Synthesis of Graphite Oxide (GO). Graphite oxide was
synthesized from graphite powder by modified Hummer’s
method [6]. 2.0 g of graphite powder was first added into
100mL concentrated H2SO4 at room temperature. Under
stirring, the mixture was cooled to 5∘C using an ice bath,
and the temperature of the mixture was kept to be below 5∘C
for 30min. KMnO4 (8.0 g) was then added gradually under
stirring and cooling, so that the temperature of the mixture
was not allowed to reach 10∘C. 100mL distilled water was
added into the mixture, stirred for 1 hr., and further diluted to
approximately 300mL with distilled water. After that, 20mL
of 30% H2O2 was added to the mixture to reduce the residual
KMnO4.The solidwas filtered, washedwith 5%HCl aqueous
solution (800 mL) to remove metal ions and with distilled
water until the pH was 6. The resulting graphite oxide (GO)
was dried at 45∘C for 24h.