1. Centre for DNA Nanotechnology (CDNA), The Interdisciplinary Nanoscience Center (iNANO), and Departments of Physics and Astronomy and of Chemistry, Aarhus University, DK-8000 Aarhus C, Denmark, Department of Physics and Astronomy, University College London (UCL), Gower Street, London WC1E 6BT, United Kingdom, and Department of Physics, School of Physical Sciences and Engineering, King’s College London, Strand, London WC2R 2LS, United Kingdom