[1] Natl Tsing Hua Univ, Dept Chem, Hsinchu 300, Taiwan
[2] Natl Taiwan Univ, Dept Chem, Taipei 106, Taiwan
[3] Natl Taiwan Univ, Dept Elect Engn, Grad Inst Photon & Optoelect, Taipei 106, Taiwan
[4] Natl Taiwan Univ, Grad Inst Elect Engn, Taipei 106, Taiwan