[1] Cent China Normal Univ, Dept Phys, Inst Nanosci & Nanotechnol, Wuhan 430079, Peoples R China
[2] Chinese Acad Sci, CAS Key Lab Design & Assembly Funct Nanostruct, Fuzhou 350002, Peoples R China
[3] Chinese Acad Sci, Fujian Prov Key Lab Nanomat, Fujian Inst Res Struct Matter, Fuzhou 350002, Peoples R China
[4] Univ Chinese Acad Sci, Beijing 100049, Peoples R China