1. Institute of Chemical Sciences and Engineering, École Polytechnique Fédérale de Lausanne (EPFL), CH-1051 Sion, Switzerland
2. Department of Chemical and Biomolecular Engineering, University of California, Berkeley, Berkeley, California 94720, United States
3. The Molecular Foundry, Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
4. Interdisciplinary Center for Electron Microscopy, École Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland