1. School of Materials Science and Engineering Key Laboratory of Electronic Packaging and Advanced Functional Materials of Hunan Province Central South University Changsha 410083 Hunan P. R. China
2. College of Biological and Chemical Engineering Guangxi University of Science and Technology Liuzhou 545006 Guangxi P. R. China
3. School of Physics and Electronics Hunan University Changsha 410083 Hunan P. R. China
4. College of Chemistry and Chemical Engineering Jishou University Jishou 416000 Hunan P. R. China