1. Department of Chemistry, Faculty of Science, Bilkent University, 06800 Ankara, Turkey
2. NANOTAM─Nanotechnology Research Center, Bilkent University, 06800 Ankara, Turkey
3. Department of Chemistry, Faculty of Science, Gazi University Teknikokullar, 06500 Ankara, Turkey
4. Department of Electrical and Electronics Engineering, Bilkent University, 06800 Ankara, Turkey
5. Department of Physics, Faculty of Science, Bilkent University, 06800 Ankara, Turkey
6. UNAM─National Nanotechnology Research Center, Bilkent University, 06800 Ankara, Turkey