After that 70 ml diluted H2SO4 (5 wt%) was added into the mixture and heated upto 90 C under
continuous stirring for 2 h. Then 3 ml H2O2 was added into the solution and stirred for another 2 h under ambient conditions. On completion of the reaction, the mixture was centrifuged (6000 rpm, 10 min) and washed with 400 ml of 3 wt% H2SO4 (3 wt%), H2O2 (0.5 wt%), and HCl (3 wt%), and then repeatedly washed with distilled water until the pH of the filtrate became neutral. Finally, the prepared GO was dispersed in distilled water and the homogeneous GO dispersion was then centrifugednand filtered.