[1] Lanzhou Univ, Cuiying Honors Coll, Lanzhou 730000, Peoples R China
[2] Lanzhou Univ, Sch Phys Sci & Technol, Lanzhou 730000, Peoples R China
[3] Gansu Acad Sci, Inst Sensor Technol, Lanzhou 730000, Peoples R China
[4] Lanzhou Univ, Minist Educ, Key Lab Special Funct Mat & Struct Design, Lanzhou 730000, Peoples R China