title: Synthesis and upconversion luminescence of NaYF4:Yb3+,Tm3+/TiO2 nanocrystal colloidal solution.
abstract: NaYF4:Yb3+,Tm3+ upconversion nanocrystals were synthesized with oleic acid as a capping ligand. The as-prepared samples were redispersed in cyclohexane, forming transparent and stable solutions which perform bright blue upconversion. Inducing TiO2 as the outer layer of the fluoride cores, we investigated the effect of TiO2 on the upconversion process. The transmission electron microscopy (TEM) analysis indicated that titania successfully formed a coating layer on the surface of NaYF4:Yb3+, Tm3+ nanoparticles, and the average diameters of the NaYF4:Yb3+,Tm3+ nanocrystals and the NaYF4:Yb3+, Tm3+/TiO2 nanoparticles are about 14 and 40 nm, respectively. Under the excitation of a 980 nm laser, NaYF4:Yb3+, Tm3+ nanocrystals and TiO2-coated NaYF4:Yb3+, Tm3 core/shell structure sample exhibited distinct upconversion luminescent properties.
authors.affiliation: State Key Laboratory on Integrated Optoelectronics, College of Electronic Science and Engineering, Jilin University, 2699 Qianjin Street, Changchun 130012, PR China.
authors.forename: Xiao-Jie
authors.initials: XJ
authors.lastname: Xue
authors.forename: Weiping
authors.initials: W
authors.lastname: Qin
authors.forename: Dai-Sheng
authors.initials: DS
authors.lastname: Zhang
authors.forename: Dan
authors.initials: D
authors.lastname: Zhao
authors.forename: Guo-Dong
authors.initials: GD
authors.lastname: Wei
authors.forename: Ke-Zhi
authors.initials: KZ
authors.lastname: Zheng
authors.forename: Li-Li
authors.initials: LL
authors.lastname: Wang
authors.forename: Guo-Feng
authors.initials: GF
authors.lastname: Wang