Massive Fabrication of Free-Standing One-Dimensional Co/Pt Nanostructures and Modulation of Ferromagnetism via a Programmable Barcode Layer Effect

Magnetic nanoparticles, which exhibit a variety of unique magnetic phenomena that are drastically different from those of their bulk counterparts, are garnering significant interest since these properties can be advantageous for utilization in a variety of applications ranging from storage media for magnetic memory devices to probes and vectors in the biomedical sciences. In this Account, we discuss the nanoscaling laws of magnetic nanoparticles including metals, metal ferrites, and metal alloys, while focusing on their size, shape, and composition effects. Their fundamental magnetic properties such as blocking temperature (T b ), spin life time (τ), coercivity (H c ), and susceptibility ( ) are strongly influenced by the nanoscaling laws, and as a result, these scaling relationships can be leveraged to control magnetism from the ferromagnetic to the superparamagnetic regimes. At the same time, they can be used in order to tune magnetic values including H c , , and remanence (M r ). For example, life time of magnetic spin is directly related to the magnetic anisotropy energy (K u V ) and also the size and volume of nanoparticles. The blocking temperature (T b ) changes from room temperature to 10 K as the size of cobalt nanoparticles is reduced from 13 to 2 nm. Similarly, H c is highly susceptible to the anisotropy of nanoparticles, while saturation magnetization is directly related to the canting effects of the disordered surface magnetic spins and follows a linear relationship upon plotting of m s 1/3 vs r -1. Therefore, the nanoscaling laws of magnetic nanoparticles are important not only for understanding the behavior of existing materials but also for developing novel nanomaterials with superior properties.Since magnetic nanoparticles can be easily conjugated with biologically important constituents such as DNA, peptides, and antibodies, it is possible to construct versatile nano-bio hybrid particles, which simultaneously possess magnetic and biological functions for biomedical diagnostics and therapeutics. As demonstrated in this Account, nanoscaling laws for magnetic components are found to be critical to the design of optimized magnetic characteristics of hybrid nanoparticles and their enhanced applicability in the biomedical sciences including their utilizations as contrast enhancement agents for magnetic resonance imaging (MRI), ferromagnetic components for nano-bio hybrid structures, and translational vectors for magnetophoretic sensing of biological species. In particular, systematic modulation of saturation magnetization of nanoparticle probes is important to maximize MR contrast effects and magnetic separation of biological targets.

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“…36 Such effects can be observed in CoPt barcode-structured nanowires with various aspect ratios. 39 The …”

Section: Shape and Compositionmentioning

confidence: 99%

Nanoscaling Laws of Magnetic Nanoparticles and Their Applicabilities in Biomedical Sciences

2008

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“…The shape anisotropy induced by deviation from spherical shapes, results in different coercivity values depending on the orientation of the nanocrystal [24] . For nanorods and nanowires, this effect depends on the aspect ratio of their lengths in the directions of crystallographic axes of the structure [53] . The blocking temperature and saturation magnetization of cobalt ferrites show the same volume dependencies for both spherical and cubic shapes.…”

Section: Effect Of Np Shapementioning

confidence: 99%

Application of alternative energy forms in catalytic reactor engineering

Houlding

Rebrov

2012

Green Processing and Synthesis

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This review provides a general overview of recent applications of magnetic nanoparticles for controlled radiofrequency (RF) heating in catalytic synthesis, mass transfer enhancement in laminar fl ow and magnetic separation. By directly delivering RF energy to magnetic materials, issues such as long heating periods and energy losses can be minimized. The main mechanisms of RF heating are briefl y reviewed. The effect of nanoparticles size, shape and composition on the effi ciency of RF heating is discussed. RF energy has been shown to be effective in many applications, however, it is still not used in chemicals due to high equipment costs.

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“…Researches on magnetic nanowires and their arrays prepared in pores of AAO templates have plenty of outcomes [1][2][3][4][5]. In recent years, with the development of the methods for preparing magnetic nanotubes, the synthesis of tubular nanostructures and the studies on the magnetic properties of nanotubes are pioneered in magnetic nanotechnology.…”

Section: Introductionmentioning

confidence: 99%

Magnetic Interaction in FeCo Alloy Nanotube Array

Zhou¹,

Wang²,

Zhu³

et al. 2011

Journal of Magnetics

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An array of FeCo nanotubes has been successfully fabricated in the pores of porous anodic aluminum oxide (AAO) templates by wetting templates method. The morphology and structure of the nanotube array were characterized by scanning electron microscopy, transmission electron microscopy and x-ray diffraction. The average diameter of the nanotubes was about 200 nm, and the length was more than 10 µm. Vibrating sample magnetometer and superconducting quantum interference device were used to investigate the magnetic properties of the nanotube array. Interaction between the nanotubes has been found to be demagnetizing as expected and the switching field distribution is broad.

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Massive Fabrication of Free-Standing One-Dimensional Co/Pt Nanostructures and Modulation of Ferromagnetism via a Programmable Barcode Layer Effect

Cited by 117 publications

References 20 publications

Nanoscaling Laws of Magnetic Nanoparticles and Their Applicabilities in Biomedical Sciences

Nanoscaling Laws of Magnetic Nanoparticles and Their Applicabilities in Biomedical Sciences

Application of alternative energy forms in catalytic reactor engineering

Magnetic Interaction in FeCo Alloy Nanotube Array

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