Fig. 8. The effects of (a–d) hydroxide and (e–h) epoxide group density on the mechanical properties of GO upon a tensile loading along armchair direction with the tensile strain of (a) 0% (b) 13.2% (c) 17.2% (d) 18.2, (e) 0% (f) 12.4% (g) 14.4% (h) 15.8%.