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A special issue of Crystals (ISSN 2073-4352). This special issue belongs to the section "Inorganic Crystalline Materials".

Deadline for manuscript submissions: closed (31 August 2023) | Viewed by 13889

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Prof. Dr. Nasrallah Deraz

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Physical Chemistry Department, Advanced Materials Technology and Mineral Resources Research Institute, National Research Centre, 33 El Bohouth st. (former El Tahrir st.), Dokki, Giza P.O. Box 12622, Egypt
Interests: metal oxides; spinel and perovskite nanomaterials; surface chemistry and catalysis; nanostructured materials and their applications
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Dear Colleagues,

Magnetic materials have long attracted the attention of scientists. However, with the technological development that the world is witnessing today, the demand has escalated, with increased interest on magnetic materials, whether crystallized or amorphous depending upon their unique physical and chemical properties. Indeed, these materials show unique structural, morphological, chemical, mechanical, optical, electric, and electrochemical properties. So, they have a verity of promising technological applications in biomedicine, high-density recording devices, color imaging, ferrofluids, magnetic refrigerators, sensors, catalysts, motors, generators, transformers, and high frequency devices

Most materials have magnetism because they produce a magnetic field in response to an applied magnetic field. Several forms of magnetic behavior have been observed in various materials, including: ferromagnetic, ferrimagnetic, paramagnetic and diamagnetic substances. Magnetism can be the key phenomenon in the preparation of novel magnetic materials with tuned properties according to the desired applications.

Crystalline and/or nanocrystalline magnetic compounds occupied a great position among the magnetic materials depending on the size and crystallization degree of their particles. The overall magnetic behavior of crystalline magnetic compounds can vary widely, depending on the structure of these compounds, particularly on their electron configuration. So, the sky is the limit for magnetic nanomaterials, depending upon innumerous technological applications. Different factors, namely, doping, heat temperature, precursors, and preparation route affect the physical and chemical properties of crystalline and/or nanocrystalline magnetic compounds.

From this perspective, the main focus of the upcoming Special Issue is to publish some recent findings and understandings containing the relationship between the development of methods for preparing crystalline and/or nanocrystalline magnetic compounds and between their structural, morphological, surface, electrical, electrochemical properties and the consequent advanced applications, taking into account all the explorations that go beyond that.

It is my pleasure to invite you to submit an original manuscript for this Special Issue. Full papers, communications, and reviews are all welcome.

Prof. Dr. Nasrallah Mohamed Deraz
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Crystals is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2600 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

magnetism
crystalline magnetic compounds
advanced manufacturing processes of magnetic materials
mechanism of fabrication of magnetic materials
magnetic functional materials
magnetic nanomaterials

Published Papers (10 papers)

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Research

15 pages, 6945 KiB

Open AccessArticle

Biosynthesis Effect of Egg White on Formation and Characteristics of NiO/NiCo₂O₄ Nanocomposites

by Ghadah M. Al-Senani, Foziah F. Al-Fawzan, Mashael Alshabanat, Omar H. Abd-Elkader, Mai Nasrallah and Mohamed Nasrallah

Crystals 2023, 13(11), 1579; https://doi.org/10.3390/cryst13111579 - 09 Nov 2023

Cited by 1 | Viewed by 811

Abstract

For the successful production of NiO/NiCo₂O₄ nanocomposites, the environmentally friendly method of egg white supplementation has been used. Several analytical techniques were employed to characterize the morphology, purity, and crystal structure of the as-prepared nanocomposites. These techniques included transmission electron microscopy (TEM), Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and X-ray diffraction (XRD). The physical adsorption and magnetic properties of the investigated composite were determined using the Brunauer–Emmett–Teller (BET) method and a vibrating-sample magnetometer (VSM), respectively. The results have shown that the as-prepared composite particles had diameters of about 10–25 nm, with uniform distribution. The XRD analysis showed that the as-synthesized composites consisted entirely of cubic structures of both NiO and spinel NiCo₂O₄ nanoparticles, with a space group of Fd3m. The FTIR analysis showed characteristic vibration modes related to metal oxides, confirming the formation of composites containing NiO and NiCo₂O₄ crystallites. The investigated composites’ saturation magnetization (M_S) and coercivity (H_C) were easily controllable because of the ingredients’ ferromagnetic (NiCo₂O₄) and antiferromagnetic (NiO) characteristics. The excellent combination of the NiO/NiCo₂O₄ nanocomposites’ properties is anticipated to make this system suitable for a wide range of applications. Full article

(This article belongs to the Special Issue Crystalline Magnetic Compounds)

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16 pages, 5220 KiB

Open AccessArticle

One Pot Synthesis, Surface, and Magnetic Properties of Ni–NiO@C Nanocomposites

by Ghadah M. Al-Senani, Foziah F. Al-Fawzan, Mashael Alshabanat, Omar H. Abd-Elkader, Mai Nasrallah and Mohamed Nasrallah

Crystals 2023, 13(10), 1497; https://doi.org/10.3390/cryst13101497 - 14 Oct 2023

Cited by 1 | Viewed by 946

Abstract

An entirely novel and creative technique was employed for producing magnetic Ni–NiO@C nanocomposites, and it was based on the utilization different amounts of finely ground and fully dried olive leaf powders. The resulting nanocomposites were identified and characterized by XRD, FTIR, SEM, EDS, TEM, and Raman techniques. The magnetic and surface characteristics of the composites, as it developed, were further evaluated using the Vibrating-Sample Magnetometer (VSM) and Brunauer–Emmett–Teller (BET) techniques. The results confirmed the success of preparing a Ni–NiO@C nanocomposites, each containing Ni and NiO in crystalline form. Through the morphology of the resulting composites, determined on the basis of an SEM analysis, it became clear to us that the particles were of a semi-spherical shape, with a clear grouping and a definition of their grain boundaries. Comparably, a TEM investigation demonstrated that the composites had a core–shell structure. The surface area of the investigated composites increases as the content of dried olive leaf powders increases due to a significant increase in the total pore volume. These composites illustrated low magnetism (4.874 and 8.648 emu/g) and coercivity (55.203 and 39.639 Oe) for a number of reasons, which will be explained. Full article

(This article belongs to the Special Issue Crystalline Magnetic Compounds)

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17 pages, 8571 KiB

Open AccessArticle

Electronic and Optical Properties of Finite Gallium Sulfide Nano Ribbons: A First-Principles Study

by Omar H. Abd-Elkader, Hazem Abdelsalam, Mahmoud A. S. Sakr, Nahed H. Teleb and Qinfang Zhang

Crystals 2023, 13(8), 1215; https://doi.org/10.3390/cryst13081215 - 05 Aug 2023

Cited by 2 | Viewed by 1003

Abstract

The electronic and optical properties of finite GaS nanoribbons are investigated using density functional theory calculations. The effect of size, edge termination, and chemical modification by doping and edge passivation are taken into account. The dynamical stability is confirmed by the positive vibration frequency from infrared spectra; further, the positive binding energies ensure the stable formation of the considered nanoribbons. Accurate control of the energy gap has been achieved. For instance, in armchair nanoribbons, energy gaps ranging from ~ 1 to 4 eV were obtained in varying sizes. Moreover, the energy gap can be increased by up to 5.98 eV through edge passivation with F-atoms or decreased to 0.98 eV through doping with Si-atoms. The density of states shows that the occupied molecular orbitals are dominated by S-atoms orbitals, while unoccupied ones are mostly contributed to by Ga orbitals. Thus, S-atoms will be the electron donor sites, and Ga-atoms will be the electron acceptors in the interactions that the nanoribbons might undergo. The nature of electron–hole interactions in the excited states was investigated using various indices, such as electron–hole overlapping, charge–transfer length, and hole–electron Coulomb attraction energy. The UV-Vis absorption spectra reveal a redshift by increasing the size in the armchair or the zigzag directions. Chemical functionalization shows a significant influence on the absorption spectra, where a redshift or blueshift can be achieved depending on the dopant or the attached element. Full article

(This article belongs to the Special Issue Crystalline Magnetic Compounds)

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16 pages, 4402 KiB

Open AccessArticle

Rapid Bio-Assisted Synthesis and Magnetic Behavior of Zinc Oxide/Carbon Nanoparticles

by Omar H. Abd-Elkader, Nasrallah M. Deraz and Lotfi Aleya

Crystals 2023, 13(7), 1081; https://doi.org/10.3390/cryst13071081 - 11 Jul 2023

Cited by 3 | Viewed by 848

Abstract

The biomimetic synthesis of a ZnO/C nanocomposite has been achieved using the egg white-assisted self-combustion method. The characterization of this composite has been carried out using different techniques, such as XRD, FTIR, Raman, SEM/EDS and TEM. A comparative study was conducted between ZnO in the form of this composite and pristine ZnO, which was prepared via the same procedures but without the egg white. The resulting ZnO had a hexagonal structure, similar to wurtzite, with a P63mc space group. When this egg white method was used to produce a ZnO-based material, a ZnO/C nanocomposite was developed, and the ZnO’s crystallite size was significantly decreased. The structural properties—including the unit cell volume, strain, atom displacement and dislocation density—of this ZnO crystal are increased as a result of the presence of a C atom. On the other hand, the length of the Zn–O bond is reduced by the presence of the C atom. Results derived from a combination of Raman, FTIR, and EDS demonstrate that the carbonaceous layers and ZnO nanoparticles were integrated with a close interfacial contact. The preparation method used here brought about obvious changes in the morphological and magnetic behaviors of the as-prepared materials. Using a small amount of egg white resulted in the transformation of the particle’s shape from a hexagonal cone-type structure to an ellipsoidal structure. Based on an analysis of diffuse reflectance, the ZnO and ZnO/C band gap values were revealed using UV–VIS spectra. ZnO and ZnO/C exhibit band gap energies of 3.09 and 2.60 eV, respectively. A phase transition from weakly ferromagnetic to completely diamagnetic magnetic was discovered. Full article

(This article belongs to the Special Issue Crystalline Magnetic Compounds)

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14 pages, 4461 KiB

Open AccessArticle

First-Principles Study of MoS₂, WS₂, and NbS₂ Quantum Dots: Electronic Properties and Hydrogen Evolution Reaction

by Omar H. Abd-Elkader, Hazem Abdelsalam, Mahmoud A. S. Sakr, Abdallah A. Shaltout and Qinfang Zhang

Crystals 2023, 13(7), 994; https://doi.org/10.3390/cryst13070994 - 21 Jun 2023

Cited by 8 | Viewed by 1259

Abstract

The electronic and catalytic properties of two-dimensional MoS₂, WS₂, and NbS₂ quantum dots are investigated using density functional theory investigations. The stability of the considered structures is confirmed by the positive binding energies and the real vibrational frequencies in the infrared spectra. The ab initio molecular dynamics simulations show that these nanodots are thermally stable at 300 K with negligible changes in the potential energy and metal–S bonds. The pristine nanodots are semiconductors with energy gaps ranging from 2.6 to 3 eV. Edge sulfuration significantly decreases the energy gap of MoS₂ and WS₂ to 1.85 and 0.75 eV, respectively. The decrease is a result of the evolution of low-energy molecular orbitals by the passivating S-atoms. The energy gap of NbS₂ is not affected, which could be due to the spin doublet state. Molecular electrostatic potentials reveal that the edge sulfur/transition metal atoms are electrophilic/nucleophilic sites, while the surface atoms are almost neutral sites. MoS₂ quantum dots show an interestingly low change in the hydrogen adsorption free energy ~0.007 eV, which makes them competitive for hydrogen evolution catalysts. Full article

(This article belongs to the Special Issue Crystalline Magnetic Compounds)

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18 pages, 18147 KiB

Open AccessArticle

Green Synthesis of Nanomagnetic Copper and Cobalt Ferrites Using Corchorus Olitorius

by Nada S. Al-Kadhi, Ghadah M. Al-Senani, Rasmiah S. Almufarij, Omar H. Abd-Elkader and Nasrallah M. Deraz

Crystals 2023, 13(5), 758; https://doi.org/10.3390/cryst13050758 - 03 May 2023

Cited by 4 | Viewed by 1214

Abstract

This study aims to develop a self-combustion method for use in the preparation of copper and cobalt ferrites. This development was based on the full use of dry leaves of Corchorus olitorius plant in order to stimulate the preparation of the studied ferrites by making full use of the small amount of carbon produced from the combustion process. The fabrication of CuFe₂O₄ and CoFe₂O₄ with spinel-type structures and the Fd3m space group is confirmed by XRD and FTIR investigations. Two major vibration bands occur laterally at 400 cm⁻¹ and 600 cm⁻¹. We were able to understand the existence of two stages through the thermal behavior based on TG-DTG analysis for the materials under investigation. The first is from room temperature to 600 °C, which indicates the formation of reacting oxides with Co or Cu ferrites, while the second is from 600–1000 °C, which indicates the growth in the ferrite fabrication. The surface morphological analyses (SEM/EDS and TEM) display formation of homogeneous and nanosized particles. The surface properties of the samples containing CoFe₂O₄ are superior compared to those of the samples not containing CuFe₂O₄. Every sample under investigation displays type-IV-based isotherms with a type-H3 hysteresis loop. The VSM approach was used to evaluate the magnetic characteristics of Cu and Co ferrites. Copper ferrites have a magnetization of 15.77 emu/g, and cobalt ferrites have a magnetization of 19.14 emu/g. Moreover, the squareness (0.263) and coercivity (716.15 G) of cobalt ferrite are higher than those of copper ferrite. Full article

(This article belongs to the Special Issue Crystalline Magnetic Compounds)

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11 pages, 2474 KiB

Open AccessArticle

Magnetic and Electronic Properties of Edge-Modified Triangular WS₂ and MoS₂ Quantum Dots

by Hazem Abdelsalam, Omar H. Abd-Elkader, Nouf S. Zaghloul and Qinfang Zhang

Crystals 2023, 13(2), 251; https://doi.org/10.3390/cryst13020251 - 01 Feb 2023

Cited by 6 | Viewed by 1692

Abstract

The magnetic and electronic properties of zigzag-triangular WS₂ and MoS₂ quantum dots are investigated using density functional theory calculations. The pristine WS₂ and MoS₂ nanodots hold permanent spin on their edges which originates from the unpaired electrons of the transition metals at the edges. The ferromagnetic spin ordering in zigzag-triangular WS₂ and MoS₂ can be transformed to antiferromagnetic ordering with S = 0 and to nonmagnetic, respectively, by edge passivation with 2H. The calculations of the Curie Temperature indicate that these magnetic states are stable and withstand room temperature. The paramagnetic susceptibility of these structures significantly decreases by edge sulfuration. Moreover, it can be converted to diamagnetic susceptibility by edge passivation with 2H as found in WS₂ nanodots. These structures are semiconductors with energy gaps of ~3.3 eV that decrease unexpectedly by edge passivation due to the existence of lone pairs from S atoms that give a high contribution to the low-energy molecular orbitals. With these preferable magnetic properties and controlled electronic ones, WS₂ and MoS₂ quantum dots are potential candidates for spintronic applications. Full article

(This article belongs to the Special Issue Crystalline Magnetic Compounds)

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17 pages, 3716 KiB

Open AccessArticle

Magnetic Behavior of Virgin and Lithiated NiFe₂O₄ Nanoparticles

by Ghadah M. Al-Senani, Foziah F. Al-Fawzan, Rasmiah S. Almufarij, Omar H. Abd-Elkader and Nasrallah M. Deraz

Crystals 2023, 13(1), 69; https://doi.org/10.3390/cryst13010069 - 31 Dec 2022

Cited by 6 | Viewed by 1510

Abstract

A series of virgin and lithia-doped Ni ferrites was synthesized using egg-white-mediated combustion. Characterization of the investigated ferrites was performed using several techniques, specifically, X-ray Powder Diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and High-resolution transmission electron microscopy (HRTEM). XRD-based structural parameters were determined. A closer look at these characteristics reveals that lithia doping enhanced the nickel ferrite lattice constant (a), unit cell volume (V), stress (ε), microstrain (σ), and dislocation density (δ). It also enhanced the separation between magnetic ions (L_A and L_B), ionic radii (r_A, r_B), and bond lengths (A-O and B-O) between tetrahedral (A) and octahedral (B) locations. Furthermore, it enhanced the X-ray density (Dx) and crystallite size (d) of random spinel nickel ferrite displaying opposing patterns of behavior. FTIR-based functional groups of random spinel nickel ferrite were determined. HRTEM-based morphological properties of the synthesized ferrite were investigated. These characteristics of NiFe₂O₄ particles, such as their size, shape, and crystallinity, demonstrate that these manufactured particles are present at the nanoscale and that lithia doping caused shape modification of the particles. Additionally, the prepared ferrite’s surface area and total pore volume marginally increased after being treated with lithia, depending on the visibility of the grain boundaries. Last, but not least, as the dopant content was increased through a variety of methods, the magnetization of virgin nickel ferrite fell with a corresponding increase in coercivity. Uniaxial anisotropy, rather than cubic anisotropy, and antisite and cation excess defects developed in virgin and lithia-doped nickel ferrites because the squareness ratio (M_r/M_s) was less than 0.5. Small squareness values strongly recommend using the assessed ferrites in high-frequency applications. Full article

(This article belongs to the Special Issue Crystalline Magnetic Compounds)

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15 pages, 4075 KiB

Open AccessArticle

Tunable Sensing and Transport Properties of Doped Hexagonal Boron Nitride Quantum Dots for Efficient Gas Sensors

by Hazem Abdelsalam, Vasil A. Saroka, Mohamed M. Atta, Omar H. Abd-Elkader, Nouf S. Zaghloul and Qinfang Zhang

Crystals 2022, 12(11), 1684; https://doi.org/10.3390/cryst12111684 - 21 Nov 2022

Cited by 11 | Viewed by 1806

Abstract

The electronic, sensing, and transport properties of doped square hexagonal boron nitride (shBN) quantum dots were investigated using density functional theory calculations. The electronic and magnetic properties were controlled by substitutional doping. For instance, heterodoping with Si and C atoms decreased the energy gap to half its value and converted the insulator shBN quantum dot to a semiconductor. Doping with a single O atom transformed the dot to spin half metal with a tiny spin-up energy gap and a wide spin-down gap. Moreover, doping and vacancies formed low-energy interactive molecular orbitals which were important for boosting sensing properties. The unmodified shBN quantum dot showed moderate physical adsorption of NO₂, acetone, CH₄, and ethanol. This adsorption was elevated by doping due to interactions between electrons in the low-energy orbitals from the doped-shBN dot and π-bond electrons from the gas. The transport properties also showed a significant change in the current by doping. For instance, the spin-up current was very high compared to the spin-down current in the shBN dots doped with an O atom, confirming the formation of spin half metal. The spin-up/down currents were strongly affected by gas adsorption, which can be used as an indicator of the sensing process. Full article

(This article belongs to the Special Issue Crystalline Magnetic Compounds)

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13 pages, 3181 KiB

Open AccessArticle

Biosynthesis, Physicochemical and Magnetic Properties of Inverse Spinel Nickel Ferrite System

by Ghadah M. Al-Senani, Foziah F. Al-Fawzan, Rasmiah S. Almufarij, Omar H. Abd-Elkader and Nasrallah M. Deraz

Crystals 2022, 12(11), 1542; https://doi.org/10.3390/cryst12111542 - 28 Oct 2022

Cited by 8 | Viewed by 1399

Abstract

Nanosized Ni ferrite has been prepared by an ecofriendly green synthesis approach based on the self-combustion method. In this route, the egg white as a green fuel was employed with two different amounts (3 and 10 mL). The XRD results display the formation of a stoichiometric NiFe₂O₄-type inverse spinel structure with a lattice parameter located at 0.8284 nm and 0.8322 nm. Additionally, the nickel ferrites’ typical crystallite size, as synthesized, ranged between 4 and 18 nm. Indicating the development of ferrite material, FTIR analysis shows two distinctive vibrational modes around 600 cm⁻¹ and 400 cm⁻¹. TEM measurements show the formation of nanosized particles with semispherical-type structure and some agglomerations. As the egg white concentration rises, the surface area, total pore volume, and mean pore radius of the material, as prepared, all decrease, and according to the surface area parameters discovered using BET analysis. Based on VSM analysis, the values of saturation magnetization are 6.6589 emu/g and 37.727 emu/g, whereas the coercivity are 159.15 G and 113.74 G. The as-synthesized Ni ferrites fit into the pseudo-single domain predicated by the squareness values (0.1526 and 0.1824). It is mentioned that increasing the egg white content would promote the magnetization of NiFe₂O₄. Full article

(This article belongs to the Special Issue Crystalline Magnetic Compounds)

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