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10 pages, 2231 KiB

Open AccessArticle

High-Moment FeCo Magnetic Nanoparticles Obtained by Topochemical H₂ Reduction of Co-Ferrites

by Alexander Omelyanchik, Gaspare Varvaro, Pierfrancesco Maltoni, Valeria Rodionova, Jean-Pierre Miranda Murillo, Federico Locardi, Maurizio Ferretti, Claudio Sangregorio, Fabio Canepa, Petr Chernavsky, Nikolai Perov and Davide Peddis

Appl. Sci. 2022, 12(4), 1899; https://doi.org/10.3390/app12041899 - 11 Feb 2022

Cited by 8 | Viewed by 1954

Abstract

Cobalt ferrite nanoparticles of different stoichiometries synthesized by a sol–gel autocombustion method were used as a starting material to obtain high-moment Fe₅₀Co₅₀ and Fe₆₆Co₃₄ metal nanoparticles by topochemical hydrogen reduction. Structural and magnetic investigations confirmed the formation [...] Read more.

Cobalt ferrite nanoparticles of different stoichiometries synthesized by a sol–gel autocombustion method were used as a starting material to obtain high-moment Fe₅₀Co₅₀ and Fe₆₆Co₃₄ metal nanoparticles by topochemical hydrogen reduction. Structural and magnetic investigations confirmed the formation of FeCo nanoparticles with crystallite sizes of about 30 nm and magnetization at 0.5 T of ~265 Am²/kg (0 K), which was larger than the expected bulk value, likely because of the incorporation in the body-centered cubic (bcc) FeCo structure of the residual C atoms present on the surface of the oxide particles. Temperature-dependent magnetization measurements in the H₂ atmosphere were also performed to investigate in detail the reduction mechanism and the effect of an external magnetic field on the process efficiency. Full article

(This article belongs to the Special Issue Advances in Magnetic Nanomaterials and Nanostructures)

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11 pages, 5516 KiB

Open AccessArticle

Nano Scaled Checkerboards: A Long Range Ordering in NiCoMnAl Magnetic Shape Memory Alloy Thin Films with Martensitic Intercalations

by Daniela Ramermann, Andreas Becker, Björn Büker, Andreas Hütten and Inga Ennen

Appl. Sci. 2022, 12(3), 1748; https://doi.org/10.3390/app12031748 - 08 Feb 2022

Cited by 1 | Viewed by 1456

Abstract

Magnetic shape memory Heusler alloys, such as NiCoMnAl, are considered as promising candidates for magnetocaloric cooling applications. Grown in thin film systems of adjacent layers with austenite and martensite crystal structures of almost equal thicknesses, a long-range ordering phenomenon in the shape of [...] Read more.

Magnetic shape memory Heusler alloys, such as NiCoMnAl, are considered as promising candidates for magnetocaloric cooling applications. Grown in thin film systems of adjacent layers with austenite and martensite crystal structures of almost equal thicknesses, a long-range ordering phenomenon in the shape of a 3D checkerboard pattern occurs in NiCoMnAl samples. The crystallographic origin of the pattern is proven by transmission electron microscopy (TEM) techniques. The darker fields of the arrangement consist of martensite nuclei superposed with austenite, while the purely austenite regions appear bright in TEM cross sections. The nucleation process is presumably triggered by inhomogeneous local elastic stray fields of primary martensitic nuclei in the austenite matrix and limited by the thicknesses of the martensite and austenite thin films. Full article

(This article belongs to the Special Issue Advances in Magnetic Nanomaterials and Nanostructures)

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15 pages, 3585 KiB

Open AccessArticle

Structural and Magnetic Properties of Nanosized Half-Doped Rare-Earth Ho_0.5Ca_0.5MnO₃ Manganite

by Alessandra Geddo Lehmann, Giuseppe Muscas, Maurizio Ferretti, Emanuela Pusceddu, Davide Peddis and Francesco Congiu

Appl. Sci. 2022, 12(2), 695; https://doi.org/10.3390/app12020695 - 11 Jan 2022

Cited by 1 | Viewed by 1760

Abstract

We investigated the structural and magnetic properties of 20 nm-sized nanoparticles of the half-doped manganite Ho_0.5Ca_0.5MnO₃ prepared by sol-gel approach. Neutron powder diffraction patterns show Pbnm orthorhombic symmetry for 10 K < T < 290 K, with lattice [...] Read more.

We investigated the structural and magnetic properties of 20 nm-sized nanoparticles of the half-doped manganite Ho_0.5Ca_0.5MnO₃ prepared by sol-gel approach. Neutron powder diffraction patterns show Pbnm orthorhombic symmetry for 10 K < T < 290 K, with lattice parameters a, b, and c in the relationship c/√2 < a < b, indicating a cooperative Jahn–Teller effect, i.e., orbital ordering OO, from below room temperature. In contrast with the bulk samples, in the interval 250 < T < 300 K, the fingerprint of charge ordering (CO) does not manifest itself in the temperature dependence of lattice parameters. However, there are signs of CO in the temperature dependence of magnetization. Accordingly, below 100 K superlattice magnetic Bragg reflections arise, which are consistent with an antiferromagnetic phase strictly related to the bulk Mn ordering of a charge exchange-type (CE-type), but characterized by an increased fraction of ferromagnetic couplings between manganese species themselves. Our results show that in this narrow band half-doped manganite, size reduction only modifies the balance between the Anderson superexchange and Zener double exchange interactions, without destabilizing an overall very robust antiferromagnetic state. Full article

(This article belongs to the Special Issue Advances in Magnetic Nanomaterials and Nanostructures)

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17 pages, 4140 KiB

Open AccessArticle

Comparison of Structure and Magnetic Properties of Ni/C Composites Synthesized from Wheat Straw by Different Methods

by Ihor Bordun, Krzysztof Chwastek, Dariusz Całus, Piotr Chabecki, Fedir Ivashchyshyn, Zenoviy Kohut, Anatoliy Borysiuk and Yuriy Kulyk

Appl. Sci. 2021, 11(21), 10031; https://doi.org/10.3390/app112110031 - 26 Oct 2021

Cited by 2 | Viewed by 1299

Abstract

Synthesis of Ni/C nanostructured composites based on a natural raw material, i.e., wheat straw, is carried out in this work. The synthesis is performed by one- and two-stage methods using NiCl₂ as the activating agent. The X-ray diffraction and EDS analyses reveal [...] Read more.

Synthesis of Ni/C nanostructured composites based on a natural raw material, i.e., wheat straw, is carried out in this work. The synthesis is performed by one- and two-stage methods using NiCl₂ as the activating agent. The X-ray diffraction and EDS analyses reveal the presence of metallic nickel in the structure of the composites, whereas magnetic measurements showed that nickel was contained in the porous carbon matrix in the nanoparticle state. For nanocomposites synthesized by the one-stage method, the largest contribution to the formation of the porous structure might be attributed to pores with radii from 5 to 30 nm; for a nanocomposite synthesized in two stages, the pore distribution function exhibits a narrow isolated peak with a maximum of around 2.6 nm. Based on the obtained magnetic data, the coercive force, specific saturation magnetization and nickel content in nanocomposites are calculated. For the measured values of the coercive force, the average size of magnetic moment carriers is determined to be ~100 nm for the two-stage synthesis nanocomposite and ~100 ÷ 110 nm for the one-stage synthesis nanocomposites. The developed Ni/C nanocomposites might be used as a cheap material for energy storage applications or as magnetically controlled adsorbents. Full article

(This article belongs to the Special Issue Advances in Magnetic Nanomaterials and Nanostructures)

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12 pages, 2943 KiB

Open AccessArticle

Enhancement of the Luminescence Properties of Eu (III) Containing Paramagnetic Saponite Clays

by Stefano Marchesi, Chiara Bisio and Fabio Carniato

Appl. Sci. 2021, 11(19), 8903; https://doi.org/10.3390/app11198903 - 24 Sep 2021

Cited by 3 | Viewed by 1526

Abstract

In this study, 1,10-phenanthroline molecules were introduced in the interlayer space of a paramagnetic synthetic saponite clay containing both Eu³⁺ and Gd³⁺ ions in structural positions. Two samples with different loading of phenanthroline dye were prepared. The resulting hybrid materials possessed [...] Read more.

In this study, 1,10-phenanthroline molecules were introduced in the interlayer space of a paramagnetic synthetic saponite clay containing both Eu³⁺ and Gd³⁺ ions in structural positions. Two samples with different loading of phenanthroline dye were prepared. The resulting hybrid materials possessed improved optical emission properties due to an efficient antenna effect from the phenanthroline to the Eu³⁺ centers; this effect was demonstrated to be higher than the metal-to-metal Gd³⁺-Eu³⁺ energy transfer previously studied. Insights on the relaxometric properties in aqueous solution of the solids after incorporation of the antenna groups were also obtained through NMR relaxometric analyses. Full article

(This article belongs to the Special Issue Advances in Magnetic Nanomaterials and Nanostructures)

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12 pages, 3581 KiB

Open AccessArticle

Polyaspartic Acid-Coated Paramagnetic Gadolinium Oxide Nanoparticles as a Dual-Modal T₁ and T₂ Magnetic Resonance Imaging Contrast Agent

by Shanti Marasini, Huan Yue, Adibehalsadat Ghazanfari, Son Long Ho, Ji Ae Park, Soyeon Kim, Hyunsil Cha, Shuwen Liu, Tirusew Tegafaw, Mohammad Yaseen Ahmad, Abdullah Khamis Ali Al Saidi, Dejun Zhao, Ying Liu, Kwon-Seok Chae, Yongmin Chang and Gang Ho Lee

Appl. Sci. 2021, 11(17), 8222; https://doi.org/10.3390/app11178222 - 04 Sep 2021

Cited by 12 | Viewed by 2319

Abstract

Surface-coating polymers contribute to nanoparticle-based magnetic resonance imaging (MRI) contrast agents because they can affect the relaxometric properties of the nanoparticles. In this study, polyaspartic acid (PASA)-coated ultrasmall Gd₂O₃ nanoparticles with an average particle diameter of 2.0 nm were synthesized [...] Read more.

Surface-coating polymers contribute to nanoparticle-based magnetic resonance imaging (MRI) contrast agents because they can affect the relaxometric properties of the nanoparticles. In this study, polyaspartic acid (PASA)-coated ultrasmall Gd₂O₃ nanoparticles with an average particle diameter of 2.0 nm were synthesized using the one-pot polyol method. The synthesized nanoparticles exhibited r₁ and r₂ of 19.1 and = 53.7 s⁻¹mM⁻¹, respectively, (r₁ and r₂ are longitudinal and transverse water–proton spin relaxivities, respectively) at 3.0 T MR field, approximately 5 and 10 times higher than those of commercial Gd-chelate contrast agents, respectively. The T₁ and T₂ MR images could be obtained due to an appreciable r₂/r₁ ratio of 2.80, indicating their potential as a dual-modal T₁ and T₂ MRI contrast agent. Full article

(This article belongs to the Special Issue Advances in Magnetic Nanomaterials and Nanostructures)

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17 pages, 4117 KiB

Open AccessFeature PaperArticle

Synthesis and Application of the Magnetic Nanocomposite GO-Chm for the Extraction of Benzodiazepines from Surface Water Samples Prior to HPLC-PDA Analysis

by Orfeas-Evangelos Plastiras, Eleni Deliyanni and Victoria Samanidou

Appl. Sci. 2021, 11(17), 7828; https://doi.org/10.3390/app11177828 - 25 Aug 2021

Cited by 9 | Viewed by 1924

Abstract

Nowadays, the interest in preparing new, cheap and simple adsorbents that are used in sample preparation is on the rise. Graphene oxide (GO) nanomaterials and nanocomposites have become increasingly popular due to the novel methods of syntheses that have been published. Owing to [...] Read more.

Nowadays, the interest in preparing new, cheap and simple adsorbents that are used in sample preparation is on the rise. Graphene oxide (GO) nanomaterials and nanocomposites have become increasingly popular due to the novel methods of syntheses that have been published. Owing to their vast specific surface area and their π-delocalized electron system they possess, they are appropriate for the adsorption of a variety of aromatic organic compounds, being utilized either as adsorbents in analytical methods or as filter materials for the removal of pollutants in water. Pharmaceutical compounds, such as benzodiazepines, end up in surface waters caused by consumption or their disposal through sewage, thus becoming pollutants. In the present study, an analytical method has been developed and validated for the determination of two model-analytes of benzodiazepines by HPLC-DAD and their sample preparation protocol which consists of the Stir bar magnetic solid phase extraction (SB-MSPE) method, evaluating therefore the nanocomposite material as a decent adsorbent. The separation took place with the usage of an analytical column C₁₈ RP-HPLC in 10 min. For the alprazolam (ALP) and the flunitrazepam (FLT), the LODs and LOQs were 3 ng/mL and 10 ng/mL, respectively, while the relative recoveries ranged between 93.6–112.9% and the RSDs were 1.11–9.50%. Finally, the material was examined for its reusability and was found that it can be used for over eight cycles of extraction/elution. Full article

(This article belongs to the Special Issue Advances in Magnetic Nanomaterials and Nanostructures)

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Review

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34 pages, 5176 KiB

Open AccessEditor’s ChoiceReview

Fe₃O₄ Nanoparticles: Structures, Synthesis, Magnetic Properties, Surface Functionalization, and Emerging Applications

by Minh Dang Nguyen, Hung-Vu Tran, Shoujun Xu and T. Randall Lee

Appl. Sci. 2021, 11(23), 11301; https://doi.org/10.3390/app112311301 - 29 Nov 2021

Cited by 161 | Viewed by 24949

Abstract

Magnetite (Fe₃O₄) nanoparticles (NPs) are attractive nanomaterials in the field of material science, chemistry, and physics because of their valuable properties, such as soft ferromagnetism, half-metallicity, and biocompatibility. Various structures of Fe₃O₄ NPs with different sizes, [...] Read more.

Magnetite (Fe₃O₄) nanoparticles (NPs) are attractive nanomaterials in the field of material science, chemistry, and physics because of their valuable properties, such as soft ferromagnetism, half-metallicity, and biocompatibility. Various structures of Fe₃O₄ NPs with different sizes, geometries, and nanoarchitectures have been synthesized, and the related properties have been studied with targets in multiple fields of applications, including biomedical devices, electronic devices, environmental solutions, and energy applications. Tailoring the sizes, geometries, magnetic properties, and functionalities is an important task that determines the performance of Fe₃O₄ NPs in many applications. Therefore, this review focuses on the crucial aspects of Fe₃O₄ NPs, including structures, synthesis, magnetic properties, and strategies for functionalization, which jointly determine the application performance of various Fe₃O₄ NP-based systems. We first summarize the recent advances in the synthesis of magnetite NPs with different sizes, morphologies, and magnetic properties. We also highlight the importance of synthetic factors in controlling the structures and properties of NPs, such as the uniformity of sizes, morphology, surfaces, and magnetic properties. Moreover, emerging applications using Fe₃O₄ NPs and their functionalized nanostructures are also highlighted with a focus on applications in biomedical technologies, biosensing, environmental remedies for water treatment, and energy storage and conversion devices. Full article

(This article belongs to the Special Issue Advances in Magnetic Nanomaterials and Nanostructures)

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24 pages, 3114 KiB

Open AccessReview

Application of Spinel and Hexagonal Ferrites in Heterogeneous Photocatalysis

by Zuzanna Bielan, Szymon Dudziak, Adam Kubiak and Ewa Kowalska

Appl. Sci. 2021, 11(21), 10160; https://doi.org/10.3390/app112110160 - 29 Oct 2021

Cited by 12 | Viewed by 3532

Abstract

Semiconducting materials display unique features that enable their use in a variety of applications, including self-cleaning surfaces, water purification systems, hydrogen generation, solar energy conversion, etc. However, one of the major issues is separation of the used materials from the process suspension. Therefore, [...] Read more.

Semiconducting materials display unique features that enable their use in a variety of applications, including self-cleaning surfaces, water purification systems, hydrogen generation, solar energy conversion, etc. However, one of the major issues is separation of the used materials from the process suspension. Therefore, chemical compounds with magnetic properties have been proposed as crucial components of photocatalytic composites, facilitating separation and recovery of photocatalysts under magnetic field conditions. This review paper presents the current state of knowledge on the application of spinel and hexagonal ferrites in heterogeneous photocatalysis. The first part focuses on the characterization of magnetic (nano)particles. The next section presents the literature findings on the single-phase magnetic photocatalyst. Finally, the current state of scientific knowledge on the wide variety of magnetic-photocatalytic composites is presented. A key aim of this review is to indicate that spinel and hexagonal ferrites are considered as an important element of heterogeneous photocatalytic systems and are responsible for the effective recycling of the photocatalytic materials. Full article

(This article belongs to the Special Issue Advances in Magnetic Nanomaterials and Nanostructures)

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