1. Department of Chemistry, The University of Memphis, Memphis, Tennessee 38152, United States
2. State Key Laboratory of Molecular Vaccinology and Molecular Diagnostics & Center for Molecular Imaging and Translational Medicine, School of Public Health, Xiamen University, Xiamen, Fujian Province 361102, P. R. China
3. Department of Physics, The University of Memphis, Memphis, Tennessee 38152, United States