Editor's Choice Articles

Editor’s Choice articles are based on recommendations by the scientific editors of MDPI journals from around the world. Editors select a small number of articles recently published in the journal that they believe will be particularly interesting to readers, or important in the respective research area. The aim is to provide a snapshot of some of the most exciting work published in the various research areas of the journal.

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Article
Analysis of the Mutual Impedance of Coils Immersed in Water
Magnetochemistry 2021, 7(8), 113; https://doi.org/10.3390/magnetochemistry7080113 - 05 Aug 2021
Cited by 5 | Viewed by 773
Abstract
Magnetic induction communication and wireless power transmission based on magnetic coupling have significant application prospects in underwater environments. Mutual impedance is a key parameter particularly required for the design of the systems. However, mutual impedance is usually extracted from measurements when the coils [...] Read more.
Magnetic induction communication and wireless power transmission based on magnetic coupling have significant application prospects in underwater environments. Mutual impedance is a key parameter particularly required for the design of the systems. However, mutual impedance is usually extracted from measurements when the coils are processed, which is obviously not conducive to the system optimization in the design phase. In this paper, a model of the mutual impedance of coils immersed in water is established. The magnetic vector potential is expressed in the form of series by artificially setting a boundary, and then the mutual impedance calculation formula of the coils immersed in water is derived. In the analysis, the effect of the conductivity of water, the excitation frequency, and the number of turns of the coils are mainly taken into account. In addition, the variation of the mutual impedance of coils in air and water with axial displacement is also compared. The models can be used to analyze the coil coupling characteristics in the presence of conductive medium, which is helpful for the design process. Full article
(This article belongs to the Special Issue Magnetically Coupled Wireless Power Transfer System)
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Article
New Photomagnetic Ionic Salts Based on [MoIV(CN)8]4− and [WIV(CN)8]4− Anions
Magnetochemistry 2021, 7(7), 97; https://doi.org/10.3390/magnetochemistry7070097 - 06 Jul 2021
Cited by 7 | Viewed by 1225
Abstract
Three new ionic salts containing [M(CN)8]4− (M = MoIV and WIV) were prepared using large complex cations based on a non-conventional motif built with the tris(2-aminoethyl)amine (noted hereafter tren) ligand, [{M’(tren)}3(μ-tren)]6+ (M’ = Cu [...] Read more.
Three new ionic salts containing [M(CN)8]4− (M = MoIV and WIV) were prepared using large complex cations based on a non-conventional motif built with the tris(2-aminoethyl)amine (noted hereafter tren) ligand, [{M’(tren)}3(μ-tren)]6+ (M’ = CuII and ZnII). The crystal structures of the three compounds show that the atomic arrangement is formed by relatively isolated anionic and cationic entities. The three compounds were irradiated with a blue light at low temperature, and show a significant photomagnetic effect. The remarkable properties of these compounds are (i) the long-lived photomagnetic metastable states for the [Mo(CN)8]4−-based compounds well above 200 K and (ii) the rare efficient photomagnetic properties of the [W(CN)8]4−-based compound. These photomagnetic properties are compared with the singlet-triplet conversion recently reported for the K4[Mo(CN)8]·2H2O compound. Full article
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Article
In Quest of Molecular Materials for Quantum Cellular Automata: Exploration of the Double Exchange in the Two-Mode Vibronic Model of a Dimeric Mixed Valence Cell
Magnetochemistry 2021, 7(5), 66; https://doi.org/10.3390/magnetochemistry7050066 - 12 May 2021
Cited by 5 | Viewed by 962
Abstract
In this article, we apply the two-mode vibronic model to the study of the dimeric molecular mixed-valence cell for quantum cellular automata. As such, we consider a multielectron mixed valence binuclear d2d1–type cluster, in which the double exchange, [...] Read more.
In this article, we apply the two-mode vibronic model to the study of the dimeric molecular mixed-valence cell for quantum cellular automata. As such, we consider a multielectron mixed valence binuclear d2d1–type cluster, in which the double exchange, as well as the Heisenberg-Dirac-Van Vleck exchange interactions are operative, and also the local (“breathing”) and intercenter vibrational modes are taken into account. The calculations of spin-vibronic energy spectra and the “cell-cell”-response function are carried out using quantum-mechanical two-mode vibronic approach based on the numerical solution of the dynamic vibronic problem. The obtained results demonstrate a possibility of combining the function of molecular QCA with that of spin switching in one electronic device and are expected to be useful from the point of view of the rational design of such multifunctional molecular electronic devices. Full article
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Article
Tuning of Structural, Dielectric, and Electronic Properties of Cu Doped Co–Zn Ferrite Nanoparticles for Multilayer Inductor Chip Applications
Magnetochemistry 2021, 7(4), 53; https://doi.org/10.3390/magnetochemistry7040053 - 14 Apr 2021
Cited by 36 | Viewed by 1522
Abstract
Herein, we report the synthesis of nanoparticles and doping of Cu-doped Co–Zn ferrites using the auto-combustion sol–gel synthesis technique. X-ray diffraction studies confirmed the single-phase structure of the samples with space group Fd3m and crystallite size in the range of 20.57–32.69 [...] Read more.
Herein, we report the synthesis of nanoparticles and doping of Cu-doped Co–Zn ferrites using the auto-combustion sol–gel synthesis technique. X-ray diffraction studies confirmed the single-phase structure of the samples with space group Fd3m and crystallite size in the range of 20.57–32.69 nm. Transmission electron microscopy micrographs and selected area electron diffraction patterns confirmed the polycrystalline nature of the ferrite nanoparticles. Energy-dispersive X-ray spectroscopy revealed the elemental composition in the absence of any impurity phases. Fourier-transform infrared studies showed the presence of two prominent peaks at approximately 420 cm−1 and 580 cm−1, showing metal–oxygen stretching and the formation of ferrite composite. X-ray photoelectron spectroscopy was employed to determine the oxidation states of Fe, Co, Zn, and Cu and O vacancies based on which cationic distributions at tetrahedral and octahedral sites are proposed. Dielectric spectroscopy showed that the samples exhibit Maxwell–Wagner interfacial polarization, which decreases as the frequency of the applied field increases. The dielectric loss of the samples was less than 1, confirming that the samples can be used for the fabrication of multilayer inductor chips. The ac conductivity of the samples increased with increasing doping and with frequency, and this has been explained by the hopping model. The hysteresis loops revealed that coercivity decreases slightly with doping, while the highest saturation magnetization of 55.61 emu/g was obtained when x = 0.1. The magnetic anisotropic constant was found to be less than 0.5, which suggests that the samples exhibit uniaxial anisotropy rather than cubic anisotropy. The squareness ratio indicates that the samples are useful in high-frequency applications. Full article
(This article belongs to the Special Issue Advances in Fine Particle Magnetism and Bio-Magnetic Materials)
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Article
Coexistence of Spin Canting and Metamagnetism in a One-Dimensional Mn(II) Compound Bridged by Alternating Double End-to-End and Double End-On Azido Ligands and the Analog Co(II) Compound
Magnetochemistry 2021, 7(4), 50; https://doi.org/10.3390/magnetochemistry7040050 - 06 Apr 2021
Cited by 6 | Viewed by 1289
Abstract
Two new compounds of general formula [M(N3)2(dmbpy)] in which dmbpy = 5,5′-dimethyl-2,2′-bipyridine, and M = Mn(II) or Co(II), have been solvothermally synthesized and characterized structurally and magnetically. The structures consist of zig-zag polymeric chains with alternating bis-µ(azide-N1)2M [...] Read more.
Two new compounds of general formula [M(N3)2(dmbpy)] in which dmbpy = 5,5′-dimethyl-2,2′-bipyridine, and M = Mn(II) or Co(II), have been solvothermally synthesized and characterized structurally and magnetically. The structures consist of zig-zag polymeric chains with alternating bis-µ(azide-N1)2M and bis-µ(azide-N1,N3)2M units in which the cis-octahedrally based coordination geometry is completed by the N,N’-chelating ligand dmbpy. The molecular structures are basically the same for each metal. The Mn(II) compound has a slightly different packing mode compared to the Co(II) compound, resulting from their different space groups. Interestingly, relatively weak interchain interactions are present in both compounds and this originates from π–π stacking between the dmbpy rings. The magnetic properties of both compounds have been investigated down to 2 K. The measurements indicate that the manganese compound shows spin-canted antiferromagnetic ordering with a Néel temperature of TN = 3.4 K and further, a field-induced magnetic transition of metamagnetism at temperatures below the TN. This finding affords the first example of an 1D Mn(II) compound with alternating double end-on (EO) and double end-to-end (EE) azido-bridged ligands, showing the coexistence of spin canting and metamagnetism. The cobalt compound shows a weak ferromagnetism resulting from a spin-canted antiferromagnetism and long-range magnetic ordering with a critical temperature, TC = 16.2 K. Full article
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Article
Finding the Limits of Magnetic Hyperthermia on Core-Shell Nanoparticles Fabricated by Physical Vapor Methods
Magnetochemistry 2021, 7(4), 49; https://doi.org/10.3390/magnetochemistry7040049 - 02 Apr 2021
Cited by 7 | Viewed by 1192
Abstract
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) [...] Read more.
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-shell structures are gaining ground. Herein we present a study on the effect of particle morphology on heating efficiency. More specifically, we use zero waste impact methods for the synthesis of metal/metal oxide Fe/Fe3O4 nanoparticles in both spherical and cubic shapes, which present an interesting venue for understanding how spin coupling across interfaces and also finite size effects may influence the magnetic response. We show that these particles can generate sufficient heat (hundreds of watts per gram) to drive hyperthermia applications, whereas faceted nanoparticles demonstrate superior heating capabilities than spherical nanoparticles of similar size. Full article
(This article belongs to the Special Issue Advances in Multifunctional Magnetic Nanomaterials)
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Article
Gd3+ Doped CoFe2O4 Nanoparticles for Targeted Drug Delivery and Magnetic Resonance Imaging
Magnetochemistry 2021, 7(4), 47; https://doi.org/10.3390/magnetochemistry7040047 - 30 Mar 2021
Cited by 7 | Viewed by 1100
Abstract
Nanoparticles of CoGdxFe2 − xO4 (x = 0%, 25%, 50%) synthesized via sol–gel auto combustion technique and encapsulated within a polymer (Eudragit E100) shell containing curcumin by single emulsion solvent evaporation technique were formulated in this study. [...] Read more.
Nanoparticles of CoGdxFe2 − xO4 (x = 0%, 25%, 50%) synthesized via sol–gel auto combustion technique and encapsulated within a polymer (Eudragit E100) shell containing curcumin by single emulsion solvent evaporation technique were formulated in this study. Testing of synthesized nanoparticles was carried out by using different characterization techniques, to investigate composition, crystallinity, size, morphology, surface charge, functional groups and magnetic properties of the samples. The increased hydrophilicity resulted in sustained drug release of 90.6% and 95% for E1(CoGd0.25Fe1.75O4) and E2(CoGd0.50Fe1.5O4), respectively, over a time span of 24 h. The relaxivities of the best-chosen samples were measured by using a 3T magnetic resonance imaging (MRI) machine, and a high r2/r1 ratio of 43.64 and 23.34 for composition E1(CoGd0.25Fe1.75O4) and E2(CoGd0.50Fe1.5O4) suggests their ability to work as a better T2 contrast agent. Thus, these novel synthesized nanostructures cannot only enable MRI diagnosis but also targeted drug delivery. Full article
(This article belongs to the Special Issue Biomedical Application of Magnetic Nanoparticles in 2022)
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Article
Phase Transformation of Kaolin-Ground Granulated Blast Furnace Slag from Geopolymerization to Sintering Process
Magnetochemistry 2021, 7(3), 32; https://doi.org/10.3390/magnetochemistry7030032 - 26 Feb 2021
Cited by 10 | Viewed by 1288
Abstract
The main objective of this research was to investigate the influence of curing temperature on the phase transformation, mechanical properties, and microstructure of the as-cured and sintered kaolin-ground granulated blast furnace slag (GGBS) geopolymer. The curing temperature was varied, giving four different conditions; [...] Read more.
The main objective of this research was to investigate the influence of curing temperature on the phase transformation, mechanical properties, and microstructure of the as-cured and sintered kaolin-ground granulated blast furnace slag (GGBS) geopolymer. The curing temperature was varied, giving four different conditions; namely: Room temperature, 40, 60, and 80 °C. The kaolin-GGBS geopolymer was prepared, with a mixture of NaOH (8 M) and sodium silicate. The samples were cured for 14 days and sintered afterwards using the same sintering profile for all of the samples. The sintered kaolin-GGBS geopolymer that underwent the curing process at the temperature of 60 °C featured the highest strength value: 8.90 MPa, and a densified microstructure, compared with the other samples. The contribution of the Na2O in the geopolymerization process was as a self-fluxing agent for the production of the geopolymer ceramic at low temperatures. Full article
(This article belongs to the Special Issue Advances in Amorphous and Nanocrystalline Magnetic Materials)
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Article
Geometrically Constrained Skyrmions
Magnetochemistry 2021, 7(2), 26; https://doi.org/10.3390/magnetochemistry7020026 - 12 Feb 2021
Cited by 8 | Viewed by 1188
Abstract
Skyrmions are chiral swirling magnetization structures with nanoscale size. These structures have attracted considerable attention due to their topological stability and promising applicability in nanodevices, since they can be displaced with spin-polarized currents. However, for the comprehensive implementation of skyrmions in devices, it [...] Read more.
Skyrmions are chiral swirling magnetization structures with nanoscale size. These structures have attracted considerable attention due to their topological stability and promising applicability in nanodevices, since they can be displaced with spin-polarized currents. However, for the comprehensive implementation of skyrmions in devices, it is imperative to also attain control over their geometrical position. Here we show that, through thickness modulations introduced in the host material, it is possible to constrain three-dimensional skyrmions to desired regions. We investigate skyrmion structures in rectangular FeGe platelets with micromagnetic finite element simulations. First, we establish a phase diagram of the minimum-energy magnetic state as a function of the external magnetic field strength and the film thickness. Using this understanding, we generate preferential sites for skyrmions in the material by introducing dot-like “pockets” of reduced film thickness. We show that these pockets can serve as pinning centers for the skyrmions, thus making it possible to obtain a geometric control of the skyrmion position. This control allows for stabilization of skyrmions at positions and in configurations that they would otherwise not attain. Our findings may have implications for technological applications in which skyrmions are used as units of information that are displaced along racetrack-type shift register devices. Full article
(This article belongs to the Special Issue Recent Advances in Nanomagnetism)
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Article
Evaluation of the Effect of Silica Fume on Amorphous Fly Ash Geopolymers Exposed to Elevated Temperature
Magnetochemistry 2021, 7(1), 9; https://doi.org/10.3390/magnetochemistry7010009 - 06 Jan 2021
Cited by 23 | Viewed by 2182
Abstract
The properties of amorphous geopolymer with silica fume addition after heat treatment was rarely reported in the geopolymer field. Geopolymer was prepared by mixing fly ash and alkali activator. The silica fume was added in 2% and 4% by weight. The geopolymer samples [...] Read more.
The properties of amorphous geopolymer with silica fume addition after heat treatment was rarely reported in the geopolymer field. Geopolymer was prepared by mixing fly ash and alkali activator. The silica fume was added in 2% and 4% by weight. The geopolymer samples were cured at room temperature for 28 days before exposed to an elevated temperature up to 1000 °C. The incorporation of 2% silica fume did not cause significant improvement in the compressive strength of unexposed geopolymer. Higher silica fume content of 4% reduced the compressive strength of the unexposed geopolymer. When subjected to elevated temperature, geopolymer with 2% silica fume retained higher compressive strength at 1000 °C. The addition of silica fume in fly ash geopolymer caused a lower degree of shrinkage and expansion, as compared to geopolymer without the addition of silica fume. Crystalline phases of albite and magnetite were formed in the geopolymer at 1000 °C. Full article
(This article belongs to the Special Issue Advances in Amorphous and Nanocrystalline Magnetic Materials)
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Article
The Microstructural Model of the Ferromagnetic Material Behavior in an External Magnetic Field
Magnetochemistry 2021, 7(1), 7; https://doi.org/10.3390/magnetochemistry7010007 - 01 Jan 2021
Cited by 7 | Viewed by 1325
Abstract
In this paper, the behavior of a ferromagnetic material is considered in the framework of microstructural modeling. The equations describing the behavior of such material in the magnetic field, are constructed based on minimization of total magnetic energy with account of limitations imposed [...] Read more.
In this paper, the behavior of a ferromagnetic material is considered in the framework of microstructural modeling. The equations describing the behavior of such material in the magnetic field, are constructed based on minimization of total magnetic energy with account of limitations imposed on the spontaneous magnetization vector and scalar magnetic potential. This conditional extremum problem is reduced to the unconditional extremum problem using the Lagrange multiplier. A variational (weak) formulation is written down and linearization of the obtained equations is carried out. Based on the derived relations a solution of a two-dimensional problem of magnetization of a unit cell (a grain of a polycrystal or a single crystal of a ferromagnetic material) is developed using the finite element method. The appearance of domain walls is demonstrated, their thickness is determined, and the history of their movement and collision is described. The graphs of distributions of the magnetization vector in domains and in domain walls in the external magnetic field directed at different angles to the anisotropy axis are constructed and the magnetization curves for a macrospecimen are plotted. The results obtained in the present paper (the thickness of the domain wall, the formation of a 360-degree wall) are in agreement with the ones available in the current literature. Full article
(This article belongs to the Special Issue Advances in Computational Electromagnetics)
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Article
Fabrication of Dy2O3 Transparent Ceramics by Vacuum Sintering Using Precipitated Powders
Magnetochemistry 2021, 7(1), 6; https://doi.org/10.3390/magnetochemistry7010006 - 28 Dec 2020
Cited by 10 | Viewed by 1685
Abstract
As a kind of promising material for a Faraday isolator used in the visible and near infrared range, Dy2O3 transparent ceramics were prepared by vacuum sintering from the nano-powders synthesized by the liquid precipitation method using ammonium hydrogen carbonate as [...] Read more.
As a kind of promising material for a Faraday isolator used in the visible and near infrared range, Dy2O3 transparent ceramics were prepared by vacuum sintering from the nano-powders synthesized by the liquid precipitation method using ammonium hydrogen carbonate as precipitant with no sintering aids. The synthesized precursor was calcinated at 950 °C–1150 °C for 4 h in air. The influences of the calcination temperature on the morphologies and phase composition of Dy2O3 powders were characterized. It is found that the Dy2O3 powder calcinated at 1000 °C for 4 h is superior for the fabrication of Dy2O3 ceramics. The Dy2O3 transparent ceramic sample prepared by vacuum sintering at 1850 °C for 10 h, and subsequently with air annealing at 1400 °C for 10 h, from the 1000 °C-calcined Dy2O3 powders, presents the best optical quality. The values of in-line transmittance of the optimal ceramic specimen with the thickness of 1.0 mm are 75.3% at 2000 nm and 67.9% at 633 nm. The Verdet constant of Dy2O3 ceramics was measured to be −325.3 ± 1.9 rad/(T·m) at 633 nm, about 2.4 times larger than that of TGG (Tb3Ga5O12) single crystals. Full article
(This article belongs to the Special Issue Magneto-Optical Ceramics)
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Article
Fabrication and Magneto-Optical Property of (Dy0.7Y0.25La0.05)2O3 Transparent Ceramics by PLSH Technology
Magnetochemistry 2020, 6(4), 70; https://doi.org/10.3390/magnetochemistry6040070 - 15 Dec 2020
Cited by 9 | Viewed by 998
Abstract
(Dy0.7Y0.25La0.05)2O3 magneto-optical transparent ceramics were successfully fabricated by pressureless sintering in reductive H2 atmosphere (PLSH). The raw powder of (Dy0.7Y0.25La0.05)2O3 was synthesized by a [...] Read more.
(Dy0.7Y0.25La0.05)2O3 magneto-optical transparent ceramics were successfully fabricated by pressureless sintering in reductive H2 atmosphere (PLSH). The raw powder of (Dy0.7Y0.25La0.05)2O3 was synthesized by a modified self-propagating high-temperature synthesis (SHS) and sintered to transparent ceramics at 1400–1600 °C in a flowing H2 atmosphere, showing good sinterability of the as-synthesized raw powder. The magneto-optical Verdet constant of (Dy0.7Y0.25La0.05)2O3 transparent ceramics was measured to be −191.57 rad/(T·m) at a wavelength of 632.8 nm. In this magneto-optical material of (Dy0.7Y0.25La0.05)2O3, relative cheaper Dy and Y were used to replace Tb, and the low cost and good magneto-optical property showed the advantage of application on Faraday isolators (FIs) and Faraday rotators (FRs). Full article
(This article belongs to the Special Issue Magneto-Optical Ceramics)
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Article
Fabrication and Magneto-Optical Properties of Yb2O3 Based Ceramics
Magnetochemistry 2020, 6(4), 63; https://doi.org/10.3390/magnetochemistry6040063 - 16 Nov 2020
Cited by 12 | Viewed by 1203
Abstract
Transparent ceramics based on ytterbium oxide have been successfully produced by vacuum sintering of self-propagating high-temperature synthesized powders with use of a La2O3 sintering aid. Phase composition and microstructure of the initial powders were studied by X-ray diffraction analysis and [...] Read more.
Transparent ceramics based on ytterbium oxide have been successfully produced by vacuum sintering of self-propagating high-temperature synthesized powders with use of a La2O3 sintering aid. Phase composition and microstructure of the initial powders were studied by X-ray diffraction analysis and scanning electron microscopy. It was found that addition of 5 mol.% of La2O3 does not cause formation of secondary phases in the Yb2O3 powders. The 4% La:Yb2O3 ceramics showed the best in-line transmittance of 73% at a wavelength of 2 μm among the studied samples. Dependence of the Verdet constant on wavelength was investigated in the range of 0.4–2 μm. The most promising finding is use of the obtained material as Faraday isolators in the wavelength region of ~1.5 μm, where there are no absorption bands, and the Verdet constant is 8.6 rad/(T*m). Full article
(This article belongs to the Special Issue Magneto-Optical Ceramics)
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Article
Ten-Coordinate Lanthanide [Ln(HL)(L)] Complexes (Ln = Dy, Ho, Er, Tb) with Pentadentate N3O2-Type Schiff-Base Ligands: Synthesis, Structure and Magnetism
Magnetochemistry 2020, 6(4), 60; https://doi.org/10.3390/magnetochemistry6040060 - 13 Nov 2020
Cited by 5 | Viewed by 1688
Abstract
A series of five neutral mononuclear lanthanide complexes [Ln(HL)(L)] (Ln = Dy3+, Ho3+ Er3+ and Tb3+) with rigid pentadentate N3O2-type Schiff base ligands, H2LH (1-Dy, 3-Ho, 4-Er [...] Read more.
A series of five neutral mononuclear lanthanide complexes [Ln(HL)(L)] (Ln = Dy3+, Ho3+ Er3+ and Tb3+) with rigid pentadentate N3O2-type Schiff base ligands, H2LH (1-Dy, 3-Ho, 4-Er and 6-Tb complexes) or H2LOCH3, (2-Dy complex) has been synthesized by reaction of two equivalents of 1,1′-(pyridine-2,6-diyl)bis(ethan-1-yl-1-ylidene))dibenzohydrazine (H2LH, [H2DAPBH]) or 1,1′-(pyridine-2,6-diyl)bis(ethan-1-yl-1-ylidene))di-4-methoxybenzohydrazine (H2LOCH3, [H2DAPMBH]) with common lanthanide salts. The terbium complex [Tb(LH)(NO3)(H2O)2](DME)2 (5-Tb) with one ligand H2LH was also obtained and characterized. Single crystal X-ray analysis shows that complexes 14 have the composition {[Ln3+(HL)(L)2−] solv} and similar molecular structures. In all the compounds, the central Ln3+ ion is chelated by two interlocked pentadentate ligands resulting in the coordination number of ten. Each lanthanide ion is coordinated by six nitrogen atoms and four oxygen atoms of the two N3O2 chelating groups forming together a distorted bicapped square antiprismatic polyhedron N6O4 with two capping pyridyl N atoms in the apical positions. The ac magnetic measurements reveal field-induced single-molecule magnet (SMM) behavior of the two dysprosium complexes (with barriers of Ueff = 29 K at 800 Oe in 1-Dy and Ueff = 70 K at 300 Oe in 2-Dy) and erbium complex (Ueff = 87 K at 1500 Oe in 4-Er); complex 3-Ho with a non-Kramers Ho3+ ion is SMM-silent. Although 2-Dy differs from 1-Dy only by a distant methoxy-group in the phenyl ring of the ligand, their dynamic magnetic properties are markedly different. This feature can be due to the difference in long-range contributions (beyond the first coordination sphere) to the crystal-field (CF) potential of 4f electrons of Dy3+ ion that affects magnetic characteristics of the ground and excited CF states. Magnetic behavior and the electronic structure of Ln3+ ions of 14 complexes are analyzed in terms of CF calculations. Full article
(This article belongs to the Section Magnetic Materials)
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Article
Fluctuation Effects of Magnetohydrodynamic Micro-Vortices on Odd Chirality in Magnetoelectrolysis
Magnetochemistry 2020, 6(3), 43; https://doi.org/10.3390/magnetochemistry6030043 - 10 Sep 2020
Cited by 8 | Viewed by 923
Abstract
The magnetic field dependence of chiral surface formation was investigated in magnetoelectrodeposition (MED) and magnetoelectrochemical etching (MEE) of copper films. The MED and MEE was conducted in magnetic fields of up to 5 T, which were parallel or antiparallel to the ionic currents. [...] Read more.
The magnetic field dependence of chiral surface formation was investigated in magnetoelectrodeposition (MED) and magnetoelectrochemical etching (MEE) of copper films. The MED and MEE was conducted in magnetic fields of up to 5 T, which were parallel or antiparallel to the ionic currents. The MED films prepared in high magnetic fields of 5 and 3 T exhibited odd chirality for magnetic field polarity, as expected on the basis of the magnetohydrodynamic (MHD) vortex model. However, the films prepared in the lower fields of 2.5 and 2 T exhibited breaking of odd chirality. Similar magnetic field dependence was observed in the surface chirality of MEE films. These results imply that the fluctuation in the self-organized state of micro-MHD vortices is responsible for the breaking of odd chirality. Full article
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Article
Redox Modulation of Field-Induced Tetrathiafulvalene-Based Single-Molecule Magnets of Dysprosium
Magnetochemistry 2020, 6(3), 34; https://doi.org/10.3390/magnetochemistry6030034 - 19 Aug 2020
Cited by 5 | Viewed by 1101
Abstract
The complexes [Dy2(tta)6(H2SQ)] (Dy-H2SQ) and [Dy2(tta)6(Q)]·2CH2Cl2 (Dy-Q) (tta = 2-thenoyltrifluoroacetonate) were obtained from the coordination reaction of the Dy(tta)3·2H [...] Read more.
The complexes [Dy2(tta)6(H2SQ)] (Dy-H2SQ) and [Dy2(tta)6(Q)]·2CH2Cl2 (Dy-Q) (tta = 2-thenoyltrifluoroacetonate) were obtained from the coordination reaction of the Dy(tta)3·2H2O units with the 2,2′-benzene-1,4-diylbis(6-hydroxy-4,7-di-tert-butyl-1,3-benzodithiol-2-ylium-5-olate ligand (H2SQ) and its oxidized form 2,2′-cyclohexa-2,5-diene-1,4-diylidenebis(4,7-di-tert-butyl-1,3-benzodithiole-5,6-dione (Q). The chemical oxidation of H2SQ in Q induced an increase in the coordination number from 7 to 8 around the DyIII ions and by consequence a modulation of the field-induced Single-Molecule Magnet behavior. Computational results rationalized the magnetic properties of each of the dinuclear complexes. Full article
(This article belongs to the Special Issue From Magnetic Anisotropy to Molecular Magnets: Theory and Experiments)
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Spin Cross-Over (SCO) Anionic Fe(II) Complexes Based on the Tripodal Ligand Tris(2-pyridyl)ethoxymethane
Magnetochemistry 2020, 6(2), 26; https://doi.org/10.3390/magnetochemistry6020026 - 07 Jun 2020
Cited by 10 | Viewed by 1773
Abstract
Reactions of Fe(II) with the tripodal chelating ligand 1,1,1-tris(2-pyridyl)ethoxymethane (py3C-OEt) and (NCE) co-ligands (E = S, Se, BH3) give a series of mononuclear complexes formulated as [Fe(py3C-OEt)2][Fe(py3C-OEt)(NCE)3]2·2CH3 [...] Read more.
Reactions of Fe(II) with the tripodal chelating ligand 1,1,1-tris(2-pyridyl)ethoxymethane (py3C-OEt) and (NCE) co-ligands (E = S, Se, BH3) give a series of mononuclear complexes formulated as [Fe(py3C-OEt)2][Fe(py3C-OEt)(NCE)3]2·2CH3CN, with E = S (1) and BH3 (2). These compounds are the first Fe(II) spin cross-over (SCO) complexes based on the tripodal ligand tris(2-pyridyl)ethoxymethane and on the versatile co-ligands (NCS) and (NCBH3). The crystal structure reveals discrete monomeric isomorph structures formed by a cationic [Fe(py3C-OEt)2]2+ complex and by two equivalent anionic [Fe(py3C-OEt)(NCE)3] complexes. In the cations the Fe(II) is facially coordinated by two py3C-OEt tripodal ligands whereas in the anion the three nitrogen atoms of the tripodal ligand are facially coordinated and the N-donor atoms of the three (NCE) co-ligands occupy the remaining three positions to complete the distorted octahedral environment of the Fe(II) centre. The magnetic studies show the presence of gradual SCO for both complexes: A one-step transition around 205 K for 1 and a two-step transition for compound 2, centered around 245 K and 380 K. Full article
(This article belongs to the Special Issue Feature Papers in Magnetochemistry)
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Article
Saturation of Specific Absorption Rate for Soft and Hard Spinel Ferrite Nanoparticles Synthesized by Polyol Process
Magnetochemistry 2020, 6(2), 23; https://doi.org/10.3390/magnetochemistry6020023 - 29 May 2020
Cited by 16 | Viewed by 1786
Abstract
Spinel ferrite nanoparticles represent a class of magnetic nanoparticles (MNPs) with enormous potential in magnetic hyperthermia. In this study, we investigated the magnetic and heating properties of spinel soft NiFe2O4, MnFe2O4, and hard CoFe2 [...] Read more.
Spinel ferrite nanoparticles represent a class of magnetic nanoparticles (MNPs) with enormous potential in magnetic hyperthermia. In this study, we investigated the magnetic and heating properties of spinel soft NiFe2O4, MnFe2O4, and hard CoFe2O4 MNPs of comparable sizes (12–14 nm) synthesized by the polyol method. Similar to the hard ferrite, which predominantly is ferromagnetic at room temperature, the soft ferrite MNPs display a non-negligible coercivity (9–11 kA/m) arising from the strong interparticle interactions. The heating capabilities of ferrite MNPs were evaluated in aqueous media at concentrations between 4 and 1 mg/mL under alternating magnetic fields (AMF) amplitude from 5 to 65 kA/m at a constant frequency of 355 kHz. The hyperthermia data revealed that the SAR values deviate from the quadratic dependence on the AMF amplitude in all three cases in disagreement with the Linear Response Theory. Instead, the SAR values display a sigmoidal dependence on the AMF amplitude, with a maximum heating performance measured for the cobalt ferrites (1780 W/gFe+Co), followed by the manganese ferrites (835 W/gFe+Mn), while the nickel ferrites (540 W/gFe+Ni) present the lowest values of SAR. The heating performances of the ferrites are in agreement with their values of coercivity and saturation magnetization. Full article
(This article belongs to the Special Issue Magnetic Nanoparticles 2020)
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Article
High Yield Synthesis and Application of Magnetite Nanoparticles (Fe3O4)
Magnetochemistry 2020, 6(2), 22; https://doi.org/10.3390/magnetochemistry6020022 - 15 May 2020
Cited by 8 | Viewed by 1689
Abstract
Magnetite nanoparticles (Fe3O4), average particle size of 12.9 nm, were synthesized de novo from ferrous and ferric iron salt solutions (total iron salt concentration of 3.8 mM) using steady-state headspace NH3(g), 3.3% v/v, at [...] Read more.
Magnetite nanoparticles (Fe3O4), average particle size of 12.9 nm, were synthesized de novo from ferrous and ferric iron salt solutions (total iron salt concentration of 3.8 mM) using steady-state headspace NH3(g), 3.3% v/v, at room temperature and pressure, without mechanical agitation, resulting in >99.9% yield. Nanoparticles size distributions were based on enumeration of TEM images and chemical compositions analyzed by: XRD, EDXRF, and FT-IR; super-paramagnetic properties were analyzed by magnetization saturation (74 emu/g). Studies included varying headspace [NH3(g)] (1.6, 3.3, 8.4% v/v), and total iron concentrations (1.0 mM, 3.8 mM, 10.0 mM, and >>10 mM). An application of the unmodified synthesized magnetite nanoparticles included analyses of tetracycline’s (50, 100, 200, 300, and 400 ppb) in aqueous, which was compared to the same tetracycline concentrations prepared in aqueous synthesis suspension with >97% extraction, analyzed with LC-MS/MS. Full article
(This article belongs to the Section Magnetic Nanospecies)
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Article
Dysprosium Single-Molecule Magnets Involving 1,10-Phenantroline-5,6-dione Ligand
Magnetochemistry 2020, 6(2), 19; https://doi.org/10.3390/magnetochemistry6020019 - 15 Apr 2020
Cited by 7 | Viewed by 1497
Abstract
The two mononuclear complexes of the formula [Dy(tta)3(L)] (1) and [Dy(hfac)3(L)] (2) (where tta- = 2-thenoytrifluoroacetylacetonate and hfac- = 1,1,1,5,5,5-hexafluoroacetylacetonate) were obtained from the coordination reaction of the Dy(tta) [...] Read more.
The two mononuclear complexes of the formula [Dy(tta)3(L)] (1) and [Dy(hfac)3(L)] (2) (where tta- = 2-thenoytrifluoroacetylacetonate and hfac- = 1,1,1,5,5,5-hexafluoroacetylacetonate) were obtained from the coordination reaction of the Dy(tta)3·2H2O or Dy(hfac)3·2H2O units with the 1,10-phenantroline-5,6-dione ligand (L). Their structures have been determined by X-ray diffraction studies on single crystals, and they revealed a supramolecular assembly of tetramers through σ-π interactions. Both complexes displayed a Single-Molecule Magnet (SMM) behavior without an external applied magnetic field. Magnetic relaxation happened through Orbach, Raman and Quantum Tunneling of the Magnetization (QTM). Wavefunction theory calculations were realized to rationalize the magnetic properties. Full article
(This article belongs to the Special Issue Feature Papers in Magnetochemistry)
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Article
Effect of Terbium Ion Substitution in Inverse Spinel Nickel Ferrite: Structural and Magnetic Study
Magnetochemistry 2020, 6(1), 14; https://doi.org/10.3390/magnetochemistry6010014 - 10 Mar 2020
Cited by 10 | Viewed by 1763
Abstract
Doping rare-earth ions into spinel ferrites can alter their electrical and magnetic properties. The present study delineates the structure–property relationship of the effect of rare-earth terbium doping in NiFe2O4 ferrite. X-ray diffraction analysis (XRD) showed unit cell lattice expansion with [...] Read more.
Doping rare-earth ions into spinel ferrites can alter their electrical and magnetic properties. The present study delineates the structure–property relationship of the effect of rare-earth terbium doping in NiFe2O4 ferrite. X-ray diffraction analysis (XRD) showed unit cell lattice expansion with increased Tb3+ content. The Fourier transform infrared spectroscopy (FTIR) results indicate preferential occupancy of Tb3+ at the octahedral B site. The magnetic parameters derived from room temperature hysteresis loops where both the saturation magnetization, Ms, and coercivity, Hc, value decreased with the Tb3+ substitution and reached a minimum value of Ms ~30.6 emu/g at x = 0.1 and Hc ~102 Oe at x = 0.075. The temperature-dependent magnetocrystalline anisotropy derived from the magnetic isotherm was observed to be the highest for x = 0.1 at 5 K with the value K1 ~1.09 × 106 J/m3. The Tb3+ doping also resulted in the Curie temperature reduction from 938 K at x = 0.0 to 899 K at x = 0.1. Full article
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Article
Design, Characterization and Molecular Modeling of New Fluorinated Paramagnetic Contrast Agents for Dual 1H/19F MRI
Magnetochemistry 2020, 6(1), 8; https://doi.org/10.3390/magnetochemistry6010008 - 11 Feb 2020
Cited by 6 | Viewed by 1447
Abstract
One major goal in medical imaging is the elaboration of more efficient contrast agents (CAs). Those agents need to be optimized for the detection of affected tissues such as cancers or tumors while decreasing the injected quantity of agents. The paramagnetic contrast agents [...] Read more.
One major goal in medical imaging is the elaboration of more efficient contrast agents (CAs). Those agents need to be optimized for the detection of affected tissues such as cancers or tumors while decreasing the injected quantity of agents. The paramagnetic contrast agents containing fluorine atoms can be used for both proton and fluorine magnetic resonance imaging (MRI), and they open the possibility of simultaneously mapping the anatomy using 1H MRI and accurately locating the agents using 19F MRI. One of the challenges in this domain is to synthesize molecules containing several chemically equivalent fluorine atoms with relatively short relaxation times to allow the recording of 19F MR images in good conditions. With that aim, we propose to prepare a CA containing a paramagnetic center and nine chemically equivalent fluorine atoms using a cycloaddition reaction between two building blocks. These fluorinated contrast agents are characterized by 19F NMR, showing differences in the fluorine relaxation times T1 and T2 depending on the lanthanide ion. To complement the experimental results, molecular dynamics simulations are performed to shed light on the 3D-structure of the molecules in order to estimate the distance between the lanthanide ion and the fluorine atoms. Full article
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Review

Review
Basic Principles and Recent Advances in Magnetic Cell Separation
Magnetochemistry 2022, 8(1), 11; https://doi.org/10.3390/magnetochemistry8010011 - 14 Jan 2022
Cited by 6 | Viewed by 1810
Abstract
Magnetic cell separation has become a key methodology for the isolation of target cell populations from biological suspensions, covering a wide spectrum of applications from diagnosis and therapy in biomedicine to environmental applications or fundamental research in biology. There now exists a great [...] Read more.
Magnetic cell separation has become a key methodology for the isolation of target cell populations from biological suspensions, covering a wide spectrum of applications from diagnosis and therapy in biomedicine to environmental applications or fundamental research in biology. There now exists a great variety of commercially available separation instruments and reagents, which has permitted rapid dissemination of the technology. However, there is still an increasing demand for new tools and protocols which provide improved selectivity, yield and sensitivity of the separation process while reducing cost and providing a faster response. This review aims to introduce basic principles of magnetic cell separation for the neophyte, while giving an overview of recent research in the field, from the development of new cell labeling strategies to the design of integrated microfluidic cell sorters and of point-of-care platforms combining cell selection, capture, and downstream detection. Finally, we focus on clinical, industrial and environmental applications where magnetic cell separation strategies are amongst the most promising techniques to address the challenges of isolating rare cells. Full article
(This article belongs to the Special Issue Magnetic Cell Separation)
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Review
Green Synthesis of Metal and Metal Oxide Nanoparticles: Principles of Green Chemistry and Raw Materials
Magnetochemistry 2021, 7(11), 145; https://doi.org/10.3390/magnetochemistry7110145 - 31 Oct 2021
Cited by 19 | Viewed by 3028
Abstract
Increased request for metal and metal oxide nanoparticles nanoparticles has led to their large-scale production using high-energy methods with various toxic solvents. This cause environmental contamination, thus eco-friendly “green” synthesis methods has become necessary. An alternative way to synthesize metal nanoparticles includes using [...] Read more.
Increased request for metal and metal oxide nanoparticles nanoparticles has led to their large-scale production using high-energy methods with various toxic solvents. This cause environmental contamination, thus eco-friendly “green” synthesis methods has become necessary. An alternative way to synthesize metal nanoparticles includes using bioresources, such as plants and plant products, bacteria, fungi, yeast, algae, etc. “Green” synthesis has low toxicity, is safe for human health and environment compared to other methods, meaning it is the best approach for obtaining metal and metal oxide nanoparticles. This review reveals 12 principles of “green” chemistry and examples of biological components suitable for “green” synthesis, as well as modern scientific research of eco-friendly synthesis methods of magnetic and metal nanoparticles. Particularly, using extracts of green tea, fruits, roots, leaves, etc., to obtain Fe3O4 NPs. The various precursors as egg white (albumen), leaf and fruit extracts, etc., can be used for the „green” synthesis of spinel magnetic NPs. “Green” nanoparticles are being widely used as antimicrobials, photocatalysts and adsorbents. “Green” magnetic nanoparticles demonstrate low toxicity and high biocompatibility, which allows for their biomedical application, especially for targeted drug delivery, contrast imaging and magnetic hyperthermia applications. The synthesis of silver, gold, platinum and palladium nanoparticles using extracts from fungi, red algae, fruits, etc., has been described. Full article
(This article belongs to the Special Issue Advances in Magnetic Force Microscopy)
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Review
NMR for Single Ion Magnets
Magnetochemistry 2021, 7(7), 96; https://doi.org/10.3390/magnetochemistry7070096 - 04 Jul 2021
Cited by 5 | Viewed by 1547
Abstract
Nuclear Magnetic Resonance is particularly sensitive to the electronic structure of matter and is thus a powerful tool to characterize in-depth the magnetic properties of a system. NMR is indeed increasingly recognized as an ideal tool to add precious structural information for the [...] Read more.
Nuclear Magnetic Resonance is particularly sensitive to the electronic structure of matter and is thus a powerful tool to characterize in-depth the magnetic properties of a system. NMR is indeed increasingly recognized as an ideal tool to add precious structural information for the development of Single Ion Magnets, small complexes that are recently gaining much popularity due to their quantum computing and spintronics applications. In this review, we recall the theoretical principles of paramagnetic NMR, with particular attention to lanthanoids, and we give an overview of the recent advances in this field. Full article
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Review
Magnetotactic Bacteria and Magnetosomes: Basic Properties and Applications
Magnetochemistry 2021, 7(6), 86; https://doi.org/10.3390/magnetochemistry7060086 - 18 Jun 2021
Cited by 16 | Viewed by 2713
Abstract
Magnetotactic bacteria (MTB) belong to several phyla. This class of microorganisms exhibits the ability of magneto-aerotaxis. MTB synthesize biominerals in organelle-like structures called magnetosomes, which contain single-domain crystals of magnetite (Fe3O4) or greigite (Fe3S4) characterized [...] Read more.
Magnetotactic bacteria (MTB) belong to several phyla. This class of microorganisms exhibits the ability of magneto-aerotaxis. MTB synthesize biominerals in organelle-like structures called magnetosomes, which contain single-domain crystals of magnetite (Fe3O4) or greigite (Fe3S4) characterized by a high degree of structural and compositional perfection. Magnetosomes from dead MTB could be preserved in sediments (called fossil magnetosomes or magnetofossils). Under certain conditions, magnetofossils are capable of retaining their remanence for millions of years. This accounts for the growing interest in MTB and magnetofossils in paleo- and rock magnetism and in a wider field of biogeoscience. At the same time, high biocompatibility of magnetosomes makes possible their potential use in biomedical applications, including magnetic resonance imaging, hyperthermia, magnetically guided drug delivery, and immunomagnetic analysis. In this review, we attempt to summarize the current state of the art in the field of MTB research and applications. Full article
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Review
Nonvolatile Voltage Controlled Molecular Spin-State Switching for Memory Applications
Magnetochemistry 2021, 7(3), 37; https://doi.org/10.3390/magnetochemistry7030037 - 11 Mar 2021
Cited by 12 | Viewed by 1688
Abstract
Nonvolatile, molecular multiferroic devices have now been demonstrated, but it is worth giving some consideration to the issue of whether such devices could be a competitive alternative for solid-state nonvolatile memory. For the Fe (II) spin crossover complex [Fe{H2B(pz)2} [...] Read more.
Nonvolatile, molecular multiferroic devices have now been demonstrated, but it is worth giving some consideration to the issue of whether such devices could be a competitive alternative for solid-state nonvolatile memory. For the Fe (II) spin crossover complex [Fe{H2B(pz)2}2(bipy)], where pz = tris(pyrazol-1-yl)-borohydride and bipy = 2,2′-bipyridine, voltage-controlled isothermal changes in the electronic structure and spin state have been demonstrated and are accompanied by changes in conductance. Higher conductance is seen with [Fe{H2B(pz)2}2(bipy)] in the high spin state, while lower conductance occurs for the low spin state. Plausibly, there is the potential here for low-cost molecular solid-state memory because the essential molecular thin films are easily fabricated. However, successful device fabrication does not mean a device that has a practical value. Here, we discuss the progress and challenges yet facing the fabrication of molecular multiferroic devices, which could be considered competitive to silicon. Full article
(This article belongs to the Special Issue Spin Crossover Materials: Towards Applications in Devices)
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Review
Laser Additive Manufacturing of Fe-Based Magnetic Amorphous Alloys
Magnetochemistry 2021, 7(2), 20; https://doi.org/10.3390/magnetochemistry7020020 - 29 Jan 2021
Cited by 11 | Viewed by 1762
Abstract
Fe-based amorphous materials offer new opportunities for magnetic sensors, actuators, and magnetostrictive transducers due to their high saturation magnetostriction (λs = 20–40 ppm) and low coercive field compared with polycrystalline Fe-based alloys, which have high magnetostriction but large coercive fields and [...] Read more.
Fe-based amorphous materials offer new opportunities for magnetic sensors, actuators, and magnetostrictive transducers due to their high saturation magnetostriction (λs = 20–40 ppm) and low coercive field compared with polycrystalline Fe-based alloys, which have high magnetostriction but large coercive fields and Co-based amorphous alloys with small magnetostriction (λs = −3 to −5 ppm). Additive layer manufacturing (ALM) offers a new fabrication technique for more complex net-shaping designs. This paper reviews the two different ALM techniques that have been used to fabricate Fe-based amorphous magnetic materials, including the structural and magnetic properties. Selective laser melting (SLM)—a powder-bed fusion technique—and laser-engineered net shaping (LENS)—a directed energy deposition method—have both been utilised to fabricate amorphous alloys, owing to their high availability and low cost within the literature. Two different scanning strategies have been introduced by using the SLM technique. The first strategy is a double-scanning strategy, which gives rise to maximum relative density of 96% and corresponding magnetic saturation of 1.22 T. It also improved the glassy phase content by an order of magnitude of 47%, as well as improving magnetic properties (decreasing coercivity to 1591.5 A/m and increasing magnetic permeability to around 100 at 100 Hz). The second is a novel scanning strategy, which involves two-step melting: preliminary laser melting and short pulse amorphisation. This increased the amorphous phase fraction to a value of up to 89.6%, and relative density up to 94.1%, and lowered coercivity to 238 A/m. On the other hand, the LENS technique has not been utilised as much as SLM in the production of amorphous alloys owing to its lower geometric accuracy (0.25 mm) and lower surface quality, despite its benefits such as providing superior mechanical properties, controlled composition and microstructure. As a result, it has been commonly used for large parts with low complexity and for repairing them, limiting the production of amorphous alloys because of the size limitation. This paper provides a comprehensive review of these techniques for Fe-based amorphous magnetic materials. Full article
(This article belongs to the Special Issue Soft and Hard Magnetic Materials: Latest Advances and Prospects)
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Review
Lanthanoid-Anilato Complexes and Lattices
Magnetochemistry 2020, 6(4), 71; https://doi.org/10.3390/magnetochemistry6040071 - 15 Dec 2020
Cited by 10 | Viewed by 1525
Abstract
In this review, we describe all the structurally characterized complexes containing lanthanoids (Ln, including La and group 3 metals: Y and Lu) and any anilato-type ligand (3,6-disubstituted-2,5-dihydroxy-1,4-benzoquinone dianion = C6O4X22−). We present all the anilato-Ln compounds [...] Read more.
In this review, we describe all the structurally characterized complexes containing lanthanoids (Ln, including La and group 3 metals: Y and Lu) and any anilato-type ligand (3,6-disubstituted-2,5-dihydroxy-1,4-benzoquinone dianion = C6O4X22−). We present all the anilato-Ln compounds including those where, besides the anilato-type ligand, there is one or more coligands or solvent molecules coordinated to the lanthanoid ions. We show the different structural types observed in these compounds: from discrete monomers, dimers and tetramers to extended 1D, 2D and 3D lattices with different topologies. We also revise the magnetic properties of these Ln-anilato compounds, including single-molecule magnet (SMM) and single-ion magnet (SIM) behaviours. Finally, we show the luminescent and electrochemical properties of some of them, their gas/solvent adsorption/absorption and exchange capacity and the attempts to prepare them as thin films. Full article
(This article belongs to the Special Issue Feature Papers in Magnetochemistry)
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Review
Magnetite (Fe3O4) Nanoparticles in Biomedical Application: From Synthesis to Surface Functionalisation
Magnetochemistry 2020, 6(4), 68; https://doi.org/10.3390/magnetochemistry6040068 - 03 Dec 2020
Cited by 83 | Viewed by 6005
Abstract
Nanotechnology has gained much attention for its potential application in medical science. Iron oxide nanoparticles have demonstrated a promising effect in various biomedical applications. In particular, magnetite (Fe3O4) nanoparticles are widely applied due to their biocompatibility, high magnetic susceptibility, [...] Read more.
Nanotechnology has gained much attention for its potential application in medical science. Iron oxide nanoparticles have demonstrated a promising effect in various biomedical applications. In particular, magnetite (Fe3O4) nanoparticles are widely applied due to their biocompatibility, high magnetic susceptibility, chemical stability, innocuousness, high saturation magnetisation, and inexpensiveness. Magnetite (Fe3O4) exhibits superparamagnetism as its size shrinks in the single-domain region to around 20 nm, which is an essential property for use in biomedical applications. In this review, the application of magnetite nanoparticles (MNPs) in the biomedical field based on different synthesis approaches and various surface functionalisation materials was discussed. Firstly, a brief introduction on the MNP properties, such as physical, thermal, magnetic, and optical properties, is provided. Considering that the surface chemistry of MNPs plays an important role in the practical implementation of in vitro and in vivo applications, this review then focuses on several predominant synthesis methods and variations in the synthesis parameters of MNPs. The encapsulation of MNPs with organic and inorganic materials is also discussed. Finally, the most common in vivo and in vitro applications in the biomedical world are elucidated. This review aims to deliver concise information to new researchers in this field, guide them in selecting appropriate synthesis techniques for MNPs, and to enhance the surface chemistry of MNPs for their interests. Full article
(This article belongs to the Special Issue Magnetic Nanoparticles 2020)
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Review
Electrocaloric Cooling: A Review of the Thermodynamic Cycles, Materials, Models, and Devices
Magnetochemistry 2020, 6(4), 67; https://doi.org/10.3390/magnetochemistry6040067 - 27 Nov 2020
Cited by 9 | Viewed by 1788
Abstract
Electrocaloric is a novel emerging not-in-kind cooling technology based on solid-state materials exhibiting the electrocaloric effect, i.e., the property of changing their temperature because of an adiabatic change in the intensity of the electric field applied. This technology has only attracted the interests [...] Read more.
Electrocaloric is a novel emerging not-in-kind cooling technology based on solid-state materials exhibiting the electrocaloric effect, i.e., the property of changing their temperature because of an adiabatic change in the intensity of the electric field applied. This technology has only attracted the interests of the scientific community in the last two decades, even though it has the main feature of being based on eco-friendly materials that, because of their solid-state nature, do not provide a direct contribution in global warming. Even if some steps have already been taken, the research fields connected to electrocaloric cooling are still open: The identification of the most appropriated thermodynamic cycle, electrocaloric refrigerants, as well as the development of efficient cooling systems. To this purpose, this review paper provides a snapshot of the electrocaloric world and compares the progress made by the inherent scientific community in all the connected fields: the thermodynamic cycles, materials, experimental devices, numerical models, energy performances and prospective cooling applications. Full article
(This article belongs to the Special Issue Magnetocaloric and Caloric Materials for Solid-State Cooling)
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Review
Recent Advances in Magnetic Nanoparticles and Nanocomposites for the Remediation of Water Resources
Magnetochemistry 2020, 6(4), 49; https://doi.org/10.3390/magnetochemistry6040049 - 09 Oct 2020
Cited by 12 | Viewed by 1875
Abstract
Water resources are of extreme importance for both human society and the environment. However, human activity has increasingly resulted in the contamination of these resources with a wide range of materials that can prevent their use. Nanomaterials provide a possible means to reduce [...] Read more.
Water resources are of extreme importance for both human society and the environment. However, human activity has increasingly resulted in the contamination of these resources with a wide range of materials that can prevent their use. Nanomaterials provide a possible means to reduce this contamination, but their removal from water after use may be difficult. The addition of a magnetic character to nanomaterials makes their retrieval after use much easier. The following review comprises a short survey of the most recent reports in this field. It comprises five sections, an introduction into the theme, reports on single magnetic nanoparticles, magnetic nanocomposites containing two of more nanomaterials, magnetic nanocomposites containing material of a biologic origin and finally, observations about the reported research with a view to future developments. This review should provide a snapshot of developments in what is a vibrant and fast-moving area of research. Full article
(This article belongs to the Section Magnetic Nanospecies)
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Review
Spin-Crossover Complexes in Direct Contact with Surfaces
Magnetochemistry 2020, 6(3), 35; https://doi.org/10.3390/magnetochemistry6030035 - 27 Aug 2020
Cited by 27 | Viewed by 2275
Abstract
The transfer of the inherent bistability of spin crossover compounds to surfaces has attracted considerable interest in recent years. The deposition of the complexes on surfaces allows investigating them individually and to further understand the microscopic mechanisms at play. Moreover, it offers the [...] Read more.
The transfer of the inherent bistability of spin crossover compounds to surfaces has attracted considerable interest in recent years. The deposition of the complexes on surfaces allows investigating them individually and to further understand the microscopic mechanisms at play. Moreover, it offers the prospect of engineering switchable functional surfaces. We review recent progress in the field with a particular focus on the challenges and limits associated with the dominant experimental techniques used, namely near-edge X-ray absorption fine structure (NEXAFS) spectroscopy and scanning tunneling microscopy (STM). One of the main difficulties in NEXAFS-based experiments is to ascertain that the complexes are in direct contact with the surfaces. We show that molecular coverage determination based on the amplitude of the edge-jump of interest is challenging because the latter quantity depends on the substrate. Furthermore, NEXAFS averages the signals of a large number of molecules, which may be in different states. In particular, we highlight that the signal of fragmented molecules is difficult to distinguish from that of intact and functional ones. In contrast, STM allows investigating individual complexes, but the identification of the spin states is at best done indirectly. As quite some of the limits of the techniques are becoming apparent as the field is gaining maturity, their detailed descriptions will be useful for future investigations and for taking a fresh look at earlier reports. Full article
(This article belongs to the Special Issue Emerging Applications and Developments in Spin Crossover Systems)
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Review
Magnetic Nanoparticles for Biomedical Purposes: Modern Trends and Prospects
Magnetochemistry 2020, 6(3), 30; https://doi.org/10.3390/magnetochemistry6030030 - 17 Jul 2020
Cited by 39 | Viewed by 2435
Abstract
The presented paper is a review article discussing existing synthesis methods and different applications of nanosized magnetic nanoparticles. It was shown that, in addition to the spectrum of properties typical for nanomaterials (primarily a large specific surface area and a high fraction of [...] Read more.
The presented paper is a review article discussing existing synthesis methods and different applications of nanosized magnetic nanoparticles. It was shown that, in addition to the spectrum of properties typical for nanomaterials (primarily a large specific surface area and a high fraction of surface atoms), magnetic nanoparticles also possess superparamagnetic properties that contribute to their formation of an important class of biomedical functional nanomaterials. This primarily concerns iron oxides magnetite and maghemite, for which in vitro and in vivo studies have shown low toxicity and high biocompatibility in comparison with other magnetic nanomaterials. Due to their exceptional chemical, biological, and physical properties, they are widely used in various areas, such as magnetic hyperthermia, targeted drug delivery, tissue engineering, magnetic separation of biological objects (cells, bacteria, viruses, DNA, and proteins), and magnetic diagnostics (they are used as agents for MRS and immunoassay). In addition to discussing the main problems and prospects of using nanoparticles of magnetic iron oxides for advanced biomedical applications, information is also reflected on their structure, production methods, and properties. Full article
(This article belongs to the Special Issue Magnetic Nanoparticles 2020)
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Review
Successes and Challenges: Inhaled Treatment Approaches Using Magnetic Nanoparticles in Cystic Fibrosis
Magnetochemistry 2020, 6(2), 25; https://doi.org/10.3390/magnetochemistry6020025 - 04 Jun 2020
Cited by 10 | Viewed by 2158
Abstract
Magnetic nanoparticles have been largely applied to increase the efficacy of antibiotics due to passive accumulation provided by enhancing permeability and retention, which is essential for the treatment of lung infections. Recurring lung infections such as in the life-shortening genetic disease cystic fibrosis [...] Read more.
Magnetic nanoparticles have been largely applied to increase the efficacy of antibiotics due to passive accumulation provided by enhancing permeability and retention, which is essential for the treatment of lung infections. Recurring lung infections such as in the life-shortening genetic disease cystic fibrosis (CF) are a major problem. The recent advent of the CF modulator drug ivacaftor, alone or in combination with lumacaftor or tezacaftor, has enabled systemic treatment of the majority of patients. Magnetic nanoparticles (MNPs) show unique properties such as biocompatibility and biodegradability as well as magnetic and heat-medicated characteristics. These properties make them suitable to be used as drug carriers and hyperthermia-based agents. Hyperthermia is a promising approach for the thermal activation therapy of several diseases, including pulmonary diseases. The benefits of delivering CF drugs via inhalation using MNPs as drug carriers afford application of sufficient therapeutic dosages directly to the primary target site, while avoiding potential suboptimal pharmacokinetics/pharmacodynamics and minimizing the risks of systemic toxicity. This review explores the multidisciplinary approach of using MNPs as vehicles of drug delivery. Additionally, we highlight advantages such as increased drug concentration at disease site, minimized drug loss and the possibility of specific cell targeting, while addressing major challenges for this emerging field. Full article
(This article belongs to the Special Issue Magnetic Nanoparticles 2020)
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Review
Nano-Structured Dilute Magnetic Semiconductors for Efficient Spintronics at Room Temperature
Magnetochemistry 2020, 6(1), 15; https://doi.org/10.3390/magnetochemistry6010015 - 16 Mar 2020
Cited by 30 | Viewed by 2946
Abstract
In recent years, many efforts have been made to develop advanced metal oxide semiconductor nanomaterials with exotic magnetic properties for modern applications w.r.t traditional analogues. Dilute magnetic semiconductor oxides (DMSOs) are promising candidates for superior control over the charge and spin degrees of [...] Read more.
In recent years, many efforts have been made to develop advanced metal oxide semiconductor nanomaterials with exotic magnetic properties for modern applications w.r.t traditional analogues. Dilute magnetic semiconductor oxides (DMSOs) are promising candidates for superior control over the charge and spin degrees of freedom. DMSOs are transparent, wide band gap materials with induced ferromagnetism in doping, with a minor percentage of magnetic 3d cation to create a long-range antiferromagnetic order. Although significant efforts have been carried out to achieve DMSO with ferromagnetic properties above room temperature, it is a great challenge that still exists. However, TiO2, SnO2, ZnO and In2O3 with wide band gaps of 3.2, 3.6, 3.2 and 2.92 eV, respectively, can host a broad range of dopants to generate various compositions. Interestingly, a reduction in the size of these binary oxides can induce ferromagnetism, even at room temperature, due to the grain boundary, presence of defects and oxygen vacancies. The present review provides a panorama of the structural analysis and magnetic properties of DMSOs based on binary metal oxides nanomaterials with various ferromagnetic or paramagnetic dopants, e.g., Co, V, Fe and Ni, which exhibit enhanced ferromagnetic behaviors at room temperature. Full article
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Review
A Review on the Optimal Design of Magnetic Nanoparticle-Based T2 MRI Contrast Agents
Magnetochemistry 2020, 6(1), 11; https://doi.org/10.3390/magnetochemistry6010011 - 28 Feb 2020
Cited by 29 | Viewed by 2415
Abstract
Relaxivity r2 and thus the contrast efficacy of superparamagnetic nanoparticles (NPs) can be enhanced via either NP’s magnetic properties or coating optimization. Numerous reports can be found about the investigation of the optimal iron oxide nanoparticles (IO NPs) size, shape, crystallinity and [...] Read more.
Relaxivity r2 and thus the contrast efficacy of superparamagnetic nanoparticles (NPs) can be enhanced via either NP’s magnetic properties or coating optimization. Numerous reports can be found about the investigation of the optimal iron oxide nanoparticles (IO NPs) size, shape, crystallinity and composition that yield high saturation magnetization (ms) values and, consequently, high r2 values. Although the use of an appropriate coating can boost up the NPs MRI contrast agent efficiency, this topic has been largely understudied. Therefore, in this review, the factors affording r2 enhancement of spherical magnetic NPs are discussed. Based on the literature, the requirements for an optimal surface coating that may increase r2 values and ensure stability and biocompatibility of NPs are listed. One of the best candidates that fulfil these requirements are liposomes with embedded magnetic NPs, so-called magneto-liposomes. The analysis of the literature elucidated the most appropriate phospholipid compositions for the relaxivity enhancement and for magneto-liposomes in vivo stability. Finally, the future directions in the development of NP-based contrast agents are given. For example, most of the synthetic NPs are recognized and eliminated as a foreign substance by the immune system. To overcome this issue, a design of a biomimetic, cell-membrane-based nanocarrier for contrast agents is proposed. Disguised with cell membranes, NPs or other active components can act as autogenous cells and thus ensure the inherent biocompatibility. Full article
(This article belongs to the Special Issue Magnetic Nanoparticles 2020)
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Review
Hybrid Nanostructured Magnetite Nanoparticles: From Bio-Detection and Theragnostics to Regenerative Medicine
Magnetochemistry 2020, 6(1), 4; https://doi.org/10.3390/magnetochemistry6010004 - 10 Jan 2020
Cited by 16 | Viewed by 2679
Abstract
Nanotechnology offers the possibility of operating on the same scale length at which biological processes occur, allowing to interfere, manipulate or study cellular events in disease or healthy conditions. The development of hybrid nanostructured materials with a high degree of chemical control and [...] Read more.
Nanotechnology offers the possibility of operating on the same scale length at which biological processes occur, allowing to interfere, manipulate or study cellular events in disease or healthy conditions. The development of hybrid nanostructured materials with a high degree of chemical control and complex engineered surface including biological targeting moieties, allows to specifically bind to a single type of molecule for specific detection, signaling or inactivation processes. Magnetite nanostructures with designed composition and properties are the ones that gather most of the designs as theragnostic agents for their versatility, biocompatibility, facile production and good magnetic performance for remote in vitro and in vivo for biomedical applications. Their superparamagnetic behavior below a critical size of 30 nm has allowed the development of magnetic resonance imaging contrast agents or magnetic hyperthermia nanoprobes approved for clinical uses, establishing an inflection point in the field of magnetite based theragnostic agents. Full article
(This article belongs to the Special Issue Magnetic Nanoparticles)
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Review
Magnetic Nanoparticles for Nanomedicine
Magnetochemistry 2020, 6(1), 3; https://doi.org/10.3390/magnetochemistry6010003 - 09 Jan 2020
Cited by 26 | Viewed by 2543
Abstract
The field of nanomedicine has recently emerged as a product of the expansion of a range of nanotechnologies into biomedical science, pharmacology and clinical practice. Due to the unique properties of nanoparticles and the related nanostructures, their applications to medical diagnostics, imaging, controlled [...] Read more.
The field of nanomedicine has recently emerged as a product of the expansion of a range of nanotechnologies into biomedical science, pharmacology and clinical practice. Due to the unique properties of nanoparticles and the related nanostructures, their applications to medical diagnostics, imaging, controlled drug and gene delivery, monitoring of therapeutic outcomes, and aiding in medical interventions, provide a new perspective for challenging problems in such demanding issues as those involved in the treatment of cancer or debilitating neurological diseases. In this review, we evaluate the role and contributions that the applications of magnetic nanoparticles (MNPs) have made to various aspects of nanomedicine, including the newest magnetic particle imaging (MPI) technology allowing for outstanding spatial and temporal resolution that enables targeted contrast enhancement and real-time assistance during medical interventions. We also evaluate the applications of MNPs to the development of targeted drug delivery systems with magnetic field guidance/focusing and controlled drug release that mitigate chemotherapeutic drugs’ side effects and damage to healthy cells. These systems enable tackling of multiple drug resistance which develops in cancer cells during chemotherapeutic treatment. Furthermore, the progress in development of ROS- and heat-generating magnetic nanocarriers and magneto-mechanical cancer cell destruction, induced by an external magnetic field, is also discussed. The crucial roles of MNPs in the development of biosensors and microfluidic paper array devices (µPADs) for the detection of cancer biomarkers and circulating tumor cells (CTCs) are also assessed. Future challenges concerning the role and contributions of MNPs to the progress in nanomedicine have been outlined. Full article
(This article belongs to the Special Issue Magnetic Nanoparticles)
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Review
Magnetic Nanoparticle Systems for Nanomedicine—A Materials Science Perspective
Magnetochemistry 2020, 6(1), 2; https://doi.org/10.3390/magnetochemistry6010002 - 02 Jan 2020
Cited by 47 | Viewed by 3665
Abstract
Iron oxide nanoparticles are the basic components of the most promising magneto-responsive systems for nanomedicine, ranging from drug delivery and imaging to hyperthermia cancer treatment, as well as to rapid point-of-care diagnostic systems with magnetic nanoparticles. Advanced synthesis procedures of single- and multi-core [...] Read more.
Iron oxide nanoparticles are the basic components of the most promising magneto-responsive systems for nanomedicine, ranging from drug delivery and imaging to hyperthermia cancer treatment, as well as to rapid point-of-care diagnostic systems with magnetic nanoparticles. Advanced synthesis procedures of single- and multi-core iron-oxide nanoparticles with high magnetic moment and well-defined size and shape, being designed to simultaneously fulfill multiple biomedical functionalities, have been thoroughly evaluated. The review summarizes recent results in manufacturing novel magnetic nanoparticle systems, as well as the use of proper characterization methods that are relevant to the magneto-responsive nature, size range, surface chemistry, structuring behavior, and exploitation conditions of magnetic nanosystems. These refer to particle size, size distribution and aggregation characteristics, zeta potential/surface charge, surface coating, functionalization and catalytic activity, morphology (shape, surface area, surface topology, crystallinity), solubility and stability (e.g., solubility in biological fluids, stability on storage), as well as to DC and AC magnetic properties, particle agglomerates formation, and flow behavior under applied magnetic field (magnetorheology). Full article
(This article belongs to the Special Issue Magnetic Nanoparticles)
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Other

Perspective
Redox Activity as a Powerful Strategy to Tune Magnetic and/or Conducting Properties in Benzoquinone-Based Metal-Organic Frameworks
Magnetochemistry 2021, 7(8), 109; https://doi.org/10.3390/magnetochemistry7080109 - 02 Aug 2021
Cited by 7 | Viewed by 1061
Abstract
Multifunctional molecular materials have attracted material scientists for several years as they are promising materials for the future generation of electronic devices. Careful selection of their molecular building blocks allows for the combination and/or even interplay of different physical properties in the same [...] Read more.
Multifunctional molecular materials have attracted material scientists for several years as they are promising materials for the future generation of electronic devices. Careful selection of their molecular building blocks allows for the combination and/or even interplay of different physical properties in the same crystal lattice. Incorporation of redox activity in these networks is one of the most appealing and recent synthetic strategies used to enhance magnetic and/or conducting and/or optical properties. Quinone derivatives are excellent redox-active linkers, widely used for various applications such as electrode materials, flow batteries, pseudo-capacitors, etc. Quinones undergo a reversible two-electron redox reaction to form hydroquinone dianions via intermediate semiquinone radical formation. Moreover, the possibility to functionalize the six-membered ring of the quinone by various substituents/functional groups make them excellent molecular building blocks for the construction of multifunctional tunable metal-organic frameworks (MOFs). An overview of the recent advances on benzoquinone-based MOFs, with a particular focus on key examples where magnetic and/or conducting properties are tuned/switched, even simultaneously, by playing with redox activity, is herein envisioned. Full article
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Perspective
Designing Magnetic NanoMOFs for Biomedicine: Current Trends and Applications
Magnetochemistry 2020, 6(3), 39; https://doi.org/10.3390/magnetochemistry6030039 - 01 Sep 2020
Cited by 6 | Viewed by 1349
Abstract
Metal–organic frameworks (MOFs) have shown a great potential in biomedicine due to their promising applications in different fields, including drug delivery, thermometry, theranostics etc. In this context, the development of magnetic sub-micrometric or nanometric MOFs through miniaturization approaches of magnetic MOFs up to [...] Read more.
Metal–organic frameworks (MOFs) have shown a great potential in biomedicine due to their promising applications in different fields, including drug delivery, thermometry, theranostics etc. In this context, the development of magnetic sub-micrometric or nanometric MOFs through miniaturization approaches of magnetic MOFs up to the nanoscale still represents a crucial step to fabricate biomedical probes, especially in the field of theranostic nanomedicine. Miniaturization processes have to be properly designed to tailor the size and shape of particles and to retain magnetic properties and high porosity in the same material, fundamental prerequisites to develop smart nanocarriers integrating simultaneously therapeutic and contrast agents for targeted chemotherapy or other specific clinical use. An overview of current trends on the design of magnetic nanoMOFs in the field of biomedicine, with particular emphasis on theranostics and bioimaging, is herein envisioned. Full article
(This article belongs to the Special Issue Feature Papers in Magnetochemistry)
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Perspective
False Chirality, Absolute Enantioselection and CP Violation: Pierre Curie’s Legacy
Magnetochemistry 2020, 6(1), 5; https://doi.org/10.3390/magnetochemistry6010005 - 15 Jan 2020
Cited by 15 | Viewed by 2172
Abstract
The 1884 suggestion of Pierre Curie (1859–1906) that the type of dissymmetry shown by collinear electric and magnetic fields may induce an enantiomeric excess, in a chemical reaction that would otherwise produce a racemic mixture, is explored in the context of fundamental symmetry [...] Read more.
The 1884 suggestion of Pierre Curie (1859–1906) that the type of dissymmetry shown by collinear electric and magnetic fields may induce an enantiomeric excess, in a chemical reaction that would otherwise produce a racemic mixture, is explored in the context of fundamental symmetry arguments. Curie’s arrangement exhibits false chirality (time-noninvariant enantiomorphism), and so it may not induce absolute enantioselection (ae) in a process that has reached thermodynamic equilibrium, since it does not lift the degeneracy of chiral enantiomers. However, it may do so in far-from-equilibrium processes via a breakdown in microscopic reversibility analogous to that observed in elementary particle processes under the influence of CP violation, the associated force possessing false chirality with respect to CP enantiomorphism. In contrast, an influence like circularly polarized light exhibiting true chirality (time-invariant enantiomorphism) lifts the degeneracy of enantiomers, and so may induce ae in all circumstances. Although to date, ae has not been observed under the influence of Curie’s arrangement of collinear electric and magnetic fields, it is argued that two different experiments have now demonstrated ae under a falsely chiral influence in systems far from equilibrium, namely in a spinning sample under a gravitational field, and in the separation of enantiomers at a ferromagnetic surface. Full article
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