Solid state forms of pure C60 and C70 were investigated at room temperature using transmission electron microscopy (TEM) techniques incorporating electron diffraction, high resolution TEM (HRTEM) and electron energy loss spectrometry (EELS). Electron diffraction patterns recorded along several zone axes indicated that C60 has a face centered cubic unit cell with Fm3m space group symmetry and lattice parameter of 1.42 nm within 5% experimental error. C70 appears to adopt close packed hexagonal symmetry (P63/mmc space group) with a0 = 1.01 nm and n0 = 1.68 nm within 5% experimental error. HRTEM imaging revealed the presence of extensive periodicity associated with C60 and C70 crystallites as well as numerous lattice defects and faults. EELS low loss spectra for C60 and C70 solids exhibit excitations analogous to graphite and amorphous carbon, such as interband π and π + σ plasmons, though at slightly lower energy losses. C70 exhibits a more intense "π plasmon" than C60. The 1s core loss spectra of both C60 and C70 show a π* transition at 285 ± 0.5 eV, and splitting of a σ* transition centered at 291 ± 0.5 eV.
ASJC Scopus subject areas
- Physics and Astronomy(all)
- Physical and Theoretical Chemistry