1. Department of Chemistry, University of Pennsylvania, 231 S. 34th Street, Philadelphia, Pennslvania 19104 United States
2. Dipartimento di Fisica e Chimica, Università degli Studi di Palermo, Via Archirafi 36, 90123 Palermo, Italy
3. Department of Materials Science and Engineering, University of Pennsylvania, 3231 Walnut Street, Philadelphia, Pennsylvania 19104 United States
4. Center for Functional Nanomaterials, Brookhaven National Laboratory, Building 735, Upton, New York 11973-5000, United States