title: Down- and up-converting dual-mode YPO4:Yb(3+),Tb(3+) nanocrystals: synthesis and spectroscopic properties.
abstract: Tetragonal YPO4 nanocrystals doped with Yb(3+) and Tb(3+) ions were synthesized by 900 °C annealing of precursors obtained with a co-precipitation method in the presence of glycerine. These materials exhibited intense green luminescence under ultraviolet excitation and up-conversion emission from the (5)D3 and (5)D4 Tb(3+) excited states after irradiation with near infrared light (λ = 980 nm). The structure and morphology of the products were analysed by recording X-ray diffraction patterns and transmission electron microscopy images. The obtained nanomaterials were single-phased with spherical shaped nanocrystals that had an average size of 18 ± 3 nm. The spectroscopic properties of YPO4:Yb(3+),Tb(3+) nanocrystals were investigated based on their excitation and emission spectra. The time-resolved luminescence traces were measured, and the luminescence lifetimes of Tb(3+) and Yb(3+) ions were calculated. The most effective dopant concentrations were determined to be 5% Yb(3+) and 15% Tb(3+), which exhibited the most intense ultraviolet excited emission and up-conversion. Because the integral intensity was observed to be dependent on the power of the pumping laser, a cooperative energy transfer (CET) mechanism underlying the observed up-conversion was proposed.
authors.affiliation: Adam Mickiewicz University, Faculty of Chemistry, Department of Rare Earths, Umultowska 89b, 61-614 Poznan, Poland. tgrzyb@amu.edu.pl.
authors.forename: Tomasz
authors.initials: T
authors.lastname: Grzyb
authors.forename: Rafal J
authors.initials: RJ
authors.lastname: Wiglusz
authors.forename: Aleksandra
authors.initials: A
authors.lastname: Gruszeczka
authors.forename: Stefan
authors.initials: S
authors.lastname: Lis