1. Department
of Chemistry, University of California, Berkeley, California 94 720, United States
2. Molecular
Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
3. Kavli Energy Nanoscience
Institute at Berkeley, Berkeley, California 94720, United States
4. Dipartimento
di Biotecnologie, Facoltà di Scienze, Universitá di Verona, Strada Le Grazie, I-37134 Verona, Italia