Carlos Martínez-Boubeta

Minimizing food wastes and finding a second life use for industrial residuals have become some of the top priorities of modern society. This work considers the use of spent eggs and mussels shells, as well as marble dust, as raw sources to develop nanoparticles involving renewable resources in both their preparation and adoption in technological ap...

this link https://www.sciencedirect.com/science/article/pii/S0013935121013499 provides free access. This work attempts to shed light on whether the COVID-19 pandemic rides on airborne pollution. In particular, a two-city study provides evidence that PM2.5 contributes to the timing and severity of the epidemic, without adjustment for confounders. T...

Magnetic nanoparticles can generate heat when exposed to an alternating magnetic field. Their heating efficacy is governed by their magnetic properties that are in turn determined by their composition, size and morphology. Thus far, iron oxides (e.g., magnetite, Fe3O4) have been the most popular materials in use, though recently bimagnetic core-she...

The nanoscale magnetic configuration of self-assembled groups of magnetite 40 nm cubic nanoparticles has been investigated by means of electron holography in the transmission electron microscope (TEM). The arrangement of the cubes in the form of chains driven by the alignment of their dipoles of single nanocubes is assessed by the measured in-plane...

Due to their small dimensions, airborne particles are able to penetrate through inhalation into many human organs, from the lungs to the cardiovascular system and the brain, which can threaten our health. This work establishes a novel approach of collecting quantitative data regarding the fraction, the composition and the size distribution of combu...

Objectives To examine the impact of concentrations of ambient fine particulate matter (PM2.5) air pollution on the incidence of COVID-19. Methods Publicly available data of COVID-19 deaths in March/October 2020 were compared with concentrations of PM2.5 measured in previous years at urban and suburban areas in Thessaloniki. Similar publicly availa...

Magnetic particle hyperthermia, in which colloidal nanostructures are exposed to an alternating magnetic field, is a promising approach to cancer therapy. Unfortunately, the clinical efficacy of hyperthermia has not yet been optimized. Consequently, routes to improve magnetic particle hyperthermia such as designing hybrid structures comprised from...

Magnetic particle hyperthermia, in which colloidal nanostructures are exposed to an alternating magnetic field, is a promising approach to cancer therapy. Unfortunately, the clinical efficacy of hyperthermia has not yet been optimized. Consequently, routes to improve magnetic particle hyperthermia such as designing hybrid structures comprised from...

The implementation of nanotechnology in drinking water treatment is a very promising field for applied research. A major part of this effort focuses on the reduction of the dimensionality of the conventional cost-effective adsorbents that have been successfully used for decades. The development of engineered nanoparticles has the potential to provi...

The implementation of nanotechnology in drinking water treatment is a very promising field for applied research. A major part of this effort focuses on reducing the building units dimensions in the existing inorganic adsorbents used for the purification of water versus heavy metal species. The development of engineered nanoparticles has the potenti...

La invención se refiere a una composición núcleo-envuelta que comprende un núcleo de nanopartículas magnéticas y una envoltura de un compuesto doble hidróxido estratificado, y su procedimiento de obtención. Además, la invención se refiere al uso de dicha composición para purificar agua contaminada, especialmente útil para la eliminación de contamin...

There has been renewed interest in the use of magnetic nanoparticles to convert high frequency electromagnetic energy into heat. During the last decade, numerous examples in the field of catalysis, lightweight thermoplastic composites for aeronautical and automotive engineering, and biomedical applications as well, have flourished. In a recent Lett...

The invention relates to core-shell composition comprising a core of magnetic nanoparticles and a shell of a layered double hydroxide compound, and its procedure of obtainment. Furthermore, the invention refers to the use of said composition for purifying contaminated water, especially useful for the removal of harmful contaminants like arsenic, to...

BACKGROUND: Over recent decades, there has been increasing global concern over public health impacts related to water pollution with arsenic. With the development of nanotechnology, nanomaterials are being proposed as alternative agents for water treatment. This study focuses on the use of core-shell nanoparticles as secondary receptors able to ope...

The design and engineering of earth-abundant catalysts that are both cost-effective and highly active for water splitting is a crucial challenge in a number of energy conversion and storage technologies. In this direction, herein we report the synthesis of Fe3O4@NiFexOy core-shell nano-heterostructures and the characterization of their electrocatal...

The fabrication procedure of hollow iron oxide nanoparticles with a large surface to volume ratio by a single-step gas condensation process at ambient temperature is presented. Fe clusters formed during the sputtering process are progressively transformed into hollow cuboids with oxide shells by the Kirkendall mechanism at the expense of oxygen cap...

We report on magnetotransport properties on La0.7Sr0.3MnO3/MgO/Fe tunnel junctions grown epitaxially on top of (001)-oriented SrTiO3 substrates by sputtering. It is shown that the magnetoresistive response depends critically on the MgO/Fe interfacial properties. The appearance of an FeOX layer by the interface destroys the �1 symmetry filtering eff...

Progress in the design of nanoscale magnets for localized hyperthermia cancer therapy has been largely driven by trial-and-error approaches, for instance, by changing of the stoichiometry composition, size, and shape of the magnetic entities. So far, widely different and often conflicting heat dissipation results have been reported, particularly as...

A theoretical prediction by Wang et al. [Phys. Rev. B 82, 054405 (2010)] suggests the preferential transmission of majority-spin states with Δ1 symmetry across a magnesium interlayer in Fe/Mg/MgO/Fe based magnetic tunnel junctions. Here, we report experiments to probe this question in CoFe/Mg/CoFe structures. We find that the strength of the interl...

We report here the first results on magnetic nanoparticles fabricated from basalt fragments of the eruption that took place in Lanzarote (Canary Islands) between 1730 and 1736, to be used in technologies of biomedicine. This approach was inspired by the strong and extremely stable remanent magnetization of slowly cooled rocks from basaltic lavas co...

The oriented attachment of magnetic nanoparticles is recognized as an important pathway in the magnetic-hyperthermia cancer treatment roadmap, thus, understanding the physical origin of their enhanced heating properties is a crucial task for the development of optimized application schemes. Here, we present a detailed theoretical analysis of the hy...

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Magnetic hyperthermia, an alternative anticancer modality, is influenced by the composition, size, magnetic properties, and degree of aggregation of the corresponding nanoparticle heating agents. Here, we attempt to evaluate the AC magnetic field heating response of Fe-based nanoparticles prepared by solar physical vapor deposition, a facile, high-...

The development of a single-phase Fe/Mn oxy-hydroxide (δ-Fe0.76Mn0.24OOH), highly efficient at adsorbing both As(III) and As(V), is reported. Its synthesis involves the co-precipitation of FeSO4 and KMnO4 in a kilogram-scale continuous process, in acidic and strongly oxidizing environments. The produced material was identified as a manganese feroxy...

Different aspects of the structure-magnetism and morphology-magnetism correlation in the ultrathin limit are studied in epitaxial Fe films grown on MgO(001). In the initial stages of growth the presence of substrate steps, intrinsically higher than an Fe atomic layer, prevent the connection between Fe islands and hence the formation of large volume...

The performance of magnetic nanoparticles is intimately entwined with their structure, mean size and magnetic anisotropy. Besides, ensembles offer a unique way of engineering the magnetic response by modifying the strength of the dipolar interactions between particles. Here we report on an experimental and theoretical analysis of magnetic hyperther...

Supplementary Info

Supporting movie file

Experimental observation of the hybridization of oxygen p states with metal states at the interface in Fe/MgO core/shell self-assembled nanostructures, obtained by vapour-phase deposition, is reported. Synchrotron-based X-ray absorption spectroscopy techniques were used to directly probe the Fe orbital character at the interfacial region. O K edge...

A great deal of research over recent decades has been motivated by the requirement to lower the concentration of chromium in drinking water. This study has been conducted to determine the feasibility of iron-based nanoparticles for chromium removal from contaminated water. Single Fe, Fe 3 O 4 and binary Fe/Fe 3 O 4 nanoparticles were grown at the 4...

The Fe-MgO core-shell morphology is proposed within the single-domain nanoparticle regime as an enhanced magnetically driven hyperthermia carrier. The combinatory use of metallic iron as a core material together with the increased particle size (37–65 nm) triggers the tuning of dipolar interactions between particles and allows for further enhanceme...

We report on a growth study of MgO films deposited on Al2O3(0001) substrates by magnetron sputtering. The films exhibited a preferred rocksalt MgO(111) orientation. Surprisingly, depending on the O2 gas flow ratio, a structure of graphiticlike wurtzite MgO(0001) has been revealed. The observed Mg-O perpendicular bond length reduction is accompanied...

The prediction and experimental demonstration of a very large magnetoresistance in Fe/MgO/Fe tunnel junctions have led to intense study of related systems in the last decade. In the present paper, we concentrate on the role of interface coordination, Fe thickness, and magnetization in the MgO/Fe/MgO mirror. By first-principles analysis, it is shown...

One of the most widely researched topics over the last dec-ades has been magnetic nanoscale systems, but recent break-throughs in high-resolution imaging techniques in modern computing and electronics towards continuously smaller devices have nourished a booming in the quest for new mate-rials and their novel applications. It is unambiguous that th...

We have studied the abrupt and hysteretic changes of resistance in MgO-based capacitor devices. The switching behavior is discussed in terms of the formation and rupture of conduction filaments due to the migration of structural defects in the electric field, together with the redox events which affects the mobile carriers. The results presented in...

Co-based nanostructures ranging from core/shell to hollow nanoparticles were prepared by varying the reaction time and the chemical environment during the thermal decomposition of Co(2)(CO)(8). Both structural characterization and kinetic model simulation illustrate that the diffusivities of cobalt and oxygen determine the growth ratio and the fina...

Luminescence spectroscopy has been used to characterize MgO films prepared by rf-sputtering. A clear correlation is found between the appearance of an emission peak centered at approximately 460 nm and the detection of ferromagnetic ordering in the samples. We suggest that cationic vacancies are responsible for the blue-light emission by introducin...

Ball-milling of magnetite powder is studied as a potential method to produce large quantities of nanostructured particles for As(III) and As(V) adsorption. Surfactant-assisted milling resulted in 30nm isolated nanoparticles with high specific surface area but limited adsorption capacity. On the opposite, when no surfactant is added, large aggregate...

Nanocomposites of the self-forming core-shell Co-MgO nanoparticles, which were of approximately 100 nm in diameter, and poly(vinylidene fluoride) (PVDF) polymer have been prepared. When the polymer is crystallized in the α-phase, the introduction of the nanoparticles leads to nucleation of the γ-phase of PVDF, increasing also the melting temperatur...

doi:10.1063/1.3561507] Zhang et al. 1 have provided excellent data on the spin-dependent tunneling properties of the nanostructured FePt/ Fe 3 O 4 system. In particular, the find, the sign of magnetore-sistance (MR) changes from negative to positive with decreasing temperature. They suggest one mechanism which may account for MR reversal is resonan...

Ball-milling of magnetite powder is studied as a potential method to produce large quantities of nanostructured particles for As(III) and As(V) adsorption. Surfactant-assisted milling resulted in 30 nm isolated nanoparticles with high specific surface area but limited adsorption capacity. On the opposite, when no surfactant is added, large aggregat...

In this work we report on the magnetic behavior of MgO thin films prepared by sputtering. A severe aging process of the ferromagnetic properties is detected in magnetic samples exposed to ambient atmosphere. However, ferromagnetism can be successively switched on again by annealing samples in vacuum. We suggest this behavior reflects the key role p...

We show both experimental evidences and Monte Carlo modeling of the effects of interparticle dipolar interactions on the hysteresis losses. Results indicate that an increase in the intensity of dipolar interactions produce a decrease in the magnetic susceptibility and hysteresis losses, thus diminishing the hyperthermia output. These findings may h...

We show both theoretical and experimental evidences of the appearance of ferromagnetism in MgO thin films. First-principles calculations allow predicting the possibility of the formation of a local moment in MgO, provided the existence of Mg vacancies which create holes on acceptor levels near the O 2p-dominated valence band. Magnetic measurements...

In this work, the possibility to obtain epitaxial perovskite/MgO/metal multilayered heterostructures has been demonstrated by sputtering techniques. The films are ferromagnetic at room temperature, with no indication of parasite phases from X-ray diffraction and electron microscopy experiments. We argue that these improvements over most previous wo...

The effects of exchange bias on core/shell structured nanoparticles are analyzed. Nanoparticles are integrated with high moment Fe–Co crystallites covered epitaxially with MgO shells. It is observed that the coercive field HC(FeCo)>HC(Co)>HC(Fe); however, the exchange bias field HE of the Co sample is higher than that of the FeCo one, while HE = 0...

We study the impact of vacancies on the magnetism of MgO and TiO2 nanoparticles, and develop fist-principle calculations to ascertain the origin of the induced polarization. Theoretically, we expect ferromagnetism only for the case of MgO with cation defects. Experimentally, we observed a small magnetic signal probably due to imperfections in the l...

Unlabelled: A one-step process for the production of nanoparticles presenting advanced magnetic properties can be achieved using vapor condensation. In this article, we report on the fabrication of Fe particles covered by a uniform MgO epitaxial shell. MgO has a lower surface energy than Fe, which results in a core-shell crystal formation. The par...

The temperature dependence of magnetoresistance (MR) of powdered samples consisting of spherical Fe/MgO core/shell nanoparticles was analyzed. A change of the MR from normal at room temperature to inverse at low temperatures was observed. Concomitant with this, samples showed a sudden increase in the electrical resistance when approaching T-V appro...

We report on tunneling conductance properties of a single Fe island enclosed by an epitaxial MgO shell. The results obtained show clear oscillations in the current-voltage curves that, along with the theoretical modeling, allow determining the electronic density of states of the iron core. Moreover, the correlation of these results with the tempera...

Iron oxide nanoparticles were synthesized by the thermal decomposition of Fe(acac)3 and Fe(CO)5. Three different homogeneous procedures were used for the controlled synthesis of Fe3O4, γ-Fe2O3 and Fe3O4/γ-Fe2O3 mixture nanocrystals. A combination of characterization techniques was used in order to distinguish these oxides. The controllable size, th...

We have examined the relationship between switching characteristics and the tunnel magnetoresistance under finite bias in microscopic low resistance (RA<30 Ω μm2) tunnel junctions with AlOx barriers. By switching the free layer with a magnetic field applied in plane along the magnetically easy axis, it is observed that the coercive field depends st...

Details of synthesis and structural characterization of highly crystalline iron oxide nanoparticles are presented together with results on the magnetic investigation as a function of the temperature and applied field. Monodisperse Fe nanoparticles were prepared by thermal decomposition of iron pentacarbonyl in the presence of oleic acid. These iron...

We have studied the magnetoresistance of single-crystalline (001) Fe films prepared by sputtering techniques and covered by epitaxial MgO or Pt protective layers. The influence of the thickness of the magnetic layer as well as of the nature of the capping layer on the Fe anisotropic magnetoresistance was investigated by four-terminal probe, measure...

The chemical nature of the different interfaces and possible segregation effects are studied in fully epitaxial Fe/MgO/Fe (001) oriented heterostructures fabricated by combined sputtering plus laser ablation deposition techniques. Auger electron spectroscopy depth profiling experiments showed that the interfaces of the MgO spacer with the Fe layers...

Multilayered TM/MgO/Fe (001) heterostructures (TM: FeCo, Co/Fe, and Fe) are grown epitaxially, to study the dependence of the magnetic coupling between the two ferromagnetic electrodes on the insulating MgO barrier width and the lateral dimensions of the structures. The crystal quality is investigated by reflection high-energy electron diffraction...