[1] Natl Res Council CNR NANOTEC, Inst Nanotechnol, C-O Campus Ecotekne,Via Monteroni, I-73100 Lecce, Italy
[2] Univ Salento, Dept Math & Phys Ennio De Giorgi, C-O Campus Ecotekne,Via Monteroni, I-73100 Lecce, Italy
[3] Jain Deemed Univ, Ctr Res Pure & Appl Sci, Bangalore 560078, Karnataka, India