(a)
(b)
(c)
(d)
Figure 1: FESEM morphology of graphene oxide aerogels after freeze drying process: (a) 2 mg/ml GO starting solution, HS method; (b) 1 mg/ml GO starting solution, HS method; (c) 0.5 mg/ml GO starting solution, HS method; (d) 6.2 mg/ml GO starting solution, DFS method.