Third, the GR-MWCNT composites were prepared via the in situ reduction of exfoliated graphene oxides. In a typical synthesis, GR-MWCNTs composites (3:1, w/w) were synthesized by mixing 0.0375 g of graphene oxide and 0.0125 g of pretreated MWCNTs with 100 mL of water, 1 mL of hydrazine solution (35 wt% in water, Aldrich) and 7 mL of ammonia solution (28 wt%in water, Aldrich) in a 500 mL round flask. After being vigorously shaken or stirred for a few minutes, the flask was put in a water bath (95 1C) for 1 h. On completion of the reaction, the powders were obtained by filtration and drying in vacuum. Finally, the powders were dispersed in 10 mL deionized water. Thus, we got GR-MWCNTs composites.