1. School of Physical Sciences and Nanotechnology, Yachay Tech University, Urcuquı́ 100119, Ecuador
2. Donostia International Physics Center (DIPC), Paseo de Manuel de Lardizabal 4, ES-20018 San Sebastían, Spain
3. Nano-Bio Spectroscopy Group and ETSF Scientific Development Center, Departamento de Fı́sica de Materiales, Universidad del Paı́s Vasco UPV/EHU, ES-20018 San Sebastián, Spain
4. Institute of Physics, Bijenička 46, HR-10000 Zagreb, Croatia
5. Department of Physics, University of Zagreb, Bijenička 32, HR-10000 Zagreb, Croatia