Upconversion luminescence and Visible‐Infrared Properties of β‐NaLuF₄:Er³⁺ Microcrystals Synthesized by the Surfactant‐Assisted Hydrothermal Method

Abstract

We report the obtention of -NaLuF 4 microcrystals doped with Er 3+ ions by the surfactant-assisted hydrothermal method. It was found that shape modulation could be realized by changing the surfactants (ethylenediaminetetraacetic acid, polyvinylpyrrolidone, and trisodium citrate) introduced into the reaction system. The surfactants can strongly control the size and shape of as-prepared samples through absorbing on the surface of primary particles and/or coordinating with rare earth ions. Hexagonal prism-like -NaLuF 4 :Er 3+ microcrystals demonstrate intense upconverted luminescence (UCL) pumped by 1.54 m infrared laser in comparison with hexagonal tube-like, disk-like, and sphere-like microcrystals, which exhibit great distinction. More interestingly, a synergistic effect combined dual mode (i.e., downconversion and upconversion) with 8% absolute enhancement rate of the red emission centered at 659 nm ( 4 F 9/2 → 4 I 15/2 ) is witnessed in hexagonal prisms -NaLuF 4 :Er 3+ phosphors by employing the dual wavelength 416 nm and 1.54 m excitation source for the first time.

Morphology Manipulation and Upconversion Luminescence Enhancement of β-NaLuF4: Er3+ Hexagonal Microtubes via Sr2+ Doping

“…As a typical upconversion matrix material, NaYF 4 crystal has attracted much attention due to its low phonon energy (<350 cm -1 ), long luminescence lifetime, and high thermal stability and has been widely studied [6,[10][11][12][13][14]. The crystal structure of NaLuF 4 is similar to NaYF 4 , with a smaller ion radius (Y 3+ = 0:89 Å, Lu 3+ = 0:86 Å), and it is also considered an ideal substitute for the ideal UC matrix [15][16][17][18][19][20]. Especially Lu 3+ in NaLuF 4 could sensitize the activator and perform volume compensation, resulting in enhanced emission.…”