Ordered Mesostructured Rare-Earth Fluoride Nanowire Arrays with Upconversion Fluorescence

Ordered mesostructured LaF 3 nanoarrays have been, for the first time, synthesized via a one-step nanocasting process using La(CF 3 COO) 3 as a precursor and mesoporous silica as a hard template. The characterization of SAXS and XRD patterns and TEM and SEM images shows that the LaF 3 nanowire arrays have long-range regularity of hexagonal mesostructure ( p 6 mm ) and single-crystalline feature. N 2 -sorption isotherms reveal that ordered mesoporous LaF 3 products have high BET specific surface area (∼75 m 2 /g), large pore volume (0.15 cm 3 /g), and narrow pore-size distribution (the mean value of 4.3 nm). The upconversion fluorescence has been realized in the Yb 3+ /Er 3+ (red/green) and Yb 3+ /Tm 3+ (blue) codoped LaF 3 nanoarrays by upconversion (UC) excitation in the near-infrared region. The UC emission population for 4 F 9/2, 2 H 11/2, 4 S 3/2, and 2 H 9/2 levels in the Yb 3+ /Er 3+ codoped LaF 3 nanowire array matrixes depends on Er 3+ concentration, the excitation density, and the specific surface areas.