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Cellulose nanocrystal and gold nanoparticles are assembled, in a unique way, to yield a novel modular glyconanomaterial whose surface is then easily engineered with one or two different headgroups, by exploiting a robust click chemistry route. We demonstrate the potential of this approach by conjugating monosaccharide headgroups to the glyconanomaterial and show that the sugars retain their binding capability to C-type lectin receptors, as also directly visualized by cryo-TEM.

Intrinsic parameters (magnetic core composition, size, shape, coating, and surface functionalization) and extrinsic parameters (solvent, magnetic field, and temperature) relevant for describing the nuclear relaxation in MNP core–shell nanoparticles are discussed.

Active modulation of the plasmonic response is at the forefront of today's research in nano-optics. For a fast and reversible modulation, external magnetic fields are among the most promising approaches. However, fundamental limitations of metals hamper the applicability of magnetoplasmonics in real-life active devices. While improved magnetic modulation is achievable using ferromagnetic or ferromagnetic-noble metal hybrid nanostructures, these suffer from severely broadened plasmonic response, ultimately decreasing their performance. Here we propose a paradigm shift in the choice of materials, demonstrating for the first time the outstanding magnetoplasmonic performance of transparent conductive oxide nanocrystals with plasmon resonance in the near-infrared. We report the highest magneto-optical response for a nonmagnetic plasmonic material employing F- and In-codoped CdO nanocrystals, due to the low carrier effective mass and the reduced plasmon line width. The performance of state-of-the-art ferromagnetic nanostructures in magnetoplasmonic refractometric sensing experiments are exceeded, challenging current best-in-class localized plasmon-based approaches.

Here, we synthesize a Au@Fe

Plasmon resonance modulation with an external magnetic field (magnetoplasmonics) represents a promising route for the improvement of the sensitivity of plasmon-based refractometric sensing. To this purpose, an accurate material choice is needed to realize hybrid nanostructures with an improved magnetoplasmonic response. In this work, we prepared core@shell nanostructures made of an 8 nm Au core surrounded by an ultrathin iron oxide shell (

[EN] Temperature treatment of magnetic Mn−Zn ferrites with the composition Mn0.6Zn0.2Fe2.2O4 up to 1100 °C results in a tremendous enhancement of the saturation magnetization by more than 60%. Employing a robust combined Rietveld refinement of powder X-ray and neutron diffraction (PXRD and NPD) data, it is revealed how a reordering of the cations takes place during the annealing step, the extent of which depends on the annealing temperature. While Zn(II) exclusively occupies tetrahedral sites throughout the whole temperature range, as the annealing temperature increases up to 700 °C, the Mn(II) cation distribution shifts from 80(7)% of the total Mn content occupying the octahedral sites (partly inverse spinel) to Mn only being present on the tetrahedral sites (normal spinel). Above 700 °C, pronounced crystallite growth is observed, followed by an increase of the saturation magnetization. Complementary techniques such as energy dispersive X-ray spectroscopy (EDS) and transmission electron microscopy (TEM) confirm an even cation distribution and the particle growth with annealing temperature. The structural changes caused by annealing of spinel ferrites directly alter the magnetic properties of the materials, thus serving as an easy handle for enhancing their magnetic properties., The authors are grateful for financial support from the European Commission through the H2020 project AMPHIBIAN (H2020-NMBP-2016-720853). Support from the Danish National Research Foundation (Center for Materials Crystallography, DNRF-93) and the Danish Center for Synchrotron and Neutron Science (DanScatt) is gratefully acknowledged. We would also like to acknowledge the assistance from instrument staff, namely, Lukas Keller at SINQ, PSI, Switzerland, and Thomas Hansen at ILL, Grenoble, France. Affiliation with the Center for Integrated Materials Research (iMAT) at Aarhus University is gratefully acknowledged by J.H., P.G.G., M.S.M., and M.C. J.H. acknowledges affiliation with the Sino-Danish Center for Education and Research (SDC).

Tuning the plasmonic response with an external magnetic field is extremely promising to achieve active magnetoplasmonic devices, such as next generation refractometric sensors or tunable optical components. Noble metal nanostructures represent an ideal platform for studying and modeling magnetoplasmonic effects through the interaction of free electrons with external magnetic fields, even though their response is relatively low at the magnetic field intensities commonly applied in standard magneto-optical spectroscopies. Here we demonstrate a large magnetoplasmonic response of silver nanoparticles by performing magnetic circular dichroism spectroscopy at high magnetic fields, revealing a linear response to the magnetic field up to 30 T. The exploitation of such high fields allowed us to probe directly the field-induced splitting of circular plasmonic modes by performing absorption spectra with static circular polarizations, giving direct experimental evidence that the magneto-optical activity of plasmonic nanoparticles arises from the energy shift of field-split circular magnetoplasmonic modes.

In this work, we demonstrate that the reduction of the local internal stress by a low-temperature solvent-mediated thermal treatment is an effective post-treatment tool for magnetic hardening of chemically synthesized nanoparticles. As a case study, we used nonstoichiometric cobalt ferrite particles of an average size of 32(8) nm synthesized by thermal decomposition, which were further subjected to solvent-mediated annealing at variable temperatures between 150 and 320 °C in an inert atmosphere. The postsynthesis treatment produces a 50% increase of the coercive field, without affecting neither the remanence ratio nor the spontaneous magnetization. As a consequence, the energy product and the magnetic energy storage capability, key features for applications as permanent magnets and magnetic hyperthermia, can be increased by ca. 70%. A deep structural, morphological, chemical, and magnetic characterization reveals that the mechanism governing the coercive field improvement is the reduction of the concomitant internal stresses induced by the low-temperature annealing postsynthesis treatment. Furthermore, we show that the medium where the mild annealing process occurs is essential to control the final properties of the nanoparticles because the classical annealing procedure (T > 350 °C) performed on a dried powder does not allow the release of the lattice stress, leading to the reduction of the initial coercive field. The strategy here proposed, therefore, constitutes a method to improve the magnetic properties of nanoparticles, which can be particularly appealing for those materials, as is the case of cobalt ferrite, currently investigated as building blocks for the development of rare-earth free permanent magnets. This work was supported by EU-H2020 AMPHIBIAN Project (Grant no. 720853). A.L.O. acknowledges support from the Universidad Pública de Navarra (Grant no. PJUPNA2020). Open access funding provided by Universidad Pública de Navarra.

Nanometric core@shell wüstite@ferrite (Fe1-xO@Fe3O4) has been extensively studied because of the emergence of exchange bias phenomena. Since their actual implementation in modern technologies is hampered by the low temperature at which bias is operating, the critical issue to be solved is to obtain exchange-coupled antiferromagnetic@ferrimagnetic nanoparticles with ordering temperature close to 300 K by replacing the divalent iron with other transition-metal ions. Here, we studied the effect of the combined substitution of Fe(II) with Co(II) and Ni(II) on the crystal structure and magnetic properties. To this aim, a series of 20 nm nanoparticles with a wüstite-based core and a ferrite shell, with tailored composition, (Co0.3Fe0.7O@Co0.8Fe2.2O4 and Ni0.17Co0.21Fe0.62O@Ni0.4Co0.3Fe2.3O4) were synthetized through a thermal-decomposition method. An extensive morphological and crystallographic characterization of the obtained nanoparticles showed how a higher stability against the oxidation process in ambient condition is attained when divalent cation doping of the iron oxide lattice with Co(II) and Ni(II) ions is performed. The dual-doping revealed to be an efficient way for tuning the magnetic properties of the final system, obtaining Ni-Co doped iron oxide core@shell nanoparticles with high coercivity (and therefore, high energy product), and increased antiferromagnetic ordering transition temperature, close to room temperature., This work is supported by EU-H2020 AMPHIBIAN Project (n. 720853) and by European Union’s Horizon 2020 research and innovation programme under grant agreement No 823717-ESTEEM3

Iron oxide nanoparticles mineralized within the internal cavity of Ferritin protein cage are extremely appealing for the realization of multifunctional therapeutic and diagnostic agents for cancer treatment by drug delivery, magnetic fluid hyperthermia (MFH) and magnetic resonance imaging. Being the maximum mean size imposed by the internal diameter of the protein shell (ca. 8 nm) too small for the use of these systems in MFH, a valuable strategy for the improvement of the hyperthermic efficiency is increasing the magnetic anisotropy by doping the iron oxide with divalent Co ions. This strategy has been demonstrated to be highly efficient in the case of iron oxide nanoparticles mineralized in Human Ferritin (HFt). However, a deterioration of nanoparticles crystallinity and consequently a reduction of the hyperthermic efficiency were observed with increasing Co-doping. In this contribution, we compare two series of Co-doped iron oxide nanoparticles (Co-doping level up to 15%) mineralized into HFt and into Ferritin from the archaea Pirococcus Furiosus (PfFt), the protein structure of which differs for the nucleation sites, with the aim of increasing the crystalline quality of the inorganic cores for larger Co doping. Highly monodisperse nanoparticles of 6-7 nm were obtained in both series. The structural and magnetic characterization indicate that the PfFt series is less subjected to crystallinity deterioration with increasing Co content with respect to the HFt one. Such difference is reflected in the hyperthermic efficiency. which reaches the maximum value for different intermediate Co-doping (10% and 5% for PfFt and HFt, respectively), and goes to zero for further Co-doping increments.

Hybrid materials composed of Superparamagnetic Iron Oxide Nanoparticles (SPIONs) and lipid self-assemblies possess a considerable applicative potential in the biomedical field, specifically, for drug/nutrients delivery. In recent works we have shown that SPION-doped lipid cubic liquid crystals undergo a cubic-to-hexagonal phase transition under the action of temperature or of an alternating magnetic fields (AMF). This transition triggers the release of drugs embedded in the lipid scaffold or in the water channels. In this contribution, we address this phenomenon in depth, to fully elucidate the structural details and optimize the design of hybrid multifunctional carriers for drug delivery. Combining Small-Angle X-Ray Scattering (SAXS) with a magnetic characteri-zation, we find that in bulk lipid cubic phases the cubic-to-hexagonal transition determines the magnetic response of SPIONs. We then extend the investigation from bulk liquid-crystalline phases to colloidal dispersions, i.e. to lipid/SPIONs nanoparticles with cubic internal structure (“magnetocubosomes”). Through Synchrotron SAXS, we monitored the structural response of magnetocubosomes while exposed to an AMF: the magnetic energy, converted into heat by SPIONs, activates the cubic-to-hexagonal transition, and can thus be used as a remote stimulus to spike drug release “on-demand”. In addition, we show that the AMF-induced phase transition in magnetocubosomes steers the re-alignment of SPIONs into linear string assemblies and connect this effect with the change in their magnetic properties, observed at the bulk level. Finally, we assess the internalization ability and cytotoxicity of magnetocubosomes in vitro on HT29 ade-nocarcinoma cancer cells, in order to test the applicability of these smart carriers in drug delivery applications

HKUST-1 metal-organic framework (MOF) and Fe3O4@HKUST-1 magnetic framework composites (MFCs) were developed by a simple and sustainable liquid assisted mechanochemical synthesis process. The growth of the MOF crystalline structure was directed on the surface of functionalized magnetite particles, which act as “crystallization germs”. The nanomaterials were characterized in their structural, morphological, and thermal properties and were tested for CO2/N2 mixture separation. All samples exhibits good carbon dioxide adsorption and selectivity for the CO2/N2 mixture. In the case of magnetic composites, the application of an external alternating magnetic field induces nanoparticles’ heating and the locally generated heat triggers carbon dioxide release from the MOF. The magnetic composites combine the adsorbing properties of the organic component and the heating capacity of magnetic nanoparticles, MNPs, representing innovative sorbent systems for the implementation of a separation technology named Magnetic Induction Swing Adsorption (MISA). This technology takes advantage of the highly efficient energy transfer typical of induction heating for the regeneration of adsorption beds and promises energy savings. The effectiveness of the desorption process depends on the magnetic materials properties and in this work has been improved by tuning the characteristic of the magnetic component.

Permanent magnets based on hard hexaferrite represent the largest family of magnets being used today by volume. They generate moderate remanence induction, but present crucial advantages in terms of availability, cost, resistance to demagnetization and corrosion and absence of eddy current losses. As a consequence, ferrites are the most logical candidate for substitution of rare-earths in selected applications that do not demand the best performing magnets. If the remanence of ferrite-based magnets was to be improved, even mildly, the door to a larger scale substitution could be opened. In this framework, we review here current strategies to improve the properties of hexaferrites for permanent magnet applications. We first discuss the potential of exploring the nanoscale. Second, progress related to controllably doping hexaferrites is revised. Third, results achieved by fabricating hard-soft magnetic composites using ferrites as the hard phase are presented. Finally, future prospects and new potential end applications for ferrite magnets are discussed.

Heterodimeric nanoparticles comprising materials with different functionalities are of great interest for fundamental research and biomedical/industrial applications. In this work, Fe3O4-Au nano-heterostructures were synthesized by a one-step thermal decomposition method. The hybrid nanoparticles comprise a highly crystalline 12 nm magnetite octahedron decorated with a single noble metal sphere of 6 nm diameter. Detailed analysis of the nanoparticles was performed by UV-visible spectroscopy, magnetometry, calorimetry and relaxometry studies. The cytotoxic effect of the nanoparticles in the human hepatic cell line Huh7 and PLC/PRF/5-Alexander was also assessed. These Fe3O4-Au bifunctional nanoparticles showed no significant cytotoxicity in these two cell lines. The nanoparticles showed a good theranostic potential for liver cancer treatment, since the r2 relaxivity (166.5 mM−1·s−1 and 99.5 mM−1·s−1 in water and HepG2 cells, respectively) is higher than the corresponding values for commercial T2 contrast agents and the Specific Absorption Rate (SAR) value obtained (227 W/gFe) is enough to make them suitable as heat mediators for Magnetic Fluid Hyperthermia. The gold counterpart can further allow the conjugation with different biomolecules and the optical sensing.

The systemic delivery of composite nanoparticles remains an outstanding challenge in cancer nanomedicine, and the principal reason is a complex interplay of biological barriers. In this regard, adaptive cell transfer may represent an alternative solution to circumvent these barriers down to the tumor microenvironment. Here, tumor-tropic macrophages are proposed as a tool to draw and vehiculate modular nanoparticles integrating magnetic and plasmonic components. The end result is a bionic shuttle that exhibits a plasmonic band within the so-called therapeutic window arising from as much as 40 pg Au per cell, magnetization in the order of 150 pemu per cell, and more than 90% of the pristine viability and chemotactic activity of its biological component, until at least two days of preparation. Its synergistic combination of plasmonic, magnetic and tumor-tropic functions is assessed in vitro for applications as magnetic guidance or sorting, with a propulsion around 4 μm s−1 for a magnetic gradient of 0.8 T m−1, the optical hyperthermia of cancer, with stability of photothermal conversion to temperatures exceeding 50∘C, and the photoacoustic imaging of cancer under realistic conditions. These results collectively suggest that a bionic design may be a promising roadmap to reconcile the efforts for multifunctionality and targeted delivery, which are both key goals in nanomedicine.

Water dispersible Gd

In this paper we report the synthesis and characterization of biocompatible multi-functional magnetic nanoparticles (MNPs) able to enhance the intracellular transport of N-methylated drugs. The Fe3O4 magnetic core was first functionalized with a mixed monolayer consisting of two different phosphonic acids having terminal acetylenic and amino groups, which provide an active platform for further functionalization with organic molecules. Then, a tetraphosphonate cavitand receptor (Tiiii) bearing an azide moiety and the N-hydroxysuccinimide (NHS) activated forms of poly(ethylene glycol) (PEG), folic acid (FA) and carboxy-X-rhodamine (Rhod) were covalently anchored on alkyne and amine moieties respectively, through 1,3-dipolar cycloaddition and EDC/NHS coupling reactions. The obtained MNPs are biocompatible and possess magnetic, luminescence and recognition properties which make them suitable for multimodal theranostic applications. In particular, combined confocal microscopy and cytotoxicity experiments showed that these multi-functional MNPs are able to recognize a specific drug "in situ'' and promote its cellular internalization, thus enhancing its efficiency.

We show the application of the singular point detection (SPD) technique to determine the magnetic anisotropy of different hard nanomaterials

We present a 1H NMR investigation of spin dynamics in two finite integer spin molecular nanomagnetic rings, namely V7Zn and V7Ni. This study could be put in correlation with the problem of Haldane gap in infinite integer spin chains. While V7Zn is an approximation of a homometallic broken chain due to the presence of s = 0 Zn2+ ion uncoupled from nearest neighbor V2+s = 1 ions, the V7Ni compound constitutes an example of a closed periodical s = 1 heterometallic chain. From preliminary susceptibility measurements on single crystals and data analysis, the exchange coupling constant J/kB results in the order of few kelvin. At room temperature, the frequency behavior of the 1H NMR spin–lattice relaxation rate 1/T1 allowed to conclude that the spin–spin correlation function is similar to the one observed in semi-integer spin molecules, but with a smaller cutoff frequency. Thus, the high-T data can be interpreted in terms of, e.g., a Heisenberg model including spin diffusion. On the other hand, the behavior of 1/T1 vs temperature at different constant fields reveals a clear peak at temperature of the order of J/kB, qualitatively in agreement with the well-known Bloembergen–Purcell–Pound model and with previous results on semi-integer molecular spin systems. Consequently, one can suggest that for a small number N of interacting s = 1 ions (N = 8), the Haldane conjecture does not play a key role on spin dynamics, and the investigated rings still keep the quantum nature imposed mainly by the low number of magnetic centers, with no clear topological effect due to integer spins.

The development of reproducible protocols to synthesize hard/soft nano-heterostructures (NHSs) with tailored magnetic properties is a crucial step to define their potential application in a variety of technological areas. Thermal decomposition has proved to be an effective tool to prepare such systems, but it has been scarcely used so far for the synthesis of Co-based metal/ferrite NHSs, despite their intriguing physical properties. We found a new approach to prepare this kind of nanomaterial based on a simple one-pot thermal decomposition reaction of metal-oleate precursors in the high boiling solvent docosane. The obtained NHSs are characterized by the coexistence of Co metal and Co doped magnetite and are highly stable in an air atmosphere, thanks to the passivation of the metal with a very thin oxide layer. The investigation of the influence of the metal precursor composition (a mixed iron–cobalt oleate), of the ligands (oleic acid and sodium oleate) and of the reaction time on the chemical and structural characteristics of the final product, allowed us to rationalize the reaction pathway and to determine the role of each parameter. In particular, the use of sodium oleate is crucial to obtain a metal phase in the NHSs. In such a way, the one-pot approach proposed here allows the fine control of the synthesis, leading to the formation of stable, high performant, metal/ferrite NHSs with tailored magnetic properties. For instance, the room temperature maximum energy product was increased up to 19 kJ m−3 by tuning the Co content in the metal precursor.

We present for the first time a method for the preparation of magnetic halloysite nanotubes (HNT) by loading of preformed superparamagnetic magnetite nanoparticles (SPION) of diameter size ∼6 nm with a hydrodynamic diameter of ∼10 nm into HNT. We found that the most effective route to reach this goal relies on the modification of the inner lumen of HNT by tetradecylphosphonic acid (TDP) to give HNT–TDP, followed by the loading with preformed oleic acid (OA)-stabilized SPION. Transmission electron microscopy evidenced the presence of highly crystalline magnetic nanoparticles only in the lumen, partially ordered in chainlike structures. Conversely, attempts to obtain the same result by exploiting either the positive charge of the HNT inner lumen employing SPIONs covered with negatively charged capping agents or the in situ synthesis of SPION by thermal decomposition were not effective. HNT–TDP were characterized by infrared spectroscopy (ATR-FTIR), thermogravimetric analysis (TGA), and ζ-potential, and all of the techniques confirmed the presence of TDP onto the HNT. Moreover, the inner localization of TDP was ascertained by the use of Nile Red, a molecule whose luminescence is very sensitive to the polarity of the environment. The free SPION@OA (as a colloidal suspension and as a powder) and SPION-in-HNT powder were magnetically characterized by measuring the ZFC-FC magnetization curves as well as the hysteresis cycles at 300 and 2.5 K, confirming that the super-paramagnetic behavior and the main magnetic properties of the free SPION were preserved once embedded in SPION-in-HNT., SPION nanoparticles are selectively loaded into halloysite lumen, keeping their superparamagnetic character.

We report the results of an unpolarized small-angle neutron-scattering (SANS) study on Mn-Zn ferrite (MZFO) magnetic nanoparticles with the aim to elucidate the interplay between their particle size and the magnetization configuration. We study different samples of single-crystalline MZFO nanoparticles with average diameters ranging between 8 to 80 nm, and demonstrate that the smallest particles are homogeneously magnetized. However, with increasing nanoparticle size, we observe the transition from a uniform to a nonuniform magnetization state. Field-dependent results for the correlation function confirm that the internal spin disorder is suppressed with increasing field strength. The experimental SANS data are supported by the results of micromagnetic simulations, which confirm an increasing inhomogeneity of the magnetization profile of the nanoparticle with increasing size. The results presented demonstrate the unique ability of SANS to detect even very small deviations of the magnetization state from the homogeneous one.

The physicochemical properties of spinel oxide magnetic nanoparticles depend critically on both their size and shape. In particular, spinel oxide nanocrystals with cubic morphology have shown superior properties in comparison to their spherical counterparts in a variety of fields, like, for example, biomedicine. Therefore, having an accurate control over the nanoparticle shape and size, while preserving the crystallinity, becomes crucial for many applications. However, despite the increasing interest in spinel oxide nanocubes there are relatively few studies on this morphology due to the difficulty to synthesize perfectly defined cubic nanostructures, especially below 20 nm. Here we present a rationally designed synthesis pathway based on the thermal decomposition of iron(III) acetylacetonate to obtain high quality nanocubes over a wide range of sizes. This pathway enables the synthesis of monodisperse Fe

Zinc substitution is often proposed as an efficient strategy to improve the performances of spinel ferrite nanoparticles, particularly related to their application as theranostic agents. In this work, a series of 8 nm spinel ferrite nanoparticles of formula CoxZnyFe3-(x+y)O4 is synthesized by thermal decomposition with the purpose of investigating the role of Zn2+ ions in modifying the structural and magnetic properties. Contrary to most of the literature on this subject, where the sum of Co and Zn is kept constant (x + y = 1), here, the amount of Co is maintained at ca. x = 0.6, corresponding to the maximum of magnetic anisotropy of the Zn-undoped system, whereas the amount of Zn is progressively varied along the series from y = 0.05 to 0.4. This approach allows enlightening the effect of the Zn introduction on the magnetic and crystal structures and, particularly, on magnetic anisotropy, which is deeply investigated by several complementary techniques. A significant increase of the saturation magnetization, M-s, upon the Zn content up to y = 0.4 is confirmed only at low temperature, whereas at room temperature, this effect is partially nullified by the weakening of the magnetic exchange coupling constants due to the increasing Zn substitution. Moreover, we demonstrate that the lattice modifications following the Zn introduction are responsible of a strong decrease of the particle magnetic anisotropy. Overall, these effects limit the use of Zn-substituted ferrites in biomedical applications like magnetic resonance imaging and magnetic fluid hyperthermia only to very low amount of Zn, as here confirmed by relaxometric and calorimetric measurements.

[object Object]Core-shell nanoparticles based on a CoxFe1-xO rock-salt core, and on a shell corresponding to cubic spinel CoxFe3-xO4, have been systematically annealed to completely oxidize and generate the fully ferrimagnetic cobalt ferrite structure. The annealing has been performed through a solvent-mediated process at high temperatures to avoid interparticle aggregation, usually observed in classical annealing methods. We carefully describe how the oxidative process occurred during the initial shell passivation and in the following O2 mediated oxidation. It has been found that the rock-salt to spinel transformation occurs via topotaxial growth over the (200)RS//(400)S and (220)RS//(440)S planes shared between the two structures. This chemical transformation depends on the amount of divalent cobalt atoms present in the oxide structures. Within this respect, the solvent-mediated annealing process permits the release of a small amount of divalent cations, which allows the stoichiometry rearrangement required to form the spinel phase. The growth occurs through a topotaxial process, which involves the formation of a mosaic texture of small spinel subdomains, separated by antiphase boundaries, into the well-defined rock-salt structure along the nanoparticles. The existence of antiphase boundaries gives rise to the presence of exchange bias phenomena even for completely oxidized nanoparticles. The exchange bias effect increases the energy product of these nanocomposites, which makes this approach appealing for the realization of a novel class of free rare-earth permanent magnets.

We report the synthesis and characterization of multi-functional monodisperse superparamagnetic Magnetic NanoParticles, MNPs, able to act as contrast agents for magnetic resonance and Magnetic Fluid Hyperthermia (MFH) mediators. The investigated samples are constituted of a magnetic core of magnetite and a biocompatible PAMAM coating. We studied two samples with the same magnetic volume but different shape, i.e. spherical and faceted. Despite the relatively large size (MNPs of 20 nm diameter) that generally leads to particles' aggregation and instability, the resulting samples were very stable. For faceted MNPs, the efficiency in contrasting Magnetic Resonance images, i.e. the nuclear transverse 1H NMR relaxivity r2, reached values of about 250/300 mM−1 s−1 at clinical frequencies f > 5 MHz, i.e. 2.5/3 times higher than the commercial compound Endorem, while the Specific Absorption Rate at Hac ∼ 10 kA m−1 and frequency f < 300 kHz (i.e. within the physiological limits) reaches 900 W g−1, suggesting this system as a potentially useful mediator for MFH. The experimental data strongly indicate the new synthesized MNP systems as good candidates for theranostic applications.

In this work we report a technique for the preparation of AuxNii-x alloy nanoparticles based on pulsed laser irradiation in liquid of Au and Ni@NiO colloidal mixtures. The structural and compositional characterization of the obtained materials, performed through X-ray diffraction and transmission electron microscopy coupled with energy dispersive X-ray spectroscopy, has shown a correlation between the final alloy composition and the different Au to Ni@NiO ratio in the irradiated mixture. With the support of theoretical calculations, we propose as possible mechanism for the formation of the alloy structures a temperature increase, enhanced by the strong absorption of gold surface plasmon resonance at resonant wavelength, and a subsequent melting of the structures. Optical characterization through UV-vis spectroscopy and magnetic characterization through SQUID magnetometry confirm a coexistence of the plasmonic and magnetic behaviors in the hybrid systems. In view of such results, AuxNi1-x alloy nanoparticles could be a promising base material for devices requiring both plasmonic and magnetic properties.

Antiferromagnetic(AFM)|ferrimagnetic(FiM) core|shell (CS) nanoparticles (NPs) of formula Co0.3Fe0.7O|Co0.6Fe2.4O4 with mean diameter from 6 to 18 nm have been synthesized through a one-pot thermal decomposition process. The CS structure has been generated by topotaxial oxidation of the core region, leading to the formation of a highly monodisperse single inverted AFM|FiM CS system with variable AFM-core diameter and constant FiM-shell thickness (∼2 nm). The sharp interface, the high structural matching between both phases, and the good crystallinity of the AFM material have been structurally demonstrated and are corroborated by the robust exchange-coupling between AFM and FiM phases, which gives rise to one among the largest exchange bias (HE) values ever reported for CS NPs (8.6 kOe) and to a strongly enhanced coercive field (HC). In addition, the investigation of the magnetic properties as a function of the AFM-core size (dAFM), revealed a nonmonotonous trend of both HC and HE, which display a maximum value for dAFM = 5 nm (19.3 and 8.6 kOe, respectively). These properties induce a huge improvement of the capability of storing energy of the material, a result which suggests that the combination of highly anisotropic AFM|FiM materials can be an efficient strategy toward the realization of novel rare-earth-free permanent magnets.

Cobalt ferrite nanoparticles have been attracting considerable interest in the recent years because of the large number of potential applications, including magnetic storage, magnetic fluid hyperthermia and as contrast agents for magnetic resonance imaging. Physical properties of this class of materials depend critically on a number of parameters, including crystallinity, stoichiometry and cation distribution. In this work we have performed a Resonant Inelastic soft X-ray Scattering (RIXS) study on a series of 5 nm cobalt-doped maghemite nanoparticles to obtain direct quantitative information on cation distribution as a function of cobalt doping. We found that the distribution of divalent cobalt is stable in the investigated doping range and slightly different from that of bulk, stoichiometric cobalt ferrite. These results confirm that cobalt doping can be used to finely tune the magnetic properties of nanostructured ferrites without modifying their structural integrity.

Dry reforming of methane is a highly endothermic reaction that produces syngas from CH4 and CO2. It operates at 800–1000 °C to meet thermodynamic constraints, achieve high equilibrium conversion and minimize catalyst deactivation due to carbon deposition. In this paper we report our experimental results on the catalytic activation of dry reforming powered by induction heating. Energy is supplied by a radiofrequency alternating magnetic field to Ni60Co40 alloy that works at the same time as catalyst for the reforming reaction and heat generator by dissipation of the electromagnetic energy. In such a way, the heat of reaction is directly provided by the catalytic bed, avoiding dissipation due to inefficient transfer from outside the reactor. Temperatures higher than 850 °C have been easily reached using Ni60Co40 pellets as heat mediators in a continuous-flow fixed-bed reactor. At this temperature methane conversion and hydrogen production occurred with yield comparable to those obtained by conventional heating. Reported evidences open new opportunities in the research of magnetic materials for industrial chemical processes.

We present multifunctional, biocompatible and biodegradable magnetic nanovectors based on different polyamidoamine (PAA) polymers tailored with different diagnostic and therapeutic properties. Using maghemite nanoparticles with average size 15.5 +/- 2.8 rim prepared by thermal decomposition, superparamagnetic nanovectors were obtained by coating the nanoparticles with synthetic polymers of PM. These have a segmented copolymer structure, and bear PAA segments containing different amount of carboxyl groups per repeating units together with PEG segments. These copolymers are thought to combine the binding properties of the carboxylated PM segments to inorganic nanoparticles, with the stealth properties of the PEG ones. The magnetic, hyperthermal and relaxometric properties of the synthesized samples were investigated. Magnetic measurements revealed that the samples are superparamagnetic at room temperature and the overall magnetic behavior is not affected by the functionalization process. Calorimetric measurements demonstrated a good heating efficiency at alternating magnetic field parameters below the human tolerability threshold (SAR of ca. 70 W/g at 260 Hz and 10.8 kA/m). H-1-NMR relaxivities were relevant compared to the values of the commercial contrast agents over the whole investigated frequency range.

Superparamagnetic iron oxide nanoparticles (SPIONs) are widely used in various biomedical applications, such as diagnostic agents in magnetic resonance imaging (MRI), for drug delivery vehicles and in hyperthermia treatment of tumors. Although the potential benefits of SPIONs are considerable, there is a distinct need to identify any potential cellular damage associated with their use. Since human ether à go-go-related gene (hERG) channel, a protein involved in the repolarization phase of cardiac action potential, is considered one of the main targets in the drug discovery process, we decided to evaluate the effects of SPIONs on hERG channel activity and to determine whether the oxidation state, the dimensions and the coating of nanoparticles (NPs) can influence the interaction with hERG channel. Using patch clamp recordings, we found that SPIONs inhibit hERG current and this effect depends on the coating of NPs. In particular, SPIONs with covalent coating aminopropylphosphonic acid (APPA) have a milder effect on hERG activity. We observed that the time-course of hERG channel modulation by SPIONs is biphasic, with a transient increase (~20% of the amplitude) occurring within the first 1-3 min of perfusion of NPs, followed by a slower inhibition. Moreover, in the presence of SPIONs, deactivation kinetics accelerated and the activation and inactivation I-V curves were right-shifted, similarly to the effect described for the binding of other divalent metal ions (e.g. Cd2+ and Zn2+). Finally, our data show that a bigger size and the complete oxidation of SPIONs can significantly decrease hERG channel inhibition. Taken together, these results support the view that Fe2+ ions released from magnetite NPs may represent a cardiac risk factor, since they alter hERG gating and these alterations could compromise the cardiac action potential.

The physicochemical properties of spinel oxide magnetic nanoparticles depend critically on both their size and shape. In particular, spinel oxide nanocrystals with cubic morphology have shown superior properties in comparison to their spherical counterparts in a variety of fields, like, for example, biomedicine. Therefore, having an accurate control over the nanoparticle shape and size, while preserving the crystallinity, becomes crucial for many applications. However, despite the increasing interest in spinel oxide nanocubes there are relatively few studies on this morphology due to the difficulty to synthesize perfectly defined cubic nanostructures, especially below 20 nm. Here we present a rationally designed synthesis pathway based on the thermal decomposition of iron(III) acetylacetonate to obtain high quality nanocubes over a wide range of sizes. This pathway enables the synthesis of monodisperse Fe3O4 nanocubes with edge length in the 9–80 nm range, with excellent cubic morphology and high crystallinity by only minor adjustments in the synthesis parameters. The accurate size control provides evidence that even 1–2 nm size variations can be critical in determining the functional properties, for example, for improved nuclear magnetic resonance T2 contrast or enhanced magnetic hyperthermia. The rationale behind the changes introduced in the synthesis procedure (e.g., the use of three solvents or adding Na-oleate) is carefully discussed. The versatility of this synthesis route is demonstrated by expanding its capability to grow other spinel oxides such as Co-ferrites, Mn-ferrites, and Mn3O4 of different sizes. The simplicity and adaptability of this synthesis scheme may ease the development of complex oxide nanocubes for a wide variety of applications., We acknowledge funding from Generalitat de Catalunya through the 2017-SGR-292 and 2017-SGR-776 projects and the Spanish Ministry of Economy, Industry and Competitiveness (MINECO) through the MAT2016-77391-R and MAT2016-79455-P projects. E.F. and F.P. acknowledge the University of Pisa for its funding through the PRA_2017_25 project. ICN2 is funded by the CERCA programme/Generalitat de Catalunya. The ICN2 is supported by the Severo Ochoa Centres of Excellence programme, funded by the Spanish Research Agency (AEI, grant no. SEV2017-0706).

We present a study on the origin of the magnetic properties of Al and Cr doped Sr hexaferrites. M- type hexaferrites are the most employed rare-earth free ceramics in the permanent magnet industry