Modified surface states of NaGdF4:Yb3+/Tm3+ up-conversion nanoparticles via a post-chemical annealing process

An amorphous layer acting as a quenching center at the surface of oleic acid-capped NaGdF4:Yb3+/Tm3+ nanoparticles is observed directly, which can be reconstructed via a novel post-chemical annealing process. The amorphous phase of the surface layer of NaGdF4:Yb3+/Tm3+ nanoparticles gradually crystallizes as the post-chemical annealing temperature increases; meanwhile, the good dispersibility of the as-obtained nanoparticles is maintained. The reduction of surface defects and higher local symmetry of the crystal field environment around the doped rare-earth ions contribute to drastically increased up-conversion (UC) emission intensity of the NaGdF4:Yb3+/Tm3+ nanoparticles. In particular, the blue emission of Tm3+ at 450 nm enhances 10-fold after the post-chemical annealing process at 250 °C compared with the counterpart without further surface-state treatments. The color gamut of well-crystallized NaGdF4:Yb3+/Tm3+ with a modified surface covers the blue to yellow region in CIE chromaticity coordinates via a non-steady-state UC process. The results indicate that the surface states of these UC nanoparticles can be feasibly improved via the post-chemical annealing process without encouraging agglomeration, which further optimizes their UC properties for practical applications.

Hydrothermal synthesis, down-/enhanced up-converting, color tuning luminescence, energy transfer and paramagnetic properties of Ln3+ (Ln = Eu/Dy, Yb/Ho)-doped Ba2GdF7 multifunctional nanophosphors

Tunable multicolor, energy transfer processes, and paramagnetic properties of the Ba₂GdF₇:Ln³⁺ (Ln = Eu/Dy, and Yb/Ho) nanophosphors were studied.

NaGdF4:Dy3+ nanofibers and nanobelts: facile construction technique, structure and bifunctionality of luminescence and enhanced paramagnetic performances

NaGdF₄:Dy³⁺ nanofibers and nanobelts with excellent luminescence-magnetic bi-functionality were fabricated via a combination of electrospinning and calcination with fluorination technology.

White light-emitting, tunable color luminescence, energy transfer and paramagnetic properties of terbium and samarium doped BaGdF5 multifunctional nanomaterials

Multicolor luminescence of BaGdF₅:Tb³⁺,Sm³⁺ nanospheres can be obtained by adjusting the excitation wavelength. The obtained phosphors also exhibit paramagnetic properties at room temperature and low temperature.

Magnetic-downconversion luminescent bifunctional BaGdF5:Dy3+,Eu3+ nanospheres: energy transfer, multicolor luminescence and paramagnetic properties

The color-tunable and white light emissions have been obtained in Dy³⁺ and Eu³⁺ co-activated BaGdF₅ phosphors by adopting different excitation wavelengths. Simultaneously, the obtained samples also exhibit paramagnetic properties at room temperature and low temperature.