1. Department of Chemistry and Biochemistry and California NanoSystems Institute, University of California, Los Angeles, Los Angeles, California 90095, United States
2. Department of Chemistry, Faculty of Science, Cairo University, Giza 12613, Egypt
3. Micro/Nano Technology Department, Space Materials Laboratory, The Aerospace Corporation, Los Angeles, California 90009, United States
4. Department of Materials Science and Engineering, University of California, Los Angeles, Los Angeles, California 90095, United States