1. Department of Mathematics and Physics, University of Puerto Rico, Cayey, Puerto Rico, USA
2. Department of Physics and Institute of Functional Nanomaterials, University of Puerto Rico, San Juan, Puerto Rico, USA
3. National Physical Laboratory (CSIR), New Delhi, India
4. Department of Biology, University of Puerto Rico, Cayey, Puerto Rico, USA
5. Department of Chemistry, University of Puerto Rico, Cayey, Puerto Rico, USA
6. Department of Natural Sciences, University of Puerto Rico, Cayey, Puerto Rico, USA