1. School of Chemistry and Chemical Engineering Guangxi University Nanning 530004 P.R. China
2. Center for Nanophase Materials Sciences Oak Ridge National Laboratory Oak Ridge Tennessee 37831 USA
3. Integrated Composites Laboratory (ICL), Department of Chemical & Biomolecular Engineering University of Tennessee Knoxville Tennessee 37996 USA
4. School of Chemistry and Biochemistry Georgia Institute of Technology Atlanta Georgia 30332 USA
5. Materials Science Technology Division Oak Ridge National Laboratory Oak Ridge Tennessee 37831 USA
6. Current address: Department of Physics and Engineering Physics Tulane University New Orleans Louisiana 70118 USA