1. Department of Chemistry, Howard University, 525 College Street, NW, Washington, DC 20059, USA.
2. Howard University Program in Atmospheric Sciences, Howard University, Washington, DC 20059, USA.
3. Department of Physics and Astronomy, Howard University, 2355 6th St., NW, Washington, DC 20059, USA.
4. Department of Mechanical Engineering, Howard University, 2300 Sixth Street, NW, Washington, DC 20059, USA.