1. Department of Chemical Sciences, University of Catania, viale A. Doria 6, 95100Catania, Italy
2. Laboratory for Molecular Surfaces and Nanotechnology, CSGI, 95125Catania, Italy
3. National Interuniversity Consortium for Materials Science and Technology (I.N.S.T.M.)Research Unit of Catania, 95125Catania, Italy
4. Reparto Carabinieri Investigazioni Scientifiche Messina, Via Monsignor D’Arrigo 5, 98122Messina, Italy
5. Consiglio Nazionale delle Ricerche, Istituto per la Microelettronica e Microsistemi, I-95121Catania, Italy