1. Department of Inorganic Chemistry, Faculty of Natural Sciences, Comenius University, SK-84215 Bratislava, Slovakia
2. Faculty of Science, Charles University in Prague, Hlavova 2038/8, CZ-12843 Prague, Czech Republic
3. Department of Physics, University of Patras, GR-26504 Patras, Greece
4. Laboratory for Advanced Materials, Comenius University Science Park, Ilkovičova 8, SK-84215 Bratislava, Slovakia