WEN Xia1, XU Qi2, WANG Hai-Jun2, DU Qin-Zhi3, ZHANG Ming-Xiao2, CHEN Shi-Hong2**
1. Teacher Training College, Beibei, Chongqing 400700, China; 2. School of Chemistry and Chemical Engineering, Southwest University, Chongqing 400715, China; 3. Chongqing No.8 Middle School, Chongqing 400030, China