1. Advanced Research Institute of Multidisciplinary Science Beijing Institute of Technology Beijing 100081 P.R. China
2. Department of Chemistry and International Institute of Nanotechnology Northwestern University 2145 Sheridan Road Evanston IL 60208-3113 USA
3. Chemical Biological Center U.S. Army Combat Capabilities Development Command 8198 Blackhawk Road Aberdeen Proving Ground Maryland 21010 USA
4. Department of Chemical and Biological Engineering Northwestern University 2145 Sheridan Road Evanston IL 60208-3113 USA