1. Institute of Atomic Physics and Spectroscopy, University of Latvia, 19, Raina Blvd., LV 1586, Riga, Latvia
2. Department of Chemistry, Vilnius University, Naugarduko str. 24, LT-03225 Vilnius, Lithuania
3. Laboratory of BioNanoTechnology,
Semiconductor Physics Institute, State Research Institute Center for Physical and Technological Sciences, A. Gostauto11, LT-01108 Vilnius, Lithuania