[1] Shanxi Normal Univ, Sch Phys & Informat Engn, Taiyuan, Peoples R China
[2] Lawrence Berkeley Natl Lab, Chem Sci Div, Berkeley, CA USA
[3] Beihang Univ, Sch Mat Sci & Engn, Beijing, Peoples R China
[4] Rensselaer Polytech Inst, Dept Phys Appl Phys & Astron, Troy, NY 12180 USA