1. ICSI-CNRS, 15 Rue Jean Starcky, 68057 Mulhouse, France, Institute of Physics, University of Basel and NCCR “Nanoscale Science”, Klingelbergstrasse 82, 4056 Basel, Switzerland, Laboratorio de Nanotécnicas, Universidad de Castilla-La Mancha, Plaza Manuel Meca 1, 13400 Almadén, Spain, Corning Incorporated, 1 Science Center Road, Corning, New York 14831, and Chemical Engineering Department, University of CaliforniaSanta Barbara, Santa Barbara, California 93106-5080