I wonder How to make graphene oxide from graphene. Actually first step is to form graphene flakes on Ti surface by RF sputtering and second step is to oxidize this graphene flakes to form graphene oxide flakes on Ti substrate as I planned. Besides, If is there a way to form graphene oxide wih one step by using RF sputtering, that can also solve the problem. But, so far I could not reach such a reference study.