1. a Department of Chemical Engineering and Materials Science , University of California , Davis , California , 95616 , USA
2. b Department of Chemistry , University of California , Davis , California , 95616 , USA
3. c National Center for Electron Microscopy, Lawrence Berkeley National Laboratory , Berkeley , California , 94720 , USA
4. d Department of Materials Science and Engineering , Massachusetts Institute of Technology , Cambridge , Massachusetts , 02139 , USA