1. Department of Chemistry, University of Puerto Rico at Cayey, 205 Ave. Antonio R Barcelo, Cayey, PR-00736, USA
2. Department of Physics and Electronics, University of Puerto Rico at Humacao, CUH Station, 100 Road 908, Humacao, PR-00791, USA
3. Department of Chemistry, University of Pennsylvania, 231S, 34th Street, Philadelphia, PA 19104-6323, USA
4. Department of Chemical & Biomolecular Engineering, 220S, 33rd Street, Philadelphia, PA 19104-6323, USA