**Author details**

Ping Hu1,2\*, Shuxiang Wu<sup>1</sup> and Shuwei Li<sup>1</sup> \*

\*Address all correspondence to: huping8@mail.sysu.edu.cn and stslsw@mail.sysu.edu.cn

1 State Key Laboratory of Optoelectronic Materials and Technologies, School of Materials Science and Engineering, Sun Yat-Sen University, Guangzhou, People's Republic of China

2 School of Mathematics and Physics, University of South China, Hengyang, People's Republic of China
