Sub 5 nm magnetite nanoparticles: Synthesis, microstructure, and magnetic properties

Wu, Jun; Ko, Seung Pil; Liu, Hong Ling; Kim, Sangsig; Ju, Jihui; Kim, Young Keun

doi:10.1016/j.matlet.2006.11.032

Cited by 105 publications

(41 citation statements)

References 25 publications

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“…As it has already been said, it is well known that saturation magnetization of iron-oxide NPs depends on their size (collective excitations) and on their surface magnetic configuration (disorder). These phenomena can reduce the saturation magnetization below the bulk expected value (Lima et al 2010;Laurent et al 2008;Wu et al 2007). One example of this effect has been published in a recent work by Laurent et al (2008).…”

Section: Resultsmentioning

confidence: 92%

Magnetic properties study of iron-oxide nanoparticles/PVA ferrogels with potential biomedical applications

et al. 2013

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A study of the magnetic behavior of maghemite nanoparticles (NPs) in polyvinyl alcohol (PVA) polymer matrices prepared by physical crosslinking is reported. The magnetic nanocomposites (ferrogels) were obtained by the in situ co-precipitation of iron salts in the presence of PVA polymer, and subsequently subjected to freezing-thawing cycles. The magnetic behavior of these ferrogels was compared with that of similar systems synthesized using the glutaraldehyde. This type of chemical crosslinking agents presents several disadvantages due to the presence of residual toxic molecules in the gel, which are undesirable for biological applications. Characteristic particle size determined by several techniques are in the range 7.9-9.3 nm. The iron oxidation state in the NPs was studied by X-ray absorption spectroscopy. Mössbauer measurements showed that the NP magnetic moments present collective magnetic excitations and superparamagnetic relaxations. The blocking and irreversibility temperatures of the NPs in the ferrogels, and the magnetic anisotropy constant, were obtained from magnetic measurements. An empirical model including two magnetic contributions (large NPs slightly departed from thermodynamic equilibrium below 200 K, and small NPs at thermodynamic equilibrium) was used to fit the experimental magnetization curves. A deviation from the superparamagnetic regime was observed. This deviation was explained on the basis of an interacting superparamagnetic model. From this model, relevant magnetic and structural properties were obtained, such as the magnitude order of the dipolar interaction energy, the NPs magnetic moment, and the number of NPs per ferrogel mass unit. This study contributes to the understanding of the basic physics of a new class of materials that could emerge from the PVA-based magnetic ferrogels.

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Section: Resultsmentioning

confidence: 92%

Magnetic properties study of iron-oxide nanoparticles/PVA ferrogels with potential biomedical applications

et al. 2013

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“…Then the solid phase reaction between the hydroxides results in the formation of Fe 3 O 4 . Recent reports reveal that the size of Fe 3 O 4 nanoparticles thus formed greatly depends on the concentration of ferrous and ferric ions [5] and the reaction temperature [6]. These results imply that the synthesis conditions influence greatly not only the Fe 3 O 4 formation reaction but also the formation of Fe(OH) 2 and -FeOOH precipitates.…”

Section: Introductionmentioning

confidence: 93%

“…The formed Fe 3 O 4 nanoparticles tend to have relatively low crystallinity, leading to poor magnetic property, when the coprecipitation is carried out at low temperature. Thus, a heating process, such as annealing and hydrothermal treatment is often employed to improve the crystallinity [6,9]. Unfortunately, this complicates the synthesis process and spoils the advantages of this method.…”

Section: Introductionmentioning

confidence: 99%

“…Unfortunately, this complicates the synthesis process and spoils the advantages of this method. In addition, it is very difficult to prepare ultrafine Fe 3 O 4 nanoparticles with a size of 10 nm or less because the Fe(OH) 2 and -FeOOH precipitates and the Fe 3 O 4 nanoparticles tend to aggregate owing to heating even though their size before heating is less than 10 nm [6]. This reduces controllable range of the particle size.…”

Section: Introductionmentioning

confidence: 99%

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Size control of magnetite nanoparticles by organic solvent-free chemical coprecipitation at room temperature

Iwasaki¹,

Mizutani²,

Watano³

et al. 2010

Journal of Experimental Nanoscience

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This study provides a facile single-step coprecipitation method for preparing size-controlled high crystalline magnetite nanoparticles in water system without using any organic solvents. In this method, an iron ions solution and an alkaline solution are simply mixed at room temperature without using any additional heating treatment. The size of obtained magnetite nanoparticles greatly depended on the coexisting anionic species in the starting solution because the coexisting anions greatly influenced both the formation of crystal nuclei and the dispersion stabilisation of formed precipitates. The size control of magnetite nanoparticles having high crystallinity and ferromagnetic property could be successfully achieved by using the effects of coexisting anions. For synthesising finer magnetite nanoparticles, the presence of lactate ion in the starting solution was effective, and coarser ones could be synthesised under higher ferrous/ferric ions molar ratios.

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“…Among the preparation methods, coprecipitation of ferrous and ferric hydroxides in water system is useful because of its simplicity of the process and relatively low environmental impact [10][11][12][13][14]. However, this method has a problem that obtained Fe 3 O 4 nanoparticles tend to have relatively low crystallinity and poor magnetic properties [15][16][17]. Therefore, following hydrothermal treatment of the suspension of precursor, ferrous hydroxide (Fe(OH) 2 )-goethite ( -FeOOH) composites, formed by the coprecipitation is effective to improve easily the crystallinity [18,19].…”

Section: Introductionmentioning

confidence: 99%

Hydrothermal synthesis of magnetite nanoparticlesviasequential formation of iron hydroxide precipitates

Iwasaki

Mizutani

Watano

et al. 2012

Journal of Experimental Nanoscience

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A novel method for preparing fine magnetite nanoparticles without using any additives and organic solvents has been developed. In this method, a sequential precipitates formation method, ferrous and ferric hydroxides are not coprecipitated but sequentially formed in an alkaline solution, and then the resulting suspension is subjected to a hydrothermal treatment. The obtained magnetite nanoparticles were characterised through scanning electron microscopy observation and X-ray diffraction analysis, and the particle size and magnetic properties were measured with a dynamic light scattering particle size analyser and a superconducting quantum interference device magnetometer, respectively. In order to prepare fine magnetite nanoparticles with a uniform size, both the formation sequence of ferrous and ferric hydroxide precipitates and the supersaturation of ferric hydroxide in the solution were essential. The ferromagnetic magnetite nanoparticles with a median size 8.5 nm were relatively easily obtained in the formation process in which a ferric sulphate solution was rapidly poured into a suspension of ferrous hydroxide particles prepared beforehand using ferric chloride and sodium hydroxide, whereas the median size of magnetite nanoparticles prepared via conventional coprecipitation route was 38.6 nm.

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Sub 5 nm magnetite nanoparticles: Synthesis, microstructure, and magnetic properties

Cited by 105 publications

References 25 publications

Magnetic properties study of iron-oxide nanoparticles/PVA ferrogels with potential biomedical applications

Magnetic properties study of iron-oxide nanoparticles/PVA ferrogels with potential biomedical applications

Size control of magnetite nanoparticles by organic solvent-free chemical coprecipitation at room temperature

Hydrothermal synthesis of magnetite nanoparticlesviasequential formation of iron hydroxide precipitates

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