title: The sp2and sp3fractions of unknown carbon materials: electron energy-loss near-edge structure analysis of C-K spectra acquired under the magic-angle condition by the electron nanobeam technique.
abstract: A method is described for the quantification of the sp2, sp3and intermediate hybridizations in several carbon (C) material samples. Electron energy-loss near-edge spectra were acquired using fast electrons (120keV) in an electron microscope in nanobeam configuration under the so-called "magic-angle" condition, and were analysed to extract the sp2and sp3fractions, and identify the possible mixed sp2+εhybridizations. The method consists in projecting the unknown spectra on a basis made up of pure sp2and sp3spectra, obtained under the same experimental conditions from graphite and diamond crystals, respectively. The residual spectra contain information about the intermediate hybridizations sp2+εoccurring in the samples. The method was successfully tested on "ab initio" numerically generated spectra relative to amorphous C materials. Finally, it was applied to actual C amorphous and pyrolytic samples, and results were compared to those obtained by the most commonly used, conventional "three-Gaussian" method. The combined application of electron diffraction and spectroscopy, in the nanobeam configuration, yielded useful information about the atomic and electronic structure from very small volumes of the unknown C material.
authors.affiliation: Italian National Institute of Health (ISS), Department of Technology and Health, Viale Regina Elena 299, 00161 Rome, Italy. Electronic address: marco.diociaiuti@iss.it.
authors.forename: Marco
authors.initials: M
authors.lastname: Diociaiuti
authors.affiliation: National Institute for Insurance against Accidents at Work (INAIL Research), Department of Occupational and Environmental Medicine, Epidemiology and Hygiene, Via Fontana Candida 1, 00040 Monte Porzio Catone, Rome, Italy.
authors.forename: Stefano
authors.initials: S
authors.lastname: Casciardi
authors.affiliation: National Institute for Insurance against Accidents at Work (INAIL Research), Department of Occupational and Environmental Medicine, Epidemiology and Hygiene, Via Fontana Candida 1, 00040 Monte Porzio Catone, Rome, Italy.
authors.forename: Renata
authors.initials: R
authors.lastname: Sisto
keywords: C hybridization; C materials; C60; Electron energy-loss spectroscopy; Magic-angle condition; Nanobeam electron diffraction; Transmission electron microscopy