1. Institute
of Functional Nanomaterials, University of Puerto Rico, San Juan, Puerto Rico 00931, United States
2. Department
of Physics, University of Puerto Rico, San Juan, Puerto Rico 00936, United States
3. Advanced Green Innovations, Chandler, Arizona 85226-2401, United States
4. Department
of Chemistry, University of Puerto Rico, San Juan, Puerto Rico 00936, United States