Single-Step Process toward Achieving Superhydrophobic Reduced Graphene Oxide

We report the first use of spark plasma sintering (SPS) as a single-step process to achieve superhydrophobic reduced graphene oxide (rGO). It was found that SPS was capable of converting smooth and electrically insulating graphene oxide (GO) sheets into highly electrically conductive rGO with minimum residual oxygen and hierarchical roughness which could be well retained after prolonged ultrasonication. At a temperature of 500 °C, which is lower than the conventional critical temperature for GO exfoliation, GO was successfully exfoliated, reduced, and hierarchically roughened. rGO fabricated by only 1 min of treatment at 1050 °C was superhydrophobic with a surface roughness (Ra) 10 times as large as that of GO as well as an extraordinarily high C:O ratio of 83.03 (atom %) and water contact angle of 153°. This demonstrates that SPS is a superior GO reduction technique, which enabled superhydrophobic rGO to be quickly and effectively achieved in one single step. Moreover, the superhydrophobic rGO fabricated by SPS showed an impressive bacterial antifouling and inactivation effect against Escherichia coli in both aqueous solution and the solid state. It is envisioned that the superhydrophobic rGO obtained in this study can be potentially used for a wide range of industrial and biomedical applications, such as the fabrication of self-cleaning and antibacterial surfaces.