Special Issue "Magnetic Nanomaterials"

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A special issue of Nanomaterials (ISSN 2079-4991).

Deadline for manuscript submissions: closed (15 February 2014)

Special Issue Editor

Guest Editor
Prof. Dr. Yurii K. Gun'ko

School of Chemistry, Trinity College Dublin, Dublin 2, Ireland
Website | E-Mail
Interests: quantum dots; magnetic nanomaterials; carbon nanomaterials; nano-bio-technology; biological imaging

Special Issue Information

Dear Colleagues,

Magnetic materials have an enormous impact to the modern science, technology and everyday life. Magnetic nanomaterials represent one of the most important and emerging class of materials in nanotechnology due to a range of potential applications, including magnetic data storage, catalysis, magnetic separation, sensing, waste water treatment and many others. In particularly, magnetic nanoparticles have been envisaged for various biomedical applications. For example, magnetic nanoparticles can be utilised as drug delivery agents, which can be localized in the body at a site of interest using an external magnetic field. When exposed to an alternating magnetic field, magnetic nanoparticles can serve as powerful heat sources destroying tumor cells, which allow to use these nanomaterials in cancer hyperthermia therapy. Magnetic fluids based on aqueous dispersions of small size. Magnetic nanoparticles have also been utilized as contrast agents for magnetic resonance imaging (MRI).

This special issue is focused on the synthesis, properties and prospective technological applications of magnetic nanomaterials in chemistry, physics, biology and medicine.

Prof. Dr. Yurii K. Gun'ko
Guest Editor

Submission

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. Papers will be published continuously (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as 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 refereed through a peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Nanomaterials 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 1000 CHF (Swiss Francs). English correction and/or formatting fees of 250 CHF (Swiss Francs) will be charged in certain cases for those articles accepted for publication that require extensive additional formatting and/or English corrections.

Keywords

  • magnetic nanoparticles
  • magnetic data storage
  • superparamagnetism
  • sensing
  • catalysis
  • nanomedicine
  • MRI
  • magnetic hyperthermia

Published Papers (10 papers)

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Editorial

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Open AccessEditorial Magnetic Nanomaterials and Their Applications
Nanomaterials 2014, 4(2), 505-507; doi:10.3390/nano4020505
Received: 16 June 2014 / Accepted: 17 June 2014 / Published: 23 June 2014
PDF Full-text (136 KB) | HTML Full-text | XML Full-text
Abstract
This Special Issue of Nanomaterials is dedicated to the development of new magnetic nanomaterials and their applications in biomedicine, catalysis, spintronics and other areas. The publications in this Issue demonstrate that the interest in magnetic nanomaterials is continuously growing and their realm is
[...] Read more.
This Special Issue of Nanomaterials is dedicated to the development of new magnetic nanomaterials and their applications in biomedicine, catalysis, spintronics and other areas. The publications in this Issue demonstrate that the interest in magnetic nanomaterials is continuously growing and their realm is expanding rapidly. Some highlights of the publications in this issue are discussed below. [...] Full article
(This article belongs to the Special Issue Magnetic Nanomaterials)

Research

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Open AccessArticle Hyperthermia Using Antibody-Conjugated Magnetic Nanoparticles and Its Enhanced Effect with Cryptotanshinone
Nanomaterials 2014, 4(2), 319-330; doi:10.3390/nano4020319
Received: 17 February 2014 / Revised: 9 April 2014 / Accepted: 17 April 2014 / Published: 23 April 2014
Cited by 5 | PDF Full-text (1063 KB) | HTML Full-text | XML Full-text
Abstract
Heat dissipation by magnetic nanoparticles (MNPs) under an alternating magnetic field can be used to selectively treat cancer tissues. Antibodies conjugated to MNPs can enhance the therapeutic effects of hyperthermia by altering antibody-antigen interactions. Fe3O4 nanoparticles (primary diameter, 20–30 nm)
[...] Read more.
Heat dissipation by magnetic nanoparticles (MNPs) under an alternating magnetic field can be used to selectively treat cancer tissues. Antibodies conjugated to MNPs can enhance the therapeutic effects of hyperthermia by altering antibody-antigen interactions. Fe3O4 nanoparticles (primary diameter, 20–30 nm) coated with polyethylenimine (PEI) were prepared and conjugated with CH11, an anti-Fas monoclonal antibody. HeLa cell growth was then evaluated as a function of antibody and MNP/antibody complex doses. HeLa cell growth decreased with increased doses of the antibody and complexes. However, MNPs alone did not affect cell growth; thus, only the antibody affected cell growth. In hyperthermia experiments conducted using an alternating magnetic field frequency of 210 kHz, cell viability varied with the intensity of the applied alternating magnetic field, because the temperature increase of the culture medium with added complexes was dependent on magnetic field intensity. The HeLa cell death rate with added complexes was significantly greater as compared with that with MNPs alone. Cryptotanshinone, an anti-apoptotic factor blocker, was also added to cell cultures, which provided an additional anti-cancer cell effect. Thus, an anti-cancer cell effect using a combination of magnetic hyperthermia, an anti-Fas antibody and cryptotanshinone was established. Full article
(This article belongs to the Special Issue Magnetic Nanomaterials)
Open AccessArticle Synthesis Characterization and Photocatalytic Studies of Cobalt Ferrite-Silica-Titania Nanocomposites
Nanomaterials 2014, 4(2), 331-343; doi:10.3390/nano4020331
Received: 23 February 2014 / Revised: 11 April 2014 / Accepted: 11 April 2014 / Published: 23 April 2014
Cited by 4 | PDF Full-text (2618 KB) | HTML Full-text | XML Full-text
Abstract
In this work, CoFe2O4@SiO2@TiO2 core-shell magnetic nanostructures have been prepared by coating of cobalt ferrite nanoparticles with the double SiO2/TiO2 layer using metallorganic precursors. The Transmission Electron Microscopy (TEM), Energy Dispersive X-Ray Analysis
[...] Read more.
In this work, CoFe2O4@SiO2@TiO2 core-shell magnetic nanostructures have been prepared by coating of cobalt ferrite nanoparticles with the double SiO2/TiO2 layer using metallorganic precursors. The Transmission Electron Microscopy (TEM), Energy Dispersive X-Ray Analysis (EDX), Vibrational Sample Magnetometer (VSM) measurements and Raman spectroscopy results confirm the presence both of the silica and very thin TiO2 layers. The core-shell nanoparticles have been sintered at 600 °C and used as a catalyst in photo-oxidation reactions of methylene blue under UV light. Despite the additional non-magnetic coatings result in a lower value of the magnetic moment, the particles can still easily be retrieved from reaction mixtures by magnetic separation. This retention of magnetism was of particular importance allowing magnetic recovery and re-use of the catalyst. Full article
(This article belongs to the Special Issue Magnetic Nanomaterials)
Open AccessArticle Evaluation of Superparamagnetic Silica Nanoparticles for Extraction of Triazines in Magnetic in-Tube Solid Phase Microextraction Coupled to Capillary Liquid Chromatography
Nanomaterials 2014, 4(2), 242-255; doi:10.3390/nano4020242
Received: 24 February 2014 / Revised: 24 March 2014 / Accepted: 25 March 2014 / Published: 2 April 2014
Cited by 6 | PDF Full-text (532 KB) | HTML Full-text | XML Full-text
Abstract
The use of magnetic nanomaterials for analytical applications has increased in the recent years. In particular, magnetic nanomaterials have shown great potential as adsorbent phase in several extraction procedures due to the significant advantages over the conventional methods. In the present work, the
[...] Read more.
The use of magnetic nanomaterials for analytical applications has increased in the recent years. In particular, magnetic nanomaterials have shown great potential as adsorbent phase in several extraction procedures due to the significant advantages over the conventional methods. In the present work, the influence of magnetic forces over the extraction efficiency of triazines using superparamagnetic silica nanoparticles (NPs) in magnetic in tube solid phase microextraction (Magnetic-IT-SPME) coupled to CapLC has been evaluated. Atrazine, terbutylazine and simazine has been selected as target analytes. The superparamagnetic silica nanomaterial (SiO2-Fe3O4) deposited onto the surface of a capillary column gave rise to a magnetic extraction phase for IT-SPME that provided a enhancemment of the extraction efficiency for triazines. This improvement is based on two phenomena, the superparamegnetic behavior of Fe3O4 NPs and the diamagnetic repulsions that take place in a microfluidic device such a capillary column. A systematic study of analytes adsorption and desorption was conducted as function of the magnetic field and the relationship with triazines magnetic susceptibility. The positive influence of magnetism on the extraction procedure was demonstrated. The analytical characteristics of the optimized procedure were established and the method was applied to the determination of the target analytes in water samples with satisfactory results. When coupling Magnetic-IT-SPME with CapLC, improved adsorption efficiencies (60%–63%) were achieved compared with conventional adsorption materials (0.8%–3%). Full article
(This article belongs to the Special Issue Magnetic Nanomaterials)
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Open AccessArticle Effect of Low-Frequency AC Magnetic Susceptibility and Magnetic Properties of CoFeB/MgO/CoFeB Magnetic Tunnel Junctions
Nanomaterials 2014, 4(1), 46-54; doi:10.3390/nano4010046
Received: 14 November 2013 / Revised: 19 December 2013 / Accepted: 24 December 2013 / Published: 2 January 2014
Cited by 1 | PDF Full-text (963 KB) | HTML Full-text | XML Full-text
Abstract
In this investigation, the low-frequency alternate-current (AC) magnetic susceptibility (χac) and hysteresis loop of various MgO thickness in CoFeB/MgO/CoFeB magnetic tunneling junction (MTJ) determined coercivity (Hc) and magnetization (Ms) and correlated that with χac
[...] Read more.
In this investigation, the low-frequency alternate-current (AC) magnetic susceptibility (χac) and hysteresis loop of various MgO thickness in CoFeB/MgO/CoFeB magnetic tunneling junction (MTJ) determined coercivity (Hc) and magnetization (Ms) and correlated that with χac maxima. The multilayer films were sputtered onto glass substrates and the thickness of intermediate barrier MgO layer was varied from 6 to 15 Å. An experiment was also performed to examine the variation of the highest χac and maximum phase angle (θmax) at the optimal resonance frequency (fres), at which the spin sensitivity is maximal. The results reveal that χac falls as the frequency increases due to the relationship between magnetization and thickness of the barrier layer. The maximum χac is at 10 Hz that is related to the maximal spin sensitivity and that this corresponds to a MgO layer of 11 Å. This result also suggests that the spin sensitivity is related to both highest χac and maximum phase angle. The corresponding maximum of χac is related to high exchange coupling. High coercivity and saturation magnetization contribute to high exchange-coupling χac strength. Full article
(This article belongs to the Special Issue Magnetic Nanomaterials)
Open AccessArticle Susceptibility of CoFeB/AlOx/Co Magnetic Tunnel Junctions to Low-Frequency Alternating Current
Nanomaterials 2013, 3(4), 574-582; doi:10.3390/nano3040574
Received: 21 August 2013 / Revised: 8 October 2013 / Accepted: 10 October 2013 / Published: 15 October 2013
Cited by 1 | PDF Full-text (1524 KB) | HTML Full-text | XML Full-text
Abstract
This investigation studies CoFeB/AlOx/Co magnetic tunneling junction (MTJ) in the magnetic field of a low-frequency alternating current, for various thicknesses of the barrier layer AlOx. The low-frequency alternate-current magnetic susceptibility (χac) and phase angle (θ) of the CoFeB/AlO
[...] Read more.
This investigation studies CoFeB/AlOx/Co magnetic tunneling junction (MTJ) in the magnetic field of a low-frequency alternating current, for various thicknesses of the barrier layer AlOx. The low-frequency alternate-current magnetic susceptibility (χac) and phase angle (θ) of the CoFeB/AlOx/Co MTJ are determined using an cac analyzer. The driving frequency ranges from 10 to 25,000 Hz. These multilayered MTJs are deposited on a silicon substrate using a DC and RF magnetron sputtering system. Barrier layer thicknesses are 22, 26, and 30 Å. The X-ray diffraction patterns (XRD) include a main peak at 2θ = 44.7° from hexagonal close-packed (HCP) Co with a highly (0002) textured structure, with AlOx and CoFeB as amorphous phases. The full width at half maximum (FWHM) of the Co(0002) peak, decreases as the AlOx thickness increases; revealing that the Co layer becomes more crystalline with increasing thickness. χac result demonstrates that the optimal resonance frequency (fres) that maximizes the χac value is 500 Hz. As the frequency increases to 1000 Hz, the susceptibility decreases rapidly. However, when the frequency increases over 1000 Hz, the susceptibility sharply declines, and almost closes to zero. The experimental results reveal that the mean optimal susceptibility is 1.87 at an AlOx barrier layer thickness of 30 Å because the Co(0002) texture induces magneto-anisotropy, which improves the indirect CoFeB and Co spin exchange-coupling strength and the χac value. The results concerning magnetism indicate that the magnetic characteristics are related to the crystallinity of Co. Full article
(This article belongs to the Special Issue Magnetic Nanomaterials)
Open AccessArticle Magnetism of Amorphous and Nano-Crystallized Dc-Sputter-Deposited MgO Thin Films
Nanomaterials 2013, 3(3), 486-497; doi:10.3390/nano3030486
Received: 13 June 2013 / Revised: 20 July 2013 / Accepted: 26 July 2013 / Published: 7 August 2013
Cited by 4 | PDF Full-text (1335 KB) | HTML Full-text | XML Full-text
Abstract
We report a systematic study of room-temperature ferromagnetism (RTFM) in pristine MgO thin films in their amorphous and nano-crystalline states. The as deposited dc-sputtered films of pristine MgO on Si substrates using a metallic Mg target in an O2 containing working gas
[...] Read more.
We report a systematic study of room-temperature ferromagnetism (RTFM) in pristine MgO thin films in their amorphous and nano-crystalline states. The as deposited dc-sputtered films of pristine MgO on Si substrates using a metallic Mg target in an O2 containing working gas atmosphere of (N2 + O2) are found to be X-ray amorphous. All these films obtained with oxygen partial pressure (PO2) ~10% to 80% while maintaining the same total pressure of the working gas are found to be ferromagnetic at room temperature. The room temperature saturation magnetization (MS) value of 2.68 emu/cm3 obtained for the MgO film deposited in PO2 of 10% increases to 9.62 emu/cm3 for film deposited at PO2 of 40%. However, the MS values decrease steadily for further increase of oxygen partial pressure during deposition. On thermal annealing at temperatures in the range 600 to 800 °C, the films become nanocrystalline and as the crystallite size grows with longer annealing times and higher temperature, MS decreases. Our study clearly points out that it is possible to tailor the magnetic properties of thin films of MgO. The room temperature ferromagnetism in MgO films is attributed to the presence of Mg cation vacancies. Full article
(This article belongs to the Special Issue Magnetic Nanomaterials)
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Review

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Open AccessReview Templated Synthesis of Magnetic Nanoparticles through the Self-Assembly of Polymers and Surfactants
Nanomaterials 2014, 4(3), 628-685; doi:10.3390/nano4030628
Received: 25 June 2014 / Accepted: 14 July 2014 / Published: 4 August 2014
Cited by 4 | PDF Full-text (19633 KB) | HTML Full-text | XML Full-text
Abstract
The synthesis of superparamagnetic nanoparticles (NPs) for various technological applications continues to be an interesting research topic. The successful application of superparamagnetic NPs to each specific area typically depends on the achievement of high magnetization for the nanocrystals obtained, which is determined by
[...] Read more.
The synthesis of superparamagnetic nanoparticles (NPs) for various technological applications continues to be an interesting research topic. The successful application of superparamagnetic NPs to each specific area typically depends on the achievement of high magnetization for the nanocrystals obtained, which is determined by their average size and size distribution. The size dispersity of magnetic NPs (MNPs) is markedly improved when, during the synthesis, the nucleation and growth steps of the reaction are well-separated. Tuning the nucleation process with the assistance of a hosting medium that encapsulates the precursors (such as self-assembled micelles), dispersing them in discrete compartments, improves control over particle formation. These inorganic-organic hybrids inherit properties from both the organic and the inorganic materials, while the organic component can also bring a specific functionality to the particles or prevent their aggregation in water. The general concept of interest in this review is that the shape and size of the synthesized MNPs can be controlled to some extent by the geometry and the size of the organic templates used, which thus can be considered as molds at the nanometer scale, for both porous continuous matrices and suspensions. Full article
(This article belongs to the Special Issue Magnetic Nanomaterials)
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Open AccessReview Superparamagnetic Nanoparticles for Atherosclerosis Imaging
Nanomaterials 2014, 4(2), 408-438; doi:10.3390/nano4020408
Received: 25 March 2014 / Revised: 15 May 2014 / Accepted: 16 May 2014 / Published: 5 June 2014
Cited by 2 | PDF Full-text (2135 KB) | HTML Full-text | XML Full-text
Abstract
The production of magnetic nanoparticles of utmost quality for biomedical imaging requires several steps, from the synthesis of highly crystalline magnetic cores to the attachment of the different molecules on the surface. This last step probably plays the key role in the production
[...] Read more.
The production of magnetic nanoparticles of utmost quality for biomedical imaging requires several steps, from the synthesis of highly crystalline magnetic cores to the attachment of the different molecules on the surface. This last step probably plays the key role in the production of clinically useful nanomaterials. The attachment of the different biomolecules should be performed in a defined and controlled fashion, avoiding the random adsorption of the components that could lead to undesirable byproducts and ill-characterized surface composition. In this work, we review the process of creating new magnetic nanomaterials for imaging, particularly for the detection of atherosclerotic plaque, in vivo. Our focus will be in the different biofunctionalization techniques that we and several other groups have recently developed. Magnetic nanomaterial functionalization should be performed by chemoselective techniques. This approach will facilitate the application of these nanomaterials in the clinic, not as an exception, but as any other pharmacological compound. Full article
(This article belongs to the Special Issue Magnetic Nanomaterials)
Open AccessReview Recent Advances in the Application of Magnetic Nanoparticles as a Support for Homogeneous Catalysts
Nanomaterials 2014, 4(2), 222-241; doi:10.3390/nano4020222
Received: 16 February 2014 / Revised: 17 March 2014 / Accepted: 20 March 2014 / Published: 2 April 2014
Cited by 51 | PDF Full-text (1022 KB) | HTML Full-text | XML Full-text
Abstract
Magnetic nanoparticles are a highly valuable substrate for the attachment of homogeneous inorganic and organic containing catalysts. This review deals with the very recent main advances in the development of various nanocatalytic systems by the immobilisation of homogeneous catalysts onto magnetic nanoparticles. We
[...] Read more.
Magnetic nanoparticles are a highly valuable substrate for the attachment of homogeneous inorganic and organic containing catalysts. This review deals with the very recent main advances in the development of various nanocatalytic systems by the immobilisation of homogeneous catalysts onto magnetic nanoparticles. We discuss magnetic core shell nanostructures (e.g., silica or polymer coated magnetic nanoparticles) as substrates for catalyst immobilisation. Then we consider magnetic nanoparticles bound to inorganic catalytic mesoporous structures as well as metal organic frameworks. Binding of catalytically active small organic molecules and polymers are also reviewed. After that we briefly deliberate on the binding of enzymes to magnetic nanocomposites and the corresponding enzymatic catalysis. Finally, we draw conclusions and present a future outlook for the further development of new catalytic systems which are immobilised onto magnetic nanoparticles. Full article
(This article belongs to the Special Issue Magnetic Nanomaterials)
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