1. Riga Technical University, Institute of Chemistry and Chemical Technology, Faculty of Natural Sciences and Technology, 3 Paula Valdena Street, Riga LV-1048, Latvia
2. Institute of Solid State Physics, University of Latvia, 8 Kengaraga Street, Riga LV-1063, Latvia
3. Department of Electrical Engineering, Yuan Ze University, 135 Yuan-Tung Road, Chungli 32003, Taiwan
4. Latvian Institute of Organic Synthesis, 21 Aizkraukles Street, Riga LV-1006, Latvia