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Estimation for diameter of superparamagnetic particles in Daphnia resting eggs

View Article: PubMed Central - PubMed

ABSTRACT

Ferromagnetic resonance (FMR) with an electron spin resonance (ESR) apparatus was investigated for super-paramagnetic particles within Daphnia resting eggs. High-field (HF) resonance lines near g=2 resulted from single superparamagnetic particles, were detected from ESR spectra of Daphnia resting eggs. The size of isolated superparamagnetic particles within Daphnia resting eggs was calculated to be approximately 13 nm in diameter by analysis of the temperature dependence of the HF line width. Small-angle X-ray scattering (SAXS) analysis of Daphnia resting eggs also showed that average size of superparamagnetic particles in diameter, equivalent to magnetite, was approximately 13 nm. The combination of FMR and SAXS measurement is very effective in estimating the size of superparamagnetic particles in biological organisms, with difficulties of preparing for samples for measurement by electron microscopy. However, Chlorella, with that Daphnia were raised, did not show FMR spectra, showing no magnetic particles within Daphnia resting eggs. Therefore, it suggested that superparamagnetic particles within Daphnia resting eggs, were mineralized in Daphnia as the result of biomineralization of Fe originated from Chlorella.

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Temperature dependence of the resonance line width of the HF resonance line.
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f3-6_53: Temperature dependence of the resonance line width of the HF resonance line.

Mentions: Figure 3 shows temperature dependence of the resonance line width ΔHR of the HF line of Daphnia resting eggs. The line width decreased abruptly above about 130 K. Similar behavior of HF line width was reported in ant11. According to Morais et al., the temperature dependence of the line width of ESR of superparamagnetic particles dispersed in non-magnetic matrix is expressed by(1)ΔHR=ΔH0Rtanh(ΔE/2kBT),where ΔE is the energy barrier for a magnetic moment of a particle to switch from one direction to another. If the particle is nearly a sphere, a cube, or other shape of high symmetry, it is given by(2)ΔE=a/K/V,where K and V are a magnetocrystalline anisotropy constant and the average volume of particles, respectively. A numerical factor a is a constant of the order of magnitude of 1, depending on the switching process. The width at the high temperature limit ΔH0R is expressed as(3)ΔH0R=5gβSn/D3,where g = electron g-factor, β = the Bohr magneton, S = the spin number associated with a magnetic ion, n = the number of magnetic ions in a particle, and D = the average particle-particle distance. Non-linear least squares fitting of the relation (1) to the results in Figure 3 gives the result that ΔH0R = 1292 Oe and ΔE/2kB = 483 K.


Estimation for diameter of superparamagnetic particles in Daphnia resting eggs
Temperature dependence of the resonance line width of the HF resonance line.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC5036663&req=5

f3-6_53: Temperature dependence of the resonance line width of the HF resonance line.
Mentions: Figure 3 shows temperature dependence of the resonance line width ΔHR of the HF line of Daphnia resting eggs. The line width decreased abruptly above about 130 K. Similar behavior of HF line width was reported in ant11. According to Morais et al., the temperature dependence of the line width of ESR of superparamagnetic particles dispersed in non-magnetic matrix is expressed by(1)ΔHR=ΔH0Rtanh(ΔE/2kBT),where ΔE is the energy barrier for a magnetic moment of a particle to switch from one direction to another. If the particle is nearly a sphere, a cube, or other shape of high symmetry, it is given by(2)ΔE=a/K/V,where K and V are a magnetocrystalline anisotropy constant and the average volume of particles, respectively. A numerical factor a is a constant of the order of magnitude of 1, depending on the switching process. The width at the high temperature limit ΔH0R is expressed as(3)ΔH0R=5gβSn/D3,where g = electron g-factor, β = the Bohr magneton, S = the spin number associated with a magnetic ion, n = the number of magnetic ions in a particle, and D = the average particle-particle distance. Non-linear least squares fitting of the relation (1) to the results in Figure 3 gives the result that ΔH0R = 1292 Oe and ΔE/2kB = 483 K.

View Article: PubMed Central - PubMed

ABSTRACT

Ferromagnetic resonance (FMR) with an electron spin resonance (ESR) apparatus was investigated for super-paramagnetic particles within Daphnia resting eggs. High-field (HF) resonance lines near g=2 resulted from single superparamagnetic particles, were detected from ESR spectra of Daphnia resting eggs. The size of isolated superparamagnetic particles within Daphnia resting eggs was calculated to be approximately 13 nm in diameter by analysis of the temperature dependence of the HF line width. Small-angle X-ray scattering (SAXS) analysis of Daphnia resting eggs also showed that average size of superparamagnetic particles in diameter, equivalent to magnetite, was approximately 13 nm. The combination of FMR and SAXS measurement is very effective in estimating the size of superparamagnetic particles in biological organisms, with difficulties of preparing for samples for measurement by electron microscopy. However, Chlorella, with that Daphnia were raised, did not show FMR spectra, showing no magnetic particles within Daphnia resting eggs. Therefore, it suggested that superparamagnetic particles within Daphnia resting eggs, were mineralized in Daphnia as the result of biomineralization of Fe originated from Chlorella.

No MeSH data available.


Related in: MedlinePlus