1. School of Materials Science and Engineering; Georgia Institute of Technology; Atlanta GA 30332 USA
2. Energy Materials Laboratory (EML), Physics Department; School of Sciences and Engineering, The American University in Cairo; New Cairo 11835 Egypt
3. School of Chemistry and Biochemistry; Georgia Institute of Technology; Atlanta GA 30332 USA
4. Qatar Energy and Environment Research Institute; Qatar Foundation; P.O. Box 5825 Doha Qatar