1. Department of Physics, University of Puerto Rico, San Juan, Puerto Rico 00931, United States
2. Department of Chemistry, North Carolina A&T State University, 1601 East Market Street, Greensboro, North Carolina 27411, United States
3. Department of Chemical Engineering, University of Puerto Rico, Mayagüez, Puerto Rico 00681, United States
4. Department of Chemistry, University of Puerto Rico, San Juan, Puerto Rico 00931, United States