1. 1CNR-Istituto di Scienze e Tecnologie Molecolari, Via Golgi 19, 20133 Milan, Italy. Birck Nanotechnology Center, Purdue University, West Lafayette, IN 47907, USA
2. 2Department of Materials Science and Engineering WW4-LKO, University of Erlangen-Nuremberg, Martensstrasse 7, D-91058 Erlangen, Germany
3. 3Nano-Meta Technologies Inc., 1281 Win Hentschel Boulevard, West Lafayette, IN 47906, USA
4. 4School of Electrical and Computer Engineering and Birck Nanotechnology Center, Purdue University, West Lafayette, IN 47907, USA