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The investigation of frequency response for the magnetic nanoparticulate assembly induced by time-varied magnetic field.

Sun J, Su Y, Wang C, Gu N - Nanoscale Res Lett (2011)

Bottom Line: It was found that the assembly was dependent upon the difference between colloidal relaxation time and field period.The same experiments on DMSA-coated γ-Fe2O3 nanoparticles exhibited that the relaxation time may be mainly determined by the magnetic size rather than the physical size.Our results may be valuable for the knowledge of dynamic assembly of colloidal particles.

View Article: PubMed Central - HTML - PubMed

Affiliation: State Key Laboratory of Bioelectronics, Southeast University, Nanjing 210096, PR China. guning@seu.edu.cn.

ABSTRACT
The field-induced assembly of γ-Fe2O3 nanoparticles under alternating magnetic field of different frequency was investigated. It was found that the assembly was dependent upon the difference between colloidal relaxation time and field period. The same experiments on DMSA-coated γ-Fe2O3 nanoparticles exhibited that the relaxation time may be mainly determined by the magnetic size rather than the physical size. Our results may be valuable for the knowledge of dynamic assembly of colloidal particles.

No MeSH data available.


Related in: MedlinePlus

SEM images of bare γ-Fe2O3 nanoparticles after solvent drying. In absence of the alternating magnetic field (a) and in presence of alternating magnetic field with different frequency (1 kHz (b), 5 kHz (c), 10 kHz (d), 50 kHz (e), 100 kHz (f), and 20 Hz (g)). The concentration of sample was 12.5 μg/ml. The naturally drying sample showed amorphous aggregates, while the field-treated samples showed more or less one-dimensional orientation. With the frequency increasing, the chain-like assembly was more and more obvious. However, for the 20-Hz alternating magnetic field, the field-treated sample re-showed the amorphous aggregates to some extent, meaning that the alternating magnetic field of the frequency had not induced the assembly of γ-Fe2O3 nanoparticles.
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Figure 2: SEM images of bare γ-Fe2O3 nanoparticles after solvent drying. In absence of the alternating magnetic field (a) and in presence of alternating magnetic field with different frequency (1 kHz (b), 5 kHz (c), 10 kHz (d), 50 kHz (e), 100 kHz (f), and 20 Hz (g)). The concentration of sample was 12.5 μg/ml. The naturally drying sample showed amorphous aggregates, while the field-treated samples showed more or less one-dimensional orientation. With the frequency increasing, the chain-like assembly was more and more obvious. However, for the 20-Hz alternating magnetic field, the field-treated sample re-showed the amorphous aggregates to some extent, meaning that the alternating magnetic field of the frequency had not induced the assembly of γ-Fe2O3 nanoparticles.

Mentions: About 4 μL of bare γ-Fe2O3 colloidal solutions was spread on a silicon wafer and subjected to alternating magnetic field until the solution was dried. In the absence of alternating magnetic field, the solvent drying brought about the amorphous aggregation of γ-Fe2O3 nanoparticles (Figure 2a). However, when the alternating magnetic field (frequency, 1 K to approximately 100 kHz) was exerted, the nanoparticles formed anisotropic structures (Figure 2b, c, d, e, f). There was a visible transition from amorphous aggregation into fibrous assembly, which reflected the enhancement of magnetic interaction with the frequency increasing. The entropy effect was experimentally excluded to result in the phenomenon because the assembled conformation was found independent upon colloidal concentration (Figure S1 in Additional file 1) [7].


The investigation of frequency response for the magnetic nanoparticulate assembly induced by time-varied magnetic field.

Sun J, Su Y, Wang C, Gu N - Nanoscale Res Lett (2011)

SEM images of bare γ-Fe2O3 nanoparticles after solvent drying. In absence of the alternating magnetic field (a) and in presence of alternating magnetic field with different frequency (1 kHz (b), 5 kHz (c), 10 kHz (d), 50 kHz (e), 100 kHz (f), and 20 Hz (g)). The concentration of sample was 12.5 μg/ml. The naturally drying sample showed amorphous aggregates, while the field-treated samples showed more or less one-dimensional orientation. With the frequency increasing, the chain-like assembly was more and more obvious. However, for the 20-Hz alternating magnetic field, the field-treated sample re-showed the amorphous aggregates to some extent, meaning that the alternating magnetic field of the frequency had not induced the assembly of γ-Fe2O3 nanoparticles.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3211873&req=5

Figure 2: SEM images of bare γ-Fe2O3 nanoparticles after solvent drying. In absence of the alternating magnetic field (a) and in presence of alternating magnetic field with different frequency (1 kHz (b), 5 kHz (c), 10 kHz (d), 50 kHz (e), 100 kHz (f), and 20 Hz (g)). The concentration of sample was 12.5 μg/ml. The naturally drying sample showed amorphous aggregates, while the field-treated samples showed more or less one-dimensional orientation. With the frequency increasing, the chain-like assembly was more and more obvious. However, for the 20-Hz alternating magnetic field, the field-treated sample re-showed the amorphous aggregates to some extent, meaning that the alternating magnetic field of the frequency had not induced the assembly of γ-Fe2O3 nanoparticles.
Mentions: About 4 μL of bare γ-Fe2O3 colloidal solutions was spread on a silicon wafer and subjected to alternating magnetic field until the solution was dried. In the absence of alternating magnetic field, the solvent drying brought about the amorphous aggregation of γ-Fe2O3 nanoparticles (Figure 2a). However, when the alternating magnetic field (frequency, 1 K to approximately 100 kHz) was exerted, the nanoparticles formed anisotropic structures (Figure 2b, c, d, e, f). There was a visible transition from amorphous aggregation into fibrous assembly, which reflected the enhancement of magnetic interaction with the frequency increasing. The entropy effect was experimentally excluded to result in the phenomenon because the assembled conformation was found independent upon colloidal concentration (Figure S1 in Additional file 1) [7].

Bottom Line: It was found that the assembly was dependent upon the difference between colloidal relaxation time and field period.The same experiments on DMSA-coated γ-Fe2O3 nanoparticles exhibited that the relaxation time may be mainly determined by the magnetic size rather than the physical size.Our results may be valuable for the knowledge of dynamic assembly of colloidal particles.

View Article: PubMed Central - HTML - PubMed

Affiliation: State Key Laboratory of Bioelectronics, Southeast University, Nanjing 210096, PR China. guning@seu.edu.cn.

ABSTRACT
The field-induced assembly of γ-Fe2O3 nanoparticles under alternating magnetic field of different frequency was investigated. It was found that the assembly was dependent upon the difference between colloidal relaxation time and field period. The same experiments on DMSA-coated γ-Fe2O3 nanoparticles exhibited that the relaxation time may be mainly determined by the magnetic size rather than the physical size. Our results may be valuable for the knowledge of dynamic assembly of colloidal particles.

No MeSH data available.


Related in: MedlinePlus