Closed π-electron network in large polyhedral multi-shell carbon nanoparticles

High Resolution Transmission Electron Microscopy (HRTEM) reveals a polyhedral multi-shell fullerene-like structure of astralen carbon nanoparticles. The polyhedra consist of large 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 ̃40 nm and ̃15 nm, respectively. Astralen particles are suggested to have defect-free sp² flat faces and all defects condense at their polyhedral edges. Multi-frequency Electron Paramagnetic Resonance (EPR) spectra of polycrystalline astralen samples reveal two main signals: a very broad signal with AH_pp > 1 T and an asymmetric relatively narrow signal that consists of two Lorentzian components in g = 2.00 region. The intensities of all X-band EPR signals show no changes on decreasing temperature down to T = 4 K. Magnetic susceptibility demonstrates strong temperature dependent orbital diamagnetism. All unusual magnetic features of astralen are attributed to prevalent itinerant spins.