Behavior of unsaturated organic molecules in the nanospace of stage-2 cesium–graphite intercalation compounds

Abstract

Intercalation reaction of benzene (C 6H 6) into CsC 24 and the characteristics of resulting ternary graphite intercalation compound (GIC) have been investigated, in comparison with the similar CsC 24–ternary GICs with ethylene (C 2H 4) and acrylonitrile (C 2H 3CN), and the behavior of these organic molecules within the interlayer nanospace has been discussed. The stability of these ternary GICs under exposure in air, in both stage structure and electrical conductivity was found to be in the order of C 2H 4–, C 6H 6– and C 2H 3CN–GICs. This result was reasonably explained as follows: the C 2H 4 molecules in the interlayer space oligomerize considerably and form network preventing diffusion of the Cs atoms in the interlayer, while the C 6H 6 molecules form only dimers or trimers and unable to form network, and the C 2H 3CN molecules, in spite of their strong tendency to polymerize, apparently do not form oligomers in the interlayer space, and its ternary GIC tends to degrade easily. By the electrical and galvanomagnetic measurements, it is revealed that the dominant carrier of these ternary GICs is electrons, even when the electrical conductivity decreases considerably after prolonged exposure in air, while the host graphite, Grafoil, shows two-carrier conduction. This fact indicates that the degradation of the ternary GICs occurs mainly at the periphery or surface layer of the crystallite, and at the inside of the crystallite, the ternary stage structure is retained unchanged.