Surface functionalization without lattice degradation of highly crystalline nanoscaled carbon materials using a carbon monoxide atmospheric plasma treatment

Atmospheric plasma treatments on various forms of carbon were performed to compare the effect of surface modification using carbon monoxide (CO) as the active gas, in comparison to the conventionally used O2. Changes in surface characteristics were analyzed using X-ray photoelectron spectroscopy (XPS) as a function of duration. The results indicated that use of O2 plasma resulted in only a limited oxygen uptake (O/C = 0.11), while CO treatments resulted in tailorable surface O/C ratios as high as 0.69, a result not attainable when using low-pressure RF plasmas (O/C < 0.1). High-resolution XPS analysis and Auger spectroscopy confirmed that a tailorable level of carbonyl functional groups could be evenly distributed throughout the surface. Both Raman and scanning tunneling microscopy (STM) indicated nano-scale degradation of the structure when using the O2 treatment. On the other hand, CO treated specimens exhibited no observable damage to the material with high levels of oxygen incorporation. Contact angle measurements verified the formation of a highly stable hydrophilic surface and excellent dispersion was observed in an aqueous solution on treated specimens after CO treatment. The CO treatment was also successfully applied to SWCNT with similar results and no degradation of structure.