1 Department of Civil and Environmental Engineering, Virginia Tech, Blacksburg, Virginia, USA. pvikes@vt.edu and Virginia Tech Institute of Critical Technology and Applied Science (ICTAS) Sustainable Nanotechnology Center (VTSuN), Blacksburg, Virginia, USA and Center for the Environmental Implications of Nanotechnology (CEINT), Duke University, Durham, North Carolina, USA.
2 Virginia Tech Institute of Critical Technology and Applied Science (ICTAS) Sustainable Nanotechnology Center (VTSuN), Blacksburg, Virginia, USA and Department of Sustainable Biomaterials, Virginia Tech, Blacksburg, Virginia, USA.