas fue dominado por las propiedades de la superficie de estas y en menor grado por las condiciones de concentración y pH usadas

Unravelling the elusive antiferromagnetic order in wurtzite and zinc blende CoO polymorph nanoparticles

Although cubic rock salt‐CoO has been extensively studied, the magnetic properties of the main nanoscale CoO polymorphs (hexagonal wurtzite and cubic zinc blende structures) are rather poorly understood. Here, a detailed magnetic and neutron diffraction study on zinc blende and wurtzite CoO nanoparticles is presented. The zinc blende‐CoO phase is antiferromagnetic with a 3rd type structure in a face‐centered cubic lattice and a Néel temperature of TN (zinc‐blende) ≈225 K. Wurtzite‐CoO also presents an antiferromagnetic order, TN (wurtzite) ≈109 K, although much more complex, with a 2nd type order along the c‐axis but an incommensurate order along the y‐axis. Importantly, the overall magnetic properties are overwhelmed by the uncompensated spins, which confer the system a ferromagnetic‐like behavior even at room temperature

Onion-like Fe3O4/MgO/CoFe2O4 magnetic nanoparticles: new ways to control magnetic coupling between soft/hard phases

The control of the magnetization inversion dynamics is one of the main challenges driving the design of new nanostructured magnetic materials for magnetoelectronic applications. Nanoparticles with onion-like architecture offer a unique opportunity to expand the possibilities allowing to combine different phases at the nanoscale and also modulate the coupling between magnetic phases by introducing spacers in the same structure. Here we report the fabrication, by a three-step high temperature decomposition method, of Fe3O4/MgO/CoFe2O4 onio-like nanoparticles and their detailed structural analysis, elemental compositional maps and magnetic response. The core/shell/shell nanoparticles present epitaxial growth and cubic shape with overall size of (29+-6) nm. These nanoparticles are formed by cubic iron oxide core of (22+-4) nm covered by two shells, the inner of magnesium oxide and the outer of cobalt ferrite of ~1 and ~2.5 nm of thickness, respectively. The magnetization measurements show a single reversion magnetization curve and the enhancement of the coercivity field, from HC~608 Oe for the Fe3O4/MgO to HC~5890 Oe to the Fe3O4/MgO/CoFe2O4 nanoparticles at T=5 K, ascribed to the coupling between both ferrimagnetic phases with a coupling constant of =2 erg/cm2. The system also exhibits exchange bias effect, where the exchange bias field increases up to HEB~2850 Oe at 5 K accompanied with the broadening of the magnetization loop of HC~6650 Oe. This exchange bias effect originates from the freezing of the surface spins below the freezing temperature TF=32 K that pinned the magnetic moment of the cobalt ferrite shell.Comment: 39 pages, 8 figure

Origin of the large dispersion of magnetic properties in nanostructured oxides: FexO/Fe3O4 nanoparticles as a case study

The intimate relationship in transition-metal oxides between stoichiometry and physiochemical properties makes them appealing as tunable materials. These features become exacerbated when dealing with nanostructures. However, due to the complexity of nanoscale materials, establishing a distinct relationship between structure-morphology and functionalities is often complicated. In this regard, in the FexO/Fe3O4 system a largely unexplained broad dispersion of magnetic properties has been observed. Here we show, thanks to a comprehensive multi-technique approach, a clear correlation between magneto-structural properties in large (45 nm) and small (9 nm) FexO/Fe3O4 core/shell nanoparticles that can explain the spread of magnetic behaviors. The results reveal that while the FexO core in the large nanoparticles is antiferromagnetic and has bulk-like stoichiometry and unit-cell parameters, the FexO core in the small particles is highly non-stoichiometric and strained, displaying no significant antiferromagnetism. These results highlight the importance of ample characterization to fully understand the properties of nanostructured metal oxide

Origin of the large dispersion of magnetic properties in nanostructured oxides: FexO/Fe3O4 nanoparticles as a case study

The intimate relationship between stoichiometry and physicochemical properties in transition-metal oxides makes them appealing as tunable materials. These features become exacerbated when dealing with nanostructures. However, due to the complexity of nanoscale materials, establishing a distinct relationship between structure-morphology and functionalities is often complicated. In this regard, in the FexO/Fe3O4 system a largely unexplained broad dispersion of magnetic properties has been observed. Here we show, thanks to a comprehensive multi-technique approach, a clear correlation between the magneto-structural properties in large (45 nm) and small (9 nm) FexO/Fe3O4 core/shell nanoparticles that can explain the spread of magnetic behaviors. The results reveal that while the FexO core in the large nanoparticles is antiferromagnetic and has bulk-like stoichiometry and unit-cell parameters, the FexO core in the small particles is highly non-stoichiometric and strained, displaying no significant antiferromagnetism. These results highlight the importance of ample characterization to fully understand the properties of nanostructured metal oxides

Reply to "comment on 'Free-Radical Formation by the Peroxidase-Like Catalytic Activity of MFe2O4 (M = Fe, Ni, and Mn) Nanoparticles'"

Recently we have reported a qualitative, quantitative and reproducible study of the generation of free radicals as a result of the surface catalytic activity of Fe3O4, Fe2O3, MnFe2O4 and NiFe2O4 nanoparticles as a function of the Fe2+/Fe3+ oxidation state under different pHs (4.8 and 7.4) and temperatures (25 ºC and 40 ºC) condition. These results were contrasted with those obtained from the in vitro experiments in BV2 cells incubated with dextran-coated magneticnanoparticles. Based on these results we affirm that our ferrite magnetic nanoparticles catalyze the formation of free radicals and the decomposition of H2O2 by a ?peroxidase-like? activity. In a comment on this article, Meunier and A. Robert question two points: First they assert that the measured free radicals are not produced by a peroxidase reaction. Also, based on a different normalization method from those reported in our work, they also discuss that the reaction is not catalytic. Here we reply the arguments of the authors about these two points.Fil: Moreno Maldonado, Ana Carolina. Instituto de Nanociencia de Aragón; ; EspañaFil: Winkler, Elin Lilian. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina. Comisión Nacional de Energía Atómica. Unidad Ejecutora Instituto de Nanociencia y Nanotecnología. - Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Unidad Ejecutora Instituto de Nanociencia y Nanotecnología; ArgentinaFil: Raineri Andersen, Mariana. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina. Comisión Nacional de Energía Atómica. Unidad Ejecutora Instituto de Nanociencia y Nanotecnología. - Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Unidad Ejecutora Instituto de Nanociencia y Nanotecnología; ArgentinaFil: Toro Cordova, Alfonso. Universidad de Zaragoza; EspañaFil: Rodriguez, Luis Miguel. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina. Comisión Nacional de Energía Atómica. Unidad Ejecutora Instituto de Nanociencia y Nanotecnología. - Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Unidad Ejecutora Instituto de Nanociencia y Nanotecnología; ArgentinaFil: Troiani, Horacio Esteban. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Mojica Pisciotti, Mary Luz. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina. Comisión Nacional de Energía Atómica. Gerencia del Área de Energía Nuclear. Instituto Balseiro; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Vasquez Mansilla, Marcelo. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina. Comisión Nacional de Energía Atómica. Unidad Ejecutora Instituto de Nanociencia y Nanotecnología. - Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Unidad Ejecutora Instituto de Nanociencia y Nanotecnología; ArgentinaFil: Tobia, Dina. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina. Comisión Nacional de Energía Atómica. Unidad Ejecutora Instituto de Nanociencia y Nanotecnología. - Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Unidad Ejecutora Instituto de Nanociencia y Nanotecnología; ArgentinaFil: Nadal, Marcela. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina. Comisión Nacional de Energía Atómica. Unidad Ejecutora Instituto de Nanociencia y Nanotecnología. - Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Unidad Ejecutora Instituto de Nanociencia y Nanotecnología; ArgentinaFil: Torres Molina, Teobaldo Enrique. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina. Comisión Nacional de Energía Atómica. Unidad Ejecutora Instituto de Nanociencia y Nanotecnología. - Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Unidad Ejecutora Instituto de Nanociencia y Nanotecnología; ArgentinaFil: de Biasi, Emilio. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina. Comisión Nacional de Energía Atómica. Unidad Ejecutora Instituto de Nanociencia y Nanotecnología. - Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Unidad Ejecutora Instituto de Nanociencia y Nanotecnología; ArgentinaFil: Ramos, Carlos Alberto. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina. Comisión Nacional de Energía Atómica. Unidad Ejecutora Instituto de Nanociencia y Nanotecnología. - Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Unidad Ejecutora Instituto de Nanociencia y Nanotecnología; ArgentinaFil: Goya, Gerardo Fabian. Universidad de Zaragoza; EspañaFil: Zysler, Roberto Daniel. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina. Comisión Nacional de Energía Atómica. Unidad Ejecutora Instituto de Nanociencia y Nanotecnología. - Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Unidad Ejecutora Instituto de Nanociencia y Nanotecnología; ArgentinaFil: Lima, Enio Junior. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina. Comisión Nacional de Energía Atómica. Unidad Ejecutora Instituto de Nanociencia y Nanotecnología. - Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Unidad Ejecutora Instituto de Nanociencia y Nanotecnología; Argentin

Anomalous Magnetization Enhancement and Frustration in the Internal Magnetic Order on (Fe0.69Co0.31)B0.4 Nanoparticles

We have studied the internal magnetic order of 3-nm (Fe0.69Co0.31)0.6B0.4 amorphous nanoparticles. These nanoparticles were dispersed in a non-magnetic matrix (non-interacting nanoparticles) to contrast them with the powder samples, where strong interparticle interactions are present. In similar fashion to the bulk alloy, this system exhibits a saturation magnetization maximum as a function of Fe composition near 69 at% Fe for the powder and dispersed samples at all temperatures. The saturation magnetization (MS) of the dispersed sample shows anomalous behavior, revealing frustration in the internal magnetic order of the particles. Unexpectedly, the MS of the non-interacting sample at low temperatures is larger than the corresponding bulk alloy or the calculated value of MS for the same Fe-Co composition. By contrast, the powder sample has low MS values and it is approximately constant in temperature

One step synthesis of magnetic particles covered with casein surfactant

The one-step coprecipitation method is used to obtain magnetic nanoparticles controlling the pH (10 and 12), and casein surfactant (CS) concentrations (1 % and 3 % (m/m)). CS has not been used so far for stabilizing magnetic iron oxide ferrofluids. The magnetic nanoparticles have a magnetite core with maghemite in surface, and a shell of polymer. The transmission electron images confirm the crystallinity, particle size distribution in the range of 5-10 nm, and the spinel structure of the nanoparticles. Mössbauer results at 80 K showed line shapes dominated by magnetic relaxation effects with sextets and combinations of sextets and doublets. The interactions of the surfactant with the nanoparticle surface are strong showing at least two surfactant layers. The magnetic behavior was evaluated by moment versus temperature and magnetic field measurements. The nanoparticles showed superparamagnetic behavior at room temperature and blocked (irreversible) behavior at 5 K. The saturation magnetization presented lower values than reported bulk systems due to the presence of a large layer of maghemite. The FC/ZFC magnetization vs. temperature curves confirmed the superparamagnetic nature of the iron oxide particles and the strong interactions for pH 12 samples and weak interactions for pH 10 samples. The particle growth was dominated by the surface properties of the nanoparticles.O método de co-precipitação numa etapa utiliza-se para obter nano partículas magnéticas que controlam o pH (10 e 12), e a concentração do surfactante caseína (1 % and 3 %(m/m)). CS não foi usado para estabilizar os ferrofluidos óxidos magnéticos. As nanopartículas magnéticas tem um centro magnético com maghemite em superfície e uma casca de polímero. As imagens de transmissão de eléctron confirmam a cristalinidade, a distribuição das partículas dum tamanho de 5-10 nm, e a estrutura de espinela das nanopartículas. Os resultados de Mössbauer a 80 K mostraram formas de linhas dominadas por efeitos de relaxação magnéticas com sextetos e combinações de sextetos e duplicados. A interações do surfactante com a superfície da nanopartículas são fortes e mostram mínimo dois camadas de surfactante. O comportamento magnético foi avaliado em momentos versus temperatura e medidas de campo magnético. As nanopartículas mostraram comportamento superparamagnético com a temperatura de estudo e bloquearam (irreversível) a 5 K. A saturação da magnetização apresentou valores menores que os valores reportados nos sistema a granel devido à presença duma grande camada de maghemite. A magnetização FC/ZFC vs. Curvas de temperatura confirma o estado superparamagnético das partículas de óxidos de ferro e as fortes interações das amostras pH12 e as fracas interações das amostras pH 10. O crescimento das partículas foi dominado pelas propriedades das superfícies das partículas.Se usa el método de coprecipitación para obtener nanopartículas magnéticas controlando el pH (10 y 12) y la concentración del caseinato de sodio (CS) (1 % y 3 %(m/m)). CS no se ha utilizado hasta el momento para estabilizar ferrofluidos magnéticos. Las partículas muestran un núcleo de magnetita, una capa de maghemita sobre el mismo, y otra capa exterior de la proteína. La microscopía electrónica de transmisión muestra partículas cristalinas, una distribución de tamaños entre 5-10 nm, y la estructura de espinela. Los resultados Mössbauer a 80 K muestran formas de línea dominadas por efectos de relajación magnética. La interacción de la proteína con la superficie de las nanopartículas es fuerte y muestra varias capas de proteína. El comportamiento magnético se evaluó mediante medidas termomagnéticas y de momento versus campo magnético. Estas revelaron un sistema superparamagnético a 300 K y bloqueado a 5 K. La magnetización de saturación mostró valores menores que en el volumen posiblemete debido a la presencia de la maghemita. Las medidas termomagnéticas confirmaron el superparamagnetismo y mostraron que las muestras obtenidas a pH 12 presentan interacciones fuertes mientras que las de pH 10 muestran interacciones débiles. El crecimiento de las partículas fue dominado por las propiedades superficiales de las partículas

Improving degradation of real wastewaters with self-heating magnetic nanocatalysts

[EN] Industrial effluents contain a wide range of organic pollutants that present harmful effects on the environment and deprived communities with no access to clean water. As this organic matter is resistant to conventional treatments, Advanced Oxidation Processes (AOPs) have emerged as a suitable option to counteract these envi-ronmental challenges. Engineered iron oxide nanoparticles have been widely tested in AOPs catalysis, but their full potential as magnetic induction self-heating catalysts has not been studied yet on real and highly contam-inated industrial wastewaters. In this study we have designed a self-heating catalyst with a finely tuned structure of small cores (10 nm) aggregates to develop multicore particles (40 nm) with high magnetic moment and high colloidal stability. This nanocatalyst, that can be separated by magnetic harvesting, is able to increase reaction temperatures (up to 90 ◦C at 1 mg/mL suspension in 5 min) under the action of alternating magnetic fields. This efficient heating was tested in the degradation of a model compound (methyl orange) and real wastewaters, such as leachate from a solid landfill (LIX) and colored wastewater from a textile industry (TIW). It was possible to increase reaction rates leading to a reduction of the chemical oxygen demand of 50 and 90%, for TIW and LIX. These high removal and degradation ability of the magnetic nanocatalyst was sustained with the formation of strong reactive oxygen species by a Fenton-like mechanism as proved by electron paramagnetic resonance. These findings represent an important advance for the industrial implementation of a scalable, non-toxic, self-heating catalysts that can certainly enhance AOP for wastewater treatment in a more sustainable and efficient way.This research was funded by the Spanish Ministry of Economy and Competitiveness under grant MAT2017-88148-R (AEI/FEDER, UE) and Consejo Superior de Invetigaciones Científícas PIE- 201960E062. This study was also supported by the USFQ Collaboration Grant 2018 Nº 11197 and the USFQ PoliGrants 2018–2019 Nº 12501. E.W., E.L.Jr and R.D.Z. acknowledge Argentine governmental agency ANPCyT (Project No. PICT-2016-0288 and PICT-2018-02565) and UNCuyo (Project No.06/ C527 and 06/C528) for the financial support.Peer reviewe