1. Department
of Chemistry and Biochemistry, University of California, Los Angeles, California 90095, United States
2. School
of Optical and Electronic Information, Huazhong University of Science and Technology, Wuhan 430074, China
3. Department
of Materials Science and Engineering, University of California, Los Angeles, California 90095, United States
4. California
Nanosystems Institute, University of California, Los Angeles, California 90095, United States