Effect of co-doped Tb<Superscript>3+</Superscript> ions on electroluminescence of ZnO:Eu<Superscript>3+</Superscript> LED

Rare earth (RE) -doped ZnO electroluminescence is worthy of investigation for phosphor-free white light-emitting diodes (LEDs) due to their pure and sharp emissions. Whereas, the low solubility of RE ions in ZnO films is found to hinder the performance of RE-doped ZnO devices. Herein, ZnO:Eu and ZnO:Eu/Tb LEDs were synthesized and the electroluminescence properties were tested. The results show that the emission intensity of ZnO: Eu/Tb LED is 8 times higher than that of ZnO: Eu LED while the input power is smaller when the concentration of terbium is proper. Furthermore, we discussed the excitation mechanism and found that the ratio of the EL intensity of the ⁵D₁ → ⁷F₁ to ⁵D₀ → ⁷F_{J (J=0???4)} transition increases with increasing Tb doping concentration, which may indicate the possibility of energy transfer from Tb³⁺ to Eu³⁺. The results are believed to be an effective strategy to improve the electroluminescence of RE-doped semiconductor for white LEDs.     

Electrospinning fabrication of color-tunable flexible composite nanofibers containing lanthanide ions

A novel color-tunable PVP/[Tb(BA)₃phen+Eu(BA)₃phen] luminescent composite nanofibers had been fabricated by single axial electrospinning. The morphology and elements components of the as-prepared nanofibers were characterized by field emission scanning electron microscopy and energy dispersive spectroscopy. The luminescent properties were systematically investigated by photoluminescence spectroscopy. The obtained nanofibers had excellent fibrous morphology and smooth surface, and the average diameter was about 200 nm. The novel luminescent composite nanofibers exhibited the green, orange and red fluorescence emission peaks at 490, 545, 592 and 616 nm, which were ascribed to the ⁵D₄ → ⁷F₆ (490 nm) and ⁵D₄ → ⁷F₅ (545 nm) energy transitions of Tb³⁺ ions, and the ⁵D₀ → ⁷F₁ (592 nm), ⁵D₀ → ⁷F₂ (616 nm) transitions of Eu³⁺ ions, respectively. The emitting color of the luminescent composite nanofibers could be tuned by adjusting the mass ratio of terbium complexes and europium complexes in a wide color range of red-yellow-green under the excitation of 274-nm single-wavelength ultraviolet light. The color-tunable luminescent composite nanofibers have potential applications in the fields of display panels, lasers and bioimaging.     

Facile electrospinning fabrication and photoluminescence of LaOI:Tb3+ one-dimensional nanomaterials

LaOI:Tb³⁺ nanomaterials including nanofibers, nanobelts, and hollow nanofibers were successfully synthesized by electrospinning combined with a double-crucible iodination method using NH₄I as iodine source for the first time. X-ray diffractometry analysis revealed that LaOI:Tb³⁺ nanostructures were phase-pure tetragonal structure with space group of P4/nmm. Scanning electron microscopy analysis showed that the diameters of LaOI:Tb³⁺ nanofibers, hollow nanofibers and the width of nanobelts were respectively 199.5 ± 30, 376.05 ± 48 nm and 5.2 ± 1.3 μm under the 95 % confidence level. The thickness of the tubewall for hollow nanofibers was 40.5 nm and the thickness of LaOI:Tb³⁺ nanobelts was 154 nm. Photoluminescence (PL) study demonstrated that the LaOI:Tb³⁺ nanomaterials exhibited the emission peaks located at 485, 544, 583 and 625 nm, which were ascribed to ⁵D₃ → ⁷F₁, ₆, ⁵D₄ → ⁷F₅, ⁵D₄ → ⁷F₄ and ⁵D₄ → ⁷F₃ of energy level transitions of Tb³⁺, respectively. The PL intensity was strongly affected by the Tb³⁺-doping concentration, and the optimum quenching concentration was 9 %. The luminescence intensity of LaOI:Tb³⁺ nanofibers was obviously stronger than that of LaOI:Tb³⁺ hollow nanofibers and nanobelts under the same measuring conditions. Commission Internationale de L’Eclairage (CIE) analysis demonstrated that the luminescence color of LaOI:9 % Tb³⁺ nanostructures were located in the green region in CIE chromaticity coordinates diagram. The possible formation mechanisms of LaOI:Tb³⁺ one dimensional nanomaterials were also proposed.     

Luminescence Spectra of Poly(methylmethacrylate)/ZnS:Eu(III),Tb(III) Composites

Colloidal zinc sulfide solutions have been prepared by reacting zinc trifluoroacetate and thioacetamide in methyl methacrylate as a reaction medium, and europium and terbium salts have been added to the solution. Using methyl methacrylate block polymerization, we have synthesized PMMA/ZnS, PMMA/ZnS:Eu(III), PMMA/ZnS:Tb(III), and PMMA/ZnS:Eu(III),Tb(III) composites. The luminescence of the composites is due to charge recombination at energy levels of structural defects and impurities in ZnS and also to ⁵D₀ → ⁷F _j and ⁵D₄ → ⁷F _j electronic transitions of the Eu³⁺ and Tb³⁺ ions. It depends on the composition and structure of the composites, excitation wavelength, and other factors. The mutual effects of the ZnS and the Eu³⁺ and Tb³⁺ ions show up as changes in the position and relative intensity of luminescence bands in the spectra of the composites.     

Synthesis and luminescence spectra of poly(methyl methacrylate)/CdS:Ln(III) composites

Cadmium sulfide was prepared by colloidal synthesis in methyl methacrylate (MMA). Europium and terbium salts were added to the colloidal solutions. Using MMA radical polymerization, we synthesized PMMA/CdS:Eu(III), PMMA/CdS:Tb(III), and PMMA/CdS:Eu(III):Tb(III) luminescent composites. Their luminescence is due to defects in the CdS crystals and the ⁵ D _о → 7Fj and ⁵ D ₄ → ⁷ F _j electronic transitions of the Eu³⁺ and Tb³⁺ ions, respectively. It depends on the composition of the materials, complexation on the surface of the colloidal particles, heat treatment time during synthesis, excitation wavelength, and other factors.     

Fabrication and luminescence of YF3:Tb3+ hollow nanofibers

YF₃:Tb³⁺ hollow nanofibers were successfully fabricated via fluorination of the relevant Y₂O₃:Tb³⁺ hollow nanofibers which were obtained by calcining the electrospun PVP/[Y(NO₃)₃ + Tb(NO₃)₃] composite nanofibers. The morphology and properties of the products were investigated in detail by X-ray diffraction, scanning electron microscope, transmission electron microscope, and fluorescence spectrometer. YF₃:Tb³⁺ hollow nanofibers were pure orthorhombic phase with space group Pnma and were hollow-centered structure with the mean diameter of 148 ± 23 nm. Fluorescence emission peaks of Tb³⁺ in the YF₃:Tb³⁺ hollow nanofibers were observed and assigned to the energy levels transitions of ⁵D₄ → ⁷F_J (J = 6, 5, 4, 3) (490, 543, 588, and 620 nm) of Tb³⁺ ions, and the ⁵D₄ → ⁷F₅ hypersensitive transition at 543 nm was the dominant emission peak. Moreover, the emitting colors of YF₃:Tb³⁺ hollow nanofibers were located in the green region in CIE chromaticity coordinates diagram. The luminescent intensity of YF₃:Tb³⁺ hollow nanofibers was increased remarkably with the increasing doping concentration of Tb³⁺ ions and reached a maximum at 7 mol% of Tb³⁺. The possible formation mechanism of YF₃:Tb³⁺ hollow nanofibers was also discussed. This preparation technique could be applied to prepare other rare earth fluoride hollow nanofibers.     

A magnetooptical study of the odd crystal field component in a terbium-yttrium aluminum garnet

We have studied the photoluminescence spectra and the luminescence magnetic circular polarization (LMCP) spectra in the region of the 4f-4f radiative transition ⁵D₄→⁷F₆ in the rare earth Tb³⁺ ion in a Y₃Al₅O₁₂ garnet matrix. A comparison of the experimental and theoretically calculated LMCP spectra allowed parameters of the odd crystal field component to be determined that removes the prohibition with respect to parity from the 4f-4f transitions in Tb³⁺ ion in the garnet structure. The energy spectra and wave functions of ⁵D₄ and ⁷F₆ multiplets of Tb³⁺ ion in a crystal field with the D₂ symmetry have been calculated.     

Facile synthesis of β-NaYF4:Ln3+ (Ln = Eu, Tb, Yb/Er, Yb/Tm) microcrystals with down- and up-conversion luminescence

β-NaYF₄:Ln³⁺ (Ln = Eu, Tb, Yb/Er, Yb/Tm) hexagonal microrods have been successfully synthesized through a facile molten salt method without any surfactant. X-ray diffraction, scanning electron microscopy (SEM), transmission electron microscopy, high-resolution transmission electron microscopy, and photoluminescence spectra were used to characterize the samples. It is found that at a preferred reaction temperature of 400 °C, the structure of β-NaYF₄ can gradually transform from microtubes to microrods as reaction time extends from 0.5 to 4 h. Furthermore, as the molar ratio of NaF:RE³⁺ (RE represents the total amount of Y³⁺ and the doped rare earth elements such as Eu³⁺, Tb³⁺, Yb³⁺/Er³⁺, or Yb³⁺/Tm³⁺) increased, the phase of sample transforms from YF₃ into NaYF₄. Under the excitation of 395 nm ultraviolet light, β-NaYF₄:5 %Eu³⁺ shows the emission lines of Eu³⁺ corresponding to ⁵D_0-3 → ⁷F _J (J = 1–4) transitions from 400 to 700 nm, resulting in red down-conversion (DC) light emission. When doped with 5 % Tb³⁺ ions, the strong DC fluorescence corresponding to ⁵D₄ → ⁷F _J (J = 6, 5, 4, 3) transitions with ⁵D₄ → ⁷F _J (green emission at 544 nm) being the most prominent group that has been observed. Moreover, upon 980 nm laser diode excitation, the Yb³⁺/Er³⁺- and Yb³⁺,Tm³⁺- co-doped β-NaYF₄ samples exhibit bright yellow and blue upconversion (UC) luminescence, respectively, by two- or three-photon UC process. The luminescence mechanisms for the doped lanthanide ions were thoroughly analyzed.     

SrWO4:Tb3+ nanoparticles: synthesis,characterization, and luminescence

Nanoparticles of SrWO₄ doped with Tb³⁺ were synthesized in ethylene glycol, Dimethyl sulfoxide, and water. X-ray powder diffractions show that the nanoparticles synthesized in all these solvents have a pure tetragonal scheelite structure without the presence of deleterious phases. Scanning electron microscopy images show that nanoparticles are in the range of 15–25 nm with an inhomogeneous nature. The emission spectra of SrWO₄:xTb³⁺ nanoparticles show the characteristic green emission (545 nm) of Tb³⁺ ions corresponding to ⁵D₄ → ⁷F₅ transition due to efficient charge transfer from WO₄ ^2? to Tb³⁺ ions, when they are excited at 254 nm. Other emissions can be observed due to ⁵D₄ → ⁷F_{6, 4, 3} transitions. The optimum concentration of Tb³⁺ ions for the highest luminescence was found to be 10 mol%. The luminescence intensity of the samples prepared in ethylene glycol is higher than that in Dimethyl sulfoxide and water. The excellent luminescence properties of SrWO₄:Tb³⁺ phosphor makes it as a potential green phosphor.     

Sol–gel synthesis and photoluminescence of M2Gd8(SiO4)6O2: RE3+ (M = Ca, Sr; RE = Tb, Eu) phosphors by different silicate sources

Eight kinds of silicate sources were adopted to prepare M₂Gd₈(SiO₄)₅O₂: RE³⁺ (M = Ca, Sr; RE = Eu, Tb) phosphors by the sol–gel method. Scanning electronic microscope (SEM) was used to compare the different configuration of patterns rely on eight different silicon sources. X-ray powder diffraction (XRD) also has been employed to analyze their microstructures and particle sizes further. All the phosphor show the characteristic emission ⁵D₄ → ⁷F_J (J = 6, 5, 4, 3) of Tb ions and ⁵D₀ → ⁷F_J (J = 1, 2) of Eu ions, indicating that the emission intensity is affected by the silicate sources.     

Synthesis and luminescence spectra of (Y<Subscript>2</Subscript>O<Subscript>3</Subscript>–YOF):Ln(III) composites

Sols were prepared by reacting yttrium, europium, and terbium trifluoroacetates with thioacetamide in ethyl acetate. The Eu³⁺ and Tb³⁺ concentrations in the sols were 0.10 to 10 wt % relative to yttrium, which corresponded to 0.061 (0.059) to 6.1 (5.9) at % Eu (Tb). The sols were converted into a gel-like state by slowly evaporating the solvent. After ripening, the gels were heat-treated at a temperature of 800°C. X-ray diffraction, differential scanning calorimetry, thermogravimetric analysis, and IR spectroscopy results showed that the resultant composites consisted predominantly of a mixture of Y₂O₃ and YOF. The Eu³⁺ and Tb³⁺ ions were shown to substitute for Y³⁺ ions in the crystal lattices of the yttrium oxide and yttrium oxyfluoride. The formation of the (Eu_0.6Y_0.4)₂O₃, Eu₂O₃, and EuOF phases was demonstrated. We determined the types and parameters of the crystal lattices of the synthesized materials in relation to activator concentrations. The luminescence of the composites is due to the ⁵ D ₀ → ⁷ F _j and ⁵ D ₄ → ⁷ F _j electronic transitions of the Eu³⁺ and Tb³⁺ ions and depends on the host and activator compositions, the excitation wavelength, and other factors.     

Molten salt synthesis,characterization, and luminescence of SrWO4, SrWO4:Tb3+ and SrWO4:Eu3+ powders

SrWO₄, SrWO₄:Tb³⁺, and SrWO₄:Eu³⁺ powders were synthesized by a method of molten salt. XRD patterns showed that the synthesized powders have a pure tetragonal scheelite structure without the presence of deleterious phases. Scanning electron microscopy images show that powders are in the range of 20–35 nm. The emission spectrum of SrWO₄ shows the emission peak in the blue spectral region. The excitation spectra of SrWO₄:Tb³⁺ and SrWO₄:Eu³⁺ show the energy transfer from WO₄ ^2? group to Tb³⁺ and Eu³⁺ ions with a high efficiency. The emission spectrum of SrWO₄:Tb³⁺ shows the green emission at 545 nm corresponding to the ⁵D₄ → ⁷F₅ transition of Tb³⁺. The emission spectrum of SrWO₄:Eu³⁺ shows the red emission located at 612 nm corresponding to the ⁵D₀ → ⁷F₂ transition of Eu³⁺. The asymmetry ratio of SrWO₄:Eu³⁺ is found to be 5.54, which indicates that the Eu³⁺ ions are located in a lower symmetric site.     

Hydrothermal synthesis and improved luminescent properties of nanosheet-based rare earth orthoborates lantern-like assemblies

Hexagonal vaterite-type LuBO₃:Tb³⁺/Eu³⁺ lantern-like phosphors have been successfully prepared by a simple hydrothermal process directly without sintering treatment. X-ray diffraction, scanning electron microscopy, transmission electron microscopy, high-resolution transmission electron microscopy, selected area electron diffraction, photoluminescence, low-voltage cathodoluminescence, and kinetic decays were used to characterize as-prepared phosphors, which present complex lantern-like 3D assemblies that are composed of nanosheets with thickness of about 23 nm and high crystallinity in spite of the moderate reaction temperature of 210 °C. The reaction mechanism and the self-assembly evolution process have been proposed. The pH, temperature, time, and ethylene glycol play critical roles in the formation of this specific hierarchical and complex 3D structure. Under UV excitation and low-voltage electron beam excitation, vaterite-type LuBO₃:Tb³⁺ samples showed the characteristic green emission of Tb³⁺ corresponding to ⁵ D ₄ → ⁷ F ₅ transitions; vaterite-type LuBO₃:Eu³⁺ particles exhibited a strong red emission corresponding to primary group electric dipole transition ⁵ D ₀ → ⁷ F ₂ with much higher R/O values (chromatically redder fluorescence, increase of 29 %) compared with samples by conventional solid-state reaction, which have potential applications in fluorescent lamps and field emission displays.     

Room-temperature photoluminescence from porous anodic alumina films with embedded terbium and europium species

Strong room-temperature terbium and europium photoluminescence, with well-resolved optical bands corresponding to electron transitions ⁵D₄→⁷F_j (j = 3–6) for Tb³⁺, and ⁵D₀→⁷F_j (j = 1–4) for Eu³⁺, was observed from porous anodic alumina films of 5–55 µm thickness after immersion in solutions of terbium or europium nitrates and subsequent heat treatment. GDOES and TEM examinations of the specimens treated with terbium ions revealed a uniform distribution of terbium across the porous anodic film thickness of 55 µm, with an increased terbium concentration toward the pore bases. Europium- and terbium-doped specimens displayed anisotropic indicatrix of luminescence for the emission wavelength of 613 nm for europium and 545 nm for terbium, with a maximum intensity in the direction along the channels of the pores that is typical for porous anodic alumina with lanthanide ions within the pores. The potential applications of porous anodic alumina doped with lanthanides through immersion in the absence of xerogel are discussed.     

Synthesis and luminescent properties of Tb3+ activated AWO4 based (A = Ca and Sr) efficient green emitting phosphors

Optically efficient terbium activated alkaline earth metal tungstate nano phosphors (AWO₄ [A = Ca, Sr]) with different doping concentrations have been prepared by mechanochemically assisted solid state metathesis reaction at room temperature for the first time. The prepared phosphors were characterized by the X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, scanning electron microscope (SEM), Fourier transform Raman (FT-Raman) spectroscopy, photoluminescence and diffuse reflectance spectroscopy measurements. The XRD and Raman spectra results showed that the prepared powders present a scheelite-type tetragonal structure. FTIR spectra exhibited a high absorption band situated at around 850 cm^?1, which was ascribed to the W–O antisymmetric stretching vibrations into the [WO₄]^2? tetrahedron groups and the SEM images reveal that the particle sizes were in the range of 20–60 nm. The excitation and the emission spectra were measured to characterize the luminescent properties of the phosphors. The excitation spectrum exhibits a charge transfer broad band along with some sharp peaks from the typical 4f–4f transitions of Tb³⁺. Under excitation of UV light, these AWO₄:xTb³⁺ (A = Ca, Sr) phosphors showed a strong emission band centered at 545 nm (green) which corresponds to ⁵ D ₄ → ⁷ F ₅ transition of Tb³⁺. Analysis of the emission spectra with different Tb³⁺ concentrations revealed that the optimum dopant concentration for CaWO₄:xTb³⁺ and SrWO₄:xTb³⁺ phosphors are about 8 and 6 mol% of Tb³⁺. The green emission intensity of the solid state meta-thesis prepared CaWO₄:0.08Tb³⁺ and SrWO₄:0.06Tb³⁺ phosphors are 1.5 and 1.2 times greater than that of the commercial LaPO₄:Ce, Tb green phosphor. All properties show that AWO₄:Tb³⁺ (A = Ca, Sr) is a very appropriate green-emitting phosphor for fluorescent lamp applications.     

NaScMo<Subscript>2</Subscript>O<Subscript>8</Subscript>:RE<Superscript>3+</Superscript> (RE = Tb,Eu, Tb/Eu,Yb/Er,Yb/Ho) phosphors: hydrothermal synthesis,energy transfer and multicolor tunable luminescence

NaScMo₂O₈:RE³⁺ (RE = Tb, Eu, Tb/Eu, Yb/Er, Yb/Ho) phosphors were successfully synthesized by surfactant-free hydrothermal method and post-calcination treatment. The energy transfer (ET) of MoO₄ ^2? → Tb³⁺ → Eu³⁺ was proved by photoluminescence spectra and decay features. Multicolor emissions (green → yellow → red) were obtained by adjusting the ratio of Tb³⁺/Eu³⁺ upon excitation into the MoO₄ ^2? at 292 nm. The ET of Tb³⁺ → Eu³⁺ was demonstrated to be a resonant type via a dipole–dipole mechanism, and the crystal distance (R _c) was calculated by the quenching concentration method. Under 980 nm excitation, the emission of NaScMo₂O₈:RE³⁺ (RE = Yb/Er, Yb/Ho) showed strong green (Yb³⁺/Er³⁺: ⁴S_3/2, ²H_11/2 → ⁴I_15/2; Yb³⁺/Ho³⁺: ⁵S₂ → ⁵I₈) luminescence, respectively. Moreover, the doping concentration of the Yb³⁺ has been optimized under a fixed concentration of Er³⁺ and Ho³⁺, respectively. The NaScMo₂O₈:RE³⁺ phosphors have potential applications for color displays and light-emitting devices due to a variety of luminous colors.     

A single nanobelt to achieve simultaneous photoluminescence–electricity–magnetism trifunction

In order to develop new-typed multifunctional composite nanobelts, polymethyl methacrylate (PMMA) is used as the matrix to construct composite nanobelts containing different amounts of Eu(BA)₃phen(BA = benzoic acid, phen = phenanthroline), polyaniline (PANI) and Fe₃O₄ nanoparticles (NPs), and Eu(BA)₃phen/PANI/Fe₃O₄/PMMA trifunctional composite nanobelts with simultaneous photoluminescence, electricity and magnetism have been successfully fabricated via electrospinning technology. The morphology and properties of the obtained composite nanobelts were characterized by X-ray diffractometry, scanning electron microscopy, vibrating sample magnetometry, fluorescence spectroscopy and Hall effect measurement system. The results indicate that the trifunctional composite nanobelts simultaneously possess excellent photoluminescence, electrical conduction and magnetic properties. Fluorescence emission peaks of Eu³⁺ ions in the composite nanobelts are observed and assigned to the energy levels transitions of ⁵D₀ → ⁷F₀ (580 nm), ⁵D₀ → ⁷F₁ (593 nm) and ⁵D₀ → ⁷F₂ (615 nm) of Eu³⁺ ions, and the ⁵D₀ → ⁷F₂ hypersensitive transition at 615 nm is the predominant emission peak. The electrical conductivity reaches up to the order of 10^?3 S/cm. Furthermore, the luminescent intensity, electrical conductivity and saturation magnetization of the composite nanobelts can be tunable by adjusting amounts of Eu(BA)₃phen, PANI and Fe₃O₄ NPs. The formation mechanism of the composite nanobelts is also proposed. The obtained photoluminescence–electricity–magnetism trifunctional composite nanobelts have potential applications in many areas such as electromagnetic interference shielding, microwave absorption, molecular electronics, biomedicine and future nanomechanics. More importantly, the design concept and construct technique are of universal significance to fabricate other trifunctional naonobelts.     

Effect of annealing temperature on the energy transfer in Eu-doped ZnO nanoparticles by chemical precipitation method

Eu-doped ZnO nanoparticles were synthesized by the chemical precipitation method and the annealing temperature effect on the structures and photoluminescence (PL) properties of the nanoparticles were briefly investigated. The X-ray diffraction and energy dispersive spectroscopy results indicated that the Eu³⁺ was successfully incorporated into the crystal lattice of ZnO host when the annealing temperature was fixed at 400 °C, but the Eu³⁺ ions were partly precipitated from the host with the annealing temperature increasing. The as-obtained ZnO: Eu nanocrystals composed of nanoparticles had an average size of 10 nm, and the valence states of europium ions in the nanocrystals were determined as tervalent. PL spectroscopy indicated that the characteristic red emissions of Eu³⁺ ions were attributed to the ⁵D₀ → ⁷F₀, ⁵D₀ → ⁷F₁ and ⁵D₀ → ⁷F₂ transitions, respectively. Moreover, the annealing temperature was found to have effect on the red emission of Eu³⁺ ions. That is to say, the energy transfer in the doped nanocrystals could be adjusted by different annealing temperatures.     

Synthesis and annealing effects on the optical spectroscopy properties of red-emitting Gd(P<Subscript>0.5</Subscript>V<Subscript>0.5</Subscript>)O<Subscript>4</Subscript>: x at.% Eu<Superscript>3+</Superscript>

In this work, Gd(P_0.5V_0.5)O₄: x at.% Eu³⁺ phosphors with different dopant concentrations (x?=?1, 3, 5, 6, 7, 9) were synthesized through chemical coprecipitation method. The phosphors were characterized by XRD, SEM, infrared spectroscopy, photoluminescence excitation, emission spectra and CIE. The results of XRD indicate that the obtained phosphors have the tetragonal phase structure. Eu³⁺ emission transitions arise mainly from the ⁵D₀ level to the ⁷F_J (J?=?0, 1, 2, 3, 4) manifolds. The emission intensity and crystalline of Gd(P_0.5V_0.5)O₄:x at% Eu³⁺ powders are increasing with annealing temperature at 600, 800, 1000, 1100, and 1200 °C, respectively. The introduction of VO₄^3? can broaden the range of UV excitation spectrum wavelength and enhance the transition between ⁵D₀ → ⁷F₁ to ⁵D₀ → ⁷F₂ for long wavelength emission. And the most dominant emission peak of Eu³⁺ for ⁵D₀ → ⁷F₂ transition is closer to pure red light at 622 nm. The maximum emission intensity of the phosphors is the concentration of 6 at.% Eu³⁺ because of the distance of the neighbor Eu³⁺ ions reaching a certain critical value and the influence of multipolar interaction. Compared to commercial phosphors Y₂O₃:Eu³⁺ and (Y,Gd)BO₃:Eu³⁺, our work yielded a longer wavelength red light emission intensity and a higher proportion of red light to orange light. All our results indicate that color purity of this phosphor turns it into a promising red phosphor in ultraviolet-pumped light-emitting diodes.     

Parallel spinnerets electrospinning construct and properties of electrical-luminescent bifunctional bistrand-aligned nanobundles

A structure of electrical-luminescent bifunctional bistrand-aligned nanobundles has been successfully fabricated by specially designed parallel spinnerets electrospinning technology. Eu(BA)₃phen (BA = benzoic acid, phen = 1,10-phenanthroline) and polyaniline (PANI) were respectively incorporated into polyvinyl pyrrolidone (PVP) and electrospun into bistrand-aligned nanobundles with PANI/PVP as one strand nanofiber and Eu(BA)₃phen/PVP as another strand nanofiber. The morphologies and properties of the final products were investigated in detail by scanning electron microscopy, transmission electron microscopy, fluorescence spectroscopy, Hall effect measurement system, and UV–Vis-NIR spectrophotometer. It is found that the as-prepared samples exhibit the nanostructures of bistrand-aligned nanobundles. The mean diameter for individual nanofiber of the bistrand-aligned nanobundles is 180 nm. The [PANI/PVP]//[Eu(BA)₃phen/PVP] bistrand-aligned nanobundles possess excellent electrical conduction and luminescent properties. Fluorescence emission peaks of Eu³⁺ are observed in the [PANI/PVP]//[Eu(BA)₃phen/PVP] electrical-luminescent bifunctional bistrand-aligned nanobundles and assigned to ⁵D₀ → ⁷F₀ (581 nm), ⁵D₀ → ⁷F₁ (592 nm), ⁵D₀ → ⁷F₂ (615 nm) energy levels transitions of Eu³⁺ ions, and the ⁵D₀ → ⁷F₂ hypersensitive transition at 615 nm is the predominant emission peak. The electrical conductivity reaches up to the order of 10^?3 S/cm. The electrical conductivity and luminescent intensity of the bistrand-aligned nanobundles can be tunable by adding various amounts of PANI and rare earth complex. The novel [PANI/PVP]//[Eu(BA)₃phen/PVP] electrical-luminescent bifunctional bistrand-aligned nanobundles have potential applications in display devices and nanomechanics, etc. owing to their excellent electrical conduction and fluorescence.