Research

22 pages, 2904 KiB

Open AccessArticle

From Structure to Function: Understanding Synthetic Conditions in Relation to Magnetic Properties of Hybrid Pd/Fe-Oxide Nanoparticles

by Alexandra Maier, Rogier van Oossanen, Gerard C. van Rhoon, Jean-Philippe Pignol, Iulian Dugulan, Antonia G. Denkova and Kristina Djanashvili

Nanomaterials 2022, 12(20), 3649; https://0-doi-org.brum.beds.ac.uk/10.3390/nano12203649 - 18 Oct 2022

Cited by 3 | Viewed by 1829

Abstract

Heterostructured magnetic nanoparticles show great potential for numerous applications in biomedicine due to their ability to express multiple functionalities in a single structure. Magnetic properties are generally determined by the morphological characteristics of nanoparticles, such as the size/shape, and composition of the nanocrystals. [...] Read more.

Heterostructured magnetic nanoparticles show great potential for numerous applications in biomedicine due to their ability to express multiple functionalities in a single structure. Magnetic properties are generally determined by the morphological characteristics of nanoparticles, such as the size/shape, and composition of the nanocrystals. These in turn are highly dependent on the synthetic conditions applied. Additionally, incorporation of a non-magnetic heterometal influences the final magnetic behavior. Therefore, construction of multifunctional hybrid nanoparticles with preserved magnetic properties represents a certain nanotechnological challenge. Here, we focus on palladium/iron oxide nanoparticles designed for combined brachytherapy, the internal form of radiotherapy, and MRI-guided hyperthermia of tumors. The choice of palladium forming the nanoparticle core is envisioned for the eventual radiolabeling with ¹⁰³Pd to enable the combination of hyperthermia with brachytherapy, the latter being beyond the scope of the present study. At this stage, we investigated the synthetic mechanisms and their effects on the final magnetic properties of the hybrid nanoparticles. Thermal decomposition was applied for the synthesis of Pd/Fe-oxide nanoparticles via both, one-pot and seed-mediated processes. The latter method was found to provide better control over morphology of the nanoparticles and was therefore examined closely by varying reaction conditions. This resulted in several batches of Pd/Fe-oxide nanoparticles, whose magnetic properties were evaluated, revealing the most relevant synthetic parameters leading to promising performance in hyperthermia and MRI. Full article

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

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14 pages, 3698 KiB

Open AccessArticle

Application of Magnonic Crystals in Magnetic Bead Detection

by Alessandra Manzin, Riccardo Ferrero and Marta Vicentini

Nanomaterials 2022, 12(19), 3278; https://0-doi-org.brum.beds.ac.uk/10.3390/nano12193278 - 21 Sep 2022

Cited by 1 | Viewed by 1410

Abstract

This paper aims at studying a sensor concept for possible integration in magnetic field-based lab-on-chip devices that exploit ferromagnetic resonance (FMR) phenomena in magnonic crystals. The focus is on 2D magnetic antidot arrays, i.e., magnetic thin films with periodic non-magnetic inclusions (holes), recently [...] Read more.

This paper aims at studying a sensor concept for possible integration in magnetic field-based lab-on-chip devices that exploit ferromagnetic resonance (FMR) phenomena in magnonic crystals. The focus is on 2D magnetic antidot arrays, i.e., magnetic thin films with periodic non-magnetic inclusions (holes), recently proposed as magnetic field sensor elements operating in the gigahertz (GHz) range. The sensing mechanism is here demonstrated for magnetic nano/microbeads adsorbed on the surface of permalloy (Ni₈₀Fe₂₀) antidot arrays with a rhomboid lattice structure and variable hole size. Through extensive micromagnetic modelling analysis, it is shown that the antidot arrays can be used as both bead traps and high-sensitivity detectors, with performance that can be tuned as a function of bead size and magnetic moment. A key parameter for the detection mechanism is the antidot array hole size, which affects the FMR frequency shifts associated with the interaction between the magnetization configuration in the nanostructured film and the bead stray field. Possible applications of the proposed device concept include magnetic immunoassays, using magnetic nano/microbeads as probes for biomarker detection, and biomaterial manipulation. Full article

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

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14 pages, 1882 KiB

Open AccessArticle

New Insights into Amino-Functionalization of Magnetic Nanoplatelets with Silanes and Phosphonates

by Jelena Papan Djaniš, Griša Grigorij Prinčič, Andraž Mavrič, Alenka Mertelj, Jernej Iskra and Darja Lisjak

Nanomaterials 2022, 12(12), 2123; https://0-doi-org.brum.beds.ac.uk/10.3390/nano12122123 - 20 Jun 2022

Cited by 1 | Viewed by 1820

Abstract

Magnetic nanoplatelets (NPLs) based on barium hexaferrite (BaFe₁₂O₁₉) are suitable for many applications because of their uniaxial magneto-crystalline anisotropy. Novel materials, such as ferroic liquids, magneto-optic composites, and contrast agents for medical diagnostics, were developed by specific surface functionalization [...] Read more.

Magnetic nanoplatelets (NPLs) based on barium hexaferrite (BaFe₁₂O₁₉) are suitable for many applications because of their uniaxial magneto-crystalline anisotropy. Novel materials, such as ferroic liquids, magneto-optic composites, and contrast agents for medical diagnostics, were developed by specific surface functionalization of the barium hexaferrite NPLs. Our aim was to amino-functionalize the NPLs’ surfaces towards new materials and applications. The amino-functionalization of oxide surfaces is challenging and has not yet been reported for barium hexaferrite NPLs. We selected two amine ligands with two different anchoring groups: an amino-silane and an amino-phosphonate. We studied the effect of the anchoring group, backbone structure, and processing conditions on the formation of the respective surface coatings. The core and coated NPLs were examined with transmission electron microscopy, and their room-temperature magnetic properties were measured. The formation of coatings was followed by electrokinetic measurements, infrared and mass spectroscopies, and thermogravimetric analysis. The most efficient amino-functionalization was enabled by (i) amino-silanization of the NPLs precoated with amorphous silica with (3-aminopropyl)triethoxysilane and (ii) slow addition of amino-phosphonate (i.e., sodium alendronate) to the acidified NPL suspension at 80 °C. Full article

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

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8 pages, 2073 KiB

Open AccessArticle

Reversal of the Pinning Direction in the Synthetic Spin Valve with a NiFeCr Seed Layer

by Shaohua Yan, Weibin Chen, Zitong Zhou, Zhi Li, Zhiqiang Cao, Shiyang Lu, Dapeng Zhu, Weisheng Zhao and Qunwen Leng

Nanomaterials 2022, 12(12), 2077; https://0-doi-org.brum.beds.ac.uk/10.3390/nano12122077 - 16 Jun 2022

Viewed by 1556

Abstract

The effect of the seed layers on the magnetic properties of the giant magnetoresistance thin films has received a lot of attention. Here, a synthetic spin valve film stack with a wedge-shaped NiFeCr seed layer is deposited and annealed following a zero-field cooling [...] Read more.

The effect of the seed layers on the magnetic properties of the giant magnetoresistance thin films has received a lot of attention. Here, a synthetic spin valve film stack with a wedge-shaped NiFeCr seed layer is deposited and annealed following a zero-field cooling procedure. The film crystallinity and magnetic properties are studied as a function of the NiFeCr seed layer thickness. It is found that the exchange coupling field from the IrMn/CoFe interface and the antiferromagnetic coupling field in the synthetic antiferromagnet both increase as the seed layer thickness increases, indicating the perfection of film texture. In this film, the critical thickness of the NiFeCr seed layer for the formation of the ordered IrMn₃ texture is about 9.3 nm. Meanwhile, a reversal of the pinning direction in the film is observed at this critical thickness of NiFeCr. This phenomenon can be explained in a free energy model by the competition effect between the exchange coupling and the interlayer coupling during the annealing process. Full article

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

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11 pages, 2707 KiB

Open AccessArticle

Distinguishing Local Demagnetization Contribution to the Magnetization Process in Multisegmented Nanowires

by Jorge Marqués-Marchán, Jose Angel Fernandez-Roldan, Cristina Bran, Robert Puttock, Craig Barton, Julián A. Moreno, Jürgen Kosel, Manuel Vazquez, Olga Kazakova, Oksana Chubykalo-Fesenko and Agustina Asenjo

Nanomaterials 2022, 12(12), 1968; https://0-doi-org.brum.beds.ac.uk/10.3390/nano12121968 - 08 Jun 2022

Cited by 2 | Viewed by 2172

Abstract

Cylindrical magnetic nanowires are promising materials that have the potential to be used in a wide range of applications. The versatility of these nanostructures is based on the tunability of their magnetic properties, which is achieved by appropriately selecting their composition and morphology. [...] Read more.

Cylindrical magnetic nanowires are promising materials that have the potential to be used in a wide range of applications. The versatility of these nanostructures is based on the tunability of their magnetic properties, which is achieved by appropriately selecting their composition and morphology. In addition, stochastic behavior has attracted attention in the development of neuromorphic devices relying on probabilistic magnetization switching. Here, we present a study of the magnetization reversal process in multisegmented CoNi/Cu nanowires. Nonstandard 2D magnetic maps, recorded under an in-plane magnetic field, produce datasets that correlate with magnetoresistance measurements and micromagnetic simulations. From this process, the contribution of the individual segments to the demagnetization process can be distinguished. The results show that the magnetization reversal in these nanowires does not occur through a single Barkhausen jump, but rather by multistep switching, as individual CoNi segments in the NW undergo a magnetization reversal. The existence of vortex states is confirmed by their footprint in the magnetoresistance and 2D MFM maps. In addition, the stochasticity of the magnetization reversal is analysed. On the one hand, we observe different switching fields among the segments due to a slight variation in geometrical parameters or magnetic anisotropy. On the other hand, the stochasticity is observed in a series of repetitions of the magnetization reversal processes for the same NW under the same conditions. Full article

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

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17 pages, 2909 KiB

Open AccessArticle

Highly Sensitive NO₂ Gas Sensors Based on MoS₂@MoO₃ Magnetic Heterostructure

by Wei Li, Mahboobeh Shahbazi, Kaijian Xing, Tuquabo Tesfamichael, Nunzio Motta and Dong-Chen Qi

Nanomaterials 2022, 12(8), 1303; https://0-doi-org.brum.beds.ac.uk/10.3390/nano12081303 - 11 Apr 2022

Cited by 12 | Viewed by 2864

Abstract

Recently, two-dimensional (2D) materials and their heterostructures have attracted considerable attention in gas sensing applications. In this work, we synthesized 2D MoS₂@MoO₃ heterostructures through post-sulfurization of α-MoO₃ nanoribbons grown via vapor phase transport (VPT) and demonstrated highly sensitive NO [...] Read more.

Recently, two-dimensional (2D) materials and their heterostructures have attracted considerable attention in gas sensing applications. In this work, we synthesized 2D MoS₂@MoO₃ heterostructures through post-sulfurization of α-MoO₃ nanoribbons grown via vapor phase transport (VPT) and demonstrated highly sensitive NO₂ gas sensors based on the hybrid heterostructures. The morphological, structural, and compositional properties of the MoS₂@MoO₃ hybrids were studied by a combination of advanced characterization techniques revealing a core-shell structure with the coexistence of 2H-MoS₂ multilayers and intermediate molybdenum oxysulfides on the surface of α-MoO₃. The MoS₂@MoO₃ hybrids also exhibit room-temperature ferromagnetism, revealed by vibrating sample magnetometry (VSM), as a result of the sulfurization process. The MoS₂@MoO₃ gas sensors display a p-type-like response towards NO₂ with a detection limit of 0.15 ppm at a working temperature of 125 °C, as well as superb selectivity and reversibility. This p-type-like sensing behavior is attributed to the heterointerface of MoS₂-MoO₃ where interfacial charge transfer leads to a p-type inversion layer in MoS₂, and is enhanced by magnetic dipole interactions between the paramagnetic NO₂ and the ferromagnetic sensing layer. Our study demonstrates the promising application of 2D molybdenum hybrid compounds in gas sensing applications with a unique combination of electronic and magnetic properties. Full article

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

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20 pages, 41214 KiB

Open AccessArticle

Large-Area Nanopillar Arrays by Glancing Angle Deposition with Tailored Magnetic Properties

by Elena Navarro, María Ujué González, Fanny Béron, Felipe Tejo, Juan Escrig and José Miguel García-Martín

Nanomaterials 2022, 12(7), 1186; https://0-doi-org.brum.beds.ac.uk/10.3390/nano12071186 - 01 Apr 2022

Cited by 4 | Viewed by 2511

Abstract

Ferromagnetic films down to thicknesses of tens of nanometers and composed by polycrystalline Fe and Fe₂O₃ nanopillars are grown in large areas by glancing angle deposition with magnetron sputtering (MS-GLAD). The morphological features of these films strongly depend on the [...] Read more.

Ferromagnetic films down to thicknesses of tens of nanometers and composed by polycrystalline Fe and Fe₂O₃ nanopillars are grown in large areas by glancing angle deposition with magnetron sputtering (MS-GLAD). The morphological features of these films strongly depend on the growth conditions. Vertical or tilted nanopillars have been fabricated depending on whether the substrate is kept rotating azimuthally during deposition or not, respectively. The magnetic properties of these nanopillars films, such as hysteresis loops squareness, adjustable switching fields, magnetic anisotropy and coercivity, can be tuned with the specific morphology. In particular, the growth performed through a collimator mask mounted onto a not rotating azimuthally substrate produces almost isolated well-defined tilted nanopillars that exhibit a magnetic hardening. The first-order reversal curves diagrams and micromagnetic simulations revealed that a growth-induced uniaxial anisotropy, associated with an anisotropic surface morphology produced by the glancing angle deposition in the direction perpendicular to the atomic flux, plays an important role in the observed magnetic signatures. These results demonstrate the potential of the MS-GLAD method to fabricate nanostructured films in large area with tailored structural and magnetic properties for technological applications. Full article

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

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18 pages, 31989 KiB

Open AccessArticle

Experimental and Modelling Analysis of the Hyperthermia Properties of Iron Oxide Nanocubes

by Riccardo Ferrero, Gabriele Barrera, Federica Celegato, Marta Vicentini, Hüseyin Sözeri, Nuray Yıldız, Ceren Atila Dinçer, Marco Coïsson, Alessandra Manzin and Paola Tiberto

Nanomaterials 2021, 11(9), 2179; https://0-doi-org.brum.beds.ac.uk/10.3390/nano11092179 - 25 Aug 2021

Cited by 13 | Viewed by 2728

Abstract

The ability of magnetic nanoparticles (MNPs) to transform electromagnetic energy into heat is widely exploited in well-known thermal cancer therapies, such as magnetic hyperthermia, which proves useful in enhancing the radio- and chemo-sensitivity of human tumor cells. Since the heat release is ruled [...] Read more.

The ability of magnetic nanoparticles (MNPs) to transform electromagnetic energy into heat is widely exploited in well-known thermal cancer therapies, such as magnetic hyperthermia, which proves useful in enhancing the radio- and chemo-sensitivity of human tumor cells. Since the heat release is ruled by the complex magnetic behavior of MNPs, a careful investigation is needed to understand the role of their intrinsic (composition, size and shape) and collective (aggregation state) properties. Here, the influence of geometrical parameters and aggregation on the specific loss power (SLP) is analyzed through in-depth structural, morphological, magnetic and thermometric characterizations supported by micromagnetic and heat transfer simulations. To this aim, different samples of cubic Fe₃O₄ NPs with an average size between 15 nm and 160 nm are prepared via hydrothermal route. For the analyzed samples, the magnetic behavior and heating properties result to be basically determined by the magnetic single- or multi-domain configuration and by the competition between magnetocrystalline and shape anisotropies. This is clarified by micromagnetic simulations, which enable us to also elucidate the role of magnetostatic interactions associated with locally strong aggregation. Full article

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

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