1. Institute for Functional Nanomaterials, University of Puerto Rico, San Juan, Puerto Rico 00931, United States
2. Department of Physics, University of Puerto Rico, Rio Piedras Campus, San Juan, Puerto Rico 00931, United States
3. National Research Council, Washington D.C. 20001, United States
4. Materials and Manufacturing Directorate, Air Force Research Laboratory, Wright-Patterson Air Force Base, Dayton, Ohio 45433, United States
5. Department of Chemistry, University of Puerto Rico, Rio Piedras Campus, San Juan, Puerto Rico 00931, United States