Fig. 7

HepG2 cell morphology after 7 days by scanning electron microscope. a Cultured on standard polystyrene plate, b cultured on graphene oxide nanofilm partly covering a standard polystyrene plate (red asterisk), c cultured on graphene oxide nanofilm. Black dotted line indicates the border between polystyrene and graphene surface. The greater red frames (scale bar: 20 µm) indicate magnified parts of the main pictures (marked by smaller red frames, scale bar: 100 µm)