1. Contribution from the Departament de Química, Universitat Autònoma de Barcelona, Bellaterra 08193, Spain, and Dipartimento di Chimica IFM, Università di Torino, Via P. Giuria 7, 10125 Torino and NIS-Nanostructured Interfaces and Surfaces - Centre of Excellence and INSTM (Materials Science and Technology) National Consortium, UdR Università di Torino, Italy