Hi Shivani,

Check this article, might help you to functionalize you graphene.

http://cdn.intechopen.com/pdfs-wm/44108.pdf

One simple route is to electrochemically oxidise the graphene  where by oxygen groups are introduced on graphene surface

i need covalant  functionalization of GR..

Hi...

It may not that much difficult, you can find it from the below article. Acid treatment of 3 : 1 H2SO4 : HNO3

DOI: 10.1039/C0JM04106H

Article: http://pubs.rsc.org/en/content/articlelanding/2011/jm/c0jm04106h#!divAbstract

You may can use surfactants like TX100 or SDS also, but it will affects the properties of graphene.

I have a small doubt about your question?

What do you want to functionalize, is it single layer graphene or single layer graphene film?

I want to functionalize single layer graphene flakes or single layer graphene film both..