Health & Environmental Research Online (HERO)


Print Feedback Export to File
2564689 
Journal Article 
Structural and magnetic resonance study of astralen nanoparticles 
Shames, AI; Katz, EA; Panich, AM; Mogilyansky, D; Mogilko, E; Grinblat, J; Belousov, VP; Belousova, IM; Ponomarev, AN 
2009 
Yes 
Diamond and Related Materials
ISSN: 0925-9635 
18 
2-3 
505-510 
WOS:000264429300093 
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 similar to 0.340 nm. Average sizes of the particles and their flat faces are of similar to 40 nm and similar to 15 nm, respectively. EPR spectra of astralen powder reveal two components: a very broad signal with Delta H(pp) > 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 (13)C NMR measurements yield nuclear spin-lattice relaxation times T(1n)similar to T(-0.612). The exponent in the temperature T(1n)(T)-dependence for astralen falls between the metallic behavior, T(1n)similar to T(-1) (Korringa relation), and the semiconductor behavior, T(1n)similar to 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. (c) 2008 Elsevier B.V. All rights reserved. 
Carbon nanoparticles; Multi-shell polyhedra; Magnetic resonance