1. Department of Materials Science and NanoEngineering Rice University Houston TX 77005 USA
2. Department of Physics VSSD College CSJM University Kanpur Uttar Pradesh 208002 India
3. Department of Chemical and Environmental Engineering University of Cincinnati Cincinnati OH 45221 USA
4. Institute of Nanochemistry and Nanobiology School of Environmental and Chemical Engineering Shanghai University Shanghai 200444 P. R. China