1. Department of Chemistry and Biochemistry, Duquesne University, Pittsburgh, PA 15282, USA
2. Department of Physics, Sogang University, Seoul, 04017, South Korea
3. Department of Materials Science and Engineering, Northwestern University, Evanston, IL, 60208-3108, USA
4. School of Resources and Chemical Engineering, Sangming University, Sanming, 365004, P.R. China
5. Centro de Estudios de Semiconductores, Departamento de Físcia, Facultad de Ciencias, Universidad de Los Andes, Mérida, 5101, Venezuela
6. Centro Nacional de Tecnologías Ópticas (CNTO), Mérida, 5101, Venezeula
7. Department of Chemistry, Chatham University, Pittsburgh, PA 15232, USA