Electrospinning synthesis, characterization and luminescence properties of La2W2O9: Eu3+ nanofibers

Low temperature micro Raman and laser induced upconversion and downconversion spectra of europium doped silver tungstate Ag2−3xEuxWO4 nanorods

“…Recently, many Eu 3? -doped tungstate based lattices (as host for the Eu 3? activators that emit the red light) have been reported for possible application as red conversion phosphors examples include CdWO 4 [2,3], SrWO 4 [4,5], Y 6 WO 12 [6], KLa(WO 4 ) 2 [7], RbGd(WO 4 ) 2 [8], NaY(WO 4 ) 2 [9], NaGd(WO 4 ) 2 [10], Na 2 Dy 4 (WO 4 ) 7 [11], La 2 W 2 O 9 [12], ZnWO 4 [13], Ba 4 Na 2 W 2 O 11 [14], MgWO 4 [15], and Li 2 Mg 2 (WO 4 ) 3 [16]. Some of these materials require high amounts of the expensive europium activator.…”

“…Considering the doping sites, characteristics such as distance between dopants, coordinate numbers, relative spatial position and electrical environments are also important in order to fully understand the photoluminescence properties [17]. Many tungstate lattices when acting as hosts for Eu 3? activators have been shown to manifest excellent luminescent efficiency and color purity as well as having high average refractive indexes [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16]. Also this class of tungsten oxides can be considered as ideal host lattices for dopants as they possess high thermal, chemical and physical stability and in addition they can often be synthesized at low temperatures.…”

RE-Based Inorganic-Crystal Nanofibers Produced by Electrospinning for Photonic Applications

“…In fact, Eu 3+ ions, also possess a series of visible emission lines that originate from the 5 D 0 and 5 D 1 multiplets with good color-tuning properties [30,72,82], that make them very interesting for lightening applications. In fact, Eu-doped nanofiber mats have already been tested in realistic LED devices [32,34] and Eu 3+ is probably the mostly studied rare earth ion in nanofiber matrixes [1,13,19,29,30,32,34,35,37,41,42,45,47,48,51,[53][54][55]61,62,67,68,76,[79][80][81][82]84,[86][87][88][89]91,101,112] including some nanobelt structures [72] and hollow structures [82]. In most of these cases, diameter of the nanofibers was less than 300 nm, with a few exceptions [35,42,76].…”

“…In fact, the addition of Tm 3+-, Sm 3+or Tb 3+ions shifts the emission color from blue, to red, to green [51]. Since most of the emission lines originate from 5 D 0 reported lifetimes usually refer to the decay of this level and concentration-dependent values range from 0.5 ms to more than 5 ms in oxide hosts [30,35,37,45,47,53,55,[80][81][82]84,86,87,89] and from 7 to 12 ms in fluorides [13,19,29,112]. In very few cases the lifetime of the 5 D j levels with j > 0 has been reported.…”

“…For example in YVO 4 the lifetime of 5 D 1 is reported to be around 7.5 µs [89], in NaGdF 4 lifetimes of 5 D 3 , 5 D 2 , 5 D 1 are 2.38, 4.04, 6.36 ms, respectively and in GdF 3 lifetimes of 5 D 3 , 5 D 2 , 5 D 1 are 2.26, 3.58, 3.88 ms, respectively. Concentration optimization of the luminescence intensity yelds an optimum concentration of Eu 3+ ions usually in the range of 5-8% [47,53,54,72,89] before the onset of concentration quenching effects, but in some compounds such as Y 2 O 3 , Y 2 O 2 S and Lu 2 O 2 S lower values (around 3%) have been reported [55,82] and in Gd 2 O 3 no concentration quenching effects have been observed up to 10% Eu 3+ concentration. Moreover, in some cases polarized emission have been observed and characterized [76,81] and in Ca (Sr)Al 2 Si 2 O 8 persistent luminescence from Eu 3+ ions has been observed with a lifetime of 157.12 s. Some of these compounds possess bifunctional properties.…”