1. Department of Chemistry, Brandeis University, 415 South Street, Waltham, Massachusetts 02453
2. Department of Chemistry, The Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong, China
3. Department of Physics, The Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong, China
4. Advanced Nanofabrication Core Lab, King Abdullah University of Science and Technology, Thuwal 23955-6900 Kingdom of Saudi Arabia