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 X 10(16) m(-3), the electron temperature of about 5.5 eV and the density of neutral oxygen atoms of 8 X 10(21) m(-3) for 20 s. The surface wettability was measured by a contact angle of water drop. The contact angle dropped from original 112 degrees down to about 1 degrees. 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. (c) 2006 Elsevier B.V. All rights reserved.