1. Mechanical and Aerospace Engineering Department, University of California, Irvine, California 92697, USA
2. Department of Chemistry, University of California, Irvine, California 92697, USA
3. Nanoscience Instruments, Inc., Phoenix, Arizona 85044, USA
4. Schmid College of Science and Technology, Chapman University, Orange, California 92866, USA
5. Materials Science and Engineering Department, University of California, Irvine, California 92697, USA