1. Nanomaterials for Bioimaging Group (nanoBIG), Departamento de Física de Materiales, Facultad de Ciencias, Universidad Autónoma de Madrid, Madrid 28049, Spain
2. Instituto Nicolás Cabrera, Facultad de Ciencias, Universidad Autónoma de Madrid, Madrid 28049, Spain
3. São Carlos Institute of Physics, University of São Paulo (USP), 13566-590 São Carlos, São Paulo, Brazil
4. Departamento de Física Teórica de la Materia Condensada and Condensed Matter Physics Center (IFIMAC), Facultad de Ciencias, Universidad Autónoma de Madrid, E28049 Madrid, Spain
5. Institute for Advanced Research in Chemical Sciences, Facultad de Ciencias, Universidad Autónoma de Madrid, 28049 Madrid, Spain
6. Federal Institute for Materials Research and Testing (BAM), Berlin 12489, Germany
7. Friedrich Schiller University (FSU), Jena 07737, Germany