1. Center of Integrative Nanotechnology Sciences; University of Arkansas at Little Rock; Little Rock AR 72204 USA
2. Department of Physics; University of Arkansas; Fayetteville AR 72701 USA
3. Department of Integrated Engineering; Minnesota State University-Mankato; Mankato MN 56001 USA
4. Department of Chemistry; University of Arkansas at Little Rock; Little Rock AR 72204 USA
5. Institute for Nanoscience and Engineering; University of Arkansas; Fayetteville AR 72701 USA