1. National Institute for Laser, Plasma and Radiation Physics, P.O. Box MG-36, RO 76900, Bucharest-Magurele, Romania
2. Centro
de Investigacion en Materiales Avanzados (CIMAV, S.C.), Unidad Monterrey, Alianza Norte 202, 66600 Apodaca, Nuevo Leon, Mexico
3. Faculty
of Chemistry, Department of Organic Chemistry, Biochemistry and Catalysis, University of Bucharest, 4−12 Regina Elisabeta Bvd., Bucharest, Romania