“…Efficient reduction of oxygencontaining moieties and defects on the basal plane of GO resulted in rGO with folded layers and a high degree of aggregation. 34,35 To study the surface wettability of the GO and rGO, the contact angle (CA) of water droplets was measured. 36,37 For example, the CA of GO synthesized via Hummer's method was found to be ∼39.9°, as shown in Figure 5f, which may be attributed to the oxygen-containing functional groups (e.g., hydroxyl, carboxyl, carbonyl, and epoxy groups) on the basal plane of GO, implying that the surface of GO is hydrophilic.…”