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Local structure and paramagnetic properties of the nanostructured carbonaceous material shungite.

Krasnovyd SV, Konchits AA, Shanina BD, Valakh MY, Yanchuk IB, Yukhymchuk VO, Yefanov AV, Skoryk MA - Nanoscale Res Lett (2015)

Bottom Line: It is found from the Raman data that carbon fraction is formed from sp(2)-hybridized clusters, size of which increases from 9 up to 12 nm after annealing of the samples.High conductivity of shungite is found to belong to the carbon nanoclusters of different sizes.The correlation reasons are a spin-spin coupling between two spin subsystems and time dependent of the Е'γ concentration during annealing process.

View Article: PubMed Central - PubMed

Affiliation: V.E. Lashkaryov Institute of Semiconductor Physics NAS of Ukraine, 03028 Kyiv, Ukraine.

ABSTRACT
Using a scanning electron microscopy, elemental analysis, electron paramagnetic resonance, and Raman scattering methods, two types of the shungite materials (Sh-II from Zazhogino deposit and shungite from a commercial filter (ShF)), with different carbon content and porosity, are studied in this work. It was established by scanning electron microscopy data that the structure of the shungite samples is formed by a micron-size agglomeration of carbon and silicon dioxide clusters. It is found from the Raman data that carbon fraction is formed from sp(2)-hybridized clusters, size of which increases from 9 up to 12 nm after annealing of the samples. High conductivity of shungite is found to belong to the carbon nanoclusters of different sizes. Big clusters give the conduction electron spin resonance signal with a Dysonian line shape with variable g-factor and line width. The careful search of the nature of two other narrow electron paramagnetic resonance signals in shungite, which used to be prescribed to fullerene-like molecules, is fulfilled. Here, it is shown that the oxygen-deficient E'γ centers are responsible for these signals. A strong correlation is revealed between the concentration of Е'γ centers and the line width of conduction electron spin resonance signal, which occurs under annealing process of the samples at T = 570 K. The correlation reasons are a spin-spin coupling between two spin subsystems and time dependent of the Е'γ concentration during annealing process.

No MeSH data available.


EPR spectra ofЕ'γcenters in the pumped off sample Sh-II-1. (1) - Pmw = −32 dB, Umod = 0.05 G. (2) - Pmw = −37 dB, Umod = 0.01 G (accumulation, n = 9). ν = 9,390 MHz.
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Fig5: EPR spectra ofЕ'γcenters in the pumped off sample Sh-II-1. (1) - Pmw = −32 dB, Umod = 0.05 G. (2) - Pmw = −37 dB, Umod = 0.01 G (accumulation, n = 9). ν = 9,390 MHz.

Mentions: In fact, line L4 consists of two narrow lines L4 and L5 with effective g-factors of 2.0006 and 2.0003, as it is seen in Figure 5 at a significant decrease of the modulation amplitude. Parameters of the L3 and L4 lines precisely coincide with parameters of Е'γ centers with the anisotropic g-tensor (g1 = 2.0018, g2 = 2.0006, and g3 = 2.0003), which are induced in silica by γ-irradiation [20,21]. It means, that the lines L3 and L4 (Figures 3 and 5) belong to the oxygen-deficiency centers formed in silicon dioxide fraction of shungite. Note that, up to now, the presence of such lines in shungite was associated with the expected presence of fullerene molecules in shungite samples [22].Figure 5


Local structure and paramagnetic properties of the nanostructured carbonaceous material shungite.

Krasnovyd SV, Konchits AA, Shanina BD, Valakh MY, Yanchuk IB, Yukhymchuk VO, Yefanov AV, Skoryk MA - Nanoscale Res Lett (2015)

EPR spectra ofЕ'γcenters in the pumped off sample Sh-II-1. (1) - Pmw = −32 dB, Umod = 0.05 G. (2) - Pmw = −37 dB, Umod = 0.01 G (accumulation, n = 9). ν = 9,390 MHz.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4385026&req=5

Fig5: EPR spectra ofЕ'γcenters in the pumped off sample Sh-II-1. (1) - Pmw = −32 dB, Umod = 0.05 G. (2) - Pmw = −37 dB, Umod = 0.01 G (accumulation, n = 9). ν = 9,390 MHz.
Mentions: In fact, line L4 consists of two narrow lines L4 and L5 with effective g-factors of 2.0006 and 2.0003, as it is seen in Figure 5 at a significant decrease of the modulation amplitude. Parameters of the L3 and L4 lines precisely coincide with parameters of Е'γ centers with the anisotropic g-tensor (g1 = 2.0018, g2 = 2.0006, and g3 = 2.0003), which are induced in silica by γ-irradiation [20,21]. It means, that the lines L3 and L4 (Figures 3 and 5) belong to the oxygen-deficiency centers formed in silicon dioxide fraction of shungite. Note that, up to now, the presence of such lines in shungite was associated with the expected presence of fullerene molecules in shungite samples [22].Figure 5

Bottom Line: It is found from the Raman data that carbon fraction is formed from sp(2)-hybridized clusters, size of which increases from 9 up to 12 nm after annealing of the samples.High conductivity of shungite is found to belong to the carbon nanoclusters of different sizes.The correlation reasons are a spin-spin coupling between two spin subsystems and time dependent of the Е'γ concentration during annealing process.

View Article: PubMed Central - PubMed

Affiliation: V.E. Lashkaryov Institute of Semiconductor Physics NAS of Ukraine, 03028 Kyiv, Ukraine.

ABSTRACT
Using a scanning electron microscopy, elemental analysis, electron paramagnetic resonance, and Raman scattering methods, two types of the shungite materials (Sh-II from Zazhogino deposit and shungite from a commercial filter (ShF)), with different carbon content and porosity, are studied in this work. It was established by scanning electron microscopy data that the structure of the shungite samples is formed by a micron-size agglomeration of carbon and silicon dioxide clusters. It is found from the Raman data that carbon fraction is formed from sp(2)-hybridized clusters, size of which increases from 9 up to 12 nm after annealing of the samples. High conductivity of shungite is found to belong to the carbon nanoclusters of different sizes. Big clusters give the conduction electron spin resonance signal with a Dysonian line shape with variable g-factor and line width. The careful search of the nature of two other narrow electron paramagnetic resonance signals in shungite, which used to be prescribed to fullerene-like molecules, is fulfilled. Here, it is shown that the oxygen-deficient E'γ centers are responsible for these signals. A strong correlation is revealed between the concentration of Е'γ centers and the line width of conduction electron spin resonance signal, which occurs under annealing process of the samples at T = 570 K. The correlation reasons are a spin-spin coupling between two spin subsystems and time dependent of the Е'γ concentration during annealing process.

No MeSH data available.