1. Department of Physics, University of Craiova, 200585 Craiova, Romania
2. Faculty of Physics, West University of Timisoara, 300223 Timisoara, Romania
3. Advanced Environmental Research Institute, West University of Timisoara, 300223 Timisoara, Romania
4. Condensed Matter Department, National Institute for Research and Development in Electrochemistry and Condensed Matter, 300254 Timisoara, Romania
5. Department of Pharmacy, “Constantin Brancusi” University of Targu-Jiu, 210185 Targu Jiu, Romania