1. Department of Physics and CICECO—Aveiro Institute of Materials University of Aveiro 3810-193 Aveiro Portugal
2. Department of Physics and Department of Chemistry and CICECO - Aveiro Institute of Materials University of Aveiro 3810-193 Aveiro Portugal
3. Department of Electrical and Computer Engineering and Instituto de Telecomunicações, Instituto Superior Técnico Universidade de Lisboa 1049-001 Lisbon Portugal