1. Laboratory of Thin Films and Nanostructures Fabrication (L3Fnano), Institute of Physics, Bento Gonçalves Avenue 9500, P.O. Box 15051, 91501-970, UFRGS, Porto Alegre, Brazil and Laboratory of Molecular Catalysis, Institute of Chemistry, Bento Gonçalves Avenue 9500, P.O. Box 15003, 91501-970, UFRGS, Porto Alegre, RS, Brazil