1. Department of Inorganic Chemistry; University of Bucharest; 23 Dumbrava Rosie St. Bucharest, Sector 2 020484 Romania
2. National Institute of Materials Physics; P.O. Box MG-7 077125 Magurele Romania
3. Department of Physical Chemistry; University of Bucharest; 4-12 Elisabeta Blvd. 030018 Bucharest Romania