Yellow-orange Luminescence Research Articles

Amber Light Emitting Samarium Incorporated Barium Cerate Perovskite with 100% Color Purity for Pharmaceutical Industry.

Numerous structural and conductive properties of barium cerate (BC) make this material a promising candidate for energy storage applications. In this work, we demonstrated that BC can be proficiently functionalized by incorporating trivalent samarium ions to give rise to optical properties. Single-phased BaCeO3:Sm3+ (BCS) phosphors were synthesized by gel combustion technique followed by calcination. The crystal structure, optical properties, and prospective applications in LEDs were investigated systematically. By linking the information acquired from the diffuse reflectance spectra with that of the PL spectra, we better understood the electronic level structure and energy transfer mechanism. Fine yellow-orange luminescence with 100% color purity (CP) and lower Correlated Color Temperature (CCT) has been achieved via energization at 348nm wavelength. The x = 0.02 Sm3+ has been identified as the optimized content for the luminescence with a quantum efficiency of 34.2%. Obtained yellow-orange coordinates (0.564, 0.435) are proximate to commercialized L3 rank amber LED (Nichia corporation). The present results signify that UV light can suitably energize the BCS phosphor to get monochromatic amber light which can be used to guard medications during manufacture and storage.

Development of Three-Layered Composite Color Converters for White LEDs Based on the Epitaxial Structures of YAG:Ce, TbAG:Ce and LuAG:Ce Garnets

This work was dedicated to the development of novel types of composite phosphor converters of white LED, based on the epitaxial structures containing Y3Al5O12:Ce (YAG:Ce) and Tb3Al5O12:Ce (TbAG:Ce) single crystalline films, steeply grown, using the liquid-phase epitaxy method, onto LuAG:Ce single crystal substrates. The influence of Ce3+ concentration in the LuAG:Ce substrate, as well as the thickness of the subsequent YAG:Ce and TbAG:Ce films, on the luminescence and photoconversion properties of the three-layered composite converters were investigated. Compared to its traditional YAG:Ce counterpart, the developed composite converter demonstrates broadened emission bands, due to the compensation of the cyan-green dip by the additional LuAG:Ce substrate luminescence, along with yellow-orange luminescence from the YAG:Ce and TbAG:Ce films. Such a combination of emission bands from various crystalline garnet compounds allows the production of a wide emission spectrum of WLEDs. In turn, the variation in the thickness and activator concentration in each part of the composite converter allows the production of almost any shade from green to orange emission on the chromaticity diagram.

Syntheses, crystal structures, DFT calculation and solid-state spectroscopic properties of new zincate(II) complexes with N-(4-substituted phenyl)-N'-(4-nitrophenyl)-oxamate

The electronic effects electron donating and withdrawing groups R on the properties of N-(4-R-phenyl)-N'-(4-nitrophenyl)oxamito zincate(II) complexes was investigated featuring R = Me (a), H (b), F (c), Cl (d) and Br (e). The N-(4-R-phenyl)-N'-(4-nitrophenyl)oxamide ligands 2 were synthesized by reacting ethyl 4-nitrooxanilate with the respective 4-substituted anilines. Subsequent treatment with [nBu4N]OH and [Zn(OAc)2(H2O)2] gave the respective zincate complexes [nBu4N]2[Zn(N-(4-nitrophenyl)-N'-(4-substituted phenyl)oxamides)2] (3). Spectroscopic methods were used to describe compounds 2a–e and 3a–e. Single crystal X-ray diffraction analysis confirmed the formation of 3a–c in the solid state. The tetrahedral coordination sphere of the zinc (II) ion features four amide nitrogen donor atoms based on two ethanediamide ligands. The UV–Vis spectra of Complexes 3a–e display a characteristic LLCT (π → π *) band, which was confirmed by TD-DFT calculations. DFT calculations show that the Zn(II) orbitals do not contribute to the HOMO or LUMO, with the latter being primarily found on the two 4-nitrophenyl rings for compounds 3a − e, while the HOMO-1 and HOMO are located on the 4-substituted phenyl rings. Notably, HOMO and LUMO energies and gabs do not differ significantly. Transitions from HOMO to LUMO + 1 are the most important for all ligands. The luminescence properties of solid compounds 3a − e were also investigated at 298 K. Solid state photoluminescence studies reveal that these complexes emit strong yellow-orange luminescence at 450–600 nm with a maximum at about ∼ 500 nm in the cyan region. Furthermore, the thermal stabilities of compounds 3a − e have been investigated.

Surface defect-rich ZnO nanostructures with high yellow-orange luminescence

ZnO nanostructures such as nanoislands, nanosheets, microflowers and nanoparticles were obtained successfully using a facile and rapid solution route employing low temperatures and reduced molar concentrations from precursor without using any surfactant agent or additional procedures. In this route, we use ZnCl2 as precursor ranging from 0.05 to 0.4 M and two hydrothermal times (2 and 4 h) to obtain different ZnO morphologies. According to SEM micrographs, the morphology of ZnO nanostructures showed a strong dependence on the ZnCl2 concentration and hydrothermal synthesis time. ZnO microflowers were obtained at 0.05 M during 2 h, while ZnO nanoislands, nanoparticles and nanosheets were observed at 0.05, 0.2 and 0.4 M, respectively, in 4 h. X-Ray diffraction and Raman results showed the wurtzite-type ZnO structure and good crystallinity in all cases. In addition, both techniques confirmed the best crystalline quality in ZnO nanoparticles followed by ZnO nanosheets. Finally, according to photoluminescence measurements, all samples exhibit a high yellow-orange emission, associated to a large number of surface defect states, such as oxygen and zinc interstitials. The largest amount of zinc interstitials and zinc vacancies were observed in ZnO nanoislands, while ZnO microflowers have the highest visible emission (followed by ZnO nanoparticles) which in turn, offered the lowest excitonic recombination from the conduction band to the valence band, which may result in a higher photocatalytic efficiency.

Design of Novel Highly Efficient Yellow-Orange Color-Tunable Luminescence in Rb2Sr1-yCayP2O7:xEu2+ Solid Solutions for White Light-Emitting Diodes.

Traditional white light-emitting diodes (WLEDs) are limited by the energy loss due to reabsorption. Integrating binary complementary color phosphors with near-ultraviolet (n-UV) LED chips can be a good solution, and the core of it is to develop yellow-emitting phosphors. In this work, we have designed Rb2Sr1-yCayP2O7:xEu2+ solid solutions with yellow-orange color-tunable luminescence. The crystal structure, luminescence properties, and potential applications for WLEDs were explored systematically. Under n-UV light excitation, the phosphors efficiently emit broadband yellow-orange emission. The reasons and mechanisms of the variation of the PL/PLE spectra have been investigated. The optimal Rb2SrP2O7:0.5% Eu2+ sample exhibits a high quantum efficiency of 72.96% with a good color purity of 87.1%. Upon combination of the BAM:Eu2+ and Rb2SrP2O7:0.5% Eu2+ phosphors with a 380 nm n-UV chip, a WLED device is fabricated and can emit white light with good performance.

Enhanced optical properties of Cd–Mg-co-doped ZnO nanoparticles induced by low crystal structure distortion

The growth of CdxMg0.125-xZn0.875O nanoparticles with yellow-orange luminescence is achieved up to 2.5 at. % Cd via a modified sol–gel process. X-ray diffraction analysis confirmed that all the nanoparticles have the hexagonal wurtzite structure. It is found that Cd doping has a considerable effect on the crystal size, microstrain, band gap, and photoluminescence of the Mg0·125Zn0·875O structure, originating from a preferred crystallographic orientation along the (101) plane of the wurtzite structure. The shift and broadening of the E2(high) mode observed in the Raman spectra due to growth-induced strain corroborates the small distortion observed in the X-ray diffraction data. The optical band gap varies from 3.21 eV to 2.74 eV, being redshifted with increasing Cd concentration (from 0 at. % to 2.5 at. %). The photoluminescence obtained with an excitation wavelength of 325 nm has a broad yellow-orange emission peak at around 640 nm due to transitions related to oxygen vacancies and interstitial oxygen atoms. We located the yellow-orange emission in the chromaticity coordinate diagram in the 2683–2777 K colour temperature region, demonstrating that CdxMg0.125-xZnO0.875 nanoparticles have potential applications in white light-emitting diodes.

Unravelling the Origin of the Yellow-Orange Luminescence in Natural and Synthetic Scapolites.

After decades of speculation without material proof, the yellow-orange luminescence of scapolite is definitely assigned to (S2)- activators trapped in [Na4] square cages. Synthetic sulfur-doped scapolites confirm the implication of sulfur species in luminescence. Formally, the emission and excitation spectra of various polysulfide species were calculated. The excellent match between theory and experiments for (S2)- dimers provides definitive proof that it is the cause of the yellow-orange luminescence in scapolite.

Cathodoluminescence Analysis of Nonmetallic Inclusions in Steel Deoxidized and Desulfurized by Rare-Earth Metals (La, Ce, Nd)

The injection of misch metal, which primarily consists of La, Ce, and Nd, into molten steel can reduce the size of nonmetallic inclusions, suppress the formation of harmful nonmetallic inclusions, and reduce the content of oxygen and sulfur in steel. To investigate the impact of misch metal on these effects, we propose a method for identifying inclusions in steel that has been deoxidized and desulfurized by misch metal using cathodoluminescence (CL) analysis within 1 minute. Based on the CL images and spectra of model steel samples that were deoxidized and desulfurized by La, Ce, or Nd metal, we demonstrate that La2O3, La2O2S, CeO2, Ce2O2S, Nd2O3, and Nd2O2S inclusions can be identified by the emitted luminescence color using cameras with sensitivity ranges of 420 to 680 and 350 to 1000 nm. La2O3, La2O2S, CeO2, Ce2O2S, Nd2O3, and Nd2O2S inclusions emitted blue-green, yellow-orange, yellow-orange, violet, blue-violet, and red luminescence, respectively when observed by a camera with a sensitivity range of 420 to 680 nm. CeO2 and Nd2O3 inclusions emitted red-orange and red-violet luminescence, respectively when observed by a camera with a sensitivity range of 350 to 1000 nm.

The Influence of the Bismuth Concentration and Heat Treatment on the Properties of Bismuth-Containing High-Silica Glass: II. Luminescence Properties

The luminescence properties of bismuth-containing high-silica glass obtained after impregnating matrices of porous glass in nitrate solutions of bismuth nitrate pentahydrate for 24–48 h followed by heat treatment in the range from 400 to 890°C are studied. It is found that the concentration of Bi(NO3)3 in the impregnating solution affects the content of bismuth in the synthesized samples stronger than the duration of the impregnation and the temperature of the heat treatment. It is established that all the samples studied in this work have blue-green luminescence (λem = 420–520 nm at λexc = 300 nm) caused by the presence of Bi3+ ions. When the concentration of bismuth in the samples is increased a long-wavelength shift of the luminescence band maximum is observed. When the heat treatment temperature is increased a shortwave shift is observed. A yellow-orange luminescence with the maximum in the λem range of 576–582 nm (λexc = 480 nm) caused by the presence of Bi2+ ions is observed for the samples with a high bismuth content (1.17–1.18 wt % of Bi2O3) heat-treated in air at ~700 and 750°C.

Organic solvents-soluble zinc(II) and cadmium(II) complexes based on 2-aryl substituted-8-hydroxyquinoline: Synthesis, crystal structures, photoluminescence, thermal and theoretical studies

Two novel C-2 position modified 8-hydroxyquinoline ligands, (E)-2-[(4-tert-butylphenyl)ethenyl]-8-hydroxyquinoline (L1) and (E)-2-[(2-chloro-3,4-dimethoxyphenyl)ethenyl]-8-hydroxyquinoline (L2) as well as their zinc(II) and cadmium(II) complexes, namely Zn2(L1)4, Cd3(L1)6, Zn3(L2)6 and Cd3(L2)6 were designed and synthesized. Thanks to the introduction of aromatic tert-butyl and methoxy, ligands L1 and L2 are highly soluble and complexes are having good solubility in dimethyl sulfoxide (DMSO) and chloroform. X-ray structural analysis indicate four complexes were in P21/c, P2/c, P1¯, C2/c space group, respectively, and exhibit a monoclinic crystal system except Zn3(L2)6, which hold a triclinic crystal system. Structural formulea and coordinating behavior of these complexes were also investigated by NMR, UV–Vis and fluorescence spectroscopic titrations in solution, revealing four complexes were well coordinated. Solid state photoluminescence studies reveal they emit strong yellow-orange luminescence at 568–612 nm with 5.47–11.79 ns lifetime. Thermogravimetric and theoretical electronic structure analysis indicate that four complexes appear to be promising candidates for the application as yellow luminescent materials.

Highly luminescent and free-standing, PVDF/doped ZnS nanocomposite films for flexible device applications

Zinc Sulphide doped with manganese (ZnS:Mn) and copper (ZnS:Cu) is well studied, due to its promising luminescence characteristics. Though there are numerous publications related to manganese and copper doped zinc sulphide, there are no reports on the growth of free standing and stable nanocomposite films of ZnS:Mn or ZnS:Cu with a polymer. The search for freestanding, flexible, mechanically and thermally stable films endowed with the excellent luminescent properties of doped zinc sulphide is the motivation behind the present studies. Poly(vinylidene flouride) (PVDF) is a fluoro polymer with impressive piezoelectric, ferroelectric and pyroelectric properties and at the same time highly flexible and processable. When PVDF/ doped ZnS nanocomposite film is placed in UV light, bright yellow orange luminescence is observed for the manganese doped film and blue luminescence, for the copper doped film. These nanocomposite films offer high prospects of wide range of applications in field emission displays, plasma displays and electroluminescent devices. By combining the yellow orange emission of ZnS:Mn and the blue emission of ZnS:Cu in the required optimised ratio, it is possible to develop white light emitting, freestanding, stable and flexible nanocomposite films of PVDF/doped ZnS.

Intercrossed Carbon Nanorings with Pure Surface States as Low‐Cost and Environment‐Friendly Phosphors for White‐Light‐Emitting Diodes

As an important energy-saving technique, white-light-emitting diodes (W-LEDs) have been seeking for low-cost and environment-friendly substitutes for rare-earth-based expensive phosphors or Pd(2+)/Cd(2+)-based toxic quantum dots (QDs). In this work, precursors and chemical processes were elaborately designed to synthesize intercrossed carbon nanorings (IC-CNRs) with relatively pure hydroxy surface states for the first time, which enable them to overcome the aggregation-induced quenching (AIQ) effect, and to emit stable yellow-orange luminescence in both colloidal and solid states. As a direct benefit of such scarce solid luminescence from carbon nanomaterials, W-LEDs with color coordinate at (0.28, 0.27), which is close to pure white light (0.33, 0.33), were achieved through using these low-temperature-synthesized and toxic ion-free IC-CNRs as solid phosphors on blue LED chips. This work demonstrates that the design of surface states plays a crucial role in exploring new functions of fluorescent carbon nanomaterials.

Vapor‐ and Mechanical‐Grinding‐Triggered Color and Luminescence Switches for Bis(σ‐fluorophenylacetylide) Platinum(II) Complexes

Square-planar bis(σ-fluorophenylacetylide) platinum(II) complexes [Pt(Me(3)SiC≡CbpyC≡C-SiMe(3))(C≡CC(6)H(4)F)(2)] (C≡CC(6)H(4)F-2 for 2, C≡CC(6)H(4)F-3 for 3, and C≡CC(6)H(4)F-4 for 4; Me(3)SiC≡CbpyC≡CSiMe(3)=5,5'-bis(trimethylsilylethynyl)-2,2'-bipyridine) were prepared and were characterized by spectroscopic and luminescence studies, and X-ray crystallography. The color and luminescence of crystalline complex 3 is specifically sensitive to CHCl(3) vapor to afford 140-180 nm of luminescence vapochromic redshift, which is useful for specific detection of CHCl(3) vapor. Complex 4 displays selective luminescence vapochromic properties to CH(2)Cl(2) and CHCl(3) vapors with a luminescence vapochromic shift response of ca. 150-200 nm. Interestingly, complexes 2-4 exhibit reversible, and naked-eye perceivable, mechanical stimuli-responsive color and luminescence changes. When solid species 2-4 are crushed gently or ground, the crystalline state is converted to an amorphous phase. Meanwhile, bright yellow-orange luminescence in the crystalline species is converted to dark red under UV light irradiation with 100-160 nm of mechanochromic shift response. A vapochromic or mechanochromic cycle was monitored by dynamic variations in emission spectra and X-ray diffraction (XRD) patterns. The halohydrocarbon vapor- or mechanical-grinding-triggered color and luminescence switches are most likely correlated to a shorted intermolecular Pt-Pt distance as that revealed in vapochromic species 4·0.5 CH(2)Cl(2) by X-ray crystallography, thus leading to an increased contribution from intermolecular Pt-Pt interaction as demonstrated by DTF computational studies.

Adsorption-luminescence determination of copper concentration using silica gel chemically modified with N-(1,3,4-thiadiazol-2-thiol)-N′-propylurea groups

Silica gel chemically modified with 1,3,4-thiadiazol-2-thiol groups recovered 99% of the copper(II) from solutions of pH 4–6; the adsorption equilibrium was attained in no more than 5 minutes. During irradiation with ultraviolet light, a yellow-orange luminescence (λmax = 575 nm) of surface copper complexes appeared in the phase of adsorbent cooled to 77 K; it was used as an analytical signal in the procedure for the low-temperature adsorption-luminescence determination of copper concentration. The detection limit was 0.3 μ g/0.1 g adsorbent. The calibration graph was linear up to 50 μg/0.1 g adsorbent. The determination of copper concentration is not affected by 10000-fold amounts of Zn(II), Cd(II), Mn(II), Co(II), Ca(II), Mg(II), and Al(III) and 300-fold amounts of Fe(III). The procedure was used to determine copper concentration in natural and technogenic waters.

Microwave synthesis of manganese-ion-doped zinc sulfide nano-phosphors using a novel monomer

ZnS:Mn 2+ nano-phosphors are synthesized via a microwave irradiation technique using zinc 2-ethylhexanoate as a novel zinc precursor. The developed process produces ZnS:Mn 2+ nano-particles having in situ capping of 2-ethylhexanoic acid on the surface, resulting in high luminescence intensity due to effective surface passivation. Surface characterization of the nano-particles indicates that 2-ethylhexanoic acid is chemisorbed as carboxylate onto the surface of ZnS:Mn 2+ nano-particles and the two oxygen atoms in the carboxylate are coordinated symmetrically to the Zn atoms, leading to the formation of the covalent Zn–O bond. The anion bound onto the nano-particle surface prevents particle agglomeration due to electrostatic repulsion between two adjacent particles. Electron spin resonance (ESR) spectrum showed a hyperfine sextet revealing the fact that Mn 2+ in ZnS was present as dispersed Mn 2+ impurities rather than Mn 2+ clusters, which would produce broad resonance without splitting. The samples showed bright yellow-orange luminescence at about 585 nm, characteristic of 4T 1 (excited) → 6A 1 (ground) transition of Mn 2+ ion at T d symmetry in ZnS.

Cathodoluminescence study of visible luminescence in hydrothermal ZnO crystals

We present a study of the visible luminescence in ZnO hydrothermal crystals. The study is carried out on oxygen polarity basal plane (000-1) plates that are sliced through several distinct growth sectors of the crystal. The plates reveal three distinct regions that display differences in the luminescence emission, especially in the visible range. These differences should be related to the variation in the distribution of impurities and native defects in the various growth sectors of hydrothermal ZnO. CL images also expose the presence of nonradiative recombination centers that are associated with point defects or complexes of point defects. CL measurements varying the acceleration voltage of the e-beam reveal that the deep levels responsible for the green luminescence, and in a minor extension those responsible for the yellow-orange luminescence are depleted near the surface. A discussion about the main hypothesis accounting for such behavior is presented.

Low-temperature sorption-luminescence determination of silver using silica gel chemically modified with mercaptopropyl groups

Silica gel chemically modified with mercaptopropyl groups extracts silver(I) from solutions in the acidity ranges from 4 M HNO3 to pH 8 and from 0.01 M HCl to pH 7. The time it takes to attain a sorption equilibrium is no more than 2 min; distribution coefficient is 1 × 105 cm3/g. Yellow-orange luminescence was produced in the adsorbent phase upon the UV irradiation of wet adsorbates cooled to the liquid-nitrogen temperature (77 K). This effect was used for the development of a procedure for the low-temperature sorption-luminescence determination of silver. The calibration graph was linear in the range 1–80 µg Ag per 0.1 g of adsorbent. The detection limit was 0.05 µg per 0.02 g of adsorbent. The relative standard deviation was no more than 6% for silver amounts higher than 5 µg.

Low-Temperature Adsorption–Luminescence Determination of Gold Using Silica Gel Chemically Modified with Mercapto Groups

Silica gel with mercaptopropyl groups covalently bonded to the surface extracts gold(III) from its hydrochloric solutions in a wide acidity range (from 6 M HCl to pH 8). An adsorption equilibrium is attained in no more than 5 min. The distribution ratio is 1.65 × 104–1 × 105 cm3/g. The intense yellow–orange luminescence (λmax = 575 nm) appearing in the adsorbent phase under UV irradiation of wet liquid-nitrogen cooled adsorbates (77 K) is used for the low-temperature adsorption–luminescence determination of gold. The calibration plot is linear in the range of 1–100 μg of gold per 0.1 g of adsorbent. The detection limit is 0.05 μg/0.1 g of adsorbent. The relative standard deviation for the determination of more than 10 μg of gold is no more than 5%.

ZnS:Mn nanocrystallites in SiO 2 matrix: preparation and properties

Mn 2+-doped ZnS nanoparticles embedded in a silica matrix were prepared by the sol–gel technique. Zinc sulfide nanoparticles were found to be well dispersed as single entities in the silica matrix. An electron spin resonance study indicated magnetically dilute discrete Mn 2+ levels rather than Mn clusters, even at higher doping concentration (5 mol.%), probably due to the presence of the SiO 2 matrix. Photoluminescence spectra showed characteristic yellow–orange luminescence due to the 4T 1→ 6A 1 transition of Mn. The emission energy was blue-shifted for higher doping concentrations.

Low-Temperature Sorption-Luminescence Determination of Copper in Natural Water Using Silica Gel Chemically Modified with Mercapto Groups

Silica gel with mercaptopropyl groups chemically bonded to its surface extracts copper from solutions with pH 2–9 with a recovery of 99.9%; the sorption equilibration time is no longer than 5 min. Ultraviolet irradiation of wet sorbates cooled to the liquid nitrogen temperature (77 K) generates yellow–orange luminescence (λmax = 585 nm), which was used as the analytical signal for the development of a procedure for the low-temperature sorption–luminescence determination of copper. The detection limit is 0.08 μg per 0.1 g of the sorbent. The determination of copper is unaffected by the interference from 104-fold amounts of Zn(II), Cd(II), Mn(II), Ni(II), Co(II), Ca(II), Mg(II), and Al(III); 103-fold amounts of Fe(III); 30-fold amounts of Bi(III); tenfold amounts of Ag(I); and fivefold amounts of Cr(VI). The procedure was used for the determination of copper in natural water.