It was then washed continually with deionized water until the pH of the filtrate was neutral [22]. The GO slurry was dried and pulverized. Potassium stays in the GO even after several times of washing. Therefore multiple washing cycles used in conjunction with bath ultrasonication in fresh ethanol are needed for the removal of residual potassium [23]. After this the GO was dried and pulverized again. Finally, the GO was heated to 1050 8C and held in the furnace for 30 s to form graphene.