1. Department of Materials Science and Engineering; Stanford University; Stanford CA 94305-4034 USA
2. Department of Chemical Engineering; SUNCAT Center for Interface Science and Catalysis; Stanford University; Stanford CA 94305-4125 USA
3. National Nanotechnology Center (NANOTEC); National Science and Technology Development Agency (NSTDA); 111 Thailand Science Park, Pahonyothin Rd. Klong Laung Pathumthani 12120 Thailand
4. Instituto de Física de São Carlos; Universidade de São Paulo; São Carlos SP 13566-590 Brazil