Formation of functional groups on graphite during oxygen plasma treatment

Improved sample wettability was obtained by oxygen plasma functionalization of pyrolytic graphite. The samples were exposed to highly dissociated oxygen plasma with the density of 1 1016 m 3, the electron temperature of about 5.5 eVand the density of neutral oxygen atoms of 8 1021 m 3 for 20 s. The surface wettability was measured by a contact angle of water drop. The contact angle dropped from original 1128 down to about 18. The functional groups were detected by XPS analyses. The survey spectrum showed a substantial increase of oxygen concentration on the surface, while high-resolution analyses showed additional oxygen was bonded onto the graphite surface in the form of C–O polar functional group responsible for the increase of the surface energy.