1. National Nanotechnology Laboratory, CNR-Istituto Nanoscienze, via Arnesano, I-73100 Lecce, Italy
2. Institute of Physical and Theoretical Chemistry, Wroclaw University of Technology, Wyb. Wyspianskiego 27, 50-370 Wroclaw, Poland
3. Dipartimento di Matematica e Fisica “Ennio De Giorgi”, Università del Salento, via Arnesano, I-73100 Lecce, Italy