Fig. 2. Images of water droplets on (a) an unmodified and (b) a modified polystyrene-based Petri dish. The contact angles of (c) unmodified and (d) modified Petri dish are 63° and 42°, respectively. The contact angle of (e) a compressed graphite pellet decreases from (f) 60° to (g) 35° after modification. The transmission electron microscopy (TEM) bright field images of (h) unmodified, (i and j) modified multi-walled carbon nanotubes (MWCNTs) and (k) unmodified and (l) modified reduced graphene oxide (rGO).