1. Department of Physics, Universidade Federal de Pernambuco (UFPE), 50670-901 Recife-PE, Brazil
2. Institute of Chemistry, São Paulo State University (UNESP), 14800-060 Araraquara-SP, Brazil
3. Chair in Hybrid Nanosystems, Nanoinstitute Munich, Faculty of Physics, Ludwig-Maximilians-Universität München, D-80539 München, Germany