1. Department of Applied Physics; Aalto University School of Science; Puumiehenkuja 2 02150 Espoo Finland
2. Departments of Chemistry and Physics; Nanoscience centre University of Jyväskylä; Survontie 9 40014 Jyväskylä Finland
3. Department of Pathology and Virology; Haartman Institute, University of Helsinki; P.O. Box 21 00014 Helsinki Finland
4. Department of Chemistry; University of Jyväskylä; Survontie 9 40014 Jyväskylä Finland