1. Department of Physics and Electronics
2. Osaka Prefecture University, Sakai
3. Osaka 599-8531
4. Japan
5. Fujian Key Laboratory of Pollution Control & Resource Reuse
6. College of Environmental Science and Engineering
7. Fujian Normal University, Fuzhou
8. Fujian 350007
9. China
10. Department of Materials Science and Engineering
11. National Tsing-Hua University
12. Hsinchu 30013
13. Republic of China
14. JST PRESTO