[1] Univ Roma Tor Vergata, Dipartimento Fis, I-00133 Rome, Italy
[2] Univ Roma Tor Vergata, MINAS Lab, I-00133 Rome, Italy
[3] Univ Roma Tor Vergata, Dipartimento Sci & Tecnol Chim, I-00133 Rome, Italy
[4] Rice Univ, Chem & Biomol Engn Dept, Houston, TX 77251 USA