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The effect of the simultaneous presence of fluorine (0.15-1.2 mg L ), bicarbonates (83.6-596 mg L ), and synthesized goethite (0.3 mg L ) at typical concentrations often found in natural groundwater samples was evaluated on the degradation of 2,4-dichlorophenoxyacetic acid (2,4-D) at pH 6.9 under simulated sunlight irradiation (300 W m ) and H O concentrations of 10 mg L . 2,4-D removal was strongly enhanced by the presence of fluoride. F could modify the surface of iron (hydr)oxide leading to the formation of surficial Fe-F bonds benefiting the formation of free OH radicals, producing upward band bending, reducing the electron-hole recombination, and enhancing the electron transfer to H O . On the other hand, bicarbonate may react with OH radicals generating CO species which could be able to participate in pollutant oxidation as well while solar light-induced H O photolysis also played an important role in removing 2,4-D. These findings suggest that “natural” tuning of iron (hydr)oxides by fluoride could take place in natural groundwater generating “natural” photocatalysts with a high activity which could participate, by adding H O , in the enhancing of sunlight photoinduced natural abiotic processes to pollutants abatement.

A co-precipitation synthesis method was used to obtain iron oxide nanoparticles coated with Yerba Mate (Ilex paraguariensis) extract. These particles have a core–shell structure with the iron oxide phase surrounded by an organic shell provided by an organic component which come from the Yerba Mate extract. Obtained nanoparticles were exhaustively characterized as powders and in aqueous colloidal suspensions using several techniques such as TEM, XRD, SAXS, TGA, ATR-FTIR, Raman and XPS spectroscopy, magnetic moment measurement and specimen ac susceptibility. All results together show that the obtained particles are single-crystal iron oxide particles with magnetite as the most probable phase. Yerba Mate extract shell mass to iron oxide core mass, mS/mc, could be increased up to 6.2 × 10−2, depending on the synthesis conditions. As a function of mS/mc the crystallite size of the nanoparticles decreased from about 15 nm to 11 nm, while saturation magnetization Ms and coercive field Hc of powders decreased. Ms. diminution was associated to increasing modification of core surface electronic states due to chemical bond of iron in iron oxide to Yerba Mate extract components; on the other hand, coercivity reduction was modelled on the basis of the increasing interparticle separation and dipolar interaction weakening, which occurs as shell thickness grows. Differences between the particle core mean size obtained with TEM, SAXS, XRD and magnetic measurements are observed. The fact that magnetic size was smaller than particle and crystallite sizes was attributed to the existence of intense dipolar interactions. It was found that low field susceptibility in a colloid sample was about 2.5 times that of the powder specimen, a result that shows that demagnetizing effects prevail in the powder specimen, while they may be absent in the colloid due to the larger interparticle mean separation expected in the latter. Analysis of powder and colloid susceptibility was done based on a recently developed model was in agreement with the one performed for the coercive field behaviour. Fil: Mercado Castro, Donaldo Fabio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas; Argentina Fil: Cipollone, Mariano Enrique. YPF - Tecnología; Argentina Fil: González, Mónica C.. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas; Argentina Fil: Sánchez, Francisco Homero. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física La Plata; Argentina

Scientific and technological researches are devoted to obtain materials capable of retaining different kinds of pollutants, contributing to contamination solutions. In this context, hydrogels have emerged as great candidates because of their excellent absorption properties as well as good mechanical, thermal and chemical properties. More specifically, ferrogels (magnetic gels) present the extra advantage of being easily manipulated by a permanent magnet. Here, we present the results derived from the application of ferrogels as efficient tools to extract heavy metal pollutants from wastewater samples. The gels were prepared following the method of freezing and thawing of a polyvinyl alcohol aqueous solution with magnetic nanoparticles coated with polyacrylic acid. Ferrogels were fully characterized and their ability to retain Cu2+ and Cd2+, as model heavy metals, was studied. Thus kinetics and mechanisms of adsorption were evaluated and modeled. The concentration of MNPs on the PVA matrix was key to improve the adsorption capability (approximately the double of retention is improved by the MNPs addition). The adsorption kinetics was determined as pseudo-second order model, whereas the Langmuir model was the most appropriate to explain the behavior of the gels. Finally reuse ability was evaluated to determine the real potential of these materials, the ferrogels demonstrated high efficiency up to about five cycles, retaining about 80–90% of their initial adsorption capability. All the results indicated that the materials are promising candidates able to compete with the commercial technology regarding to water remediation. Fil: Areal, Maria Pia. Universidad Nacional de Mar del Plata; Argentina Fil: Arciniegas Vaca, Magda Lorena. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; Argentina Fil: Horst, María Fernanda. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Química del Sur. Universidad Nacional del Sur. Departamento de Química. Instituto de Química del Sur; Argentina Fil: Lassalle, Verónica Leticia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Química del Sur. Universidad Nacional del Sur. Departamento de Química. Instituto de Química del Sur; Argentina Fil: Sánchez, Francisco Homero. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física La Plata; Argentina Fil: Alvarez, Vera Alejandra. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; Argentina Fil: Gonzalez, Jimena Soledad. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; Argentina

(Fe30Cu70)96B4 (FCB) alloys were produced in an induction furnace and then reduced in size by mechanical milling in stainless steel vials in an Ar atmosphere. Structural, morphological, and magnetic characterization techniques were used to investigate the evolution of powder alloys as a function of their milling time (0, 12, 24, 36, 48, and 60 h). Structural analysis by X-ray diffraction confirmed that all samples exhibit a crystalline fcc structure and space group Fm-3 m. As the milling time increases, the induced stress increments, leading to changes in the lattice parameter value and atomic volume. Thus, lattice parameter values are approximately in the range a = 0. 3614–0.3626 nm. TEM analysis confirmed that after 12 h of milling, the FCB system was made up of nanoparticles with diameters between 6 and 8.2 nm. ZFC-FC measurements revealed that the samples are ferromagnetic at room temperature. Nevertheless, due to the particle's nanometric size, a superparamagnetic-like behavior was evidenced with a blocking temperature (TB) below 60 K. M(H) loops were fitted using a distribution of Langevin functions, obtaining a maximum saturation magnetization Ms ~ 25 emu/g after 24 h of milling. Likewise, the FCB system is magnetically soft a room temperature with coercive field values below (132 Oe). Finally, Mossbauer spectroscopy showed that the superparamagnetic-like behavior could be associated with the Cu matrix's nanoparticle size and Fe atom behavior.

Magnetic hyperthermia, a modality that uses radio frequency heating assisted with single-domain magnetic nanoparticles, is becoming established as a powerful oncological therapy. Much improvement in nanomaterials development, to enhance their heating efficiency by tuning the magnetic colloidal properties, has been achieved. However, methodological standardization to accurately and univocally determine the colloidal properties required to numerically reproduce a specific heating efficiency using analytical expressions still holds. Thus, anticipating the hyperthermic performances of magnetic colloids entails high complexity due to polydispersity, aggregation and dipolar interactions always present in real materials to a greater or lesser degree. Here, by numerically simulating the experimental results and using real biomedical aqueous colloids, we analyse and compare several approaches to reproduce experimental specific absorption rate values. Then, we show that the relaxation time, determined using a representative mean activation energy consistently derived from four independent experiments accurately reproduces experimental heating efficiencies. Moreover, the so-derived relaxation time can be used to extrapolate the heating performance of the magnetic nanoparticles to the other field conditions within the framework of the linear response theory. We thus present a practical tool that may truly aid the design of medical decisions., Facultad de Ciencias Exactas, Instituto de Física La Plata

The recently published Mean Field Interacting Superparamagnet Model (MFISP model), which introduces the effective demagnetizing factor N E , is tested in specimens having a random-like spatial distribution of magnetic nanoparticles, where different hierarchies of clustering are present. These specimens are ferrogel PVA/iron oxide beads synthesized by a one-pot route, having spheroidal shapes and sizes of about 1 mm, and chain and disk-like arrays (superstructures) of beads. Raman analyses indicated that magnetic nanoparticles are composed by a mixture of magnetite and maghemite. Beads swell 208 % by hydration in about 40 min. The increase of the ac susceptibility as a function of hydration time closely reflects the effect of bead swelling, in agreement with the expected diminution of dipole-dipole interactions. Measured susceptibility is analyzed in terms of the susceptibility χ of non-interacting particles and the effective demagnetizing factor N E of the specimen, which depends on swelling. The Specific Absorption Rate of electromagnetic power by the beads grows with the hydration time in agreement with ac susceptibility behavior For long hydration times susceptibility and high field magnetization decrease. This is explained by the occurrence of oxidation of magnetite / maghemite to hematite. Isothermal magnetization experiments are performed on each macrostructure in two perpendicular principal directions each. Results are consistently described with the MFISP model by considering two hierarchies of clustering: beads themselves and clusters within the beads. From the whole set of experiments, it is possible to estimate values for the volume fractions of particles in clusters and clusters in beads, given by x pc = 0.46 ( 15 ) and x cb = 0.16 ( 5 ) . The susceptibility of non-interacting particles, χ = 13 ( 4 ) , is also obtained, which results about five times larger than the measured (apparent) one. The MFISP model proves to be a convenient and efficient tool for the analysis of magnetization studies of complex 3d dispersions of magnetic nanoparticles, allowing an experimental determination of relevant physical information, otherwise not accessible by magnetic measurements.

We present a simple, scalable, and low-cost route for producing aqueous colloids of nanometer size Fe cores coated with iron oxide and stabilized with sodium citrate. The Fe cores were obtained by mechanosynthesis by means of a highly exothermic solid-state reaction between FeCl3 and Mg, in a dispersive inert NaCl medium. The optimal experimental conditions for achieving a full reaction were determined with a Retsch 2000 oscillatory mill. Then the production yield was successfully 16-fold scaled using a rotatory Fritsch Pulverissete 7 mill. To provide biocompatibility and facilitate colloid stabilization, the Fe cores were coated with a Fe-oxide shell produced by chemical coprecipitation, and finally, the system Fe/FeOx was functionalized with sodium citrate in water. The so-obtained Fe/FeOx@Cit (4/3

We have demonstrated the synthesis of high-quality monocrystalline magnetite nanocubes through the introduction of palmitic acid as surfactant in a thermal decomposition synthesis of an organic Fe precursor. Unlike the standard thermal decomposition synthesis route, we report the avoid of the reducing agent and a modification in the synthesis heating ramp. Structural and magnetic properties were investigated showing well defined cubic shaped nanoparticles with a backsim40nm edge and magnetic features close to bulk magnetite. We associate the bulk-like magnetic performance and properties to the highly crystalline structure of the nanocubes. Fil: Orozco Henao, Juan Manuel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física La Plata; Argentina Fil: Muraca, Diego. Universidade Estadual de Campinas; Brasil Fil: Sanchez, Francisco Homero. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física La Plata; Argentina Fil: Mendoza Zélis, Pedro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física La Plata; Argentina

A comprehensive study of relevant aspects of the physics behind in vitro magnetic assisted transfection, or magnetofection is presented. Magnetofection experiments were performed as a function of culture-magnet distance for a fixed time of 30 min, as a function of time for a fixed separation of about 1 mm, and under special geometries chosen to elucidate the relative effects of gravitational and magnetic forces. It is shown that under appropriate conditions, in vitro magnetofection can be performed with almost equal easiness in any desired space direction, even against gravity. Redistribution of magnetic nanoparticles in a colloid, with an initial uniform distribution, was studied with the same experimental setup used in magnetofection experiments, as a function of time, and as a function of culture-magnet relative position. It was found that magnetic nanoparticles tend to arrange into concentrated regions with ring or circle shapes, and that final distribution depends strongly on relative position. Cellular uptake of magnetic nanoparticles was estimated for standard magnetofection and for no applied magnetic field experiments. A consistent description of results is given by comparing magnetofection efficiency, nanoparticles uptake and redistribution experiments. The results presented here constitute novel information that will contribute to gaining deeper understanding of how magnetofection proceeds and how can be improved. They impact directly on in vivo procedures, providing conceptual tools to optimize setup geometry and magnetic field application time.

A model describing the effect of magnetic dipolar interactions on the susceptibility of magnetic nanopillars is presented. It is an extension of a recently reported model for three-dimensional randomlike dispersions of nearly spherical nanoparticles in equilibrium [Sánchez et al., Phys. Rev. B 95, 134421 (2017)2469-995010.1103/PhysRevB.95.134421], to well-ordered arrays of nanoparticles out of equilibrium. To test it, a high-quality benchmark consisting of a two-dimensional hexagonal arrangement of quasi-identical parallel nickel nanopillars embedded in a porous alumina template was fabricated. This model is based on an effective demagnetizing tensor, which only depends on a few morphological parameters of the sample, as the nearest-neighbor distance between pillars and the volume fraction of pillars in the specimen. It allows us to obtain the nanopillar intrinsic susceptibility tensor from the magnetic response of the nanopillar ensemble. The values of the in-plane and normal-to-plane susceptibility of the sample are successfully predicted by the model. Furthermore, the model reproduces the susceptibility in the applied field direction, measured for different applied field angles. In this way, it provides a simple and accurate treatment to account for the complex magnetic effects produced by dipolar interactions., Facultad de Ciencias Exactas, Instituto de Física La Plata

We present a device based on a parallel LC resonant circuit optimized to generate altemating magnetic fields of 100 kHz frequency and amplitude adjustable from 2 to 15 kA/m. It is suitable for research aimed to the development of new nanotherapies that involve the use of magnetic materials and alternating magnetic field for fighting cancer, like magnetic hyperthermia and drug and gene delivery triggered by magnetic stimuli. The equipment is portable, air-cooled, versatile and functional to allow expérimentation with materials, in vitro and in vivo. In addition, the design guarantees environmental bioterium conditions (ventilation, Ught, noise, humidity and temperature) for in vivo and of cell culture conditions (pH, temperature, osmotic pressure, partial pressure of O2 and CO2) required for in vitro experiments. Fil: Gonzalez, Sergio Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones en Electrónica, Control y Procesamiento de Señales. Universidad Nacional de La Plata. Instituto de Investigaciones en Electrónica, Control y Procesamiento de Señales; Argentina. Universidad Nacional de La Plata. Facultad de Ingeniería. Departamento de Electrotecnia; Argentina Fil: Spinelli, Enrique Mario. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones en Electrónica, Control y Procesamiento de Señales. Universidad Nacional de La Plata. Instituto de Investigaciones en Electrónica, Control y Procesamiento de Señales; Argentina. Universidad Nacional de La Plata. Facultad de Ingeniería. Departamento de Electrotecnia; Argentina Fil: Veiga, Alejandro Luis. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones en Electrónica, Control y Procesamiento de Señales. Universidad Nacional de La Plata. Instituto de Investigaciones en Electrónica, Control y Procesamiento de Señales; Argentina. Universidad Nacional de La Plata. Facultad de Ingeniería. Departamento de Electrotecnia; Argentina Fil: Coral, Diego Fernando. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física La Plata; Argentina Fil: Fernández van Raap, Marcela Beatriz. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física La Plata; Argentina Fil: Mendoza Zélis, Pedro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física La Plata; Argentina Fil: Pasquevich, Gustavo Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física La Plata; Argentina Fil: Sánchez, Francisco Homero. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física La Plata; Argentina

Long term gamma spectroscopy experiments involving single channel analyzer equipment depend upon thermal stability of the detector and its associated high voltage supply. Assuming constant discrimination levels, a drift in the detector gain impacts the output rate, producing an effect on the output spectrum. In some cases (e.g. single energy resonant absorption experiments) data of interest can be completely lost. We present a digital self adapting discrimination strategy that tracks emission line shifts using statistical measurements on a predefined region of interest of the spectrum. It is developed in the form of a synthesizable module that can be intercalated in the digital processing chain. It requires a moderate to small amount of digital resources and can be easily activated and deactivated. Fil: Veiga, Alejandro Luis. Universidad Nacional de La Plata. Facultad de Ingeniería; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física La Plata; Argentina Fil: Grunfeld, Christian Martin. Universidad Nacional de La Plata. Facultad de Ingeniería; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física La Plata; Argentina Fil: Pasquevich, Gustavo Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física La Plata; Argentina. Universidad Nacional de La Plata. Facultad de Ingeniería; Argentina Fil: Mendoza Zélis, Pedro. Universidad Nacional de La Plata. Facultad de Ingeniería; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física La Plata; Argentina Fil: Martínez, N.. Comisión de Investigaciones Científicas ; Argentina Fil: Sánchez, Francisco Homero. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física La Plata; Argentina

Element-And site-specific magnetic hysteresis-loops measurements on a zinc ferrite (ZnFe2O4) thin film were performed by X-ray magnetic circular dichroism. Results show that iron in octahedral and tetrahedral sites of spinel structure are coupled antiferromagnetically between them, and when magnetic field is applied the magnetic moment of the ion located at octahedral sites aligns along the field direction. The magnetic measurements reveal a distinctive response of the surface with in-plane anisotropy and an effective anisotropy constant value of 12.6 kJ/m3. This effective anisotropy is due to the combining effects of demagnetizing field and, volume and surface magnetic anisotropies KV =3.1 kJ/m3 and KS =16 μJ/m2. Fil: Mendoza Zélis, Pedro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física La Plata; Argentina. Universidad Nacional de La Plata. Facultad de Ingeniería; Argentina Fil: Pasquevich, Gustavo Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física La Plata; Argentina. Universidad Nacional de La Plata. Facultad de Ingeniería; Argentina Fil: Salcedo Rodriguez, Karen Lizeth. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física La Plata; Argentina Fil: Sánchez, Francisco Homero. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física La Plata; Argentina Fil: RodrÍguez Torres, Claudia Elena. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física La Plata; Argentina

Magnetic hydrophobic aerogels (MHA) in the form of nanocomposites of silica and maghemite (g-Fe2O3) were prepared by one step sol–gel procedure followed by supercritical solvent extraction. Silica alcogels were obtained from TEOS, MTMS, methanol and H2O, and Fe(III) nitrate as magnetic precursor. The hydrophobic property was achieved using the methytrimethoxysilane (MTMS) as coprecursor for surface modification. The so produced nanocomposite aerogels are monolithic, hydrophobic and magnetic. The interconnected porous structure hosts � 6 nm size g-Fe2O3 particles, has a mean pore diameter of 5 nm, and a specific surface area (SSA) of 698 m 2 /g. Medium range structure of MHA is determined by SAXS, which displays the typical fractal power law behavior with primary particle radius of � 1 nm. Magnetic properties of the nanoparticle ensembles hosted in them are studied by means of dc-magnetometry.

Quality of Mossbauer spectra is strongly related to the performance of source velocity modulator. Traditional electromechanical driving techniques demand hard-edged square or triangular velocity waveforms that introduce long settling times and demand careful driver tuning. For this work, the behavior of commercial velocity transducers and drive units was studied under different working conditions. Different velocity reference waveforms in constant-acceleration, constant-velocity and programmable-velocity techniques were tested. Significant improvement in spectrometer efficiency and accuracy was achieved by replacing triangular and square hard edges with continuous smooth-shaped transitions. A criterion for best waveform selection and synchronization is presented and attainable enhancements are evaluated. In order to fully exploit this driving technique, a compact microprocessor-based architecture is proposed and a suitable data acquisition system implementation is presented. System linearity and efficiency characterization are also shown.

Polyvinyl alcohol (PVA) ferrogels were easily obtained through a one-pot technique that involves co-precipitation of iron salts in the presence of a PVA solution, followed by freezing–thawing cycles of the resulting nanoparticles (NPs) dispersions. The protecting effect of PVA enabled the synthesis of small magnetic NPs that did not agglomerate in the initial solution allowing the synthesis of well-dispersed ferrogels by physical cross-linking. Physical properties of the physically cross-linked ferrogels, as swelling ability, melting temperature, and crystallinity, were barely affected by the presence of NPs, presenting similar or improved values when compared with chemically cross-linked systems. Ferrogels showed superparamagnetic properties at room temperature that combined with the absence of toxic residues arising from cross-linking agents make them ideal candidates for their use in biomedical applications (artificial muscles, drug delivery, and sensors among others).

Mossbauer absorption line tracking methodology, under a constant velocity strategy, is used for a quasi-continuous observation of the \(\upalpha \)-transition on slightly non stoichiometric Fe1 + x S alloy. To this end, two strategies were applied: an intelligent absorption line tracking with a control algorithm that uses the data measured in the previous region to establish the position of the next partial spectral range; and a predetermined line tracking in which temperature evolution of a partial spectral region of interest (ROI) is programmed. The latter uses results from the former, in order to achieve a quasi-continuous partial spectral observation. These experiments clearly demonstrate that line tracking allows a more efficient use of the radioactive source, as the effort is concentrated in a partial region of the spectra from which the desired information can be obtained.

The structural and magnetic properties of Fe 10 at% doped SnO2 powders milled for different times have been investigated. XAS results demonstrate the dilution of Fe atoms in the rutile structure after 5 h of milling. Fe atoms have almost one oxygen vacancy near neighbour. At RT the sample presents the superposition of paramagnetic and ferromagnetic behaviours. When temperature decreases a progressive blocking process was observed. Below 100 K a field shift of hysteresis loops is evident indicating magnetic coupling between ferromagnetic/antiferromagnetic phases.

Fe-doped TiO2 samples with different Fe content prepared by mechanical alloying have been investigated by means of Mossbauer spectroscopy at 300 and 4.2 K. The results indicate the coexistence of Fe2 + and Fe3 + ions in paramagnetic states at room temperatures in the rutile structure. All samples present magnetic order at 4.3 K. When the Fe concentration increases the Fe ions in the rutile matrix became closer giving the possibility of strong magnetic interactions between them. The temperature evolution of the magnetic order was followed for the 15 at.% of Fe sample. The Fe-doped oxide formed for this composition orders below 20 K reaching an almost totally magnetic ordered state at 4.3 K.

A new experimental setup and methodology that allows the automatic tracking of a Mossbauer absorption line as its energy position varies during the experiment is introduced. As a test the sixth spectral line of FeSn2 was tracked while temperature was varied between room temperature and a value slightly above its Neel temperature.

Mossbauer effect spectroscopy and thermal analysis techniques were applied to characterize polyaniline composites successfully synthesized by embedding Fe oxide nanoparticles (about 10–13 nm) in a polymeric matrix in the presence of dodecyl benzene sulfonic acid and Hel (dopant). Thermal techniques provided quantitative information on iron oxide content and on polyaniline stability and transformations. Mossbauer results indicated that for the whole studied composition range, 3.4 to 100 iron oxide wt.%, composites hold maghemite particles. A preliminary study of the conductivity of the nanocomposites was performed. The largest conductivity was observed for a 8 wt.% maghemite composite where all particles are magnetically unblocked at room temperature within the Mossbauer time window.

Fe-doped nanosized SnO 2 powders were prepared by mechanosynthesis using rutile SnO 2 and hematite Fe 2 O 3 as starting materials. The estimated grain size of the obtained rutile structure was between 10 and 20 nm. Mossbauer spectroscopy shows the presence of two interactions corresponding to 3+ and 2+ iron oxidation states with similar relative fractions. The magnetic measurements exhibit ferromagnetic- (FML) and superparamagnetic-like (SML) behavior. Evidence of a system of strongly interacting particles was found.

Samples of Sn0.90Fe0.10O2 were prepared by mechanosynthesis method. The structure and magnetic behavior of the samples have been investigated by X-ray diffraction (XRD) and Mossbauer spectroscopy. It has been found that for short milling times a small percentage of the initial hematite remains simultaneously with the formation of metallic Fe. Additionally a paramagnetic contribution appears in the Mossbauer spectra. For milling times, over 2 h, the iron ions are in paramagnetic states having +3 and +2 oxidation states while by XRD only the rutile structure diffraction lines were observed.

Transition-Metal-doped TiO2 thin films, with nominal composition Ti₀.₉TM₀₁O₂-δ (TM = Mn, Fe, Co, Ni, Cu), were grown by pulsed laser deposition (PLD), in order to study the role of dopants in the origin and significance of room temperature ferromagnetism in these systems. The crystallographic structures and their magnetic properties were characterized and the experimental results are compared to ab-initio calculations previously reported. The films are ferromagnetic at room temperature in the cases of Fe, Co, Ni and even Cu impurities, but not in the case of Mn doping. Our results support the hypothesis that oxygen vacancies play a key role in the origin of magnetism in doped TiO2 films, and can explain the diversity of magnetic moments observed experimentally for films grown under different conditions., Instituto de Física La Plata

A magnetic and structural characterization of SnO 2 doped with 10 at% of Fe prepared by mechanical alloying is presented. X-ray diffraction indicates a good dissolution of Fe in the SnO 2 structure, while Mossbauer spectroscopy shows that the doped material (where Fe atoms are in the +2 and +3 oxidation states) does not display a magnetically ordered pattern at room temperature. AC-susceptibility measurements present a behavior consistent with a system of magnetically coupled single-domain units, at the frontier between the behaviors of a cluster spin glass and of an interacting superparamagnetic (SPM) particle system. RT magnetization results display the typical shape of the SPM regime, although a weak hysteresis has been observed.

We present here a systematic study of the structural and magnetic properties of a series of alloys around a central composition Al50Cu20Fe30, obtained by mechanical alloying. The samples have BCC crystalline structure with partial B2 order. Thermal annealing, through differential scanning calorimetry measurements, just removes some defects but does not change the crystalline structure. AC susceptibility measurements show that in spite of their structural similarity these samples have quite different magnetic behaviors. Furthermore, most of the samples show a complex magnetic evolution with temperature. Some samples have a cluster glass-like behavior at low temperatures and a superparamagnetic-like one at higher temperatures. A model of magnetic clusters originating in composition fluctuations across the alloy is proposed to explain the observed magnetic properties.

Transition metal doped TiO 2 samples, with nominal composition TM 5 (TiO 2 ) 95 (TM=Mn, Fe, Co and Ni), were obtained by thermal treatment at 673, 773 and 973 K in air to study the role of impurities in the origin of magnetism. X-ray diffraction (XRD) experiments only detect the rutile phase in the 673 K thermally treated samples but evidence of other phases was detected by Mossbauer spectroscopy and ac-susceptibility measurements. All samples presented magnetic behaviour. The estimated magnetic moments were lower than those obtained by ab initio calculations.

B-Chronic Lymphocytic Leukemia (B-CLL) usually follows an adverse, relentless clinical course by slowly developing drug resistance to fludarabine and other chemotherapeutic agents, as well as by acquiring new different genetic abnormalities. As B-CLL cells spontaneously produce high amounts of Reactive Oxygen Species (ROS) having an altered redox state in relation to that of normal B lymphocytes, we decided to probe different metal Zinc nanoparticles (ZnNPs) and quantify the levels of Singlet Oxigen (SO) to see if variations of its intracellular concentrations could execute and accelerate deadly programs in leukemic cells rather than in normal B lymphocytes, when applied with Photodynamic Therapy (PDT). In this way, we developed and tested a variety of metal ZnNPs of which one made of 0.5% Manganese Doped Zinc Oxide (ZnO:Mn) was finally selected for further testing as it had the best fludarabine resistant B-CLL cells in vitro killing activity, specially when combined with PDT. An interesting and rapidly dying process of B-CLL cells, known as autophagy, was always seen under Transmission Electronic Microscopy (TEM) when incubated with these 0.5% Mn doped ZnO NPs. This phenomenon correlated well with those intracellular increases of SO when PDT was administered, and measured by a novel method first described by us. As this therapy seems to be very specific to fludarabine resistant B-CLL cells, producing almost no damage to normal lymphocytes, it could surely contribute in the near future as a new innovative targeted strategy to be delivered in the clinical setting for the definitive benefit of these bad prognostic patients., Facultad de Ciencias Médicas, Instituto de Investigaciones Bioquímicas de La Plata, Facultad de Ciencias Exactas

Mossbauer transmission recorded at fixed photon energies as a function of a given physical parameter such as temperature, external field, etc. (Mossbauer scan), is being developed as a useful quantitative tool, complementary of Mossbauer spectroscopy. Scans are performed at selected energies, suitable for the observation of a given physical property or process. It is shown that one of main advantages of this approach is the higher speed at which the external physical parameter can be swept, which allows the recording of quasicontinuous experimental response functions as well as the study of processes which occur too fast to be followed by Mossbauer spectroscopy. The applications presented here are the determination of the temperature dependence of the 57Fe hyperfine field in FeSn2, the thermal evolution and nanocrystallization kinetics of amorphous Fe73.5Si13.5Cu1Nb3B9 and complex behaviour could be related to polarization effects which appear in thick absorbers [10]. To confmn this behaviour, a few spectra were recorded under external fields (H j =−70.6, −15.3 and 0 Oe). In Figure 5b,c, the full circles are the values Tr(E 5,H j ) and Tr(E6,Hj), respectively obtained from the spectra, and they agree with the behaviour revealed by the scan. The analysis of the physics beneath these results is left for a forthcoming article, but we found worthily to remark that its observation was possible by performing only one scan at energy E 5.

A prototype of a programmable constant-velocity scaler is presented. This instrument allows the acquisition of partial Mossbauer spectra in selected energy regions using standard drivers and transducers. It can be fully operated by a remote application, thus data acquisition can be automated. The instrument consists of a programmable counter and a constant-velocity reference. The reference waveform generator is amplitude modulated with 13-bit resolution, and is programmable in a wide range of frequencies and waveforms in order to optimize the performance of the transducer. The counter is compatible with most standard SCA, and is configured as a rate-meter that provides counts per selectable time slice at the programmed velocity. As a demonstration of the instrument applications, a partial Mossbauer spectrum of a natural iron foil was taken. Only positive energies were studied in 512 channels, accumulating 20 s per channel. A line width of 0.20 mm/s was achieved, performing with an efficiency of 80%.

We present a study of crystalline structure, local environment around the magnetic atoms and magnetic behaviour of Fe 0.3 Ti 0.7 O 2-δ films, produced by Pulsed Laser Deposition, as a function of oxygen pressure and substrate temperature. Dark films were obtained by deposition at low O 2 pressure (between 2 x 10 -3 and 10 -2 Pa). These films are ferromagnetic with coercivities around 0.03-0.04T. Fe atoms are found to be predominantly metallic Fe. Transparent films were obtained when deposition was performed at high O 2 pressure (between 4 and 20 Pa). Fe atoms are mainly in +3 valence state. These films have a component magnetically ordered probably corresponding to α-Fe(Ti) 2 O 3 and a paramagnetic one attributed to Fe substituted anatase. After a thermal treatment Fe changes to + 2 valence state and α-Fe(Ti) 2 O 3 orders in the ilmenite phase increasing ten times the saturation magnetization of the magnetically ordered (hysteretic) component.

We present here a study of the structural and magnetic properties of a series of mechanically alloyed intermetallics around a central composition Al 5 0 Cu 2 0 Fe 3 0 , varying the Cu and Fe content. All the samples have bcccrystalline structure with partial B2 order and show no evidence of a magnetic splitting in the Mossbauer spectra. Thermal annealing, removes some defects but do not change this structural feature. All the studied alloys show, at room temperature, a hysteresis loop that may be interpreted in terms of two magnetic components coming respectively from superparamagnetic and ferromagnetic-like regions. The parameters characterizing thess magnetic properties change with composition but no systematic behavior could be deduced.

The local structure around Hf in Nd15.78Fe76.3−xHfxB7.8 ( x = 0.1 and 0.2) submitted to conventional and solid hydrogenation–disproportionation–desorption–recombination (HDDR) sequence was studied by extended X-ray absorption fine structure (EXAFS) in order to understand the relation between the presence of Hf and magnetic anisotropy found only in solid-HDDR samples. EXAFS results show that Hf is not in the Nd2Fe14B structure but incorporated into a local atomic arrangement (HfB ClNa-type) which is the same for as-cast, solid and conventional HDDR samples. It is concluded that the magnetic anisotropy induced by Hf addition to NdFeB alloys must be related to microstructural features.

An attempt to produce massive magnetic semiconductors by doping TiO2 with 5 at% of Fe using the ball milling technique is presented here. Local environment surrounding magnetic impurity atoms in the partially reacted alloys have been investigated using Mossbauer spectroscopy. Results indicate that fully reacted samples cannot be achieved under the different experimental conditions tested and that the only resulting phase that displays magnetism at room temperature is the unreacted α -Fe.

The crystallisation kinetics of MM 2.5 Fe 79 B 18.5 (MM=Mischmetal), was followed by means of Mossabuer effect experiments at constant acceleration, Mossbauer thermal scan, thermomagnetic and calorimetric measurements. It was determined that the as-quenched ribbons are amorphous with a T c of 668 K and the crystallisation, at low heating rates, occurs in two steps: in the first step, it precipitates a dilute α-(Fe, RE) solid solution, while in the second Fe 2 B and more α-(Fe, RE) are crystallised from the remnant Fe-impoverished amorphous matrix.

Mossbauer thermal scans combined with a newly developed data analysis methodology have proved to be suitable in order to obtain temperature dependence of the hyperfine fields in a case where two distinct crystallographic sites are present. Demonstration is achieved by studying Fe 3 Si compound which has a DO 3 structure.

The alloy Fe 65 Ni 20 Nb 6 B 9 was obtained from the elemental constituents in a high-energy planetary ball mill and subsequently thermally treated at 873 and 900 K in order to obtain the equilibrium phases. The as-prepared nanocrystalline alloy consists primarily of metastable BCC α-Fe(Ni) nanocrystals while the treated ones consist of a mixture of BCC (ferromagnetic) and FCC (paramagnetic at room temperature) phases. Hysteresis loops at 5 and 300 K present low remanence and coercivity. As-prepared sample exhibits the best soft magnetic properties. In all samples, the susceptibility curves suggest magnetic collective (long-range order) behavior with a maximum between 70 and 90 K. This feature is caused by nanometric-sized magnetic particles. The huge difference between blocking and irreversibility temperatures in the field cooling and zero-field cooling scans indicates a wide grain-size distribution.

Alloys with compositions Nd60−xCxFe30Al10 (x=0, 1, 5 and 10) were processed by melt spinning at a tangential speed of 5 m/s. The as-cast ribbons were characterized by X-ray diffraction, Mossbauer Effect spectroscopy and their room temperature hysteresis loops. The substitution of Nd by C is found to affect the phase selection, from mainly DHCP-Nd for x=0 to DHCP-Nd /FCC-Nd for the other ones. Mossbauer spectra of all the as-cast samples indicate that Fe is present in crystalline magnetic phases as well as in a paramagnetic one. The major crystalline phase was identified as a μ-type (or A1) metastable phase, which is reported to have a large anisotropy field and a relatively high saturation polarization. Interstitial C stabilizes the μ-type phase and improves its average hyperfine field. The magnetic measurements display an increase of coercivity and remanence with the C concentration.

The effects of the cooling rate on the microstructure and magnetic properties of the melt-spun Nd60Fe30Al10 alloys are investigated by Mossbauer Effect (ME) spectroscopy and magnetic hysteresis loops measurements at different temperatures. It is found that the hard magnetic properties of these alloys are likely to be related to the presence of clusters of a metastable crystalline μ-type phase. It is observed that as the cooling rate increases, the amount of this magnetic μ-like phase component decreases in the benefit of an amorphous Nd-rich phase. This phase has an iron concentration, which increases with increasing the wheel speed, is paramagnetic at room temperature and becomes superparamagnetic below approximately 50 K and 100 K for slow and high cooling rates, respectively.

The local atomic arrangements and the nanoscopically dispersed phases in melt spun Nd 60 Fe 30 Al 10 alloys are investigated by Mōssbauer spectroscopy. It is found that the hard magnetic properties of these alloys are likely to be related to the presence of clusters of a metastable crystalline μ-type phase.

A constant-velocity Mossbauer spectrometer with controlled temperature sweep of the sample is presented. The equipment was developed for Mossbauer thermal scanning experiments, allowing the determination of the evolution of the magnetic hyperfine field with temperature. It is based in a three level architecture implemented in a medium sized personal computer (PC). The instrument runs the widely used Linux operating system, supporting several custom microprocessor-based boards, extending the hardware capabilities of the PC. This scheme optimizes the required time for the experiment, exploiting in the background the full capabilities of modern multitasking operating systems in terms of networking, graphical user interfaces, and data storage. The prototype was tested applying the method to the simplest case, i.e., a symmetric sextet collapsing into a singlet. It was found that required times are an order of magnitude smaller than those demanded by the conventional methodology. The results obtained for the 57...

Fe x Au 100− x alloys have been produced for the first time by mechanical alloying. X-ray diffractograms show FCC peaks. From the X-ray diffracion peak-widths we estimate the final grain size, which vary with x from 112 nm (for x =15) to 32 nm (for x =30). Lattice parameter decreases with concentration (minimum 0.401 nm at x =30), but above Vegard's law values. Susceptibility measurements show cluster-glass behaviour. Critical temperatures are consistently lower than similar alloys produced by arc melting followed by fast quenching. A magnetic phase diagram is presented. Giant magnetoresistance is present in all samples, with a maximum at x =25. This effect is caused by the dispersion of small iron clusters produced by the mechanical work.

In the present work, a quantitative analysis of the phase compositions by Mössbauer effect spectroscopy of solid and conventional hydrogen disproportionated Pr13.7Fe80.3B6.0 and Pr13.7Fe63.5Co16.7Zr0.1B6.0 alloys was carried out. Significant amounts of intermediate borides t-Fe3B and Pr(Fe,Co)12B6 were detected after solid hydrogen disproportionation treatment in Pr13.7Fe80.3B6.0 and Pr13.7Fe63.5Co16.7Zr0.1B6.0 alloys, respectively. After conventional hydrogenation-disproportionation-desorption-recombination treatment these phases were not detected and in no case residual Pr2Fe14B-phase was found. It was observed that the amount of intermediate borides after disproportionation can be correlated with the degree of texture after recombination at various temperatures. Fil: Saccone, Fabio Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física La Plata; Argentina Fil: Torres Rodríguez, C.E.. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física La Plata; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Departamento de Física; Argentina Fil: Sánchez, Francisco Homero. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Departamento de Física; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física La Plata; Argentina Fil: Gutfleisch, O.. Leibniz Institute for Solid State and Materials Research; Alemania