1. Clausthal University of Technology Institute of Organic Chemistry Leibnizstrasse 6 D-38678 Clausthal-Zellerfeld Germany
2. Fraunhofer Heinrich Hertz Institute HHI Fiber Optical Sensor Systems Am Stollen 19H D-38640 Goslar Germany
3. University of Helsinki Department of Chemistry P.O. Box 55 FIN-00014 Helsinki Finland