1. Department of Physics and Astronomy, University of Texas at San Antonio, One UTSA Circle, San Antonio, Texas 78249, United States
2. International Iberian Nanotechnology Laboratory, Avda Mestre Jose Veiga, Braga 4715, Portugal
3. Departamento de Química, Universidad Simón Bolívar, Apartado 89000, Caracas 1080-A, Venezuela