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Single Sheet Functionalized Graphene by Oxidation and Thermal Expansion of Graphite

Summary: Articles
Single Sheet Functionalized Graphene by Oxidation and Thermal
Expansion of Graphite
Michael J. McAllister, Je-Luen Li,,,| Douglas H. Adamson, Hannes C. Schniepp,
Ahmed A. Abdala,, Jun Liu,X,O Margarita Herrera-Alonso, David L. Milius,
Roberto Car,, Robert K. Prud'homme, and Ilhan A. Aksay*,
Department of Chemical Engineering, Department of Chemistry, and Princeton Institute for the Science
and Technology of Materials, Princeton UniVersity, Princeton, New Jersey 08544, and Sandia National
Laboratories, Albuquerque, New Mexico 87185
ReceiVed December 26, 2006. ReVised Manuscript ReceiVed February 6, 2007
A detailed analysis of the thermal expansion mechanism of graphite oxide to produce functionalized
graphene sheets is provided. Exfoliation takes place when the decomposition rate of the epoxy and hydroxyl
sites of graphite oxide exceeds the diffusion rate of the evolved gases, thus yielding pressures that exceed
the van der Waals forces holding the graphene sheets together. A comparison of the Arrhenius dependence
of the reaction rate against the calculated diffusion coefficient based on Knudsen diffusion suggests a
critical temperature of 550 C which must be exceeded for exfoliation to occur. As a result of their
wrinkled nature, the functionalized and defective graphene sheets do not collapse back to graphite oxide
but are highly agglomerated. After dispersion by ultrasonication in appropriate solvents, statistical analysis
by atomic force microscopy shows that 80% of the observed flakes are single sheets.


Source: Aksay, Ilhan A. - Department of Chemical Engineering, Princeton University


Collections: Materials Science