This paper describes the electrochemical performance of carbon onions as electrode materials in electrical double layer capacitors with water electrolytes. Onion‐like carbon (OLC) species were produced by vacuum annealing of detonation nanodiamonds (NDs) powder at 1170–2170 K. The material capability of the charge accumulation in the electric double layer was estimated using the voltammetric technique. The correlations between specific capacitance, surface area and conductivity were found. Charge‐discharge measurements revealed a dependence of the specific capacitance of OLC on the degree of diamond particle graphitization and defectness of particle surfaces. Promising capacitance values, ranging within 20−40 F g–1 and within 70−100 F g–1 were found for the OLC materials operating respectively in acid electrolytic solution (1 M H2SO4) and alkaline electrolytic solution (6 M KOH). (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Ab initio calculations of dielectric function and electron energy loss (EEL) function of periodically rippled armchair-edged graphene were performed in the framework of the random-phase approximation. The bending of graphene was found to remove restrictions on the electron transitions being forbidden in the flat graphene for certain light polarization. As a result, new peaks appear in the optical absorption spectrum and EEL spectrum of rippled graphene. Energy position, intensity, and width of the peaks are sensitive to the height of out-of-plane graphene bending that can be used in construction of graphene-based materials with variable transparency window.

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X-ray emission spectroscopy has been applied to examine the electronic structure of onion-like carbon (OLC) generated by the annealing treatment of nanodiamonds (ND). The C Kα spectra of OLC produced in the temperature range of 1600−1900 K were found to be markedly different from the spectrum of particles formed at 2140 K and to be characterized by better ordering of graphitic shells. The latter spectrum was shown to be very similar to the C Kα of polycrystalline graphite, while the former ones exhibited a significant increase of the high-energy maximum that might be caused by the defect structure of graphitic networks forming at the intermediate temperatures. The experimental spectra were compared with the theoretical spectra from quantum-chemical semiempirical AM1 calculation of several models:  a fullerene molecule, C240, having icosahedral structure, a C240 molecule incorporating a greater number of nonhexagonal rings, and a holed structure formed by removing pentagons from the icosahedral molecule. The density of high-energy electronic states in the valence band of the graphitic cage was found to be practically invariant to a change in ring statistics but to significantly increase because of localization of electrons on the zigzag sites of a hole boundary.