Magnetic and EPR studies of edge-localized spin paramagnetism in multi-shell nanographites derived from nanodiamonds

V. Yu Osipov; A. I. Shames; T. Enoki; K. Takai; M. Endo; T. Hayashi; Y. Kaburagi; A. Ya Vul'

doi:10.1016/j.diamond.2008.09.015

Magnetic and EPR studies of edge-localized spin paramagnetism in multi-shell nanographites derived from nanodiamonds

V. Yu Osipov, A. I. Shames, T. Enoki, K. Takai, M. Endo, T. Hayashi, Y. Kaburagi, A. Ya Vul'

Department of Physics

Research output: Contribution to journal › Article › peer-review

18 Scopus citations

Abstract

Prolonged (up to 2 h) heat treatment at 1600 °C of nanodiamond particles (5 nm) leads to their conversion to the mixture of quasi-spherical carbon onions and multi-shell polyhedral nanographites. Structural and magnetic properties of two (A and B) series of nanographite samples obtained at various annealing intervals were studied. XRD data show that both multi-shell nanographite samples have practically the same crystalline structures. HRTEM evidences that the most of particles obtained by short time (7 min) annealing have a spherical like shape whereas the long time (~ 2 h) annealing leads to the majority of particles having a polyhedral shape with a hollow inside. Electronic and magnetic properties of these nanocarbons were investigated by magnetic susceptibility and EPR. Annealing results in entire transformation of the EPR signal of nanodiamond to new EPR signals of various line shapes and widths. These signals are extremely sensitive to ambient oxygen. Concentrations for all EPR active spins vary from ~ 1 × 10¹⁹ spins/g (7 min) to ~ 2 × 10¹⁹ spins/g (2 h). Temperature dependences of EPR spectra' parameters were obtained for vacuum-processed samples within the range 4-600 K. Intensity vs. T plots may be well-fitted by the combination of Curie-Weiss and temperature-independent Pauli susceptibility contributions. The latter one increases on heat treatment. Significant extension of electron spin-lattice relaxation time on decreasing temperature was found.

Original language	English
Pages (from-to)	220-223
Number of pages	4
Journal	Diamond and Related Materials
Volume	18
Issue number	2-3
DOIs	https://doi.org/10.1016/j.diamond.2008.09.015
State	Published - 1 Feb 2009

Keywords

Edge electronic states
Electron paramagnetic resonance
Graphite nanoparticles
Magnetic susceptibility

ASJC Scopus subject areas

Electronic, Optical and Magnetic Materials
General Chemistry
Mechanical Engineering
Materials Chemistry
Electrical and Electronic Engineering

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10.1016/j.diamond.2008.09.015

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@article{0cf6e5bc85d746fdbb36a3b858b1e814,

title = "Magnetic and EPR studies of edge-localized spin paramagnetism in multi-shell nanographites derived from nanodiamonds",

abstract = "Prolonged (up to 2 h) heat treatment at 1600 °C of nanodiamond particles (5 nm) leads to their conversion to the mixture of quasi-spherical carbon onions and multi-shell polyhedral nanographites. Structural and magnetic properties of two (A and B) series of nanographite samples obtained at various annealing intervals were studied. XRD data show that both multi-shell nanographite samples have practically the same crystalline structures. HRTEM evidences that the most of particles obtained by short time (7 min) annealing have a spherical like shape whereas the long time (~ 2 h) annealing leads to the majority of particles having a polyhedral shape with a hollow inside. Electronic and magnetic properties of these nanocarbons were investigated by magnetic susceptibility and EPR. Annealing results in entire transformation of the EPR signal of nanodiamond to new EPR signals of various line shapes and widths. These signals are extremely sensitive to ambient oxygen. Concentrations for all EPR active spins vary from ~ 1 × 1019 spins/g (7 min) to ~ 2 × 1019 spins/g (2 h). Temperature dependences of EPR spectra' parameters were obtained for vacuum-processed samples within the range 4-600 K. Intensity vs. T plots may be well-fitted by the combination of Curie-Weiss and temperature-independent Pauli susceptibility contributions. The latter one increases on heat treatment. Significant extension of electron spin-lattice relaxation time on decreasing temperature was found.",

keywords = "Edge electronic states, Electron paramagnetic resonance, Graphite nanoparticles, Magnetic susceptibility",

author = "Osipov, {V. Yu} and Shames, {A. I.} and T. Enoki and K. Takai and M. Endo and T. Hayashi and Y. Kaburagi and Vul', {A. Ya}",

note = "Funding Information: V. Yu. O. thanks the Japanese Society for the Promotion of Science (JSPS) and the Tokyo Institute of Technology for the fellowship and financial support in FY 2004/2005, 2008. Authors also thank New Energy Development Organization of Japan (NEDO, grant #04IT4) for the financial support. A. Ya. V. and V. Yu. O. thank the Russian Federal Agency for Science and Innovation for the financial support in the frame of project 2007-3-2.3-07-02-00.",

year = "2009",

month = feb,

day = "1",

doi = "10.1016/j.diamond.2008.09.015",

language = "English",

volume = "18",

pages = "220--223",

journal = "Diamond and Related Materials",

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publisher = "Elsevier B.V.",

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TY - JOUR

T1 - Magnetic and EPR studies of edge-localized spin paramagnetism in multi-shell nanographites derived from nanodiamonds

AU - Osipov, V. Yu

AU - Shames, A. I.

AU - Enoki, T.

AU - Takai, K.

AU - Endo, M.

AU - Hayashi, T.

AU - Kaburagi, Y.

AU - Vul', A. Ya

N1 - Funding Information: V. Yu. O. thanks the Japanese Society for the Promotion of Science (JSPS) and the Tokyo Institute of Technology for the fellowship and financial support in FY 2004/2005, 2008. Authors also thank New Energy Development Organization of Japan (NEDO, grant #04IT4) for the financial support. A. Ya. V. and V. Yu. O. thank the Russian Federal Agency for Science and Innovation for the financial support in the frame of project 2007-3-2.3-07-02-00.

PY - 2009/2/1

Y1 - 2009/2/1

N2 - Prolonged (up to 2 h) heat treatment at 1600 °C of nanodiamond particles (5 nm) leads to their conversion to the mixture of quasi-spherical carbon onions and multi-shell polyhedral nanographites. Structural and magnetic properties of two (A and B) series of nanographite samples obtained at various annealing intervals were studied. XRD data show that both multi-shell nanographite samples have practically the same crystalline structures. HRTEM evidences that the most of particles obtained by short time (7 min) annealing have a spherical like shape whereas the long time (~ 2 h) annealing leads to the majority of particles having a polyhedral shape with a hollow inside. Electronic and magnetic properties of these nanocarbons were investigated by magnetic susceptibility and EPR. Annealing results in entire transformation of the EPR signal of nanodiamond to new EPR signals of various line shapes and widths. These signals are extremely sensitive to ambient oxygen. Concentrations for all EPR active spins vary from ~ 1 × 1019 spins/g (7 min) to ~ 2 × 1019 spins/g (2 h). Temperature dependences of EPR spectra' parameters were obtained for vacuum-processed samples within the range 4-600 K. Intensity vs. T plots may be well-fitted by the combination of Curie-Weiss and temperature-independent Pauli susceptibility contributions. The latter one increases on heat treatment. Significant extension of electron spin-lattice relaxation time on decreasing temperature was found.

AB - Prolonged (up to 2 h) heat treatment at 1600 °C of nanodiamond particles (5 nm) leads to their conversion to the mixture of quasi-spherical carbon onions and multi-shell polyhedral nanographites. Structural and magnetic properties of two (A and B) series of nanographite samples obtained at various annealing intervals were studied. XRD data show that both multi-shell nanographite samples have practically the same crystalline structures. HRTEM evidences that the most of particles obtained by short time (7 min) annealing have a spherical like shape whereas the long time (~ 2 h) annealing leads to the majority of particles having a polyhedral shape with a hollow inside. Electronic and magnetic properties of these nanocarbons were investigated by magnetic susceptibility and EPR. Annealing results in entire transformation of the EPR signal of nanodiamond to new EPR signals of various line shapes and widths. These signals are extremely sensitive to ambient oxygen. Concentrations for all EPR active spins vary from ~ 1 × 1019 spins/g (7 min) to ~ 2 × 1019 spins/g (2 h). Temperature dependences of EPR spectra' parameters were obtained for vacuum-processed samples within the range 4-600 K. Intensity vs. T plots may be well-fitted by the combination of Curie-Weiss and temperature-independent Pauli susceptibility contributions. The latter one increases on heat treatment. Significant extension of electron spin-lattice relaxation time on decreasing temperature was found.

KW - Edge electronic states

KW - Electron paramagnetic resonance

KW - Graphite nanoparticles

KW - Magnetic susceptibility

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U2 - 10.1016/j.diamond.2008.09.015

DO - 10.1016/j.diamond.2008.09.015

M3 - Article

AN - SCOPUS:59649091415

SN - 0925-9635

VL - 18

SP - 220

EP - 223

JO - Diamond and Related Materials

JF - Diamond and Related Materials

IS - 2-3

ER -

Magnetic and EPR studies of edge-localized spin paramagnetism in multi-shell nanographites derived from nanodiamonds

Abstract

Keywords

ASJC Scopus subject areas

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