title: Controlled synthesis and optical spectroscopy of lanthanide-doped KLaF₄ nanocrystals.
abstract: KLaF(4), as a good host matrix for trivalent lanthanide (Ln(3+)) ions to fabricate upconversion (UC) or downconversion (DC) phosphors, has been rarely reported. Herein, monodisperse (∼10 nm) cubic-phase Ln(3+)-doped KLaF(4) nanocrystals (NCs) were synthesized via a facile thermal decomposition method. Upon excitation at 980 nm, UC luminescence properties of KLaF(4):Ln(3+)/Yb(3+) (Ln = Tm, Ho, Er) NCs were comprehensively surveyed. Particularly, after coating an inert KLaF(4) shell, the green and red UC luminescence intensity of KLaF(4):Er(3+)/Yb(3+) NCs was enhanced ∼35 times, and the corresponding UC lifetimes of (4)S(3/2) and (4)F(9/2) levels of Er(3+) were observed significantly prolonged from 42 and 68 μs in core-only NCs to 87 and 136 μs in core/shell counterparts. Furthermore, intense DC luminescence was also achieved in Ce(3+)/Tb(3+) and Eu(3+) doped KLaF(4) NCs, with absolute quantum yields of 39.8% (Tb(3+)) and 17.3% (Eu(3+)). The luminescence lifetimes of (5)D(0) (Eu(3+)) and (5)D(4) (Tb(3+)) were determined to be 4.2 and 4.7 ms, respectively. Water-soluble Ln(3+)-doped KLaF(4) NCs featuring excellent monodispersion, long luminescence lifetime, and high UC/DC efficiency may have versatile and promising applications as luminescent nano-biolabels.
authors.affiliation: Key Laboratory of Optoelectronic Materials Chemistry and Physics, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian 350002, China.
authors.forename: Rui
authors.initials: R
authors.lastname: Liu
authors.forename: Datao
authors.initials: D
authors.lastname: Tu
authors.forename: Yongsheng
authors.initials: Y
authors.lastname: Liu
authors.forename: Haomiao
authors.initials: H
authors.lastname: Zhu
authors.forename: Renfu
authors.initials: R
authors.lastname: Li
authors.forename: Wei
authors.initials: W
authors.lastname: Zheng
authors.forename: En
authors.initials: E
authors.lastname: Ma
authors.forename: Xueyuan
authors.initials: X
authors.lastname: Chen