1. Surface and Aqueous Geochemistry Group, Department of Geological & Environmental Sciences, Stanford University, Stanford, California 94305-2115, United States
2. Center for Environmental Implications of NanoTechnology (CEINT), P.O. Box 90287, Duke University, Durham, North Carolina 27708-0287, United States
3. Department of Civil and Environmental Engineering, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, United States
4. Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025, United States
5. Department of Chemistry, Université Pierre et Marie Curie (Paris 6), Paris, France