Light Display Systems Research Articles

Controlled synthesis and tunable photoluminescence properties of LaOBr:Eu3+ nanostructures

Eu3+ doped lanthanum oxybromide (LaOBr) nanostructures including nanofibers, nanoribbons, and hollow nanofibers were fabricated for the first time via calcining the electrospun PVP/[La(NO3)3+Eu(NO3)3+NH4Br] composites. X-ray diffraction analysis results showed that LaOBr:Eu3+ nanostructures were tetragonal in structure with space group of P4/nmm. The morphologies and sizes of the LaOBr:Eu3+ nanostructures were studied by scanning electron microscope and transmission electron microscope. The mean diameter of the nanofibers and hollow nanofibers, and the width of nanoribbons are 118.02 ± 14.21, 115.84 ± 13.37 nm, and 1.56 ± 0.25 μm, respectively. Under the excitation of 289 nm ultraviolet light, LaOBr:Eu3+ nanostructures exhibit the red emissions of predominant peak at 618 nm, which is ascribed to the 5D0 → 7F2 transition of the Eu3+ ions. It is found that the optimum doping concentration of the Eu3+ ions in the LaOBr:Eu3+ nanofibers is 5 %. Interestingly, we found that the luminescence intensity of nanofibers is obviously greater than that of the hollow nanofibers and nanoribbons for LaOBr:Eu3+ under the same measuring conditions. Moreover, the color emissions of LaOBr:Eu3+ nanostructures can be tuned by adjusting the concentration of Eu3+ and the morphologies of nanomaterials. The obtained LaOBr:Eu3+ nanostructures may be promising nanomaterials for applications in the fields of light display systems and optoelectronic devices.

Morphology controllable and highly luminescent monoclinic LaPO4:Eu3+ microspheres

Abstract A facile, but effective, two-step method was developed to prepare monoclinic LaPO4:Eu3+ microspheres composed of microprisms with a controllable morphology. XRD and SEM studies revealed a spherical morphology and crystalline structure for the resulting material. It was also found that LaPO4:Eu3+ microspheres prepared at 800 °C showed a higher luminescent intensity than primary hexagonal LaPO4:Eu3+ microprisms. Furthermore, the luminescent performance of LaPO4:Eu3+ microspheres was demonstrated to reach the standards of the LaPO4:Eu3+ bulk material under the same conditions. These results suggest possibilities for the use of as-synthesized monoclinic LaPO4:Eu3+ microspheres as alternatives to replace intrinsically uneven bulk materials for many application areas, including light display systems and optoelectronic devices.

Hydrothermal Synthesis, Characterization and Luminescence Properties of YbVO<SUB>4</SUB>:Ln<SUP>3+</SUP> (Ln<SUP>3+</SUP> = Er<SUP>3+</SUP>, Tm<SUP>3+</SUP>, Ho<SUP>3+</SUP>) Nanocrystals

Ytterbium orthovanadate YbVO4 nanocrystals with uniform size and shape were successfully synthesized through a facile hydrothermal approach using sodium tartrate (Na2tar) as the chelating ligand. X-ray diffraction (XRD), energy-dispersive X-ray spectrum (EDX), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED) and photoluminescence (PL) spectra were taken to characterize the phases, morphologies, sizes, and luminescence properties of the samples. The results indicate that the YbVO4 samples can be rationally modified in size and morphology by altering the Na2tar content, pH value and reaction time. The possible formation mechanism of the YbVO4 samples is proposed on the basis of time-dependent experiments. Additionally, the UC luminescence properties and the emission mechanisms of YbVO4:Ln3+ (Ln3+ = Er3+, Tm3+, Ho3+) samples were systematically investigated, which show green (Er3+, 4S(3/2), 2H(11/2) --> 4I(15/2)), blue (Tm3+, 1G(4) --> 3H(6)) and green (Ho3+, 5S(2) --> 5I(8)) luminescence under 980 nm NIR excitation, respectively. These merits of multicolor emissions in the visible region endow this kind of material with potential applications in the field of light display systems, lasers, and optoelectronic devices.

Facile chemical conversion synthesis and luminescence properties of uniform YF3 nanowires

Well-dispersed YF3 nanowires were synthesized by a designed hydrothermal conversion method with Y(OH)3 nanowires as precursor. Various equipments were used to characterize the samples. The results show that Y(OH)3 nanowires precursor was prepared through a simple hydrothermal process, which then served as the precursor for the fabrication of YF3 nanowires by a hydrothermal process. The whole process was carried out under aqueous conditions without any organic solvent, surfactant or catalyst. The conversion process from Y(OH)3 precursor to YF3 nanowires was investigated by time-dependent experiments. The possible formation mechanism of YF3 nanowires was presented in detail. Under UV excitation, 5%(mass fraction) Eu3+ or 5%(mass fraction) Tb3+ doped YF3 samples exhibit strong red or green emission, corresponding to the characteristic lines of Eu3+ and Tb3+, respectively. Moreover, the luminescence colors of the Eu3+ and Tb3+ codoped YF3 samples can be tuned from red, yellow and green-yellow to green by simply adjusting the relative doping concentrations of the activator ions under a single wavelength excitation, which might find potential applications in the fields of, such as, light display systems and optoelectronic devices.

Preparation and luminescence of La2O3:Ln3+(Ln3+= Eu3+, Tb3+, Dy3+, Sm3+, Er3+, Ho3+, Tm3+, Yb3+/Er3+, Yb3+/Ho3+) microspheres

Multicolor and monodisperse La2O3:Ln3+ (Ln3+ = Eu3+, Tb3+, Dy3+, Sm3+, Er3+, Ho3+, Tm3+, Yb3+/Er3+, Yb3+/Ho3+) microspheres were prepared by a homogeneous precipitation method followed by a subsequent calcination process. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared (FT-IR), thermogravimetric and differential thermal analysis (TG-DTA), and photoluminescence (PL) spectra were employed to characterize the samples. The results indicate that the La2O3 microspheres can be well indexed to the hexagonal La2O3 phase. In addition, the possible formation mechanism and the chemical reaction of each step to form spherical La2O3 microspheres are proposed according to the concerned analysis. The as-obtained particles show strong light emission with different colors corresponding to different Ln3+ ions under ultraviolet-visible light excitation. Under 980 nm NIR irradiation, the Lu2O3:Ln3+ (Ln3+ = Yb3+/Er3+, and Yb3+/Ho3+) microspheres exhibit characteristic up-conversion emissions of red (Er3+, 2H11/2, 4S3/2, 2H11/2 → 4I15/2), and green (Ho3+, 5F4, 5S2, 5F5 → 5I8), respectively. These merits of multicolor emissions in the visible region endow this kind of material with potential applications in the field of light display systems, lasers, and optoelectronic devices.

Facile fabrication and photoluminescence properties of rare-earth-doped Gd2O3 hollow spheres via a sacrificial template method

Rare-earth-doped gadolinium oxide (Gd₂O₃) hollow spheres were successfully fabricated on a large scale by using PS spheres as sacrificed templates and urea as a precipitating agent, which involved the deposition of an inorganic coating Gd(OH)CO3 on the surface of PS spheres and subsequent calcination in the air. Various approaches including X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared (FT-IR), thermogravimetric and differential thermal analysis (TG-DTA), as well as photoluminescence spectroscopies were used to characterize the samples. The results indicate that the sample is composed of uniform hollow Gd₂O₃ spheres with a mean particle size of about 2.3 μm and these hollow spheres have the mesoporous shell that are composed of a large amount of nanoparticles. The possible mechanism of evolution from PS spheres to the amorphous precursor and to the final hollow Gd₂O₃ spheres have been proposed. The as-obtained samples show strong light emission with different colors corresponding to different Ln³⁺ ions under ultraviolet-visible light and electron-beam excitation. Under 980 nm NIR irradiation, Gd₂O₃:Ln³⁺ (Ln³⁺ = Yb³⁺/Er³⁺, Yb³⁺/Tm³⁺ and Yb³⁺/Ho³⁺) exhibit characteristic up-conversion (UC) emissions of red (Er³⁺, ²H11/2, ⁴S3/2, ⁴F9/2 → ⁴I15/2), blue (Tm³⁺, ¹G₄ → ³H₆) and green (Ho³⁺, ⁵F₄, ⁵S₂ → ⁵I₈), respectively. These merits of multicolor emissions in the visible region endow these kinds of materials with potential applications in the field of light display systems, lasers, optoelectronic devices, and MRI contrast agents.

Facile Synthesis and Effect of Eu, Tb Co-doping On the Tunable Luminescent Properties of YBO3

ABSTRACTEu3+/Tb3+co-doped YBO3 three-dimensional (3D) microstructures have been hydrothermally prepared by adjusting solvent and the molar ratio of Y3+ to B (Y/B) at 180 °C. The whole process was carried out under alkaline conditions without the use of any surfactant or catalyst. Characterizations of the samples are carried out using X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and high-resolution TEM (HRTEM). The photoluminescence (PL) colors of YBO3 sample co-doped with Eu3+ and Tb3+ under ultraviolet excitation can be tuned from red, through yellow and green-yellow, to green by changing the relative doping concentrations of the two activator ions. These phosphors with multicolor emissions in the visible region be potentially used as labels for light-display systems, optoelectronic devices and biological molecules.

Electrospinning preparation of LaOBr:Tb3+ nanostructures and their photoluminescence properties

Tb3+-doped LaOBr nanostructures including nanofibers, nanobelts, and hollow nanofibers were synthesized for the first time via calcinating the electrospun polyvinyl pyrrolidone/[La(NO3)3 + Tb(NO3)3 + NH4Br] composites. X-ray diffraction analysis revealed that LaOBr:Tb3+ nanostructures are tetragonal in structure with space group of P4/nmm. The morphologies and sizes of LaOBr:Tb3+ nanostructures were investigated using scanning electron microscope and transmission electron microscope. Under the excitation of 254-nm ultraviolet light, LaOBr:Tb3+ nanostructures exhibit the green emissions of predominant peak at 543 nm, which is ascribed to 5D4 → 7F5 transition of Tb3+ ions. It is found that the optimum doping concentration of Tb3+ ions in the LaOBr:Tb3+ nanofibers is 3 %. Interestingly, we found that the luminescence intensity of hollow nanofibers is obviously greater than that of nanofibers and nanobelts for LaOBr:Tb3+ under the same measuring conditions. Moreover, the luminescence of LaOBr:Tb3+ nanostructures are located in the green region in Commission Internationale de L’Eclairage chromaticity coordinates diagram. The formation mechanisms of LaOBr:Tb3+ nanofibers, nanobelts, and hollow nanofibers were also proposed. LaOBr:Tb3+ nanostructures are promising nanomaterials for applications in the fields of light display systems and optoelectronic devices.

Hydrothermal synthesis and luminescent properties of NaLa(MoO4)2:Eu3+,Tb3+ phosphors

Eu3+ and Tb3+ co-doped NaLa(MoO4)2 phosphors with various shapes have been synthesized by a simple conventional hydrothermal method. The morphology of the materials was found to be manipulated by changing the pH value of the precursor hydrothermal media. Uniform NaLa(MoO4)2 3D microspheres could be trapped at pH 5 and the spindle-like NaLa(MoO4)2 microstructures were obtained at pH 7. When the pH value was adjusted to 9, the flower-like NaLa(MoO4)2 microstructures were obtained. The luminescent properties of the NaLa(MoO4)2:Eu3+/Tb3+ samples with different morphologies prepared at different starting pH values were studied. The results show that the emission intensity of the product obtained at pH 5 is the strongest. Besides, under ultraviolet excitation the luminescence colors of NaLa(MoO4)2 samples co-doped with Eu3+ and Tb3+ can be tuned from red, through yellow and green–yellow, to green by simply adjusting the relative doping concentrations of the activator ions. This merit of multicolor emissions in the visible region endows the as-prepared products with potential application in the fields of light-display systems and optoelectronic devices.

Self‐Assembled NaY(WO4)2 Hierarchical Dumbbells: Microwave‐Assisted Hydrothermal Synthesis and Their Tunable Upconversion Luminescent Properties

AbstractMicronano self‐assembled NaY(WO4)2 hierarchical dumbbells were synthesized by a microwave‐assisted hydrothermal approach, followed by a heat treatment. The growth mechanism of the precursor was investigated and it was found that the amount of trisodium citrate plays a crucial role in the assembly process of the precursor. Under 980 nm excitation, Yb3+/Er3+, Yb3+/Tm3+, and Yb3+/Ho3+ codoped NaY(WO4)2 samples exhibit strong green, blue, and yellow emissions, respectively. The luminescence colors of Yb3+/Ho3+/Tm3+ tridoped NaY(WO4)2 samples can be tuned from blue through white to yellow by simply adjusting the doping concentrations of the activator ions under 980 nm excitation. The tunable luminescence may be potentially applied in fields such as light display systems and multicolor biological labeling.

General and facile method to fabricate uniform Y2O3:Ln3+ (Ln3+ = Eu3+, Tb3+) hollow microspheres using polystyrene spheres as templates

Well-dispersed, uniform Y2O3:Ln3+ (Ln3+ = Eu3+, Tb3+) hollow microspheres have been successfully prepared via a urea-assisted homogeneous precipitation method using polystyrene (PS) as templates, followed by a subsequent calcination process. X-Ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared (FT-IR), thermogravimetric analysis (TGA), photoluminescence (PL) spectra, and cathodoluminescence (CL) spectra were employed to characterize the samples. The results demonstrate that the samples can be well indexed to the pure cubic phase of Y2O3. The TEM and SEM images indicate that the shell of the uniform hollow spheres, whose diameter is about 2.1 μm, is composed of many uniform nanoparticles with diameters of around 20 nm. Upon ultraviolet (UV) and low-voltage electron beam excitation, the Y2O3:Ln3+ (Ln3+ = Eu3+, Tb3+) samples exhibit bright red (Eu3+, 5D0 → 7F2), and green (Tb3+, 5D4 → 7F5) luminescence. This material may find potential applications in light display systems, optoelectronic devices and drug delivery based on the uniform hollow structure, dimensions, and luminescence properties. Furthermore, this synthesis route may be of great significance in the preparation of other hollow spherical materials.

Self-assembled growth of LuVO4 nanoleaves: hydrothermal synthesis, morphology evolution, and luminescence properties

In the present paper, LuVO4 nanoleaves have been synthesized via a facile and low-cost complexant-assisted hydrothermal approach. The phases, morphologies, sizes, and luminescence properties of the as-prepared products were well characterized by means of XRD, FT-IR, SEM, TEM, SAED, EDX, HRTEM, PL, and CL. The results indicate that the phase, morphology, and size of the LuVO4 samples can be tuned in a controlled manner by altering the amount of Na2tar, the pH value of the initial solution, and the reaction time. The crystal growth was thoroughly investigated, and a possible formation mechanism was proposed. Upon UV and low-voltage electron beam excitation, the LuVO4:Ln3+ (Ln3+ = Eu3+, Dy3+, Sm3+, Er3+) samples exhibit bright red (Eu3+, 5D0 → 7F2), green-yellow (Dy3+, 4F9/2 → 6H13/2), orange-red (Sm3+, 4G5/2 → 6H7/2) and green (Er3+, 4S3/2 → 4I15/2) luminescence. Furthermore, the UC luminescence properties, as well as the emission mechanisms of LuVO4:Yb3+/Ln3+ (Ln3+ = Er3+, Tm3+, Ho3+) samples, were systematically investigated, which show respective green (Er3+, 4S3/2, 2H11/2 → 4I15/2), blue (Tm3+, 1G4 → 3H6) and red (Ho3+, 5F5 → 5I8) luminescence under 980 nm NIR excitation. These merits of multicolor emissions in the visible region endow this kind of material with potential applications in the field of light display systems, lasers, and optoelectronic devices.

Fabrication and luminescence properties of Al 2O 3:Tb 3+ microspheres via a microwave solvothermal route

Al 2O 3:Tb 3+ green phosphors were synthesized via a microwave solvothermal and thermal decomposition route, and characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), photoluminescence (PL) spectra, and decay curves. XRD results indicate that Tb 3+ doped samples are γ-Al 2O 3 after being calcined at 773 K. SEM results show that the particles of Al 2O 3:Tb 3+ are hierarchically nanostructured microspheres assembled from nanosheets. The PL spectra indicate that the 5D 4→ 7F 5 (545 nm) electric dipole transition is the most intensive when excited at 235 nm. It is shown that 0.7 mol% of doping concentration of Tb 3+ ions in γ-Al 2O 3:Tb 3+ is optimum. According to Dexter's theory, the critical distance between Tb 3+ ions for energy transfer was determined to be 18.4 Å. It is found that the curve followed the single-exponential decay. The excellent chromaticity coordinates of Al 2O 3:Tb 3+ phosphors, as defined by the International Commission on Illumination (CIE), indicate that it is a good candidate for use in light display systems and optoelectronic devices.

Hydrothermal synthesis of YBO3:Tb3+ microflowers and their luminescence properties

Three-dimensional flowerlike YBO3:Tb3+ phosphors have been successfully prepared by an efficient surfactant-free hydrothermal process directly without further sintering treatment. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive X-ray (EDS) spectrometry, selected area electron diffraction (SAED), photoluminescence (PL) spectra were used to characterize the samples. The as-obtained samples present flowerlike agglomerates composed of nanoflakes with thickness of 20nm and high crystallinity in spite of the moderate reaction temperature of 180°C. The reaction mechanism has been considered as a dissolution/precipitation mechanism; the self-assembly evolution process has been proposed on homocentric layer-by-layer growth style. The different luminescent intensity with different molar ratio of Y–Tb [Y:Tb=8:2; 7:3; 6:4; 5:5; 4:6], YBO3:Tb3+ phosphors exhibit different light (white, red, green) under ultraviolet excitation, which might find potential applications in the fields such as light display systems and optoelectronic devices.

Highly Uniform YBO3 Hierarchical Architectures: Facile Synthesis and Tunable Luminescence Properties

Highly uniform pancake-like YBO(3) hierarchical architectures have been successfully prepared by a designed two-step hydrothermal method. Yttrium precursor microprisms were first synthesized according to a simple hydrothermal route. Subsequently, nearly monodisperse multilayered YBO(3) products with a pancake-like shape were synthesized at the expense of the precursor during the hydrothermal process. The whole process was carried out under aqueous conditions without the use of any organic solvent, surfactant, or catalyst. The conversion process from the precursor to YBO(3) products has been investigated by time-dependent XRD experiments. Extending this method, other LnBO(3) (Ln=Ho, Er, Tm, Yb) samples with well-defined shape and dimensionality have also been obtained by a similar synthetic process. The luminescence colors of YBO(3) samples co-doped with Eu(3+) and Tb(3+) under ultraviolet or low-voltage electron beam excitation can be tuned from red, through yellow and green-yellow, to green by simply adjusting the relative doping concentrations of the activator ions. This merit of multicolor emissions in the visible region endows materials of this kind with potential application in the fields of light-display systems and optoelectronic devices.

Self-Assembled 3D Urchin-Like NaY(MoO4)2:Eu3+/Tb3+ Microarchitectures: Hydrothermal Synthesis and Tunable Emission Colors

Novel 3D urchin-like NaY(MoO4)2 microarchitectures have been successfully synthesized by a complexing-agent-assisted hydrothermal process followed by a subsequent heat treatment process. The shape and size of the double alkaline rare earth molybdates precursor microstructures can be tuned effectively by controlling the reaction conditions, such as reaction time, the amount of organic additive trisodium citrate (Cit3−), and the kinds of organic additives. The possible formation mechanism for urchin-like microarchitectures has been presented. It is found that the Cit3− organic molecule, acting as the chelating agent and shape modifier, plays a key role in fine-tuning the precursor microstructures. The as-formed precursor could transform into NaY(MoO4)2 with their original urchin-like morphology and slight shrinkage in the size after postannealing process. Under UV and low-voltage electron beam excitation, 5 mol % Eu3+ and 5 mol % Tb3+ doped NaY(MoO4)2 samples exhibit strong red and green emission, corresponding to the characteristic lines of Eu3+ and Tb3+, respectively. Moreover, the luminescence colors of the Eu3+ and Tb3+ codoped NaY(MoO4)2 samples can be tuned from red, yellow, and green-yellow to green by simply adjusting the relative doping concentrations of the activator ions under a single wavelength excitation, which might find potential applications in the fields such as light display systems and optoelectronic devices.

Self-templated and self-assembled synthesis of nano/microstructures of Gd-based rare-earth compounds: morphology control, magnetic and luminescence properties

Nearly monodisperse NaGdF(4) and GdF(3) nanowires/nanorods as well as GdBO(3) microplates/microflowers have been successfully prepared by a designed chemical conversion approach using Gd(OH)(3) nanowires/nanorods as precursors via a facile hydrothermal approach. The Gd(OH)(3) nanowires/nanorods precursors were prepared through a simple hydrothermal process, which then served as sacrificial templates for the fabrication of NaGdF(4) and GdF(3) nanowires/nanorods as well as GdBO(3) microplates/microflowers by a hydrothermal process. The possible formation mechanisms for the corresponding Gd(3+)-based various products are presented in detail. We have investigated the magnetic properties of the NaGdF(4), GdF(3), and GdBO(3) samples. The as-obtained Eu(3+) doped NaGdF(4), GdF(3), and GdBO(3) samples show the strong characteristic red emission of Eu(3+) under ultraviolet excitation. Moreover, the luminescence colors of the Eu(3+) and Tb(3+) co-doped GdBO(3) samples can be tuned from red, through orange, yellow and green-yellow, to green by simply adjusting the relative doping concentrations of the activator ions under a single wavelength excitation, which might find potential applications in the fields such as light display systems and optoelectronic devices. More importantly, this simple method is expected to allow the large-scale production of other complex rare-earth compounds with controllable morphologies and sizes, and exploration of the morphology and phase-dependent photoluminescence properties.

Facile Chemical Conversion Synthesis and Luminescence Properties of Uniform Ln3+ (Ln = Eu, Tb)-Doped NaLuF4 Nanowires and LuBO3 Microdisks

Uniform NaLuF(4) nanowires and LuBO(3) microdisks have been successfully prepared by a designed chemical conversion method. The lutetium precursor nanowires were first prepared through a simple hydrothermal process. Subsequently, uniform NaLuF(4) nanowires and LuBO(3) microdisks were synthesized at the expense of the precursor by a hydrothermal conversion process. The whole process was carried out in aqueous condition without any organic solvents, surfactant, or catalyst. The conversion processes from precursor to the final products have been investigated in detail. The as-obtained Eu(3+) and Tb(3+)-doped LuBO(3) microdisks and NaLuF(4) nanowires show strong characteristic red and green emissions under ultraviolet excitation or low-voltage electron beam excitation. Moreover, the luminescence colors of the Eu(3+) and Tb(3+) codoped LuBO(3) samples can be tuned from red, orange, yellow, and green-yellow to green by simply adjusting the relative doping concentrations of the activator ions under a single wavelength excitation, which might find potential applications in the fields such as light display systems and optoelectronic devices.

Acoustic light scanner and display system: Reich, A., Lipnick, R., Schoen, G.A. US Patent 3, 488, 503 (6 January 1970) (Filed 19 April 1965) (2308)

Acoustic light scanner and display system: Reich, A., Lipnick, R., Schoen, G.A. US Patent 3, 488, 503 (6 January 1970) (Filed 19 April 1965) (2308)

Flying qualities - An integral part of a stability augmentation system

During the conception, development, and flight testing of a stability augmentation system designed to improve the structural response characteristics of the B-52, it was necessary to provide flying qualities criteria and to conduct piloted simulator studies to assure that the B-52 flying qualities were improved or maintained. The fixed-base simulator studies utilized a point light projection display system and a B-52 cockpit display and included the effect of random turbulence. The results of the studies conducted for the lateral-directional axis are presented. In the piloted simulation study the Dutch roll frequency and damping were varied while other pertinent lateral-directional parameters were maintained constant. It was found that the Dutch roll damping required to provide satisfactory flying qualities in turbulence was significantly greater than the damping required in essentially calm air. Improvements in the handling qualities as verified by flight test are also presented.