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15 pages, 3659 KiB

Open AccessCommunication

Rapid Magneto-Sonoporation of Adipose-Derived Cells

by Miriam Filippi, Boris Dasen and Arnaud Scherberich

Materials 2021, 14(17), 4877; https://doi.org/10.3390/ma14174877 - 27 Aug 2021

Cited by 2 | Viewed by 1662

By permeabilizing the cell membrane with ultrasound and facilitating the uptake of iron oxide nanoparticles, the magneto-sonoporation (MSP) technique can be used to instantaneously label transplantable cells (like stem cells) to be visualized via magnetic resonance imaging in vivo. However, the effects of [...] Read more.

By permeabilizing the cell membrane with ultrasound and facilitating the uptake of iron oxide nanoparticles, the magneto-sonoporation (MSP) technique can be used to instantaneously label transplantable cells (like stem cells) to be visualized via magnetic resonance imaging in vivo. However, the effects of MSP on cells are still largely unexplored. Here, we applied MSP to the widely applicable adipose-derived stem cells (ASCs) for the first time and investigated its effects on the biology of those cells. Upon optimization, MSP allowed us to achieve a consistent nanoparticle uptake (in the range of 10 pg/cell) and a complete membrane resealing in few minutes. Surprisingly, this treatment altered the metabolic activity of cells and induced their differentiation towards an osteoblastic profile, as demonstrated by an increased expression of osteogenic genes and morphological changes. Histological evidence of osteogenic tissue development was collected also in 3D hydrogel constructs. These results point to a novel role of MSP in remote biophysical stimulation of cells with focus application in bone tissue repair. Full article

(This article belongs to the Special Issue Magnetic Nanomaterials)

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19 pages, 4799 KiB

Open AccessArticle

Out-of-Plane Magnetic Anisotropy in Ordered Ensembles of Fe_yN Nanocrystals Embedded in GaN

by Andrea Navarro-Quezada, Katarzyna Gas, Tia Truglas, Viola Bauernfeind, Margherita Matzer, Dominik Kreil, Andreas Ney, Heiko Groiss, Maciej Sawicki and Alberta Bonanni

Materials 2020, 13(15), 3294; https://doi.org/10.3390/ma13153294 - 24 Jul 2020

Cited by 10 | Viewed by 2268

Abstract

Phase-separated semiconductors containing magnetic nanostructures are relevant systems for the realization of high-density recording media. Here, the controlled strain engineering of Ga

δ

FeN layers with Fe

_{y}

N embedded nanocrystals (NCs) via Al

_{x}

Ga

_{1 - x}

N buffers with different [...] Read more.

Phase-separated semiconductors containing magnetic nanostructures are relevant systems for the realization of high-density recording media. Here, the controlled strain engineering of Ga

δ

FeN layers with Fe

_{y}

N embedded nanocrystals (NCs) via Al

_{x}

Ga

_{1 - x}

N buffers with different Al concentration

0 < x_{Al} < 41

% is presented. Through the addition of Al to the buffer, the formation of predominantly prolate-shaped

ε

-Fe

_{3}

N NCs takes place. Already at an Al concentration

x_{Al}

≈ 5% the structural properties—phase, shape, orientation—as well as the spatial distribution of the embedded NCs are modified in comparison to those grown on a GaN buffer. Although the magnetic easy axis of the cubic

γ

’-Ga

_{y}

Fe

_{4 - y}

N nanocrystals in the layer on the

x_{Al} = 0 %

buffer lies in-plane, the easy axis of the

ε

-Fe

_{3}

N NCs in all samples with Al

_{x}

Ga

_{1 - x}

N buffers coincides with the

[0001]

growth direction, leading to a sizeable out-of-plane magnetic anisotropy and opening wide perspectives for perpendicular recording based on nitride-based magnetic nanocrystals. Full article

(This article belongs to the Special Issue Magnetic Nanomaterials)

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16 pages, 5463 KiB

Open AccessFeature PaperArticle

Following the Martensitic Configuration Footprints in the Transition Route of Ni-Mn-Ga Magnetic Shape Memory Films: Insight into the Role of Twin Boundaries and Interfaces

by Milad Takhsha Ghahfarokhi, Lucia Nasi, Francesca Casoli, Simone Fabbrici, Giovanna Trevisi, Riccardo Cabassi and Franca Albertini

Materials 2020, 13(9), 2103; https://doi.org/10.3390/ma13092103 - 01 May 2020

Cited by 7 | Viewed by 2625

Abstract

Magnetic shape memory Heuslers have a great potential for their exploitation in next-generation cooling devices and actuating systems, due to their “giant” caloric and thermo/magnetomechanical effects arising from the combination of magnetic order and a martensitic transition. Thermal hysteresis, broad transition range, and [...] Read more.

Magnetic shape memory Heuslers have a great potential for their exploitation in next-generation cooling devices and actuating systems, due to their “giant” caloric and thermo/magnetomechanical effects arising from the combination of magnetic order and a martensitic transition. Thermal hysteresis, broad transition range, and twinning stress are among the major obstacles preventing the full exploitation of these materials in applications. Using Ni-Mn-Ga seven-modulated epitaxial thin films as a model system, we investigated the possible links between the phase transition and the details of the twin variants configuration in the martensitic phase. We explored the crystallographic relations between the martensitic variants from the atomic-scale to the micro-scale through high-resolution techniques and combined this information with the direct observation of the evolution of martensitic twin variants vs. temperature. Based on our multiscale investigation, we propose a route for the martensitic phase transition, in which the interfaces between different colonies of twins play the major role of initiators for both the forward and reverse phase transition. Linking the martensitic transition to the martensitic configuration sheds light onto the possible mechanisms influencing the transition and paves the way towards microstructure engineering for the full exploitation of shape memory Heuslers in different applications. Full article

(This article belongs to the Special Issue Magnetic Nanomaterials)

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15 pages, 5026 KiB

Open AccessArticle

Magnetic Properties of Electrospun Magnetic Nanofiber Mats after Stabilization and Carbonization

by Nadine Fokin, Timo Grothe, Al Mamun, Marah Trabelsi, Michaela Klöcker, Lilia Sabantina, Christoph Döpke, Tomasz Blachowicz, Andreas Hütten and Andrea Ehrmann

Materials 2020, 13(7), 1552; https://doi.org/10.3390/ma13071552 - 27 Mar 2020

Cited by 37 | Viewed by 3538

Abstract

Magnetic nanofibers are of great interest in basic research, as well as for possible applications in spintronics and neuromorphic computing. Here we report on the preparation of magnetic nanofiber mats by electrospinning polyacrylonitrile (PAN)/nanoparticle solutions, creating a network of arbitrarily oriented nanofibers with [...] Read more.

Magnetic nanofibers are of great interest in basic research, as well as for possible applications in spintronics and neuromorphic computing. Here we report on the preparation of magnetic nanofiber mats by electrospinning polyacrylonitrile (PAN)/nanoparticle solutions, creating a network of arbitrarily oriented nanofibers with a high aspect ratio. Since PAN is a typical precursor for carbon, the magnetic nanofiber mats were stabilized and carbonized after electrospinning. The magnetic properties of nanofiber mats containing magnetite or nickel ferrite nanoparticles were found to depend on the nanoparticle diameters and the potential after-treatment, as compared with raw nanofiber mats. Micromagnetic simulations underlined the different properties of both magnetic materials. Atomic force microscopy and scanning electron microscopy images revealed nearly unchanged morphologies after stabilization without mechanical fixation, which is in strong contrast to pure PAN nanofiber mats. While carbonization at 500 °C left the morphology unaltered, as compared with the stabilized samples, stronger connections between adjacent fibers were formed during carbonization at 800 °C, which may be supportive of magnetic data transmission. Full article

(This article belongs to the Special Issue Magnetic Nanomaterials)

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15 pages, 3876 KiB

Open AccessArticle

Structural and Magnetic Properties of FePd Thin Film Synthesized by Electrodeposition Method

by Gabriele Barrera, Federico Scaglione, Matteo Cialone, Federica Celegato, Marco Coïsson, Paola Rizzi and Paola Tiberto

Materials 2020, 13(6), 1454; https://doi.org/10.3390/ma13061454 - 23 Mar 2020

Cited by 10 | Viewed by 2768

Abstract

Bimetallic nanomaterials in the form of thin film constituted by magnetic and noble elements show promising properties in different application fields such as catalysts and magnetic driven applications. In order to tailor the chemical and physical properties of these alloys to meet the [...] Read more.

Bimetallic nanomaterials in the form of thin film constituted by magnetic and noble elements show promising properties in different application fields such as catalysts and magnetic driven applications. In order to tailor the chemical and physical properties of these alloys to meet the applications requirements, it is of great importance scientific interest to study the interplay between properties and morphology, surface properties, microstructure, spatial confinement and magnetic features. In this manuscript, FePd thin films are prepared by electrodeposition which is a versatile and widely used technique. Compositional, morphological, surface and magnetic properties are described as a function of deposition time (i.e., film thickness). Chemical etching in hydrochloric acid was used to enhance the surface roughness and help decoupling crystalline grains with direct consequences on to the magnetic properties. X-ray diffraction, SEM/AFM images, contact angle and magnetic measurements have been carried out with the aim of providing a comprehensive characterisation of the fundamental properties of these bimetallic thin films. Full article

(This article belongs to the Special Issue Magnetic Nanomaterials)

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17 pages, 8902 KiB

Open AccessArticle

Structural and Optical Characteristics of Highly UV-Blue Luminescent ZnNiO Nanoparticles Prepared by Sol–Gel Method

by Ashraf H. Farha, Abdullah F. Al Naim, Javed Mazher, Olfa Nasr and Mohamed Helmi Hadj Alouane

Materials 2020, 13(4), 879; https://doi.org/10.3390/ma13040879 - 15 Feb 2020

Cited by 9 | Viewed by 2383

Abstract

A simple single pot sol–gel method is used to prepare ZnNiO nanoparticles at assorted Ni doping levels, 1, 3, 7 and 10 wt.%. Structural and optical properties of nanoparticles are studied by X-ray diffraction (XRD), UV–visible diffuse reflection spectroscopy (DRS), photoluminescence (PL) measurements, [...] Read more.

A simple single pot sol–gel method is used to prepare ZnNiO nanoparticles at assorted Ni doping levels, 1, 3, 7 and 10 wt.%. Structural and optical properties of nanoparticles are studied by X-ray diffraction (XRD), UV–visible diffuse reflection spectroscopy (DRS), photoluminescence (PL) measurements, scanning electron microscopy (SEM), μ-Raman and X-ray photoelectron-spectroscopy (XPS). A single substitutional solid solution phase is detected in the wurtzite ZnNiO nanoparticles at various doping levels. XRD peak splitting and shifting is ascribed to reduced wurtzite character and presence of crystalline strain in nanoparticles at higher level of Ni doping. The Kubelka-Munk function of DRS data reveals the presence of the Burstein-Moss effect in the optical absorption of ZnNiO nanoparticles. Photoluminescence studies show intense UV-blue emission from ZnNiO nanoparticles. The UV PL also exhibits the Burstein-Moss blue shift in the ZnNiO luminescence. Raman analyses also confirms the wurtzite structure of ZnNiO nanoparticles; however, crystal structural defects and bond stiffness increase with Ni doping. The optical and structural studies presented in this work are pointing towards a multivalent Ni substitution in the nanoparticles. Full article

(This article belongs to the Special Issue Magnetic Nanomaterials)

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9 pages, 2008 KiB

Open AccessFeature PaperArticle

Temperature Dependence of the Magnetic Properties of IrMn/CoFeB/Ru/CoFeB Exchange Biased Synthetic Antiferromagnets

by Edoardo Albisetti, Giuseppe Scaramuzzi, Christian Rinaldi, Matteo Cantoni, Riccardo Bertacco and Daniela Petti

Materials 2020, 13(2), 387; https://doi.org/10.3390/ma13020387 - 14 Jan 2020

Cited by 11 | Viewed by 4431

Abstract

Synthetic antiferromagnets (SAF) are widely used for a plethora of applications among which data storage, computing, and in the emerging field of magnonics. In this framework, controlling the magnetic properties of SAFs via localized thermal treatments represents a promising route for building novel [...] Read more.

Synthetic antiferromagnets (SAF) are widely used for a plethora of applications among which data storage, computing, and in the emerging field of magnonics. In this framework, controlling the magnetic properties of SAFs via localized thermal treatments represents a promising route for building novel magnonic materials. In this paper, we study via vibration sample magnetometry the temperature dependence of the magnetic properties of sputtered exchange bias SAFs grown via magnetron sputtering varying the ferromagnetic layers and spacer thickness. Interestingly, we observe a strong, reversible modulation of the exchange field, saturation field, and coupling strength upon heating up to 250 °C. These results suggest that exchange bias SAFs represent promising systems for developing novel artificial magnetic nanomaterials via localized thermal treatment. Full article

(This article belongs to the Special Issue Magnetic Nanomaterials)

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15 pages, 1945 KiB

Open AccessArticle

Glassy Magnetic Behavior and Correlation Length in Nanogranular Fe-Oxide and Au/Fe-Oxide Samples

by L. Del Bianco, F. Spizzo, G. Barucca, G. Marangoni and P. Sgarbossa

Materials 2019, 12(23), 3958; https://doi.org/10.3390/ma12233958 - 29 Nov 2019

Cited by 4 | Viewed by 2429

Abstract

In nanoscale magnetic systems, the possible coexistence of structural disorder and competing magnetic interactions may determine the appearance of a glassy magnetic behavior, implying the onset of a low-temperature disordered collective state of frozen magnetic moments. This phenomenology is the object of an [...] Read more.

In nanoscale magnetic systems, the possible coexistence of structural disorder and competing magnetic interactions may determine the appearance of a glassy magnetic behavior, implying the onset of a low-temperature disordered collective state of frozen magnetic moments. This phenomenology is the object of an intense research activity, stimulated by a fundamental scientific interest and by the need to clarify how disordered magnetism effects may affect the performance of magnetic devices (e.g., sensors and data storage media). We report the results of a magnetic study that aims to broaden the basic knowledge of glassy magnetic systems and concerns the comparison between two samples, prepared by a polyol method. The first can be described as a nanogranular spinel Fe-oxide phase composed of ultrafine nanocrystallites (size of the order of 1 nm); in the second, the Fe-oxide phase incorporated non-magnetic Au nanoparticles (10–20 nm in size). In both samples, the Fe-oxide phase exhibits a glassy magnetic behavior and the nanocrystallite moments undergo a very similar freezing process. However, in the frozen regime, the Au/Fe-oxide composite sample is magnetically softer. This effect is explained by considering that the Au nanoparticles constitute physical constraints that limit the length of magnetic correlation between the frozen Fe-oxide moments. Full article

(This article belongs to the Special Issue Magnetic Nanomaterials)

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Review

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44 pages, 7252 KiB

Open AccessReview

Nanoparticles for Magnetic Heating: When Two (or More) Is Better Than One

by Jesus G. Ovejero, Federico Spizzo, M. Puerto Morales and Lucia Del Bianco

Materials 2021, 14(21), 6416; https://doi.org/10.3390/ma14216416 - 26 Oct 2021

Cited by 8 | Viewed by 3219

Abstract

The increasing use of magnetic nanoparticles as heating agents in biomedicine is driven by their proven utility in hyperthermia therapeutic treatments and heat-triggered drug delivery methods. The growing demand of efficient and versatile nanoheaters has prompted the creation of novel types of magnetic [...] Read more.

The increasing use of magnetic nanoparticles as heating agents in biomedicine is driven by their proven utility in hyperthermia therapeutic treatments and heat-triggered drug delivery methods. The growing demand of efficient and versatile nanoheaters has prompted the creation of novel types of magnetic nanoparticle systems exploiting the magnetic interaction (exchange or dipolar in nature) between two or more constituent magnetic elements (magnetic phases, primary nanoparticles) to enhance and tune the heating power. This process occurred in parallel with the progress in the methods for the chemical synthesis of nanostructures and in the comprehension of magnetic phenomena at the nanoscale. Therefore, complex magnetic architectures have been realized that we classify as: (a) core/shell nanoparticles; (b) multicore nanoparticles; (c) linear aggregates; (d) hybrid systems; (e) mixed nanoparticle systems. After a general introduction to the magnetic heating phenomenology, we illustrate the different classes of nanoparticle systems and the strategic novelty they represent. We review some of the research works that have significantly contributed to clarify the relationship between the compositional and structural properties, as determined by the synthetic process, the magnetic properties and the heating mechanism. Full article

(This article belongs to the Special Issue Magnetic Nanomaterials)

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50 pages, 6023 KiB

Open AccessReview

A Perspective on Modelling Metallic Magnetic Nanoparticles in Biomedicine: From Monometals to Nanoalloys and Ligand-Protected Particles

by Barbara Farkaš and Nora H. de Leeuw

Materials 2021, 14(13), 3611; https://doi.org/10.3390/ma14133611 - 28 Jun 2021

Cited by 8 | Viewed by 2830

Abstract

The focus of this review is on the physical and magnetic properties that are related to the efficiency of monometallic magnetic nanoparticles used in biomedical applications, such as magnetic resonance imaging (MRI) or magnetic nanoparticle hyperthermia, and how to model these by theoretical [...] Read more.

The focus of this review is on the physical and magnetic properties that are related to the efficiency of monometallic magnetic nanoparticles used in biomedical applications, such as magnetic resonance imaging (MRI) or magnetic nanoparticle hyperthermia, and how to model these by theoretical methods, where the discussion is based on the example of cobalt nanoparticles. Different simulation systems (cluster, extended slab, and nanoparticle models) are critically appraised for their efficacy in the determination of reactivity, magnetic behaviour, and ligand-induced modifications of relevant properties. Simulations of the effects of nanoscale alloying with other metallic phases are also briefly reviewed. Full article

(This article belongs to the Special Issue Magnetic Nanomaterials)

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