1. University of Bucharest, Faculty of Physics, Magurele, Romania
2. University “POLITEHNICA” of Bucharest, Faculty of Applied Chemistry and Materials Science, Polizu, Bucharest, Romania
3. University of Bucharest, Faculty of Physics, 3Nano-SAE Research Centre, Bucharest-Magurele, Romania
4. University of Niš, Faculty of Technology Leskovac, Bulevar Oslobodjenja, Leskovac, Serbia