Up/down conversion luminescence properties of (Na0.5Gd0.5)MoO4:Ln(3+) (Ln = Eu, Tb, Dy, Yb/Er, Yb/Tm, and Yb/Ho) microstructures: synthesis, morphology, structural and magnetic investigation

作者：Krishnan Rajagopalan; Thirumalai Jagannathan^*

来源：New Journal of Chemistry, 2014, 38(8): 3480-3491.

DOI：10.1039/c4nj00165f

Novel bi-pyramid-like (Na0.5Gd0.5)MoO4:Ln(3+) (Ln = Eu, Tb, Dy, Yb/Er, Yb/Ho, and Yb/Tm) hierarchical microstructures are synthesized via the EDTA-aided hydrothermal route. Time-dependent experiments were carried out and the morphological evolution was discussed, which signposted that the present method corresponded to a typical Ostwald ripening process for the formation of bi-pyramid-like structures. Elemental mapping analysis confirms the incorporation and uniform distribution of all the elements. Phase purity and crystal structure of the as-synthesized phosphor were analyzed by the X-ray diffraction (XRD) technique. Fourier transform infrared spectroscopy (FTIR) results confirm that for scheelite tetragonal symmetry, F-2 (nu(3)) modes of vibrations are IR active. (Na0.5Gd0.5)MoO4 was demonstrated to be a good host material for down- and up-conversion luminescence, which were strongly dependent on the hydrothermal reaction time interval. The down-conversion luminescence properties of (Na0.5Gd0.5)MoO4 doped with Eu3+, Tb3+, Dy3+ were studied. Under 980 nm NIR excitation intense up-converted visible emissions were observed in (Na0.5Gd0.5)MoO4:Yb3+/Ln(3+) (Ln = Er, Tm, and Ho), which shows green (H-2(11/2) -> 4 vertical bar(15/2) of Er3+ at 525 nm), blue ((1)G(4) -> H-3(6) of Tm3+ at 474 nm), and yellow (S-5(2) ->> (5)vertical bar(8) and F-5(5) -> (5)vertical bar(8) of Ho3+ at 541 nm and 660 nm, respectively) luminescence. Also, Yb3+/Er3+-doped samples exhibit luminescence in the near infrared (combination of Er3+/Yb3+ at 977 nm, Er3+ at 1530 nm) region. The energy transfer process, fluorescence decay time, and colour coordinates were analyzed for both down- and up-conversion luminescence. Further, the magnetic properties of (Na0.5Gd0.5)MoO4:Ln(3+) (Ln = Eu and Yb/Er) as-prepared bi-pyramid-like structure exhibit typical paramagnetic behavior.

• 出版日期2014-8