1. Nanoscience Center; Department of Chemistry; P.O. Box 35, FI-40014 University of Jyväskylä; Jyväskylä Finland
2. Department of Electrical Energy Engineering; Tampere University of Technology; P.O. Box 692 33101 Tampere Finland
3. Technical Research Centre of Finland; P.O. Box 1607 33101 Tampere Finland