Preparation and Photoluminescence of GdVO₄:Eu Nanophosphors for Flexible and Transparent Displays

Abstract

Europium ion doped metal orthovanadate (MVO 4 :Eu, M = Y, Gd, La) has been widely used as commercial red-emitting phosphors in cathode ray tubes (CRTs), and fluorescent lamps, 1,2 with photoluminescence quantum yields of up to 95%.3,4 Commercial micron-sized MVO 4 :Eu phosphors are generally prepared by high-temperature solid-state reactions. However, these micron-sized phosphors cannot be used in flexible and transparent displays due to their high scattering. Because nano-sized materials do not show any scattering in the visible region, inorganic nanophosphors have received much attention for their applicability in flexible and transparent display devices. 5-7MVO 4 :Eu nanophosphors have been prepared by soft reactions, such as hydrothermal, solvothermal, sonochemical, microemulsion, and polymer-assisted methods.8-14 Despite there have been numerous studies of the synthesis of MVO 4 :Eu nanophosphors, most attention has focused on the synthesis of powder-type MVO 4 :Eu phosphors. Monodispersed nanophosphors prepared by soft reactions can easily agglomerate in organic solvents. Transparent suspensions of nanophosphors without an agglomeration in organic solvents are needed for these phosphors to be used in flexible and transparent displays. However, there are few reports of preparing transparent suspensions of nanophosphors. Transparent suspensions of small amounts of YVO 4 :Eu nanophosphors in hexane have been prepared using surfactant-assisted hydrothermal reactions in a waterhexane bilayer system.15 In this system, most of the YVO 4 :Eu nanophosphors aggregated in the water phase that is not adequate for the flexible and transparent displays. New methods for the large-scale synthesis of nanophosphors are required that can prepare phosphors in single organic solvent phase. This work reports the first simple method of preparing transparent suspensions of GdVO 4 :Eu nanophosphors in toluene. The optimal conditions for the phosphors' bright emission were also examined.GdVO 4 :Eu nanophosphors were prepared by solvothermal reactions from Gd-oleate, Eu-oleate, and tetraoctylammonium-VO 4 complexes in toluene in the presence of oleic acid and oleylamine. Gd-oleate and Eu-oleate were obtained by transferring aqueous Gd(NO 3 ) 3 and Eu(NO 3 ) 3 to the toluene phase by adding sodium oleate in toluene. Tetraoctylammonium-VO 4 was obtained by transferring NH 4 VO 3 in water with NH 4 OH to toluene by introducing tetraoctylammonium bromide in toluene. Typical powder X-ray diffraction (XRD) patterns of GdVO 4 :Eu phosphors prepared at 80°C (Figure 1) indicated a structure matching that of tetragonal GdVO 4 (JCPDS 17-0260, a = 0.7212 nm, c = 0.6348 nm). The ionic radius of Eu 3+ (0.0950 nm) is slightly larger than that of Gd 3+ (0.0938 nm), Eu 3+ ions are allowed to its facile occupation of Gd 3+ sites in the host GdVO 4 structure. 16 The broad XRD peak also indicates that the GdVO 4 :Eu was present as nanoparticles. The XRD patterns confirm that the GdVO 4 :Eu phosphor was synthesized without impurities. High-resolution tr...

The influence of high magnetic field on electric-dipole emission spectra of Eu3+ in different single crystals

“…As a typical host sensitizing PL material, GdVO4:Eu 3+ shows the character that its emission intensity and efficiency mainly depend on the host absorption and energy transfer from the host to activators. From the literature, 17,18 it has been reported that Gd 3+ ions in the host lattice increase their absorption of VUV/UV excitation energy, and change the crystal eld of the host lattice. Should the increase of PL intensity be ascribed to the absorption increase of Gd 3+ ions?…”

Multifunctional Eu3+- and Er3+/Yb3+-doped GdVO4 nanoparticles synthesized by reverse micelle method

“…GdVO 4 :Eu 3+ NPs have been successfully synthesized via a facile solvothermal route 4 8 , a urea hydrolysis method 9 , a co-precipitation synthesis 10 , as well as facile hydrothermal methods 11 12 . Using these methods, tetragonal particles (d ~ 70 nm), spherical particles (d ~ 40 nm), ellipsoid particles (d ~ 20 nm, l ~ 25 nm), nanorods (d ~ 5 nm, l ~ 20 nm), and nanowires (d = 15 nm, l = a few microns) were fabricated 8 9 10 11 12 . Submicronic polyhedrons with formula GdVO 4 :RE 3+ (RE 3+ = Sm 3+ , Dy 3+ , Er 3+ ) (d ~ 300 nm) were obtained by facile hydrothermal methods 13 .…”

NIR emitting GdVO4:Nd nanoparticles for bioimaging: The role of the synthetic pathway

“…Thus, the adopted synthetic procedure should guarantee a precise control over the particles' dimensions. Several synthetic strategies have been proposed for the preparation of GdVO 4 nanoparticles doped with rare earth ions, including sol-gel 32 , urea hydrolysis 33 , electrospinning 34 , and hydro/solvothermal methods 35,36 . Inagaki et al developed a synthesis to obtain GdVO 4 :Nd/Yb nanoparticles with an homogenous dimensional distribution (around 20 nm), but this approach requires a complex microreaction method followed by an autoclave treatment 25 .…”