1. Laboratory of Nano-Biophysics, Clemson Nanomaterials Center, Department of Physics and Astronomy, Clemson University, Clemson, South Carolina 29634
2. Department of Pharmaceutical Sciences, Skaggs School of Pharmacy and Pharmaceutical Science, University of Colorado-Anschutz Medical Campus, Aurora, Colorado 80045
3. Laboratory of Nano-Biophysics, Clemson Nanomaterials Center, Department of Physics and Astronomy, Clemson University, Clemson, South Carolina 29634 and Center for Optical Materials Science and Engineering Technologies (COMSET), Clemson, South Carolina 29625