Combined study of the ground and excited states of carbon onions by electron energy-loss spectroscopy: Comparison with highly ordered pyrolytic graphite

Highlights: • ELNES and ECOSS were acquired under the same conditions for CNOs and graphite. • The ELNESs were divided into three peaks by three-Gaussian function method. • The Compton profile difference indicates stronger electron localization in CNOs. • Both ground and excited states of CNOs are quite different from those of graphite. Herein, an extensive electron energy loss spectroscopy (EELS) study presents the electronic structure properties of carbon nano-onions (CNOs) and graphite under same acquisition conditions, respectively. The low-loss and core-loss EELS spectra were recorded at the so-called "magic angle" on the optic axis in a transmission electron microscope. Through the "three-Gaussian" method we found the second peak in the core-loss spectrum of CNOs is markedly different from that of graphite. Valence Compton profiles were obtained by recording the EELS at a large scattering angle. The CNOs and graphite Compton profile difference indicates stronger electron localization in CNOs. From this comparison, we are able to conclude that the electronic structure properties of the ground and excited states of CNOs are quite different from those of graphite.