Structural and magnetic resonance study of astralen nanoparticles

A. I. Shames, E. A. Katz, A. M. Panich, D. Mogilyansky, E. Mogilko, J. Grinblat, V. P. Belousov, I. M. Belousova, A. N. Ponomarev

Research output: Contribution to journalArticlepeer-review

36 Scopus citations

Abstract

Using HRTEM, XRD and Raman spectroscopy we demonstrated a polyhedral multi-shell fullerene-like structure of astralen particles. The polyhedra consist of large defect-free flat graphitic faces connected by defective edge regions with presumably pentagon-like structure. The faces comprise a stacking of 20-50 planar graphene sheets with inter-sheet distance of ~ 0.340 nm. Average sizes of the particles and their flat faces are of ~ 40 nm and ~ 15 nm, respectively. EPR spectra of astralen powder reveal two components: a very broad signal with ΔHpp > 1 T and an asymmetric narrow one centered close to g = 2.0. The latter consists of two overlapping Lorentzian lines. All spectral components are independent of the ambient pressure. The intensities of all EPR signals show no changes on decreasing temperature from T = 300 K down to 4 K demonstrating the Pauli paramagnetism. Temperature dependent 13C NMR measurements yield nuclear spin-lattice relaxation times T1n ~ T- 0.612. The exponent in the temperature T1n(T)-dependence for astralen falls between the metallic behavior, T1n ~ T- 1 (Korringa relation), and the semiconductor behavior, T1n ~ T- 0.5. The unusual magnetic resonance features are attributed to delocalized charge carriers which amount considerably exceeds that of spins localized in defects on astralen edges.

Original languageEnglish
Pages (from-to)505-510
Number of pages6
JournalDiamond and Related Materials
Volume18
Issue number2-3
DOIs
StatePublished - 1 Feb 2009

Keywords

  • Carbon nanoparticles
  • Magnetic resonance
  • Multi-shell polyhedra

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Chemistry (all)
  • Mechanical Engineering
  • Materials Chemistry
  • Electrical and Electronic Engineering

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