then collected and dried in a vacuum oven at 40 C overnight
prior to the storage in the powder form for further use. In the modied process, for synthesis of GO-2 and GO-3, a 0.5 g graphite powder was suspended in 37.5 ml of H2SO4 by stirring the mixture for 20 min. Subsequently, 85% H3PO4 of desired volume (for GO-2 ¼ 5 ml and GO-3 ¼ 10 ml) was then added, and the mixture was allowed to stir for another 15 min before the addition of KMnO4 (4.5 g). The reaction mixture was allowed to stir at room temperature for 5 days. Aer that we followed the similar procedure, as described previously.