1. Department of Chemistry, University of Arkansas at Little Rock, Little Rock, AR 72204, USA
2. Laser Dynamics Laboratory, School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, Georgia 30332-0400, USA
3. Department of Biology, University of Arkansas at Little Rock, Little Rock, AR 72204, USA
4. University of Arkansas for Medical Sciences, Winthrop P. Rockefeller Cancer Institute, Arkansas Nanomedicine Center, Department of Radiation Oncology, 4301 W Markham St, Little Rock, AR 72205, USA