1. Catalan Institute of Nanoscience and Nanotechnology (ICN2)CSIC and the Barcelona Institute of Science and Technology (BIST) Campus UAB Bellaterra, Barcelona 08193 Spain
2. Laboratory of Photomolecular ScienceInstitute of Chemical Sciences and EngineeringEcole Polytechnique Fédérale de Lausanne CH‐1015 Lausanne Switzerland