Controlled synthesis and novel luminescence properties of string SrWO₄:Eu³⁺ nanobeans

One-dimensional SrWO4:Eu(3+) nanostructures were prepared by a hydrothermal method. The structures and morphologies of the nanocrystals were characterized by X-ray diffraction, Raman spectroscopy, transmission electron microscopy, and scanning electron microscopy. The results indicated that the phase compositions, morphologies and sizes and luminescence properties of SrWO4:Eu(3+) are related to the initial reactant content and reaction time, and lower initial reactant content is beneficial for the formation of the string SrWO4:Eu(3+) nanobeans. The photoluminescence properties of SrWO4:Eu(3+) were investigated in detail. In the emission spectra of SrWO4:Eu(3+), the (5)D0→(7)F1 is dominant when the excitation wavelength is 295 nm, while the (5)D0→(7)F2 is dominant when the excitation wavelengths are in the range of 363-537 nm. Obviously, the string SrWO4:Eu(3+) nanobeans have multiple luminescence centers or emitting states. The excitation spectra of SrWO4:Eu(3+) contain several sharp peaks attributed to f-f transitions of Eu(3+) ions and a broad excitation band assigned to the overlap of WO4(3-) absorption and charge transfer transition between Eu(3+) and O(2-). The intensity ratio of the broad excitation band to the sharp excitation peaks changed with the emission wavelength as well as the Eu(3+) content. In addition, Eu(3+) ions occupy higher symmetry sites in SrWO4:Eu(3+) nanocrystals with increasing the particle size of nanocrystals. The effect of Tb(3+) as well as Gd(3+) ions on the photoluminescence of SrWO4:Eu(3+) was also investigated.