Synthetic, Natural and Natural-Synthetic Hybrid Magnetic Structures: Technology and Application

A special issue of Magnetochemistry (ISSN 2312-7481). This special issue belongs to the section "Magnetic Nanospecies".

Deadline for manuscript submissions: closed (20 July 2023) | Viewed by 42285

Special Issue Editors

Department of Micro and Nanoelectronics, Saint Petersburg Electrotechnical University “LETI”, 197022 Saint Petersburg, Russia
Interests: magnetic composites; radio-wave absorbing materials; electromagnetic measurements; sol–gel; nanomaterials; theranostics; superparamagnetism; magnetic nanoparticles; biomineralization; magnetosomes; continuous flow synthesis
Special Issues, Collections and Topics in MDPI journals

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Guest Editor
International Research Center “X-ray Coherent Optics”, Immanuel Kant Baltic Federal University, 236022 Kaliningrad, Russia
Interests: magnetism and magnetic materials; X-ray methods for studying materials; micro- and nanostructures

Special Issue Information

Dear Colleagues,

This issue is devoted to the study of magnetic structures, including magnetic nanoparticles, of three main classes: synthetic structures, natural structures, and hybrid natural–synthetic structures. It covers aspects of classical and modern soft chemistry techniques used to obtain magnetic structures such as the sol–gel process and continuous flow synthesis in microfluidic chip reactors. Automated synthesis of magnetic nanoparticles is the only step to the biomineralization processes occurring in bacterial magnetosomes; thus, these natural ferrimagnets have attracted a great amount of scientific interest to the mechanisms providing such high chemical and crystallinity perfection. The yield of bacterial magnetosomes is very low, and the created bioreactors do not allow industrial-scale production of magnetic nanoparticles for biomedical and other applications. For this reason, hybrid structures consisting of natural and synthetic components are also of interest. To understand the physical and chemical mechanisms determining the magnetic properties of such structures, the issue also addresses theoretical modeling tasks. Finally, the practical use of these magnetic structures in solving technical and biomedical problems is also considered.

In this Special Issue, original research articles and reviews are welcome. Research areas may include (but are not limited to) the following:

  1. Magnetotactic bacteria, being in nature, cultivation, isolation of magnetosomes;
  2. Features of physical and chemical properties and magnetic state of magnetosomes;
  3. Magnetic structures based on natural magnetic ores, their study, and possible applications;
  4. Synthetic magnetic structures, including nature-like and biomimetic;
  5. Hybrid magnetic structures based on synthetic and natural components for microwave absorption, biomedicine, and other applications;
  6. Micromagnetic modeling of natural, synthetic, and hybrid magnetic structures;
  7. New methods of synthesis and study of magnetic structures.

We look forward to receiving your contributions.

Dr. Kamil G. Gareev
Dr. Ksenia Chichay
Guest Editors

Manuscript Submission Information

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Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2700 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • magnetic nanoparticles
  • soft chemistry
  • sol–gel
  • continuous flow synthesis
  • natural ferrimagnets
  • biomineralization
  • magnetotactical bacteria
  • magnetosomes
  • natural–synthetic magnetic structures
  • theoretical modeling

Published Papers (17 papers)

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Research

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14 pages, 11436 KiB  
Article
Synthesis and Characterization of Hematite, Magnetite and Maghemite Supported on Silica Gel
by P. A. Chernavskiy, A. A. Novakova, G. V. Pankina, D. A. Pankratov, S. I. Panfilov and G. A. Petrovskaya
Magnetochemistry 2023, 9(11), 228; https://doi.org/10.3390/magnetochemistry9110228 - 15 Nov 2023
Viewed by 1281
Abstract
A new method for obtaining nanosized particles of iron oxides using porous silica gel is proposed. In situ magnetometry was used to study the reduction of hematite deposited on silica gel during the thermolysis of glucose. The formed magnetite and maghemite obtained by [...] Read more.
A new method for obtaining nanosized particles of iron oxides using porous silica gel is proposed. In situ magnetometry was used to study the reduction of hematite deposited on silica gel during the thermolysis of glucose. The formed magnetite and maghemite obtained by subsequent oxidation of the magnetite were studied using X-ray diffraction and Mossbauer spectroscopy. It was shown that both the size of the oxide particles and the phase composition significantly depended on the porous structure of the silica gel. In particular, the formation of superparamagnetic maghemite particles on silica gels with pore sizes of 30, 15 and 10 nm was demonstrated. Full article
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9 pages, 986 KiB  
Article
Some Magnetic Properties and Magnetocaloric Effects in the High-Temperature Antiferromagnet YbCoC2
by Denis Alexandrovich Salamatin, Vladimir Nikolaevich Krasnorussky, Mariya Viktorovna Magnitskaya, Alexei Valeryevich Semeno, Alexander Vladimirovich Bokov, Atanas Velichkov, Zbigniew Surowiec and Anatoly Vasilyevich Tsvyashchenko
Magnetochemistry 2023, 9(6), 152; https://doi.org/10.3390/magnetochemistry9060152 - 08 Jun 2023
Cited by 1 | Viewed by 1059
Abstract
The YbCoC2 compound, which crystallizes in a base-centered orthorhombic unit cell in the Amm2 space group CeNiC2 structure, is unique among Yb-based compounds due to the highest magnetic ordering temperature of TN=27 K. Magnetization measurements [...] Read more.
The YbCoC2 compound, which crystallizes in a base-centered orthorhombic unit cell in the Amm2 space group CeNiC2 structure, is unique among Yb-based compounds due to the highest magnetic ordering temperature of TN=27 K. Magnetization measurements have made it possible to plot the H-T magnetic phase diagram and determine the magnetocaloric effect of this recently discovered high-temperature heavy-fermion compound, YbCoC2. YbCoC2 undergoes spin transformation to the spin-polarized state through a metamagnetic transition in an external magnetic field. The transition is found to be of the first order. The dependencies of magnetic entropy change ΔSm(T)—have segments with positive and negative magnetocaloric effects for ΔH6 T. For ΔH=9 T, the magnetocaloric effect becomes positive, with a maximum ΔSm(T) value of 4.1 J (kg K)−1 at TN and a refrigerant capacity value of 56.6 J kg−1. Full article
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13 pages, 2802 KiB  
Article
Controlling the Magnetic Properties of La0.9A0.1Mn0.9Cr0.1O3 (A: Li, K, Na) Powders and Ceramics by Alkali Ions Doping
by Paweł Głuchowski, Ruslan Nikonkov, Daniela Kujawa, Wiesław Stręk, Tomas Murauskas, Andrius Pakalniškis, Aivaras Kareiva, Andrii Yaremkevych, Olena Fesenko, Aliaksandr Zhaludkevich and Dmitry Karpinsky
Magnetochemistry 2023, 9(6), 140; https://doi.org/10.3390/magnetochemistry9060140 - 25 May 2023
Viewed by 1022
Abstract
Nanocrystalline La0.9A0.1Mn0.9Cr0.1O3 (A: Li, K, Na) powders have been synthesized by combustion method. The powders were used to prepare ceramics by high-pressure low-temperature sintering technique. For all samples the structure, elemental composition and morphology [...] Read more.
Nanocrystalline La0.9A0.1Mn0.9Cr0.1O3 (A: Li, K, Na) powders have been synthesized by combustion method. The powders were used to prepare ceramics by high-pressure low-temperature sintering technique. For all samples the structure, elemental composition and morphology were studied using X-ray diffraction (XRD), Raman spectroscopy, Energy-Dispersive X-ray Spectroscopy (EDS) and Scanning electron microscopy (SEM). Magnetic properties were studied using magnetometry methods and the valency changes of the cations after alkali ions doping were studied using X-ray photoelectron spectroscopy (XPS). The influence of the sintering pressure on the structural and magnetic properties of the manganites doped with different alkali ions and chromium was also investigated. Magnetization properties were studied as a function of sintering pressure and type of the dopant. Chemical doping with alkali ions as well as external pressure significantly changed the magnetic properties of the compounds. It was found that the magnetic properties of the manganites could be predictably modified through the use of a suitable dopant element. Full article
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13 pages, 3142 KiB  
Article
Effect of an External Magnetic Field on the Hydrogen Reduction of Magnetite Nanoparticles in a Polymer Matrix
by Petr Chernavskii, Sveta Ozkan, Galina Karpacheva, Galina Pankina and Nikolai Perov
Magnetochemistry 2023, 9(5), 123; https://doi.org/10.3390/magnetochemistry9050123 - 07 May 2023
Viewed by 1090
Abstract
A hybrid electromagnetic nanomaterial, which is a matrix based on a conjugated polymer of poly-3-amine-7-methylamine-2-methylphenazine with dispersed magnetite nanoparticles immobilized on multi-walled carbon nanotubes, has been synthesized. In situ magnetometry was used to study the kinetics of the hydrogen reduction of Fe3 [...] Read more.
A hybrid electromagnetic nanomaterial, which is a matrix based on a conjugated polymer of poly-3-amine-7-methylamine-2-methylphenazine with dispersed magnetite nanoparticles immobilized on multi-walled carbon nanotubes, has been synthesized. In situ magnetometry was used to study the kinetics of the hydrogen reduction of Fe3O4 immobilized in the structure of a ternary nanocomposite in magnetic fields of different intensities. An increase in the magnetite reduction reaction rate with the formation of metallic iron nanoparticles at T=420C and at a magnetic field strength in the range of 60–3000 Oe was observed. The dependence of the degree of conversion of Fe3O4 on the magnetic field strength was established. Full article
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13 pages, 4938 KiB  
Communication
MHD Hybrid Nanofluid Flow over a Stretching/Shrinking Sheet with Skin Friction: Effects of Radiation and Mass Transpiration
by Angadi Basettappa Vishalakshi, Rudraiah Mahesh, Ulavathi Shettar Mahabaleshwar, Alaka Krishna Rao, Laura M. Pérez and David Laroze
Magnetochemistry 2023, 9(5), 118; https://doi.org/10.3390/magnetochemistry9050118 - 27 Apr 2023
Cited by 6 | Viewed by 1788
Abstract
The study of inclined magnetohydrodynamics (MHD) mixed convective incompressible flow of a fluid with hybrid nanoparticles containing a colloidal combination of nanofluids and base fluid is presented in the current research. Al2O3-Cu/H2O hybrid nanofluid [...] Read more.
The study of inclined magnetohydrodynamics (MHD) mixed convective incompressible flow of a fluid with hybrid nanoparticles containing a colloidal combination of nanofluids and base fluid is presented in the current research. Al2O3-Cu/H2O hybrid nanofluid is utilized in the current analysis to enhance the heat transfer analysis. The impact of radiation is also placed at energy equation. The main research methodology includes that the problem provided equations are first transformed into non-dimensional form, and then they are obtained in ordinary differential equations (ODEs) form. Then using the solutions of momentum and transfers equations to solve the given ODEs to get the root of the equation. The main purpose includes the resulting equations are then analytically resolved with the aid of suitable boundary conditions. The results can be discussed with various physical parameters viz., stretched/shrinked-Rayleigh number, stretching/shrinking parameter, Prandtl number, etc. Besides, skin friction and heat transfer coefficient can be examined with suitable similarity transformations. The main significance of the present work is to explain the mixed convective fluid flow on the basis of analytical method. Main findings at the end we found that the transverse and tangential velocities are more for more values of stretched/shrinked-Rayleigh number and mass transpiration for both suction and injection cases. This is the special method it includes stretched/shrinked-Rayleigh number, it contributes major role in this analysis. The purpose of finding the present work is to understand the analytical solution on the basis of mixed convective method. Full article
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24 pages, 6887 KiB  
Article
Investigation of the Prospects for the Use of Iron-Containing Nanocomposites Doped with Rare Earth Elements as Catalysts for the Purification of Aqueous Media
by Kayrat K. Kadyrzhanov, Artem L. Kozlovskiy, Kamila B. Egizbek, Sholpan N. Kubekova, Inesh E. Kenzhina and Maxim V. Zdorovets
Magnetochemistry 2023, 9(3), 87; https://doi.org/10.3390/magnetochemistry9030087 - 22 Mar 2023
Viewed by 1144
Abstract
The great interest in nanostructured magnetic composites is due to their great prospects for use as a basis for the development of catalysts for the adsorption of manganese in wastewater. Interest in magnetic nanocomposites in this direction is primarily due to the possibility [...] Read more.
The great interest in nanostructured magnetic composites is due to their great prospects for use as a basis for the development of catalysts for the adsorption of manganese in wastewater. Interest in magnetic nanocomposites in this direction is primarily due to the possibility of extracting them from water media using ordinary magnets, which allows them to be used again. Additionally, it is worthwhile to note interest in research related to increasing the efficiency of adsorption, as well as an increase in the number of repeated cycles of operation. In this regard, the main goal of this study is to study the prospects for applying the method of mechanochemical synthesis for the creation of iron-containing nanocomposites doped by rare-earth elements Gd, Ce, Y, and Nd in order to obtain optimal catalysts for cleaning water media. During the studies, structural properties and phase composition of synthesized nanocomposites were established, as well as ultra-thin parameters of the magnetic field. It has been established that the kinetic curves of the adsorption process can be described by a pseudo-first-order model, and the process of manganese adsorption itself is associated with the cationic interaction of manganese ions with the surface of nanocomposites. The kinetic curves of degradation were determined, as well as the influence of the number of cyclic tests on the adsorption of manganese for synthesized nanocomposites, depending on the type of dopant and phase composition, respectively. Iron-containing nanocomposites doped with gadolinium and neodymium have been found to have the highest adsorption efficiency and corrosion resistance. Particular attention is paid to the study of the stability of storage of nanocomposites for a long time, as well as the preservation of their adsorbent properties in the purification of aqueous media. It has been determined that the modification of nanostructures with the help of rare earth compounds leads to an increase in resistance to degradation, as well as to the preservation of the efficiency of adsorption for 5–7 cycles in comparison with Fe2O3 nanoparticles, for which low resistance to degradation was observed. Full article
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14 pages, 3950 KiB  
Article
Influence of the Preparation Technique on the Magnetic Characteristics of ε-Fe2O3-Based Composites
by Dmitriy O. Testov, Kamil G. Gareev, Ivan K. Khmelnitskiy, Andrei Kosterov, Leonid Surovitskii and Victor V. Luchinin
Magnetochemistry 2023, 9(1), 10; https://doi.org/10.3390/magnetochemistry9010010 - 28 Dec 2022
Cited by 2 | Viewed by 2696
Abstract
ε-Fe2O3 is an iron(III) oxide polymorph attracting an increasing interest due to its unique magnetic properties combining extremely high coercivity and relatively large saturation magnetization. We review existing methods for the ε-Fe2O3 synthesis focusing on synthesis speed, [...] Read more.
ε-Fe2O3 is an iron(III) oxide polymorph attracting an increasing interest due to its unique magnetic properties combining extremely high coercivity and relatively large saturation magnetization. We review existing methods for the ε-Fe2O3 synthesis focusing on synthesis speed, repeatability, manufacturability and purity of the final product. Samples of ε-Fe2O3 have been synthesized using the two methods that appear the most promising: silica gel impregnation and microemulsion. In both cases, ε-Fe2O3 and α-Fe2O3 are present in the final product as attested by X-ray diffraction patterns and magnetic properties (maximum coercive force at 300 K~1 Tesla). Two different precursors, iron(III) nitrate and iron(II) sulfate, have been used in the silica gel impregnation method. Somewhat surprisingly, iron sulfate proved superior yielding ε-Fe2O3 content of 69% in the total iron oxide product, compared to 25% for iron nitrate under the same synthesis conditions. These results pave the way for modifying the existing ε-Fe2O3 synthesis methods aiming to increase the content of the epsilon phase in the final product and, consequently, improve its physicochemical properties. Full article
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28 pages, 9713 KiB  
Article
Stability Analysis of Buoyancy Magneto Flow of Hybrid Nanofluid through a Stretchable/Shrinkable Vertical Sheet Induced by a Micropolar Fluid Subject to Nonlinear Heat Sink/Source
by Umair Khan, Aurang Zaib, Anuar Ishak, Abeer M. Alotaibi, Sayed M. Eldin, Nevzat Akkurt, Iskandar Waini and Javali Kotresh Madhukesh
Magnetochemistry 2022, 8(12), 188; https://doi.org/10.3390/magnetochemistry8120188 - 14 Dec 2022
Cited by 12 | Viewed by 1665
Abstract
The utilization of hybrid nanofluids (HNs) to boost heat transfer is a promising area of study, and thus, numerous scientists, researchers, and academics have voiced their admiration and interest in this area. One of the main functions of nanofluids is their dynamic role [...] Read more.
The utilization of hybrid nanofluids (HNs) to boost heat transfer is a promising area of study, and thus, numerous scientists, researchers, and academics have voiced their admiration and interest in this area. One of the main functions of nanofluids is their dynamic role in cooling small electrical devices such as microchips and associated gadgets. The major goal of this study is to perform an analysis of the buoyancy flow of a shrinking/stretching sheet, whilst considering the fascinating and practical uses of hybrid nanofluids. The influence of a nonlinear heat source/sink induced by a micropolar fluid is also inspected. Water-based alumina and copper nanoparticles are utilized to calculate the fine points of the fluid flow and the features of heat transfer. The governing equations are framed with acceptable assumptions and the required similarity transformations are used to turn the set of partial differential equations into ordinary differential equations. The bvp4c technique is used to solve the simplified equations. Dual solutions are presented for certain values of stretching/shrinking parameters as well as the mixed convective parameter. In addition, the shear stress coefficient in the first-branch solution (FBS) escalates and decelerates for the second-branch solution (SBS) with the superior impact of the magnetic parameter, the mass transpiration parameter, and the solid nanoparticles volume fraction, while the contrary behavior is seen in both (FB and SB) solutions for the larger values of the material parameter. Full article
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18 pages, 4150 KiB  
Article
Indocyanine Green-Containing Magnetic Liposomes for Constant Magnetic Field-Guided Targeted Delivery and Theranostics
by Dmitry V. Korolev, Galina A. Shulmeyster, Maria S. Istomina, Alexey I. Nikiforov, Ilia V. Aleksandrov, Valentin G. Semenov and Michael M. Galagudza
Magnetochemistry 2022, 8(10), 127; https://doi.org/10.3390/magnetochemistry8100127 - 16 Oct 2022
Cited by 3 | Viewed by 1590
Abstract
The aim of the present study was to develop magnetic liposomes (MLPSs) incorporating an agent with the ability to act both as a photosensitizer and as a fluorophore for optical imaging. We therefore aimed to develop a preparation method for indocyanine green (ICG)-containing [...] Read more.
The aim of the present study was to develop magnetic liposomes (MLPSs) incorporating an agent with the ability to act both as a photosensitizer and as a fluorophore for optical imaging. We therefore aimed to develop a preparation method for indocyanine green (ICG)-containing MLPS, followed by a detailed characterization of their physicochemical and magnetic properties. The ability of intravenously administered ICG-containing MLPSs to accumulate in tissue exposed to a constant magnetic field was tested in vivo. Using the thin film hydration method, 170-nm aqueous liposomes containing magnetic nanoparticles and indocyanine green were synthesized, followed by a detailed characterization of their physicochemical properties. It was shown that ICG-containing MLPSs possess the properties of T2 contrast for MRI. Apart from this, ICG-containing MLPSs were clearly visualized using near infrared fluorescent imaging, which was demonstrated in in vivo experiments showing an accumulation of ICG-containing MLPSs in the zone of magnetic field distribution produced by a previously implanted constant magnet in the tissue. Although not directly tested in the present study, therapeutic applications of ICG-containing MLPSs include magnetic hyperthermia, as well as the photodynamic, photothermal, and photoacoustic effects of ICG. Taking into account the fact that liposomes, iron oxide nanoparticles, and ICG are all FDA-approved agents, it is highly likely that ICG-containing MLPSs could be successfully translated to clinical practice. Full article
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9 pages, 352 KiB  
Article
Magnetic, Electric and Optical Properties of Ion Doped CuCr2O4 Nanoparticles
by Angel Todorov Apostolov, Iliana Naumova Apostolova and Jilia Mihailowa Wesselinova
Magnetochemistry 2022, 8(10), 122; https://doi.org/10.3390/magnetochemistry8100122 - 07 Oct 2022
Cited by 1 | Viewed by 1113
Abstract
The magnetic, electric and optical properties of pure and ion doped CuCr2O4 - bulk and nanoparticles are investigated theoretically. The magnetization Ms and the band gap Eg decrease with increasing particle size. By Co ion doping Ms [...] Read more.
The magnetic, electric and optical properties of pure and ion doped CuCr2O4 - bulk and nanoparticles are investigated theoretically. The magnetization Ms and the band gap Eg decrease with increasing particle size. By Co ion doping Ms and the polarization P show a maximum whereas by Pr ion doping they decrease with increasing the doping concentration. The dielectric constant decreases with enhancing Pr dopants. It is shown that the difference between the doping and host ions radii leads to appearing of a compressive or tensile strain and to different exchange interaction constants in the doped state. Eg decreases by Co doping, whereas it increases by Pr doping. Full article
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16 pages, 3493 KiB  
Article
Solid-State Self-Assembly of a Linear Hexanuclear Copper(II) Oxamate Complex with Alternating Antiferro- and Ferromagnetic Coupling
by Ana Luísa A. Lage, Luísa A. Ribeiro, Antônio C. Doriguetto, Carlos B. Pinheiro, Wallace C. Nunes, Emerson F. Pedroso and Cynthia L. M. Pereira
Magnetochemistry 2022, 8(10), 116; https://doi.org/10.3390/magnetochemistry8100116 - 28 Sep 2022
Cited by 1 | Viewed by 1686
Abstract
In this work, we describe the synthesis, crystal structure and magnetic properties of the neutral hexacopper(II) complex of formula {[Cubpca)]2[Cu(dmopba)(H2O)]}2·4H2O (1), where Hbpca = bis(2-pyridylcarbonyl)-amide and dmopba = 4,5-dimethyl-1,2-phenylenebis(oxamato). Single crystals of 1 [...] Read more.
In this work, we describe the synthesis, crystal structure and magnetic properties of the neutral hexacopper(II) complex of formula {[Cubpca)]2[Cu(dmopba)(H2O)]}2·4H2O (1), where Hbpca = bis(2-pyridylcarbonyl)-amide and dmopba = 4,5-dimethyl-1,2-phenylenebis(oxamato). Single crystals of 1 were obtained from the stoichiometric reaction (1:2 molar ratio) of the mononuclear copper(II) complexes (n-Bu4N)2[Cu(dmpba)] and [Cu(bpca)(H2O)2]NO3·2H2O through slow diffusion techniques in water as a solvent. The crystal structure of 1 shows that two neutral {[Cu(bpca)]2[Cu(dmopba)(H2O)]} trinuclear units are connected through double out-of-plane copper to outer carboxylate oxygen atoms resulting in a unique oxamate-bridged linear hexanuclear complex. Hydrogen bonds among adjacent entities involving the non-coordinated water molecules result in a supramolecular 3D network. Magnetic measurements on 1 show the occurrence of moderate antiferromagnetic intratrinuclear interactions between the copper(II) ions from the [Cu(bpca)]+ and [Cu(dmopba)(H2O)]2− fragments across the oxamate bridge and a weak intertrinuclear ferromagnetic interaction between the copper(II) ions that occurs between the two central [Cu(bpca)]+ fragments mediated by the carboxylate groups from the oxamate bridge [J = −31.96(2) cm−1 and J′ = +1.34(2) cm−1; H = J (S1·S2 + S2·S3 + S1′·S2′ + S2′·S3′) + J′ (S1·S1′)]. Full article
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9 pages, 2277 KiB  
Article
Synthesis and Single Crystal Growth by Floating Zone Technique of FeCr2O4 Multiferroic Spinel: Its Structure, Composition, and Magnetic Properties
by Ruslan Batulin, Mikhail Cherosov, Airat Kiiamov, Almaz Zinnatullin, Farit Vagizov, Dmitrii Tayurskii and Roman Yusupov
Magnetochemistry 2022, 8(8), 86; https://doi.org/10.3390/magnetochemistry8080086 - 05 Aug 2022
Cited by 4 | Viewed by 2094
Abstract
We present the new synthesis root of spinel-structure FeCr2O4 and its single crystal growth by the optical floating zone method, ensuring its single phase and near-ideal composition. The advantage of the proposed synthesis method is the creation of the reducing [...] Read more.
We present the new synthesis root of spinel-structure FeCr2O4 and its single crystal growth by the optical floating zone method, ensuring its single phase and near-ideal composition. The advantage of the proposed synthesis method is the creation of the reducing atmosphere in the oven needed for preserving the Fe2+ oxidation state via decomposition of the iron (II) oxalate FeC2O4 used as one of the initial components. The occurrence of the Fe3+ ions in the obtained polycrystalline samples as well as grown single crystals was carefully monitored by means of Mössbauer spectroscopy. Magnetic susceptibility and heat capacity temperature dependences reveal a sequence of the structural (138 K) and magnetic (at 65 K and 38 K) phase transition characteristics for the FeCr2O4 compound. Full article
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8 pages, 925 KiB  
Article
Revisiting the Potential Functionality of the MagR Protein
by Alexander Pekarsky, Herwig Michor and Oliver Spadiut
Magnetochemistry 2021, 7(11), 147; https://doi.org/10.3390/magnetochemistry7110147 - 11 Nov 2021
Viewed by 2641
Abstract
Recent findings have sparked great interest in the putative magnetic receptor protein MagR. However, in vivo experiments have revealed no magnetic moment of MagR at room temperature. Nevertheless, the interaction of MagR and MagR fusion proteins with silica-coated magnetite beads have proven useful [...] Read more.
Recent findings have sparked great interest in the putative magnetic receptor protein MagR. However, in vivo experiments have revealed no magnetic moment of MagR at room temperature. Nevertheless, the interaction of MagR and MagR fusion proteins with silica-coated magnetite beads have proven useful for protein purification. In this study, we recombinantly produced two different MagR proteins in Escherichia coli BL21(DE3) to (1) expand earlier protein purification studies, (2) test if MagR can magnetize whole E. coli cells once it is expressed to a high cytosolic, soluble titer, and (3) investigate the MagR-expressing E. coli cells’ magnetic properties at low temperatures. Our results show that MagR induces no measurable, permanent magnetic moment in cells at low temperatures, indicating no usability for cell magnetization. Furthermore, we show the limited usability for magnetic bead-based protein purification, thus closing the current knowledge gap between theoretical considerations and empirical data on the MagR protein. Full article
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7 pages, 1086 KiB  
Article
Enriched Synthesis of Magnetosomes by Expanding the Magnetospirillum magneticum AMB-1 Culture at Optimal Iron Concentration
by Yazhen Hong, Ranjith Kumar Kankala, Ruqi Yu, Huaqing Liu and Yuangang Liu
Magnetochemistry 2021, 7(8), 115; https://doi.org/10.3390/magnetochemistry7080115 - 11 Aug 2021
Cited by 2 | Viewed by 2271
Abstract
The Magnetospirillum magneticum AMB-1 species is one of the most widely used magnetotactic bacterial strains for producing magnetosomes under laboratory conditions. Nevertheless, there exist several challenges in expanding and purifying the AMB-1 culture due to the restricted culture conditions. In an attempt to [...] Read more.
The Magnetospirillum magneticum AMB-1 species is one of the most widely used magnetotactic bacterial strains for producing magnetosomes under laboratory conditions. Nevertheless, there exist several challenges in expanding and purifying the AMB-1 culture due to the restricted culture conditions. In an attempt to enrich the production of magnetosomes, this study reports the utilization of fermenter culture, which substantially promotes the cell densities at different concentrations of iron content. The experimental results confirmed magnetosomes’ high yield (production rate of 21.1 mg L−1) at the iron content of 0.2 μmol L−1. Moreover, different characterization techniques systematically confirmed the coated lipid membrane, particle size, dispersity, stability, and elemental composition of magnetosomes. Notably, the fermenter culture-based process resulted in highly discrete, dispersed, and stable magnetosomes with an average particle diameter of 50 nm and presented the integrated lipid membrane around the surface. The chemical composition by EDS of magnetosomes represented the presence of various elements, i.e., C, O, Na, P, and Fe, at appropriate proportions. In conclusion, the culture method in our study effectively provides a promising approach towards the culture of the magnetotactic bacterium for the enriched production of magnetosomes. Full article
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Review

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50 pages, 3678 KiB  
Review
Diversity of Iron Oxides: Mechanisms of Formation, Physical Properties and Applications
by Kamil G. Gareev
Magnetochemistry 2023, 9(5), 119; https://doi.org/10.3390/magnetochemistry9050119 - 27 Apr 2023
Cited by 6 | Viewed by 6560
Abstract
Iron oxide compounds have naturally formed during the whole of Earth’s history. Synthetic compositions with iron oxides are produced with the use of various techniques and widely used for scientific and applied purposes. This review considers an attempt to classify all the information [...] Read more.
Iron oxide compounds have naturally formed during the whole of Earth’s history. Synthetic compositions with iron oxides are produced with the use of various techniques and widely used for scientific and applied purposes. This review considers an attempt to classify all the information on different iron oxide compound formation mechanisms and intended applications in biomedicine, catalysis, waste remediation, geochemistry, etc. All the literature references analyzed were divided into several groups by their number of included iron oxide compounds: compositions containing only one compound (e.g., magnetite or wüstite), including various polymorphs of iron(III) oxide (α-, β-, γ-, ε-, ζ-, δ-Fe2O3); compositions with two different distinguishable iron oxide phases (e.g., maghemite and hematite); compositions containing non-crystalline phases (amorphous iron oxide or atomic clusters); and compositions with mixed iron oxide phases (indistinguishable separate iron oxide phases). Diagrams on the distribution of the literature references between various iron oxide compounds and between various applications were built. Finally, the outlook on the perspectives of further iron oxide studies is provided. Full article
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22 pages, 3493 KiB  
Review
Magnetotactic Bacteria and Magnetosomes: Basic Properties and Applications
by Kamil G. Gareev, Denis S. Grouzdev, Petr V. Kharitonskii, Andrei Kosterov, Veronika V. Koziaeva, Elena S. Sergienko and Maxim A. Shevtsov
Magnetochemistry 2021, 7(6), 86; https://doi.org/10.3390/magnetochemistry7060086 - 18 Jun 2021
Cited by 26 | Viewed by 10599
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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Comment on Vishalakshi et al. MHD Hybrid Nanofluid Flow over a Stretching/Shrinking Sheet with Skin Friction: Effects of Radiation and Mass Transpiration. Magnetochemistry 2023, 9, 118
by Asterios Pantokratoras
Magnetochemistry 2024, 10(4), 26; https://doi.org/10.3390/magnetochemistry10040026 - 11 Apr 2024
Viewed by 169
Abstract
In Figure 1, in [...] Full article
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