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In the quest for effective gas sensors for breath analysis, magnetoelastic resonance-based gas sensors (MEGSs) are remarkable candidates. Thanks to their intrinsic contactless operation, they can be used as non-invasive and portable devices. However, traditional monitoring techniques are bound to slow detection, which hinders their application to fast bio-related reactions. Here we present a method for real-time monitoring of the resonance frequency, with a proof of concept for real-time monitoring of gaseous biomarkers based on resonance frequency. This method was validated with a MEGS based on a Metglass 2826 MB microribbon with a polyvinylpyrrolidone (PVP) nanofiber electrospun functionalization. The device provided a low-noise (RMS = 1.7 Hz), fast (<2 min), and highly reproducible response to humidity (Δf = 46−182 Hz for 17−95% RH), ammonia (Δf = 112 Hz for 40 ppm), and acetone (Δf = 44 Hz for 40 ppm). These analytes are highly important in biomedical applications, particularly ammonia and acetone, which are biomarkers related to diseases such as diabetes. Furthermore, the capability of distinguishing between breath and regular air was demonstrated with real breath measurements. The sensor also exhibited strong resistance to benzene, a common gaseous interferent in breath analysis., Competing Interests: The authors declare no conflict of interest.

Different studies carried out in the last three decades on the magnetic susceptibility of the spinel ZnFe 2 O 4 ferrite have revealed the positive character of its Curie-Weiss temperature, contradicting its observed antiferromagnetic behavior which is characterized by a well-defined susceptibility peak centered around the Neel temperature (10 K). Some approaches based on ab initio calculations and mixture of interactions have been attempted to explain this anomaly. This work shows how for very low values of the inversion parameter, the small percentage of Fe atoms located in tetrahedral sites gives rise to the appearance of ferrimagnetic clusters around them. Superparamagnetism of these clusters is the main cause of the anomalous Curie-Weiss behavior. This finding is supported experimentally from the thermal dependence of the inverse susceptibility and its evolution with the degree of inversion.

Ferromagnetic films down to thicknesses of tens of nanometers and composed by polycrystalline Fe and Fe 2 O 3 nanopillars are grown in large areas by glancing angle deposition with magnetron sputtering (MS-GLAD). The morphological features of these films strongly depend on the growth conditions. Vertical or tilted nanopillars have been fabricated depending on whether the substrate is kept rotating azimuthally during deposition or not, respectively. The magnetic properties of these nanopillars films, such as hysteresis loops squareness, adjustable switching fields, magnetic anisotropy and coercivity, can be tuned with the specific morphology. In particular, the growth performed through a collimator mask mounted onto a not rotating azimuthally substrate produces almost isolated well-defined tilted nanopillars that exhibit a magnetic hardening. The first-order reversal curves diagrams and micromagnetic simulations revealed that a growth-induced uniaxial anisotropy, associated with an anisotropic surface morphology produced by the glancing angle deposition in the direction perpendicular to the atomic flux, plays an important role in the observed magnetic signatures. These results demonstrate the potential of the MS-GLAD method to fabricate nanostructured films in large area with tailored structural and magnetic properties for technological applications.

The antiferromagnetic (AFM) transition of the normal ZnFe 2 O 4 has been intensively investigated with results showing a lack of long-range order, spin frustrations, and a "hidden" entropy in the calorimetric properties for inversion degrees δ ≈ 0 or δ = 0. As δ drastically impacts the magnetic properties, it is logical to question how a δ value slightly different from zero can affect the magnetic properties. In this work, (Zn 1-δ Fe δ )[Zn δ Fe 2-δ ]O 4 with δ = 0.05 and δ = 0.27 have been investigated with calorimetry at different applied fields. It is shown that a δ value as small as 0.05 may affect 40% of the unit cells, which become locally ferrimagnetic (FiM) and coexists with AFM and spin disordered regions. The spin disorder disappears under an applied field of 1 T. Mossbauer spectroscopy confirms the presence of a volume fraction with a low hyperfine field that can be ascribed to these spin disordered regions. The volume fractions of the three magnetic phases estimated from entropy and hyperfine measurements are roughly coincident and correspond to approximately 1/3 for each of them. The "hidden" entropy is the zero point entropy different from 0. Consequently, the so-called "hidden" entropy can be ascribed to the frustrations of the spins at the interphase between the AFM-FiM phases due to having δ ≈ 0 instead of ideal δ = 0.

This manuscript presents the first measurement program and data collection on the Dinatrans track transition solution after it was installed in a track section in the north of Spain (Galicia). The Dinatrans solution was created to address the limitations of several track transition solutions. This novel solution consists of two inner and outer rails from slab track to ballast track, pads with different stiffness over sleepers of variable lengths installed from ballast track to slab track, and a simple substructure formed by non-structural concrete poured over the natural ground. The main objective of this research was to assess the suitability and the initial performance of the Dinatrans track transition solution. The measured variables for these initial real-world tests were vertical accelerations on sleepers, shear stress on rails, vertical displacements on rails and vertical displacements on sleepers. All measurements of these variables were obtained in an in-situ program by installing vertical accelerometers and LVDTs on the track structure and extensometer gauges on the rails and sleepers. The methodology and the procedures followed are described. The Dinatrans initial solution was compared with the Standard solution used in Spain using these initial measurements. This field analysis provides an initial understanding of the performance of the new track transition. Further measurements will be required to check the track transition performance over the long term; however, no maintenance works have been necessary since construction (2016).

The Pechini method has been used as a synthetic route for obtaining self-assembling magnetic and plasmonic nanoparticles in hybrid silica nanostructures. This manuscript evaluates the influence of shaking conditions, reaction time, and pH on the size and morphology of the nanostructures produced. The characterization of the nanomaterials was carried out by transmission electron microscopy (TEM) to evaluate the coating and size of the nanomaterials, Fourier-transform infrared spectroscopy (FT-IR) transmission spectra to evaluate the presence of the different coatings, and thermogravimetric analysis (TGA) curves to determine the amount of coating. The results obtained show that the best conditions to obtain core-satellite nanostructures with homogeneous silica shells and controlled sizes (<200 nm) include the use of slightly alkaline media, the ultrasound activation of silica condensation, and reaction times of around 2 h. These findings represent an important framework to establish a new general approach for the click chemistry assembling of inorganic nanostructures.

This work describes the preparation, characterization and functionalization with magnetic nanoparticles of a bone tissue-mimetic scaffold composed of collagen and hydroxyapatite obtained through a biomineralization process. Bone remodeling takes place over several weeks and the possibility to follow it in vivo in a quick and reliable way is still an outstanding issue. Therefore, this work aims to produce an implantable material that can be followed in vivo during bone regeneration by using the existing non-invasive imaging techniques (MRI). To this aim, suitably designed biocompatible SPIONs were linked to the hybrid scaffold using two different strategies, one involving naked SPIONs (nMNPs) and the other using coated and activated SPIONs (MNPs) exposing carboxylic acid functions allowing a covalent attachment between MNPs and collagen molecules. Physico-chemical characterization was carried out to investigate the morphology, crystallinity and stability of the functionalized materials followed by MRI analyses and evaluation of a radiotracer uptake ([ 99m Tc]Tc-MDP). Cell proliferation assays in vitro were carried out to check the cytotoxicity and demonstrated no side effects due to the SPIONs. The achieved results demonstrated that the naked and coated SPIONs are more homogeneously distributed in the scaffold when incorporated during the synthesis process. This work demonstrated a suitable approach to develop a biomaterial for bone regeneration that allows the monitoring of the healing progress even for long-term follow-up studies.

The potential use of electrodeposition to synthesize a hybrid magnetostrictive/magnetoelectric layered system is shown in this paper. By appropriately adjusting pH, growth potential, and electrolyte composition, it is possible to achieve thin films in which magnetoelectric oxide GaFeO 3 (GFO) is formed in close contact with magnetostrictive metallic FeGa alloy. X-ray diffractometry shows the formation of FeGa as well as GFO and Fe oxides. Electron microscopy observations reveal that GFO mainly segregates in grain boundaries. Samples are ferromagnetic with an isotropic magnetic behavior in the sample plane. Magnetic stripes are observed by magnetic force microscopy and are correlated to Fe 3 O 4 . When its segregation is minimal, the absence of stripes can be used to monitor Fe oxide segregation.

Magnetite nanoparticles (MNPs) with 12, 34 and 53 nm sizes have been measured by AC-magnetometry at 50 kHz and 57 mT maximum applied field. The MNPs form chains under the AC-field, and the dynamics of the formation can be studied by measuring hysteresis cycles at different times. The measurement time has been varied from 5 ms to 10 s and for different initial temperatures of 5, 25 and 50 °C. The chain formation, identified by the increase of susceptibility and remanence with the measurement time, appears only for 34 nm particles. It has been observed that saturation, remanence and susceptibility at low (high) fields increase (decrease) with time. For the other two samples, these magnitudes are independent of time. At low fields, the heating efficiency is higher at 5 °C than at 50 °C, whereas it shows an opposite behaviour at higher fields; the origin of this behaviour is discussed in the article. Additionally, the relaxation times, τ N and τ B , have been calculated by considering the influence of the applied field. Chain formation requires translation and rotation of MNPs; therefore, the Brownian mechanism plays a fundamental role. It is found that magnetic reversal for 12 nm MNPs is mainly due to Néel relaxation. However, in the case of 34 nm MNPs, both mechanisms, Néel and Brownian relaxation, can be present depending on the amplitude of the field; for μ 0 H < 22 mT, the physical rotation of the particle is the dominant mechanism; on the other hand, for μ 0 H > 22 mT, both mechanisms are present within the size distribution. This highlights the importance of taking the field intensity into account to calculate relaxation times when analysing the relaxation mechanisms of magnetic colloids subjected to AC fields., Competing Interests: The authors declare no competing financial or non-financial interest., (This journal is © The Royal Society of Chemistry.)

To modulate the properties of degradable implants from outside of the human body represents a major challenge in the field of biomaterials. Polylactic acid is one of the most used polymers in biomedical applications, but it tends to lose its mechanical properties too quickly during degradation. In the present study, a way to reinforce poly-L lactic acid (PLLA) with magnetic nanoparticles (MNPs) that have the capacity to heat under radiofrequency electromagnetic fields (EMF) is proposed. As mechanical and degradation properties are related to the crystallinity of PLLA, the aim of the work was to explore the possibility of modifying the structure of the polymer through the heating of the reinforcing MNPs by EMF within the biological limit range f · H < 5·× 10 9 Am -1 ·s -1 . Composites were prepared by dispersing MNPs under sonication in a solution of PLLA. The heat released by the MNPs was monitored by an infrared camera and changes in the polymer were analyzed with differential scanning calorimetry and nanoindentation techniques. The crystallinity, hardness, and elastic modulus of nanocomposites increase with EMF treatment.

Macroscopic materials with nanoscopic properties have recently been synthesized by self-assembling defined nanoparticles to form self-supported networks, so-called aerogels. Motivated by the promising properties of this class of materials, the search for versatile routes toward the controlled assembly of presynthesized nanoparticles into such ultralight macroscopic materials has become a great interest. Overcoating procedures of colloidal nanoparticles with polymers offer versatile means to produce aerogels from nanoparticles, regardless of their size, shape, or properties while retaining their original characteristics. Herein, we report on the surface modification and assembly of various building blocks: photoluminescent nanorods, magnetic nanospheres, and plasmonic nanocubes with particle sizes between 5 and 40 nm. The polymer employed for the coating was poly(isobutylene- alt -maleic anhydride) modified with 1-dodecylamine side chains. The amphiphilic character of the polymer facilitates the stability of the nanocrystals in aqueous media. Hydrogels are prepared via triggering the colloidally stable solutions, with aqueous cations acting as linkers between the functional groups of the polymer shell. Upon supercritical drying, the hydrogels are successfully converted into macroscopic aerogels with highly porous, open structure. Due to the noninvasive preparation method, the nanoscopic properties of the building blocks are retained in the monolithic aerogels, leading to the powerful transfer of these properties to the macroscale. The open pore system, the universality of the polymer-coating strategy, and the large accessibility of the network make these gel structures promising biosensing platforms. Functionalizing the polymer shell with biomolecules opens up the possibility to utilize the nanoscopic properties of the building blocks in fluorescent probing, magnetoresistive sensing, and plasmonic-driven thermal sensing., Competing Interests: The authors declare no competing financial interest., (© 2021 The Authors. Published by American Chemical Society.)

Here it is investigated the effect of the antiferromagnet Cr 2 O 3 on the magnetic properties of ferromagnetic Fe 72 Ga 28 thin films. Sputtered Fe 72 Ga 28 layers have their magnetization in the sample plane with a magnetic fluctuation that gives rise to magnetic ripple. In order to turn its magnetization into the out of plane (OOP) direction, it has been magnetically coupled with Cr 2 O 3 that has magnetic moments along the c-axis, that is the perpendicular direction when properly aligned. Cr 2 O 3 has been obtained from Cr oxidation, whereas Fe 72 Ga 28 has been deposited on top of it by sputtering in the ballistic regime. Although a uniaxial in-plane magnetic anisotropy is expected for Fe 72 Ga 28 thickness above 100 nm, the interfacial coupling with Cr 2 O 3 prevents this anisotropy. The formation of stripe domains in Fe 72 Ga 28 above a critical thickness reveals the enhancement of the out of plane component of the Fe 72 Ga 28 magnetization with respect to uncoupled layers. Due to the interface coupling, the Fe 72 Ga 28 magnetization turns into the out-of-plane direction as its thickness is gradually reduced, and a perpendicular magnetic anisotropy of 3·10 6 erg·cm -3 is inferred from experimental results. Eventually, the coupling between Cr 2 O 3 and Fe 72 Ga 28 promotes an exchange-bias effect that has been well fitted by means of the random field model.

The following work addresses new configurations of sensing array platforms that are composed of Co-based amorphous ferromagnetic microwires (MWs) to obtain an enhanced modulation of the microwave scattering effects through the application of low strength DC or AC magnetic fields. An amorphous MW is an ultrasoft ferromagnetic material (coercivity ~0.2 Oe) with a circumferential magnetic anisotropy that provides a high surface sensitivity when it is subjected to an external magnetic field. Firstly, microwave scattering experiments are performed as a function of the length and number of MWs placed parallel to each other forming an array. Subsequently, three array configurations are designed, achieving high S 21 scattering coefficients up to about -50 dB. The influence of DC and AC magnetic fields on S 21 has been analyzed in frequency and time domains representation, respectively. In addition, the MWs sensing array has been overlapped by polymeric surfaces and the variations of their micrometric thicknesses also cause strong changes in the S 21 amplitude with displacements in the frequency that are associated to the maximum scattering behavior. Finally, a new concept for amplifying microwave scattering is provided by intercalating Cu MWs into the linear Co-based arrays. The designed mixed system that is composed by Co-based and Cu MWs exhibits a higher S 21 coefficient when compared to a single Co-based MW system because of higher electrical conductivity of Cu. However, the ability to modulate the resulting electromagnetic scattering is conferred by the giant magneto-impedance (GMI) effects coming from properties of the ultrasoft amorphous MWs. The mixed array platform covers a wide range of sensor applications, demonstrating the feasibility of tuning the S 21 amplitude over a wide scattering range by applying AC or DC magnetic fields and tuning the resonant frequency position according to the polymeric slab thickness.

The scientific community has made great efforts in advancing magnetic hyperthermia for the last two decades after going through a sizeable research lapse from its establishment. All the progress made in various topics ranging from nanoparticle synthesis to biocompatibilization and in vivo testing have been seeking to push the forefront towards some new clinical trials. As many, they did not go at the expected pace. Today, fruitful international cooperation and the wisdom gain after a careful analysis of the lessons learned from seminal clinical trials allow us to have a future with better guarantees for a more definitive takeoff of this genuine nanotherapy against cancer. Deliberately giving prominence to a number of critical aspects, this opinion review offers a blend of state-of-the-art hints and glimpses into the future of the therapy, considering the expected evolution of science and technology behind magnetic hyperthermia.

The hexagonal close packed surface of gold shows a 22 × 3 "herringbone" surface reconstruction which makes it unique among the (111) surfaces of all metals. This long-range energetically favored dislocation pattern appears in response to the strong tensile stress that would be present on the unreconstructed surface. Adsorption of molecular and atomic species can be used to tune this surface stress and lift the herringbone reconstruction. Here we show that herringbone reconstruction can be controllably lifted in ultrahigh vacuum at cryogenic temperatures by precise hot electron injection in the presence of hydrogen molecules. We use the sharp tip of a scanning tunneling microscope (STM) for charge carrier injection and characterization of the resulting chain nanostructures. By comparing STM images, rotational spectromicroscopy and ab initio calculations, we show that formation of gold atomic chains is associated with release of gold atoms from the surface, lifting of the reconstruction, dissociation of H 2 molecules, and formation of surface hydrides. Gold hydrides grow in a zipper-like mechanism forming chains along the [11̅0] directions of the Au(111) surface and can be manipulated by further electron injection. Finally, we demonstrate that Au(111) terraces can be transformed with nearly perfect terrace selectivity over distances of hundreds of nanometers.

A combination of high-energy ball milling, vacuum filtering, and sedimentation processes has been demonstrated to be a useful approach to reduce, in a controlled way, the length of as-cast Fe 73.5 Si 13.5 Nb 3 Cu 1 B 9 amorphous magnetic microwires (MWs) and annealed material at 550 °C in nitrogen conditions. Homogeneous compositional microstructures with fairly narrow size distributions between 1300 and 11.7 μm are achieved, exhibiting tunable response as a soft magnetic material and as a microwave absorber. From the magnetic perspective, the soft magnetic character is increased with smaller length of the MWs, whereas the remanence has the opposite behavior mainly due to the structural defects and the loss of the shape anisotropy. From the microwave absorption perspective, a novel potential applicability is tested in these refined microstructures. This innovation consists of coatings based on commercial paints with a filling percentage of 0.55% of MWs with different lengths deposited on metallic sheets. Large attenuation values around -40 dB are obtained in narrow spectral windows located in the GHz range, and their position can be varied by combining different optimized lengths of MW. As an example of this powerful mechanism for absorbing microwaves at specific frequencies, MW lengths of 2 mm and 50 μm are chosen, where precise tailoring of the minimum reflection loss ( R L ) is obtained in a range between 8.85 and 13.25 GHz. To confirm these experimental results, an effective medium standard model proposed for electrical permittivity is used. Experimental and theoretical results are consistent and these novel composites are also proposed as a feasible candidate for designing frequency-selective microwave absorbers on demand, with low filling percentages and high absorption intensity values.

It is well stablished that heating efficiency of magnetic nanoparticles under radiofrequency fields is due to the hysteresis power losses. In the case of microwires (MWs), it is not clear at all since they undergo non-coherent reversal mechanisms that decrease the coercive field and, consequently, the heating efficiency should be much smaller than the nanoparticles. However, colossal heating efficiency has been observed in MWs with values ranging from 1000 to 2800 W/g, depending on length and number of microwires, at field as low as H = 36 Oe at f = 625 kHz. It is inferred that this colossal heating is due to the Joule effect originated by the eddy currents induced by the induction field B = M + χH parallel to longitudinal axis. This effect is observed in MWs with nearly zero magnetostrictive constant as Fe 2.25 Co 72.75 Si 10 B 15 of 30 μm magnetic diameter and 5 mm length, a length for which the inner core domain of the MWs becomes axial. This colossal heating is reached with only 24 W of power supplied making these MWs very promising for inductive heating applications at a very low energy cost.

The electrosynthesis of iron oxide nanoparticles offers a green route, with significant energy and environmental advantages. Yet, this is mostly restricted by the oxygen solubility in the electrolyte. Gas-diffusion electrodes (GDEs) can be used to overcome that limitation, but so far they not been explored for nanoparticle synthesis. Here, we develop a fast, environmentally-friendly, room temperature electrosynthesis route for iron oxide nanocrystals, which we term gas-diffusion electrocrystallization (GDEx). A GDE is used to generate oxidants and hydroxide in-situ, enabling the oxidative synthesis of a single iron salt (e.g., FeCl 2 ) into nanoparticles. Oxygen is reduced to reactive oxygen species, triggering the controlled oxidation of Fe 2+ to Fe 3+ , forming Fe 3-x O 4-x (0 ≤ x ≤ 1). The stoichiometry and lattice parameter of the resulting oxides can be controlled and predictively modelled, resulting in highly-defective, strain-heavy nanoparticles. The size of the nanocrystals can be tuned from 5 nm to 20 nm, with a large saturation magnetization range (23 to 73 A m 2 kg -1 ), as well as minimal coercivity (~1 kA m -1 ). Using only air, NaCl, and FeCl 2 , a biocompatible approach is achieved, besides a remarkable level of control over key parameters, with a view on minimizing the addition of chemicals for enhanced production and applications.

The aim of this work is to synthesize a magnetic magnetite/multi-walled carbon nanotube (Fe 3 O 4 /MWCNT) catalyst by a method combining co-precipitation and hydrothermal treatments for the efficient removal of diclofenac (DCF) by catalytic wet peroxide oxidation (CWPO). The support (MWCNTs) shows a moderate-large surface area and good adsorption capacity, leading to the improvement of the magnetite (Fe 3 O 4 ) dispersion on its surface. The response surface methodology (RSM) was applied in order to find out the effect of the reaction parameters on DCF removal, allowing to establish the optimum operating conditions (T = 60 °C, [H 2 O 2 ] 0  = 2.7 mM, [catalyst] = 1.0 g L -1 ). The optimum CWPO experiment showed an outstanding catalytic activity at non-modified pH solution (6.7), obtaining a 95% of DCF removal after 3 h reaction time; this high efficiency can be attributed to the synergistic effect of the iron-based catalyst with the high quantity of • OH radicals generated on the surface of the catalyst. In addition, the Fe 3 O 4 /MWCNT material exhibited good reusability along three consecutive reaction cycles, finding a pollutant removal close to 95% in each cycle of 3 h reaction time. Additionally, a degradation mechanism pathway was proposed for the removal of DCF by CWPO. The versatility of the material was finally demonstrated in the treatment of different environmentally relevant aqueous matrices (a wastewater treatment plant effluent, surface water, and hospital wastewater), obtaining an effective reduction in the ecotoxicity values.

Co-based amorphous microwires presenting the giant magnetoimpedance effect are proposed as sensing elements for high sensitivity biosensors. In this work we report an experimental method for contactless detection of stress, temperature, and liquid concentration with application in medical sensors using the giant magnetoimpedance effect on microwires in the GHz range. The method is based on the scattering of electromagnetic microwaves by FeCoSiB amorphous metallic microwires. A modulation of the scattering parameter is achieved by applying a magnetic bias field that tunes the magnetic permeability of the ferromagnetic microwires. We demonstrate that the OFF/ON switching of the bias activates or cancels the amorphous ferromagnetic microwires (AFMW) antenna behavior. We show the advantages of measuring the performing time dependent frequency sweeps. In this case, the AC-bias modulation of the scattering coefficient versus frequency may be clearly appreciated. Furthermore, this modulation is enhanced by using arrays of microwires with an increasing number of individual microwires according to the antenna radiation theory. Transmission spectra show significant changes in the range of 3 dB for a relatively weak magnetic field of 15 Oe. A demonstration of the possibilities of the method for biomedical applications is shown by means of wireless temperature detector from 0 to 100 °C.

Efficient and low cost detection of harmful volatile organic compounds (VOCs) is a major health and environmental need in industrialized societies. For this, tailor-made porous coordination polymers are emerging as promising molecular sensing materials thanks to their responsivity to a wide variety of external stimuli and could be used to complement conventional sensors. Here, a non-porous crystalline 1D Fe(ii) coordination polymer acting as a porous acetonitrile host is presented. The desorption of interstitial acetonitrile is accompanied by magneto-structural transitions easily detectable in the optical and electronic properties of the material. This structural switch and therefore its (opto)electronic readout are reversible under exposure of the crystal to acetonitrile vapor. This simple and robust iron-based coordination polymer could be ideally suited for the construction of multifunctional sensor devices for volatile acetonitrile and potentially for other organic compounds.

The purpose of this work is to fabricate self-assembled microstructures by the sol-gel method and study the morphological, structural and compositional dependence of ε-Fe 2 O 3 nanoparticles embedded in silica when glycerol (GLY) and cetyl-trimethylammonium bromide (CTAB) are added as steric agents simultaneously. The combined action of a polyalcohol and a surfactant significantly modifies the morphology of the sample giving rise to a different microstructure in each of the studied cases (1, 3 and 7 days of magnetic stirring time). This is due to the fact that the addition of these two compounds leads to a considerable increase in gelation time as GLY can interact with the alkoxide group on the surface of the iron oxide precursor micelle and/or be incorporated into the hydrophilic chains of CTAB. This last effect causes the iron oxide precursor micelles to be interconnected forming aggregates whose size and structure depend on the magnetic stirring time of the sol-gel synthetic route. In this paper, crystalline structure, composition, purity and morphology of the sol-gel coatings densified at 960 °C are examined. Emphasis is placed on the nominal percentage of the different iron oxides found in the samples and on the morphological and structural differences. This work implies the possibility of patterning ε-Fe 2 O 3 nanoparticles in coatings and controlling their purity by an easy one-pot sol-gel method., Competing Interests: The authors declare that there is no conflict of interest regarding the publication of this article., (This journal is © The Royal Society of Chemistry.)

In this study, we evaluate the magnetic properties and cytotoxic effect of magnetic nanoparticles (MNPs) based on magnetite and Mn, Co and Ni ferrites, obtained by electrochemical synthesis. These nanoparticles have almost spherical shape and an mode size of 9±1 nm. The electrochemical synthesis produces a single crystallographic phase with a spinel-like structure in all cases. Magnetization saturation at room temperature varies with the composition of the ferrites from M S (Fe₃O₄) > M S (MnFe₂O₄) > M S (CoFe₂O₄) > M S (NiFe₂O₄). Ferrite MNPs present low magnetic remanence indicating a superparamagnetic-like response at room temperature. However, the different values of magnetic anisotropy and size produce variations in the values of coercivity and susceptibility of the ferrite MNPs. The cytotoxicity of the different ferrites was evaluated by internalizing MNP in HeLa cancer cells. Although magnetite and Mn ferrite present low toxicity for all the concentrations studied, significant cytotoxic effect were observed when incubating the cells with high concentration of Co and Ni ferrites.

We report the structural, morphological and optical activities of a paramagnetic manganite (La 0.33 Ca 0.67 MnO 3 ) synthesized at 900 °C. A simple method of formation of complex was employed. A complex was formed between a pre-prepared manganite dissolved in HCl and reacted with an organic ligand (ethyl 4-nitrobenzoate). The optical and antimicrobial properties of a complex were determined. The Ultraviolet-visible and Fourier-transform infra-red spectroscopy were used in monitoring optical activities of the resulting product. It was observed to absorb in the visible region (205 nm and 256 nm). The peaks observed from the infra-red spectra indicated that the reaction occurred at the nitroso end of the ethyl 4-nitrobenzoate. The bacterial inhibitory property of the LCMO-ethyl 4-nitrobenzoate was determined against Pseudomonas aeruginosa, Candida albican, Aspergillus niger and Staphylococcus auerus. It was observed to inhibit the growth of all the microbes with zone of inhibitions of 60 mm, 56 mm, 45 mm and 32 mm, for Pseudomonas aeruginosa, Candida albican, Aspergillus niger and Staphylococcus auerus, respectively. •The method used was simple and a complex was formed within 6 h without the use of complicated equipment.•The method requires no heat treatment and can be prepared at room temperature.•LCMO-ethyl 4-nitrobenzoate was biologically active against Pseudomonas aeruginosa , Candida albican , Aspergillus niger and Staphylococcus aureus .

In order to understand the properties involved in the heating performance of magnetic nanoparticles during hyperthermia treatments, a systematic study of different γ-Fe₂O₃ and Fe₃O₄ nanoparticles has been done. High-frequency hysteresis loops at 50 kHz carried out on particles with sizes ranging from 6 to 350 nm show susceptibility χ increases from 9 to 40 for large particles and it is almost field independent for the smaller ones. This suggests that the applied field induces chain ordering in large particles but not in the smaller ones due to the competition between thermal and dipolar energy. The specific absorption rate (SAR) calculated from hysteresis losses at 60 mT and 50 kHz ranges from 30 to 360 W/g Fe , depending on particle size, and the highest values correspond to particles ordered in chains. This enhanced heating efficiency is not a consequence of the intrinsic properties like saturation magnetization or anisotropy field but to the spatial arrangement of the particles., Competing Interests: The authors declare no conflict of interest.

The present manuscript reports the use of hybrid magneto-plasmonic nanoparticles (HMPNPs) based on iron oxide nanoparticles and Au nanorods as colloidal nanoheaters. The individual synthesis of the magnetic and plasmonic components allowed optimizing their features for heating performance separately, before they were hybridized. Besides, a detailed characterization and finite element simulations were carried out to explain the interaction effects observed between the phases of the HMPNPs. The study also analyzed the heating power of these nanostructures when they were excited with infrared light and AC magnetic fields, and compared this with the heating power of their plasmonic and magnetic components. In the latter case, the AC magnetization curves revealed that the magnetic dipolar interactions increase the amount of heat released by the hybrid nanostructures.

We here present a simple model of a vibrating sample magnetometer (VSM). The system allows recording magnetization curves at room temperature with a resolution of the order of 0.01 emu and is appropriated for macroscopic samples. The setup can be mounted with different configurations depending on the requirements of the sample to be measured (mass, saturation magnetization, saturation field, etc.). We also include here examples of curves obtained with our setup and comparison curves measured with a standard commercial VSM that confirms the reliability of our device.

This article describes a novel synthetic route to obtain hybrid nanostructures that combine the plasmonic properties of gold nanorods with the magnetic properties of iron oxide nanoparticles in a robust silica nanostructure. The silica matrix enhances the physico-chemical stability of the nanostructure and preserves its magneto-plasmonic properties by avoiding the interface between gold and iron oxide. In addition, the magneto-plasmonic features of the nanohybrids can be tuned due to the independent synthesis of each component. The magnetic and plasmonic properties of these nanostructures can potentially enhance the photoacoustic detection of circulating tumor cells. Graphical abstract Schematic presentation of a hybrid magneto-plasmonic nanoparticle with an Au@Fe 3 O 4 @SiO 2 core-satellite-shell arrangement. The magnetic and plasmonic responses of this kind of nanostructure enable magnetic trapping and photoacoustic detection of circulating tumor cells.

We present here a new free space method to measure the magnetic permeability of a single amorphous magnetic microwire (AMM) at microwave frequencies. The technique consists in inducing a high frequency electric current along the AMM axis by illumination with an electromagnetic wave at antenna resonance conditions. Fitting the induced electric current to the Hallen-Pocklington equation allows computing the relative magnetic permeability of the microwire as a function of the wave frequency. The method results particularly useful for the study of the giant magnetoimpedance effect of AMM by measuring the magnetic permeability upon the application of DC magnetic fields.

In this work, we demonstrate theoretically and experimentally the possibility of tuning the electromagnetic properties of metamaterials with magnetic fields by incorporating amorphous magnetic microwires. The large permeability of these wires at microwave frequencies allows tuning the resonance of the metamaterial by using magnetic fields of the order of tens of Oe. We describe here the physical basis of the interaction between a prototypical magnetic metamaterial with magnetic microwires and electromagnetic waves plus providing detailed calculations and experimental results for the case of an array of Split Ring Resonators with Co-based microwires.

We analyze here the magneto-optical measurements of hybrid materials containing metallic and oxide ferromagnetic phases. We show that the magnetization curves obtained with this technique can be fairly different to those obtained with standard magnetometry techniques and cannot be representative of the contribution of each phase to the magnetization of the material, due to the very different optical properties of metals and oxides. However, a proper numerical analysis of the magneto-optical measurements allows estimating the fraction of each phase present in the material.

Radiofrequency is a technology used in physical rehabilitation by physicians and physiotherapists for more than fifteen years, although there exist doubts on how it works. Indiba is a particular method that applies a voltage difference of 448 KHz between two electrodes, creating an electric current between them. These electrodes are an active one that is placed on different areas of the body and a passive one that is left on the same position during the treatment. There are two different types of active electrodes: the capacitive one and the resistive one. In this paper, it has been studied how the different electrodes affect the current density inside the body and thus how they affect the efficacy of the treatment. It shows how finite element calculations should help physicians in order to better understand its behavior and improve the treatments.

Promising advances in nanomedicine such as magnetic hyperthermia rely on a precise control of the nanoparticle performance in the cellular environment. This constitutes a huge research challenge due to difficulties for achieving a remote control within the human body. Here we report on the significant double role of the shape of ellipsoidal magnetic nanoparticles (nanorods) subjected to an external AC magnetic field: first, the heat release is increased due to the additional shape anisotropy; second, the rods dynamically reorientate in the orthogonal direction to the AC field direction. Importantly, the heating performance and the directional orientation occur in synergy and can be easily controlled by changing the AC field treatment duration, thus opening the pathway to combined hyperthermic/mechanical nanoactuators for biomedicine. Preliminary studies demonstrate the high accumulation of nanorods into HeLa cells whereas viability analysis supports their low toxicity and the absence of apoptotic or necrotic cell death after 24 or 48 h of incubation.

The controlled assembly of building blocks to achieve new nanostructured materials with defined properties at different length scales through rational design is the basis and future of bottom-up nanofabrication. This work describes the assembly of the idealized protein building block, the consensus tetratricopeptide repeat (CTPR), into monolayers by oriented immobilization of the blocks. The selectivity of thiol-gold interaction for an oriented immobilization has been verified by comparing a non-thiolated protein building block. The physical properties of the CTPR protein thin biomolecular films including topography, thickness, and viscoelasticity, are characterized. Finally, the ability of these scaffolds to act as templates for inorganic nanostructures has been demonstrated by the formation of well-packed gold nanoparticles (GNPs) monolayer patterned by the CTPR monolayer., (Copyright © 2016 Elsevier B.V. All rights reserved.)

The capability of synthesizing Fe-based antiferromagnetic metal alloys would fuel the use of electrodeposition in the design of new magnetic devices such as high-aspect-ratio spin valves or new nanostructured hard magnetic composites. Here we report the synthesis of high quality antiferromagnetic FeMn alloys electrodeposited from chloride-based electrolytes. We have found that in order to grow homogeneous FeMn films it is necessary to incorporate a large concentration of NH4Cl as an additive in the electrolyte. The study of the structure and magnetic properties shows that films with composition close to Fe50Mn50 are homogeneous antiferromagnetic alloys. We have established a parameter window for the synthesis of FeMn alloys that show antiferromagnetism at room temperature.

While being key to understanding their intriguing physical properties, the origin of nanophase separation in manganites and other strongly correlated materials is still unclear. Here, experimental evidence is offered for the origin of the controverted phase separation mechanism in the representative La1-xCaxMnO3 system. For low hole densities, direct evidence of Mn(4+) holes localization around Ca(2+) ions is experimentally provided by means of aberration-corrected scanning transmission electron microscopy combined with electron energy loss spectroscopy. These localized holes give rise to the segregated nanoclusters, within which double exchange hopping between Mn(3+) and Mn(4+) remains restricted, accounting for the insulating character of perovskites with low hole density. This localization is explained in terms of a simple model in which Mn(4+) holes are bound to substitutional divalent Ca(2+) ions.

AuFe nanoparticles with mean diameters d p  = 13.2 nm have been prepared by inert-gas condensation. Conventional and high-resolution transmission electron microscopy and energy-dispersive x-ray spectroscopy investigations show that the particles are mostly icosahedra. Scanning transmission electron microscopy-energy-dispersive x-ray spectroscopy and scanning transmission electron microscopy-electron energy-loss spectroscopy show that the as-grown particles exhibit a core-shell structure. The shell is mainly composed of an amorphous FeO layer. Although Fe and Au are immiscible in the bulk, the particle cores are found to be homogeneously mixed at the atomic level with a local composition of around Au84Fe16 (at.%). AuFe nanoparticles exhibit a complex magnetic structure in which the core behaves as a spin glass with a freezing temperature of 35 K, whereas the amorphous FeO shell behaves as a ferro-ferrimagnetic system. On annealing above 300 °C, the AuFe icosahedra phases separate into their elemental constituents. Hence the as-grown AuFe icosahedra are metastable, thereby implying that the bulk phase diagram also applies for nanoscopic materials.

Background: Quite often, magnetoencephalography (MEG) measurements are contaminated by a series of artifacts that degrade the quality of the various source localization methods applied to them. In particular, eye blinking, minor head movement and related activities are a constant source of measurement contamination. In order to solve this problem, trial selection and rejection is applied, a task that is usually performed manually., New Method: The present work shows an automatic trial selection and rejection algorithm based on clustering techniques. These techniques employ a measurement of the dissimilarity of the items belonging to a set. This measure, based on the projection of the eigenvector corresponding to the largest eigenvalue of the covariance matrix, is provided and its rationale is explained. Subsequently, covariance matrices belonging to the selected cluster are averaged and used in the well-known Linearly Constrained Minimum Variance (LCMV) Beamformer., Results: The results show a marked improvement of the specificity of the localization algorithm compared to the application of the LCMV without clustering., Comparison With Existing Method(s): The method shows a marked reduction in computational cost compared with other data cleaning procedure widely used: Independent Component Analysis (ICA)., Conclusions: Thus, we propose clustering techniques to be used in brain localization activity algorithms., (Copyright © 2013 Elsevier B.V. All rights reserved.)

Gold nanoparticles have been synthesized inside ethosomes, vesicles composed of phospholipid, ethanol, and water, which could be very efficient not only in delivery probes to the skin but also as diagnostic and therapeutic multimodal agents. High efficiency encapsulation of gold nanoparticles is achieved by a simple strategy: the nanoparticles synthesis occurs simultaneously with the ethosomes formation in the absence of any undesirable reducing agents. A three-dimensional reconstruction of a gold-embedded ethosome generated by cryoelectron tomography reveals that the gold particle is localized inside the lipid bilayer, leaving the ethosome surface and core free for further functionalization. The resulting gold nanoparticles are homogeneous in size and shape and, depending on synthesis temperature, the size ranges from 10 to 20 nm, as revealed by TEM. The ethosome-nanoparticles hybrids' size has been investigated by means of dynamic light scattering and has been found to vary with temperature and gold salt concentration from 700 to 400 nm. Gold nanoparticles-encapsulated ethosomes offer a versatile platform for the enhancement of pharmacological efficacy in transdermal and dermal delivery systems.

The purpose of this work is to study the changes of the bioimpedance from its 'in vivo' value to the values measured in a few hours after the excision from the body. The evolution of electrical impedance with time after surgical extraction has been studied on two porcine organs: the liver and the kidney. Both in vivo and ex vivo measurements of electrical impedance, measuring its real and imaginary components, have been performed. The in vivo measurements have been carried out with the animal anaesthetized. The ex vivo measurements have been made more than 2 h after the extraction of the organ. The latter experiment has been carried out at two different stabilized temperatures: at normal body temperature and at the standard preservation temperature for transplant surgery. The measurements show a correlation between the biological evolution and the electrical bioimpedance of the organs, which increases from its in vivo value immediately after excision, multiplying its value by 2 in a few hours.

Neutron diffraction and X-ray absorption near-edge structure (XANES) studies have been performed in La0.5Ca0.5MnO2.5, La0.5Sr0.5MnO2.5 and Nd0.5Sr0.5MnO2.5 oxygen-deficient perovskite compounds obtained by topotactic reduction. They all exhibit a brownmillerite structure with G-type antiferromagnetic ordering. Mn2+, Mn3+ and Mn4+ coexist at the octahedral sites, whereas only Mn2+ is placed in the tetrahedral positions. A magnetic moment of 1.6 microB has been detected at the tetrahedral layers, which can be explained by assuming Mn2+ is in a low-spin configuration.

We experimentally show that it is possible to induce room-temperature ferromagnetic-like behavior in ZnO nanoparticles without doping with magnetic impurities but simply inducing an alteration of their electronic configuration. Capping ZnO nanoparticles ( approximately 10 nm size) with different organic molecules produces an alteration of their electronic configuration that depends on the particular molecule, as evidenced by photoluminescence and X-ray absorption spectroscopies and altering their magnetic properties that varies from diamagnetic to ferromagnetic-like behavior.