1. Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany
2. National
Graphene Institute, University of Manchester, Booth Street East, Manchester M13 9PL, United Kingdom
3. School
of Physics and Astronomy, University of Manchester, Oxford Road, Manchester M13 9PL, United Kingdom
4. School of
Chemistry, University of Manchester, Oxford Road, Manchester M13 9PL, United Kingdom
5. Laboratory
for Chemistry of Novel Materials, University of Mons, Place du Parc 20, B-7000 Mons, Belgium