1. Department of Chemistry, Department of Biology, Department of Physics, and Center for Functional Nanoscale Materials, Clark Atlanta University, Atlanta, GA 30314, USA
2. Department of Electrical and Computer Engineering, Center for Materials for Information Technology, The University of Alabama, Tuscaloosa, AL 35487, USA
3. Department of Civil and Chemical Engineering, University of Tennessee at Chattanooga, Chattanooga, TN 37403, USA