1. College of Chemistry and Chemical Engineering
2. Anyang Normal University
3. Anyang 455000
4. China
5. Key Laboratory for Micro-/Nano-Optoelectronic Devices of the Ministry of Education
6. School of Physics and Electronics
7. Hunan University
8. Changsha 410082
9. P. R. China
10. Department of Physics
11. The Chinese University of Hong Kong