1. Riga Technical University, Faculty of Materials Science and Applied Chemistry, 3/7 Paula Valdena St., Riga LV-1048, Latvia
2. Latvian Institute of Organic Chemistry, 21 Aizkraukles St., Riga LV-1006, Latvia
3. Riga Technical University, Faculty of Computer Science and Information Technology, 10 Zunda krastmala, Riga LV-1048, Latvia
4. University of Latvia, Institute of Solid State Physics, 8 Ķengaraga St., Riga LV-1063, Latvia