(810c) On the Intrinsic Wettability of Graphene

On the Intrinsic Wettability of Graphene

Zhiting Li², Yongjin Wang¹, Andrew Kozbial¹, Feng Zhou², Lei Li¹and Haitao Liu²

¹Department of Chemical and Petroleum Engineering and ²Department of Chemistry, University of Pittsburgh, Pittsburgh, PA, 15261, U.S.A.

The water wettability of graphene plays a key role in many important applications, not only defining the interaction between graphene and its environment but also directly impacting many of its properties, such as charge doping, carrier mobility, wetting, and adhesion. Here we report the effect of airborne hydrocarbon contaminants on the wettability of supported CVD graphene. We show that the water contact angle (WCA) of a freshly prepared supported graphene surface increases upon exposure to ambient air. Infrared (IR) spectroscopy and X-ray photoelectron spectroscopy (XPS) showed that airborne hydrocarbon adsorbed onto graphitic surface during this process. Both thermal annealing and controlled UV/O₃ treatment could partially remove the hydrocarbon contaminant and resulted in a concurrent decrease in the WCA. Our findings indicate that graphitic surfaces are more hydrophilic than previously believed and suggest that the previously reported hydrophobic nature of graphitic surface is due to unintentional hydrocarbon contamination from ambient air. The theoretical calculation results also support the experimental findings.