The reduced graphene oxide sheets (RGO) was synthesized
from GO reduction by hydrazine. The reduction reaction
was carried out by adding hydrazine (1.2 mL) into
the dispersion of GO (60 mg GO in 20 mL water). After
the mixture was sonicated for 1 h and kept stirring for
24 h at 50 8C, RGO was obtained by filtering the product
and drying in vacuum.