1. Catalan Institute of Nanoscience and Nanotechnology (ICN2), CSIC, and BIST, Campus UAB, 08193 Barcelona, Spain
2. QuantaLab & International Iberian Nanotechnology Laboratory (INL), Av. Mestre José Veiga, 4715-330 Braga, Portugal
3. ICREA - Institució Catalana de Recerca i Estudis Avançats, 08010 Barcelona, Spain