Excellent Luminescent Characteristics Research Articles

Luminescence of Phosphor Balls Prepared Using Melt Quenching Synthesis Method

Well-grown M3MgSi2O8(M = Ca, Sr and Ba):Eu2+ phosphors were synthesized by novel melt quenching synthesis method. The luminescence property of the Sr3MgSi2O8:Eu2+ phosphor synthesized by the melt synthesis method is comparable to those of the sample synthesized by a conventional solid state reaction. Sintered phosphor balls with excellent luminescent characteristics were obtained.

Photonics and application of dipyrrinates in the optical devices

In this paper spectral-luminescent, lasing, photochemical, and sensory characteristics of a number of Zn(II) and B(III) coordination complexes with dipyrrinates with different structures are presented. We have discussed relations of the structure of investigated compounds and formed solvates with their optical characteristics. The results showed that alkyl substituted dipyrrinates derivatives have excellent luminescent characteristics and demonstrated effective lasing upon excitation of Nd:YAG-laser. They can be used as active media for liquid tunable lasers. Zinc and boron fluoride complexes of dipyrrinates with heavy atoms in structure don't have fluorescence but have long-lived emission due to increased nonradiative intersystem processes in the excited state by the mechanism of a heavy atom. For solid samples based on halogenated complexes was found dependency of the long-lived emission intensity of the oxygen concentration in gas flow. The presence of line segment indicates the possibility of the use of these complexes as a basis for creation of optical sensors for oxygen. Moreover, results of a study of halogen-substituted aza-complexes under irradiation are presented. Such complexes are promising for the creating media for generation of singlet oxygen (1O2), which is important for photodynamic therapy in medicine and photocatalytic reactions in the industry.

OSLdating and luminescence characteristics of aeolian deposits and their source material in Dalarna, central Sweden

Aeolian dunes, coversands, glacifluvial deltas and paraglacial mass‐movement deposits in Bonäsheden and Skattungheden in Dalarna, central Sweden were dated by optically stimulated luminescence (OSL) on quartz. TheOSLages confirm that the majority of the dunes started forming directly after deglaciation, as suggested by previous investigators. Dune formation seems to have lasted at least 1500 years, untilc. 9 ka. Four younger episodes of sand drift resulting in coversand deposition were dated byOSLand/or radiocarbon to 4100±200 a, 1569–1412 cal. aBP, 970±60 a and 150±10 a. The youngest one is related to changes in land use, while the older ones may be due to regional climatic changes. The dated quartz had excellent luminescence characteristics; the luminescence was bright and dominated by the fast signal component, which made it possible to successfully analyse even untreated material, so‐called range‐finder dating. These characteristics are most likely inherited from one of the source rocks of the Quaternary deposits – the Mesoproterozoic Dala sandstone, which we show to also have very good luminescence properties.

Three-dimensional epitaxy of single crystalline semiconductors by polarity-selective multistage growth

Despite recent advances in three-dimensional (3D) fabrication, the epitaxial growth of finely controlled, single crystalline 3D structures is still constrained. In this study, we demonstrate the step-by-step growth of hierarchical 3D architectures composed of single crystalline semiconductors. To achieve this goal, we first established control of the preferential growth direction of ZnO crystals by polarity-selective crystallization during the low-temperature solution-phase synthesis. The time-dependent analysis showed that the binding of a citrate additive to the positively charged, top (0001) surface of ZnO crystals led to an inversion of the growth anisotropy from predominantly the vertical direction to the lateral direction with more than a 10 times increase in the width-to-height ratio. With further fine optimization of the charge balance, we minimized the interruption of citrate ions for epitaxial and iterative stacking of Zn and O ions, and achieved single-crystalline hexaplates. This feature was further combined with multistage epitaxial growth of the nanocrystal constituents, producing a 3D, single crystalline semiconductor with excellent luminescent characteristics.

Luminescence and Morphology Control of Phosphor Materials Synthesized by Melt Synthesis Method

Efficient and well-grown SrAl2O4:Eu,Dy phosphors were synthesized by an innovative melt synthesis method. The luminescent intensity and after-grow intensity of the SrAl2O4:Eu,Dy phosphors synthesized by the melt synthesis method are comparable to those of the sample synthesized by a conventional solid state reaction. Sintered phosphor balls with excellent luminescent characteristics were obtained.

Towards more robust chronologies of coastal progradation: Optically stimulated luminescence ages for the coastal plain at Moruya, south-eastern Australia

Accurate chronologies are fundamental for detailed analysis of palaeoenvironmental conditions, archaeological reconstructions and investigations of Holocene coastal morphological changes. Chronological data enable estimation of rates of shoreline progradation, and provide appropriate context for forecasting future coastal changes. A previously reported radiocarbon chronology for the Moruya coastal plain in south-eastern Australia indicated a decelerating overall rate of progradation with minimal net seaward shoreline movement in the past ~2500 years. Single-grain and multi-grain aliquot optically stimulated luminescence (OSL) analyses demonstrate that marine sands from this region have excellent luminescence characteristics. A series of OSL ages across this coastal barrier indicates a remarkably linear trend of Holocene shoreline progradation. The linear trend of seaward shoreline movement indicates that the barrier has grown at an average rate of 0.27 m/yr with successive ridge formation every ~110 years. The oldest ridge on the barrier appears to correspond to cessation of rapid post-glacial sea-level rise, and the large foredune at the seaward margin of the barrier is <400 years old. The contrast between the existing radiocarbon chronology and the OSL ages reported in this study implies the need for a more cautious interpretation of coastal barrier chronologies, in Australia and around the world, where they have been based on radiocarbon dating of shell hash.

Studies on preparation and luminescent character of Er3+/Zn2+-(SBA-15) composite materials

In this study, SBA-15 surface was modified with silane reagent. Then, the EDTA was grafted on the surface of the modification SBA-15. The Zn2+/Er3+ was grafted on the surface of the SBA-15 porous, and Er3+/Zn2+-(SBA-15) composite materials were prepared. The organic ligands EDTA enhanced the energy-transfer efficiency from the triplet level of ligands to the 4f electrons of Er3+ ion, and enhanced the luminescence intensity of the Er3+ ion. At the same time, Zn composite material has strong absorption to ultraviolet light, which has superior furtherance action to rare earth ion luminescence. The temperature quenching effect of Er3+ could be suppressed when it was introduced into porous of SBA-15. These factors provided the prepared materials with much higher relative luminescent intensities. The prepared Er3+/Zn2+-(SBA-15) composite materials showed the excellent luminescent characteristics.

Self‐Catalytic Growth of β‐Ga2O3 Nanostructures by Chemical Vapor Deposition

In this work, we have studied the synthesis of single crystalline self‐catalyzed beta gallium oxide (β‐Ga2O3) nanostructures by chemical vapor deposition technique. We have adopted a new approach to grow the nanostructures instead of using conventional foreign metal nano‐catalyst based‐approaches. The as‐grown nanostructures including nanowires and nanosheets (NSHs) were grown on spin‐coated Ga2O3 films. The structural studies such as X‐ray diffraction, Raman and transmission electron microscope (TEM) investigations on the nanostructures showed monoclinic phase of Ga2O3 and single crystalline structure. Furthermore, high‐resolution TEM with a selected area electron diffraction pattern recorded on a single β‐Ga2O3 nanowire and nanosheet verified their single crystalline nature, having [001] as favorable growth direction. The energy dispersive X‐ray spectroscopy‐elemental mapping of as‐grown nanostructures indicated uniform distribution of Ga and O. Cathodoluminescence imaging and spectrum revealed excellent luminescence characteristics of nanostructures with a broad UV‐blue emission band (1.80–4.20 eV nm) centered at 2.64 eV. This study also highlights the growth mechanism of NSHs. These β‐Ga2O3 nanostructures have great potential in nanofunctional devices.

The Synthesis and Morphology Control of High after-Grow Intensity SrAl<sub>2</sub>O<sub>4</sub>: Eu, Dy Phosphors

High after-grow intensity with controllable morphology SrAl2O4: Eu, Dy phosphors were synthesized by an innovative combustion-melted-salt-assistant-Sol-Gel (CMSASG) method, by using Oxides, Carbonate, Nitric acid, Polyethylene glycols and Urea as raw materials, Gel-forming at 100°C, Combustion under 450°C, Melted-salt-calcination at 1250°C. The luminescent intensity and after-grow intensity of the SrAl2O4: Eu, Dy phosphors with the suitable pair-dope synthesized by CMSASG method are higher than those of commercial samples. The size of the phosphor with excellent luminescent characteristics and shape of sphericity or near sphericity synthesized can be controlled from about 200 nm to 10 μm.

Layer-structured phase-segregation of red-emitting quantum dots from green-emitting small molecule-embedded polymer film

Recently a great deal of research on colloidal nanocrystals, so-called quantum dots (QDs), has shown their importance as a wavelength converter for solid-state lighting devices, due to the nanometer-sized particles' lack of optical scattering, excellent luminescence characteristics, and solution-based synthesis process. More specifically, it is also confirmed that layer by layer assembled QDs with a sequential stacking of green emitter on top of red emitter is highly desirable for efficient white-light generation when it comes to a wavelength converter for blue light-emitting diodes (LEDs). For example, S. Nizamoglu et al. reported that by stacking cyan/yellow/red nanocrystals-embedded polymer films on top of LEDs as a remote-type wavelength converter, re-absorption between the nanocrystals is reduced. In order to form a layer structured QDs-embedding film, the selfsegregation of luminophore guests in one host polymer is expected to be more desirable than physically contacting two luminophore layers, since there is no polymer-air-polymer inter-boundaries, and consequently, less light scattering and reflection. It is successfully demonstrated by V. Bulovic’s group that they could control the phase-segregation of a QDs upper layer from a QDs/polymer composite by using solvent evaporation during spin-coating, and they suggested application of this method be focused on an electroluminescence device. However, up until now there is no report on the formation of a self-segregated QDs upper-layer with a luminescent molecule-embedded polymer bottom layer, although it could be considered as an optimum structure for a film-type wavelength converter. Here, we report that by engineering the surface free energy of QDs and host film mixed with organic dye, an amorphous polymer film can be layer-type phase-segregated by thermal annealing, as shown in Scheme I. It is confirmed that the increase of concentration of the small molecule occurs in the bottom layer. Eventually, a double layer with green and red emission in separated layers is formed and the photoluminescence (PL) intensity of the film is increased after annealing. To our knowledge, this is the first report showing that a green and red wavelength-converting film can be fabricated with this desirable layer structure by a simple self-segregation method. Analysis was mainly focused on characterizing the structural and PL evolution of the film.

Microstructure and luminescent properties of Ce:Lu2SiO5 ceramic scintillator by spark plasma sintering

Spark plasma sintering (SPS) processing was employed to fabricate cerium (Ce3+) ions doped lutetium silicate (Lu2SiO5) translucent scintillation ceramics. Polycrystalline Ce:Lu2SiO5 ceramic bulks were densified from as-prepared powder by spark plasma sintering at 1350°C for 5min under pressure of 50MPa. Translucent monolithic Ce:Lu2SiO5 ceramic specimen was obtained with excellent luminescent characteristics after being annealed in air at 1000°C for 15h. Under 360nm UV excitation, a broad emission peak centered at about 425nm was detected for Ce:Lu2SiO5 ceramic. The luminescence intensity of annealed ceramic sample (doped by 0.5mol% Ce3+) was 3 times greater than that of BGO single crystal under X-ray excitation. The decay constant under γ-ray excitation of Cs-137 radioactive source was measured to 44.36ns. The good luminescent characteristics made Ce:Lu2SiO5 polycrystalline ceramics a promising scintillator candidate with high performance for radiation detection in future.

Enhancement of luminescent intensity of calixarene-oxetane polymer doped with europium complex

Calixarene molecules are originally known as inclusion compounds in host-guest chemistry, which can bind various metal ions and organic molecules. We investigated the binding property of calixarene polymer against trivalent europium (Eu3+) complex which possesses excellent luminescent characteristics. An interaction, i.e. coordination structure, is established between calixarene polymer and Eu3+ complex, which results in an effective suppression of concentration quenching of Eu3+ complex and enhancement of luminescent intensity in high concentration.

Influence of Sintering Temperature on Photoluminescence of Gd2O3:Eu3+ Phosphors Prepared by Liquid Phase Reaction Method

Nanostructured materials with diameters less than 100 nm have been studied vigorously in recent years. Many studies have been devoted on exceptional optical properties induced by quantum confinement for fundamental research and applications. For excellent luminescence characteristics, phosphor particles have to acquire fine size, narrow size distribution, non-aggregation, good crystalline, and spherical morphology. A liquid-phase reaction method was chosen in this study due to the low reaction temperature. Gd2O3:Eu3+ phosphors were synthesized by the liquid-phase reaction method and the effect of activation temperature on optical properties of the phosphors was investigated.

Preparation and photoluminescence characteristics of Tb-, Sm- and Dy-doped Y 2O 3 nanofibers by electrospinning

An electrospinning–calcination strategy was established to fabricate Y 2O 3 nanofibers doped with rare earth ions (Tb, Sm and Dy) using electrospun PVA/RE(NO 3) x /Y(NO 3) 3 composite nanofibers as precursors ( x=3.4). The prepared nanofibers were characterized by XRD, FESEM, EDS, (HR)TEM and PL analyses. Based on the experimental results, a solid–solid growth mechanism (SS) was proposed to describe the formation of inorganic crystalline fibers from organic/inorganic composite nanofibers by calcination. It was determined that carbonaceous nanoparticles that were formed in the process of pre-carbonization adsorbed Y 2O 3:RE nanoparticles to grow Y 2O 3:RE crystal, and the resultant nanofibers exhibited a typical crystalline domain with grain boundary. The obtained Y 2O 3:RE nanofibers possessed excellent luminescent characteristics and could be used as an appreciable luminescent material.

Fabrication and Luminescent Properties of Translucent Ce<sup>3+</sup>:Lu<sub>2</sub>SiO<sub>5</sub> Ceramics by Spark Plasma Sintering

The spark plasma sintering (SPS) technique was employed to investigate the fabrication of cerium-doped lutetium orthosilicate (Ce:Lu2SiO5, LSO) polycrystalline scintillation ceramics starting from nanosized Ce:LSO powders synthesized by sol-gel processing. Fully-densed polycrystalline Ce:LSO ceramics with fine grains were fabricated on optimal sintering conditions of 1350°C for 5 min under pressure of 50 MPa. Translucent monolithic Ce:LSO ceramic sample was obtained with excellent luminescent characteristics after being annealed in air at 1000°C for 15 hrs. Under 360 nm UV excitation, a broad emission peak centered at 425 nm was detected for Ce:LSO ceramic, with a short decay time of only 9.67 ns. The luminescence intensity of annealed sample(doped by 0.5mol% Ce3+) is 3 times greater than that of BGO crystal under X-ray excitation. The good luminescent characteristics make Ce:LSO polycrystalline ceramics a promising scintillator candidate with high performance for radiation detection in future.

High Mobility and Luminescent Efficiency in Organic Single‐Crystal Light‐Emitting Transistors

AbstractA high‐performance ambipolar light‐emitting transistor (LET) that has high hole and electron mobilities and excellent luminescence characteristics is described. By using this device, a conspicuous light‐confined edge emission and current‐density‐dependent spectral evolution are observed. These findings will result in broader utilization of device potential and they provide a promising route for realizing electrically driven organic lasers.

Synthesis and modification of red oxide phosphors for low voltage excitation

New red oxide phosphors Y2O3:Eu3+,Si4+ and (Y,Gd)2O3:Eu3+,Si4+,Bi3+ are synthesized by a coprecipitation method. Relative cathodoluminescence (CL) brightness at low voltages (⩽1 kV) is analyzed. At the low voltage excitation, luminance of the synthesized phosphors is higher than that of other commercially available red phosphors Y2O2S:Eu3+ and Y2O3:Eu3+. In particular, the difference of relative brightness between the commercially available phosphors and the synthesized Y2O3:Eu3+,Si4+ is larger at low voltages (⩽500 V) than at higher voltages. The synthesized (Y,Gd)2O3:Eu3+,Si4+,Bi3+ phosphor gives the same level of brightness as that of Y2O3:Eu3+,Si4+ at voltages greater than 500 V. (Y,Gd)2O3:Eu3+,Si4+,Bi3+ is coated with a conductive material SnO2:Eu3+. The coating of SnO2:Eu3+ shows a considerable improvement in brightness without a color shift. The excellent luminescence characteristics of (Y,Gd)2O3:Eu3+,Si4+,Bi3+ coated with SnO2:Eu3+, studied using field emitter arrays, suggests that our synthesized phosphor is practically applicable to field emission display devices.

Synthesis and luminescent properties of a EuIIIcomplex with a macrocyclic ligand incorporating 2,2′-bipyridyl-1,1′-dioxide units

A novel ligand incorporating two 2,2′-bipyridyl-1,1′-dioxide units forms a very stable EuIII complex, which exhibits very excellent luminescent characteristics in water solution.