1. Department of Chemistry, Fuzhou University, Fuzhou 350002, P. R. China, Department of Chemistry, Fujian Normal University, Fuzhou 350007, P. R. China, Department of Physics, Xiamen University, Xiamen 361005, P. R. China, Institute of Material Physical Chemistry, Huaqiao University, Quanzhou 362011, P. R. China, and Department of Chemistry, Peking University, Beijing 100081, P. R. China