1. Department of Chemistry, University of Cape Town, Private Bag Rondebosch, Cape Town, 7701, South Africa, Department of Chemical Engineering, Vanderbilt University, VU Station B 351604, Nashville, Tennessee 37235, Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, Nanomaterials Theory Institute, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, and Department of Earth and Planetary Science, University of California, Berkeley, California 94720