1. Department of Chemistry and Biochemistry, University of California, Los Angeles, California 90095
2. California NanoSystems Institute, University of California, Los Angeles, California 90095
3. Department of Craniofacial Biology, MUSC College of Dental Medicine, Charleston, South Carolina 29425
4. FEI Company, 5350 NE Dawson Creek Drive, Hillsboro, Oregon 97124
5. School of Dentistry and Dental Research Institute, University of California, Los Angeles, California 90095
6. International Center for Materials Nanoarchitectonics Satellite (MANA), National Institute for Materials Science (NIMS), Tsukuba 305-0047, Japan