1. University of Oulu, Research Unit of Sustainable Chemistry, P.O. Box 3000, FI-90014 University of Oulu, Finland
2. University of Jyvaskyla, Kokkola University Consortium Chydenius, Talonpojankatu 2B, FI-67100 Kokkola, Finland
3. University of Oulu, Optoelectronics and Measurement Techniques Unit, 90570 Oulu, Finland