1. Nano-Science Center and Department of Chemistry, University of Copenhagen, Universitetsparken 5, 2100 Copenhagen Ø, Denmark
2. Department of Electronic Engineering, Università di Roma “Tor Vergata”, Via del Politecnico 1, 00133 Rome, Italy
3. Consiglio Nazionale delle Ricerche, ISMN, Via Salaria km 29.6, 00017 Monterotondo, Rome, Italy