EDTA-assisted phase conversion synthesis of (Gd_0.95RE_0.05)PO₄ nanowires (RE = Eu, Tb) and investigation of photoluminescence

Abstract

Hexagonal (Gd0.95RE0.05)PO4·nH2O nanowires ~300 nm in length and ~10 nm in diameter have been converted from (Gd0.95RE0.05)2(OH)5NO3·nH2O nanosheets (RE = Eu, Tb) in the presence of monoammonium phosphate (NH4H2PO4) and ethylene diamine tetraacetic acid (EDTA). They were characterized by X-ray diffraction, thermogravimetry, electron microscopy, and Fourier transform infrared and photoluminescence spectroscopies. It is shown that EDTA played an essential role in the morphology development of the nanowires. The hydrothermal products obtained up to 180 °C are of a pure hexagonal phase, while monoclinic phosphate evolved as an impurity at 200 °C. The nanowires undergo hexagonal→monoclinic phase transformation upon calcination at ≥600 °C to yield a pure monoclinic phase at ~900 °C. The effects of calcination on morphology, excitation/emission, and fluorescence decay kinetics were investigated in detail with (Gd0.95Eu0.05)PO4 as example. The abnormally strong 5D0→7F4 electric dipole Eu3+ emission in the hexagonal phosphates was ascribed to site distortion. The process of energy migration was also discussed for the optically active Gd3+ and Eu3+/Tb3+ ions.

Ultralight Magnetic Nanofibrous GdPO4 Aerogel

“…The obtained images are given in Figure . Several studies reported that during the annealing process at 900 °C temperature, when phase transformation occurs, anisotropic nanoparticles of trigonal LnPO 4 tend to deform and sinter badly. ,, This, however, is not true in our case, where virtually identical morphological features of both the as-prepared and annealed aerogel samples were observed. This can be evaluated from Figure .…”

Tb3+, Eu3+ Co-doped CsPbBr3 QDs Glass with Highly Stable and Luminous Adjustable for White LEDs

“…Figure S3 shows that the lifetime of Tb 3+ increased progressively from 363.445 to 540.526 ns when increasing the doping concentration to 0.5% and then decreased to 470.211 ns up to 0.9%. The former is caused by surface species and the removal of luminescence-quenching defects, whereas the latter is mainly caused by increasing effective refractive index of the glass via vital crystallite . A slight lifetime elongation through increasing the doping concentration was also detected for the Tb 3+ emission.…”

Upconversion luminescence and favorable temperature sensing performance of eulytite-type Sr3Y(PO4)3:Yb3+/Ln3+ phosphors (Ln=Ho, Er, Tm)

“…Eulytite-type orthophosphate M 3 A(PO 4 ) 3 (M = Ca, Sr or Ba; A = La, Gd, Y or Lu) possesses high physical, chemical and structure stabilities [20,21], and may thus serve as an important family of phosphor hosts. It should be noted that many other types of inorganic compounds, such as GdPO 4 orthophosphate [22] and NaLn(WO 4 ) 2 tungstate (Ln = La-Lu, and Y) [23], also draw great interest for phosphor applications. For downconversion (DC) luminescence, You et al [24] prepared Eu 2+ /Mn 2+ co-doped Sr 3 Lu(PO 4 ) 3 by solidstate reaction at 1300°C for 3 h in a CO atmosphere and investigated its luminescence and Eu 2+ -Mn 2+ energy transfer; Liang et al [25] produced Ba 3 La(PO 4 ) 3 :Ln 3+ (Ln = Tb, Eu) phosphors via solid reaction at 1200-1250°C for 5-8 h in a thermal carbon atmosphere for color-tunable luminescence; Xia et al [26] synthesized a series of (Ba,Sr) 3 Lu(PO 4 ) 3 :Eu 2+ phosphors by solid reaction at 1300°C for 4 h under a 10%H 2 -90%N 2 gas mixture, and the blue shift of Eu 2+ emission with increasing Sr/Ba ratio was discussed in detail; Xia et al [27] also synthesized eulytite-type Ba 3 Eu(PO 4 ) 3 and Sr 3 Eu(PO 4 ) 3 compounds via solid reaction at 1250°C for 10 h in air, and systematically compared their crystal structures and photoluminescence; Guo et al [28] [11] and BiPO 4 [29].…”