Surface Modification of Glassy Carbon by Radio-frequency Discharge Plasma

Abstract

The surface modification of glassy carbon (GC) by radio-frequency (13.56 MHz) discharge plasma was investigated to obtain the surface modification mechanism. The GC surface became remarkably hydrophilic by argon cold plasma. The relation between the surface characteristic (the wettability of water) of GC and the plasma condition was estimated experimentally. Furthermore, the GC surface was observed by SEM. From these results, the following facts were found.The contact angle of water on GC was reduced from 90° to 15° by the argon discharge plasma treatment with the input power of 50 W for 60 sec. in setting GC on the powered electrode. The GC surface was etched remarkably in this treatment. The water wettability on the GC surface increased as the ion density or the energy of the plasma increased. The contact angle of water on GC increased from 15°to 52° in air at the room temperature for 24 hours or increased in O2, though it was almost constant under the vacuum condition.These facts suggest that the formation of the active radical as well as the hydrophilic group would give rise to the decrease of the contact angle of water on GC by the argon plasma treatment.