Controlling magnetic properties of iron oxide nanoparticles using post-synthesis thermal treatment

Panchal, Vineet; Bhandarkar, Upendra; Neergat, Manoj; Suresh, K. A.

doi:10.1007/s00339-013-7610-x

Cited by 16 publications

(6 citation statements)

References 32 publications

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“…Thermal decomposition syntheses are quickly becoming the most common route to obtain magnetic nanoparticles. However, recent work has uncovered that the thermal decomposition routes may actually proceed by formation of a nonmagnetic Wüstite phase, and that formation of the magnetic magnetite/maghemite phases proceeds afterward due to oxidation upon exposure to atmospheric oxygen. − Furthermore, detailed high-resolution transmission electron microscopy studies suggest the presence of defects and polycrystalline particles, which may ultimately affect magnetic and functional properties of the nanoparticles. , This has led to the development of postsynthesis thermal oxidative treatments to improve the magnetic properties of the nanoparticles. − However, while such treatments are successful for small (<15 nm) particles, they become less effective as particle size increases (>20 nm) or require extremely long (>30 h) processing times. This and other observations led us to hypothesize that lack of oxygen in the thermal decomposition reaction medium is a major obstacle for the reproducible synthesis of oxide-based nanoparticles through thermal decomposition.…”

Section: The Magnetic Diameter: An Important But Often Neglected Prop...mentioning

confidence: 99%

“…35, 36 This has led to the development of post-synthesis thermal oxidative treatments to improve the magnetic properties of the nanoparticles. 37–39 However, while such treatments are successful for small (<15 nm) particles, they become less effective as particle size increases (>20 nm), or require extremely long (>30 h) processing times. This and other observations led us to hypothesize that lack of oxygen in the thermal decomposition reaction medium is a major obstacle for the reproducible synthesis of oxide-based nanoparticles through thermal decomposition.…”

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confidence: 99%

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Thermal Decomposition Synthesis of Iron Oxide Nanoparticles with Diminished Magnetic Dead Layer by Controlled Addition of Oxygen

et al. 2017

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Decades of research focused on size and shape control of iron oxide nanoparticles have led to methods of synthesis that afford excellent control over physical size and shape, but comparatively poor control over magnetic properties. Popular synthesis methods based on thermal decomposition of organometallic precursors in the absence of oxygen have yielded particles with mixed iron oxide phases, crystal defects and poorer than expected magnetic properties, including the existence of a thick “magnetically dead layer” experimentally evidenced by a magnetic diameter significantly smaller than the physical diameter. Here, we show how single crystalline iron oxide nanoparticles with few defects and similar physical and magetic diameter distributions can be obtained by introducing molecular oxygen as one of the reactive species in the thermal decomposition synthesis. This is achieved without the need for any post-synthesis oxidation or thermal annealing. These results address a significant challenge in the synthesis of nanoparticles with predictable magnetic properties and pave way to advances in applications of magnetic nanoparticles.

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Section: The Magnetic Diameter: An Important But Often Neglected Prop...mentioning

confidence: 99%

mentioning

confidence: 99%

Thermal Decomposition Synthesis of Iron Oxide Nanoparticles with Diminished Magnetic Dead Layer by Controlled Addition of Oxygen

et al. 2017

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“…[1][2][3][4][5][6][7][8][9][10][11] Among various iron-based nanomaterials, the antiferromagnetic nanosized iron oxide and hydroxide systems, together with their preparation and characterization, have attracted special attention in materials science. These antiferromagnetic nanomaterials exhibit interesting magnetic properties that are significantly different from those of their corresponding bulk counterparts.…”

Section: Introductionmentioning

confidence: 99%

“…During the past decade iron-based nanomaterials have been at the focus of research interest due to a variety of interesting physical properties and their huge potential for applications, such as magnetic seals and inks, magnetic recording media, catalysts, pigments, ferrofluids, contrast agents for magnetic resonance imaging, therapeutic agents for cancer treatment, immunoassays, targeted drug delivery vehicles, and magnetic hyperthermia. − Among various iron-based nanomaterials, the antiferromagnetic nanosized iron oxide and hydroxide systems, together with their preparation and characterization, have attracted special attention in materials science. These antiferromagnetic nanomaterials exhibit interesting magnetic properties that are significantly different from those of their corresponding bulk counterparts.…”

Section: Introductionmentioning

confidence: 99%

Silica-Coated and Bare Akaganeite Nanorods: Structural and Magnetic Properties

et al. 2015

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We report on structural and magnetic properties of uniform silica coated akaganeite nanorods with length of L ~ 80 ± 15 nm and diameter D ~ 15 ± 5 nm as well as silica shell thickness of about 5 nm. Unexpected negative difference between field-cooled (FC) and zero-field-cooled (ZFC) magnetization ∆M= M FC -M ZFC < 0, room temperature ferromagnetism and exchange bias effect have been found. The nanorods are investigated by X-ray powder diffraction (XRPD), transmission electron microscopy (TEM) and vibrating sample magnetometer (VSM) measurements. The magnetic measurements were also performed on bare akaganeite nanorods in order to discriminate the effects of silica coating on the magnetic properties. The measured coercivity and exchange bias effect of bare β-FeOOH nanorods are much lower compared with same properties of SiO 2 @β-FeOOH nanorods emphasizing effect of silica coating on the magnetic properties. These results are discussed considering the core-shell structure of akaganeite nanorods i.e. the inner part of the akaganeite nanorod has antiferromagnetic ordering, whereas the nanorod surface exhibits some disorder spin state.

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“…The magnetic properties of superparamagnetic nanoparticles are known to depend strongly on several different parameters, such as structure, size, shape, anisotropy and surface chemistry. [38][39][40][41] Using the ferrouid route, the concentration of iron oxide nanoparticles could not be increased beyond the upper limit of 0.68 vol% Fe 3 O 4 (0.64 wt% Fe). This is likely because of the electrostatic repulsion between the ferrouid particles, which ultimately prevents the formation of a complete monolayer of nanoparticles on the platelet surface (see ESI †).…”

Section: Magnetic Properties Of Fe 3 O 4 @Al 2 O 3 Plateletsmentioning

confidence: 99%

Multifunctional microparticles with uniform magnetic coatings and tunable surface chemistry

et al. 2014

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Microplatelets and fibers that can be manipulated using external magnetic fields find potential applications as miniaturized probes, micromirrors in optical switches, remotely actuated micromixers and tunable reinforcements in composite materials. Controlling the surface chemistry of such microparticles is often crucial to enable full exploitation of their mechanical, optical and sensorial functions. Here, we report a simple and versatile procedure to directly magnetize and chemically modify the surface of inorganic microplatelets and polymer fibers of inherently non-magnetic compositions. As opposed to other magnetization approaches, the proposed non-aqueous sol-gel route enables the formation of a dense and homogeneous coating of superparamagnetic iron oxide nanoparticles (SPIONs) on the surface of the microparticles. Such coating provides a suitable platform for the direct chemical functionalization of the microparticles using catechol-based ligands displaying high affinity towards iron oxide surfaces. By adsorbing for example nitrodopamine palmitate (ND-PA) on the surface of hydrophilic magnetite-coated alumina platelets (Fe 3 O 4 @Al 2 O 3 ) we can render them sufficiently surface active to generate magnetically responsive Pickering emulsions. We also show that microplatelets and fibers coated with a uniform iron oxide layer can be easily manipulated using low magnetic fields despite their intrinsic non-magnetic nature. These examples illustrate the potential of the proposed approach in generating functional, magnetically responsive microprobes and building blocks for several emerging applications.

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Controlling magnetic properties of iron oxide nanoparticles using post-synthesis thermal treatment

Cited by 16 publications

References 32 publications

Thermal Decomposition Synthesis of Iron Oxide Nanoparticles with Diminished Magnetic Dead Layer by Controlled Addition of Oxygen

Thermal Decomposition Synthesis of Iron Oxide Nanoparticles with Diminished Magnetic Dead Layer by Controlled Addition of Oxygen

Silica-Coated and Bare Akaganeite Nanorods: Structural and Magnetic Properties

Multifunctional microparticles with uniform magnetic coatings and tunable surface chemistry

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