1. Department of Chemical Engineering, Columbia University, New York, New York 10027, United States
2. Center for Functional Nanomaterials, Brookhaven National Laboratory, Upton, New York 11973, United States
3. College of Engineering and Applied Sciences, Nanjing University, Nanjing 210093, China
4. Department of Applied Physics and Applied Mathematics, Columbia University, New York, New York 10027, United States
5. Department of Physics and Astronomy, University of California, Irvine, California 92697, United States