1. Institute of Physics, University of Brasília, 70919-970, Brasília, DF, Brazil
2. Department of Physics, Federal University of Pelotas, PO Box 354, 96010-900, Pelotas, RS, Brazil
3. Institute of Nanotechnology Hermann-von-Helmholtz-Platz, Karlsruhe Institute of Technology, 76021, Karlsruhe, Germany
4. Chemistry Department, Federal University of Paraná, 81531-980, Curitiba, PR, Brazil
5. Institute of Physics and International Center of Physics, University of Brasília, 70919-970, Brasília, DF, Brazil