Orange-red Luminescence Research Articles

A cyano-bridged Cu(i)-based organic framework coupled with the C-C bond cleavage of acetonitrile for selective and sensitive sensing of Fe3+ ions.

A cyano-bridged Cu(i) organic framework based on [Cu6(CN)6]n was synthesized, in which cyano anions were generated in situ from the C-C bond cleavage of acetonitrile. The as-synthesized compound displays orange-red luminescence and is further proven to be a promising Fe3+ luminescent sensor with high selectivity and sensitivity.

Bright luminescence of diamonds with Ge-V centers

We report on the quantum yield (η) and decay time (τ) measurements at room temperature for the bright red-orange (602nm) luminescence from new germanium-vacancy (Ge-V) centers in nano- and microcrystalline diamonds synthesized at high pressure and high temperature. The values η = 3 ± 1% and τ = 6.2±0.2ns were found. The Stokes shift measured as the energy difference between the maxima of the luminescence and luminescence excitation spectra is negligible. The relative intensity of the zero-phonon line constitutes up to 70% of the total intensity of the luminescence. Results of our ab initio DFT calculations for the ground-state electronic and vibrational structure of (Ge-V)- in diamond are presented and discussed.

Optimization of photoluminescence of GdAl3(BO3)4:Sm3+ phosphors for solid state lighting devices

The GdAl3(BO3)4:Sm3+ phosphors prepared by solid-state reaction method were characterized through thermal, structural and photoluminescence studies at room temperature only. The observed X-ray diffraction peaks were well consistent with JCPDS No. 83-1907. When excited with 406 nm wavelength, the studied phosphors exhibit orange-red luminescence through 4G5/2 → 6H5/2, 4G5/2 → 6H7/2 and 4G5/2 → 6H9/2 transitions. The concentration of Sm3+ ions was optimized to be 0.01 mol% for intense luminescence in GdAl3(BO3)4:Sm3+ phosphors. Beyond 0.01 mol% of Sm3+ ions concentration, luminescence quenching was observed due to energy transfer among the excited Sm3+ ions through cross-relaxation and dipole-dipole interaction mechanisms. The GdAl3(BO3)4:0.01 mol% Sm3+ phosphor was identified as a notable host material to emit intense orange-red luminescence for various solid state lighting devices under 406 nm excitation.

Structure and luminescence properties of Eu3+-doped trigonal double-perovskite Ba2Lu0.667WO6

Eu3+-doped tungstate Ba2Lu0.667WO6 was synthesized by the sol-gel method. The X-ray diffraction (XRD) patterns and structural refinement indicate that the matrix Ba2Lu0.667WO6 is trigonal double-perovskite structure. The phosphors were characterized by the scanning electron microscope (SEM), diffuse reflection, photoluminescence spectra and decay curves. It was found that the undoped host shows blue emission. The optimal doping concentration of Ba2Lu0.667WO6:Eu3+ is about 12 mol%. This phosphor can be efficiently excited by near-ultraviolet and blue light to realize the stronger orange-red luminescence. The phosphor presents the dominated 5D0→7F1 transition at a low doping level, and the 5D0→7F2 transition increases its intensity in the Eu3+-heavily doped samples. The host has the ability to converse UV light to blue, orange-red color. The thermal stability of the red-emission was investigated. The high activation energy of Ba2Lu0.667WO6:Eu3+ phosphor is very valuable for the application in W-LED devices. The different luminescence features were discussed on the base of the crystal structure.

Synthesis, structure, luminescence, and color features of the Eu- and Cu-doped calcium apatite

Europium-substituted copper-doped calcium hydroxyapatites with common chemical composition Ca10-xEux(PO4)6O2H2–x–y–δCuy (x = 0.23–0.42; y = 0–0.27) were synthesized via solid state reaction. Obtained materials were analyzed by powder XRD, UV–Vis, Raman, luminescence spectroscopy, and colorimetry. Crystal structure characterization (including unit cell parameters, atomic positions, and position occupancies) was provided using the Rietveld refinement method in the P63/m space group. It was established that europium ions occupied the Ca(2) position only and the copper ions were located at the (0,0,0) position inside the hexagonal channel. Europium-substituted copper-doped apatites exhibit light pink color in comparison with the bright red-violet europium-free copper-doped calcium hydroxyapatite. Adversely to the europium-free samples europium-substituted, samples show the visible orange-red luminescence. Versatile analysis of the obtained materials showed that they are promising to be used as the low-toxic inorganic pigments with additional luminescent properties.

Application of the Metal-Organic Framework [Eu(BTC)] as a Luminescent Marker for Gunshot Residues: A Synthesis, Characterization, and Toxicity Study.

The 3D metal-organic framework (MOF) [Eu(BTC)] (where BTC = trimesic acid) was synthesized in 20 min by a microwave-assisted hydrothermal method with a yield of 89%. A structural and spectroscopic study, performed by X-ray diffraction, thermogravimetry, and photoluminescence spectroscopy, showed that this framework has high crystallinity, thermal stability, and luminescence. This MOF had a red-orange luminescence when excited with ultraviolet (UV) radiation (λ = 254 nm) and a high potential for use as a luminescent marker for gunshot residues (GSR). When added to 9 mm nontoxic ammunition, it greatly improved quality of the crime scene investigation, allowing for direct visualization of the luminescent GSR on the shooter's hand and firearm and at the firing range using only a portable UV lamp. The marked luminescent GSR was easily collected and characterized by nondestructive techniques, including with a Video Spectral Comparator and scanning electron microscopy/energy-dispersive spectroscopy, wherein the presence of Eu3+ ions was confirmed. Furthermore, the oral acute toxicity of this MOF was assessed in adult female Wistar rats using the Organisation for Economic Cooperation and Development 423 guidelines. This study classified the MOF [Eu(BTC)] in a less toxic Globally Harmonized System category (category 5), with a LD50 (lethal dose) of 5000 mg/kg, ensuring a wide security range for its application.

Orange-red luminescence in KAl1−xPO4F:Eux3+ (0.1 ≤ x ≤ 1.0) halophosphate phosphor by a novel facile combustion method

Red-emitting phosphor KAl1-xPO4F:Eux3+ (0.1≤x≤1.0) were fabricated by combustion process at temperature 750°C. The XRD patterns did not indicate presence of the starting constituents and other likely phases which are an indirect evidence for the formation of the desired compound. The photoluminescence study shows that the intensity of electric dipole transition (5D0→7F2) at 613nm dominates over that of magnetic dipole transition (5D0→7F1) at 595nm. The FTIR also shows peaks appearing at 585.41–827.92cm−1 and 912.99–1074.12cm−1 correspond to the bending vibrations (v4 region) and stretching vibrations (v3 region) of PO43− group, respectively. The chromaticity coordinate of KAlPO4F:Eu3+ phosphor (x=0.674, y=0.325) is much closer to National Television Standard Committee (NTSC) standard value for red phosphor (x=0.670, y=0.330). All the spectrum features indicate that KAlPO4F:Eu3+ might be a promising phosphor for lighting or w-LEDs.

Synthesis of luminescent KY3F10 nanopowder multi-doped with lanthanide ions by a co-precipitation method

A series of KY3F10 nanophosphors doped with Gd3+, Ce3+ and Eu3+ ions were obtained with the use of a co-precipitation method. The resulting products were white precipitates, consisting of spherical particles with diameter about 150–200 nm, which was confirmed using transmission electron microscopy (TEM) technique. Powder X-ray diffraction (XRD) and energy dispersive X-ray analysis (EDX) measurements confirmed appropriate structures of the nanoparticles obtained. Spectroscopic properties of the products were examined on the basis of the measured excitation/emission spectra and luminescence decay curves. The synthesized samples showed orange-red luminescence, characteristic for Eu3+ ions. The reaction process was performed in required alkaline pH adjusted with the use of ethylenediaminetetraacetic acid (EDTA) and potassium hydroxide. The samples containing large amounts of Gd3+ dopant ions exhibited a tendency to form products with different morphologies.

Hybrid salts of binuclear Bi(III) halide complexes with 1,2-bis(pyridinium)ethane cation: Synthesis, structure and luminescent behavior

Reactions between 1,2-bis(pyridinium)ethane bromide ((BPE)Br2) and [BiCl6]3−/[BiBr6]3− in HCl or HBr results in isostructural binuclear complexes (BPE)2[Bi2X10] (X=Cl (1) and Br (2)) which were characterized by X-ray diffractometry, IR and Raman spectroscopy. Both complexes manifest orange-red luminescence in solid state.

Synthesis and photoluminescence properties of a novel reddish orange-emitting Sm3+-doped strontium borosilicate phosphor

Sr3−2xSmxNaxB2SiO8 phosphors were synthesized by the solid-state reactions. X-ray diffraction, diffuse reflection, photoluminescence excitation and emission, as well as fluorescence decay measurements were utilized to investigate the structural and spectral properties of the samples. The results indicated that Sr3−2xSmxNaxB2SiO8 phosphors could be efficiently excited by the near-ultraviolet light to realize a novel reddish orange luminescence corresponding to the characteristic transitions 4G5/2→6HJ (J = 5/2, 7/2, 9/2, 11/2) of Sm3+ ions, with a maximum intensity at 600 nm. Based on the theoretical calculation, the dipole–dipole interaction was dominantly involved concentration quenching of Sm3+ in the phosphors, and the critical transfer distance (Rc) was determined to be 13.59 Å. Furthermore, Judd-Ofelt analysis was applied to evaluate three phenomenological Judd-Ofelt intensity parameters (Ωλ, λ = 2, 4, 6), and in turn radiative properties such as radiative transition probabilities (AR), radiative lifetimes (τR) and fluorescence branching ratios (βR) for the excited 4G5/2 luminescent level of Sm3+ ions were determined. Upon 402 nm excitation, the composition-optimized Sr2.90Sm0.05Na0.05B2SiO8 exhibited the preferable photoluminescence intensity and CIE coordinates of (0.534, 0.448). These results suggest that the Sm3+-doped Sr3B2SiO8 phosphors are competitive as the reddish orange-emitting phosphor-converted materials for application in near-ultraviolet-pumped LEDs.

Effect of GeO2 content on structural and spectroscopic properties of antimony glasses doped with Sm3+ ions

Antimony-based glasses with different germanium oxide content doped with Sm3+ ions have been developed. On the basis of decomposition of absorption bands (FTIR) in the mid infrared region, was determined that antimony and germanium ions are the glass-forming ions, setting up the lattice of fabricated glasses. The effect of GeO2/Sb2O3 ratio in fabricated glass doped with samarium ions on thermal, structural and luminescent properties was also investigated. Characteristic bright reddish-orange luminescence from the 4G5/2 state to the lower lying levels 6HJ with J = 5/2, 7/2, 9/2 and 11/2 with maximum intensity at the wavelength of 603 nm originating from 4G5/2 → 6H7/2 transition was observed. The asymmetry nature of molecular structure around samarium ion have been determined from intensity ratio between 4G5/2 → 6H9/2 (ED) and 4G5/2 → 6H5/2 (MD) transitions. An introduction of GeO2 to the antimony glass results in the increasing of 4G5/2 lifetime and decreasing of the orange-to-red intensity ratio, which is are related to reduction of non-briding oxygens.

Photoluminescence properties of a novel red phosphor Sr3Ga2O5Cl2:Eu3+

Eu3+-doped Sr3Ga2O5Cl2 phosphors were synthesized successfully via a two-step solid-state reaction method. Phase purity and morphology of the phosphor were confirmed by XRD and SEM techniques. In the excitation spectra of Sr3Ga2O5Cl2:Eu3+ phosphor, the broad excitation band centering at 310 nm is due to the combination of charge transfer from Eu3+→O2− and host absorption. And it matches well the emission wavelength from UV LEDs. Sr3Ga2O5Cl2:Eu3+ phosphors show a bright orange–red luminescence under excitation with 301 nm. However, concentration quenching of Eu3+ in Sr3Ga2O5Cl2:Eu3+ occurs at a low content of 0.07 in this work. The quenching mechanism of Sr3Ga2O5Cl2:Eu3+ was discussed in detail on the basis of the experimental results.

Effect of host structure on the photoluminescence properties of Ln3TaO7:Eu3+ red phosphors

Eu3+ doped Ln3TaO7 (Ln=La, Gd, Y, Lu) red phosphors were prepared using a solid state route. The Ln3+ substitution induces variation of crystalline structure from a defect fluorite to weberite types with increased ordering of the cations from Lu to La. These phosphors show strong absorptions at near UV wavelength and emit orange–red luminescence. The increased trend in luminescence lifetime further surmises uniform distribution of Eu3+ ions from Lu to La. The luminescence intensity and quantum efficiency are closely related to the degree of ordering of the cations in the lattice. The Eu3+ luminescence in La3TaO7 embodies the structural variation through intense multiband 5D0→7F0,1,2,4 transitions to only dominant hypersensitive electric dipole 5D0→7F2 transition. All the Eu3+ emission transitions (5D0→7F0,1,2,4) are more intense in La3TaO7 host due to increased polarizability and covalent nature of Eu3+ bonding environment with the surrounding.

Spectroscopic properties of K4SrSi3O9 doped with Sm3+

Sm3+ doped K4SrSi3O9 red phosphor, was synthesized for the first time by the conventional solid state method. The X-ray powder diffraction confirmed that obtained phosphor was single phase. Excitation and emission spectra and decay curves were measured to characterize the luminescent properties of the obtained material. K4SrSi3O9:Sm3+ exhibits red–orange luminescence originating mainly from equally intense 4G5/2→6H7/2 (with its maximum at 598.5nm) and 4G5/2→6H9/2 (at 651nm) transitions. The luminescence is quenched in the samples doped above 2% of Sm3+ due to non-radiative energy transfer between Sm ions at different sites. The interaction between Sm3+ ions is dipole–quadrupole type and the critical radius for energy transfer was calculated from Inokuti-Hirayama model to be 15.0Å and 14.2Å for 300K and 77K respectively.

Warm White Light Emitting Diodes with Gelatin-Coated AgInS2/ZnS Core/Shell Quantum Dots.

Cadmium-free and water-soluble AgInS2/ZnS core/shell quantum dots (QDs) with a cost of 2.5 $/g are synthesized in an electric pressure cooker. The QD powders with different Ag/In ratios exhibit bright yellow, orange, and orange-red luminescence under UV light. Their absolute photoluminescence quantum yields (PLQYs) can reach as high as 50.5, 57, and 52%, respectively. Because gelatin is used as the capping agent, the concentrated QDs/gelatin solution can be directly utilized as phosphor for the fabrication of white light-emitting diodes (LEDs) by a simple drop-drying process without the need of resin package. Warm-white LEDs are obtained by combining orange-emitting QDs with blue InGaN chip. As-fabricated warm-white LED exhibits a luminous efficacy of 39.85 lm/W, a correlated color temperature (CCT) of 2634 K and a color rendering index (CRI) of 71 at a drive current of 20 mA. Furthermore, the electroluminescence (EL) stability of LED device and thermal stability of as-prepared QDs are evaluated.

Iridium(III) complexes based on 5-nitro-2-(2′,4′-difluorophenyl)pyridyl: Syntheses, structures and photoluminescence properties

A series of cyclometalated Ir(III) complexes [Ir(dFNppy)2(PPh3)L] (PPh3=triphenylphosphine, L=Cl−, 1; NCS−, 2; NCO−, 3; N3−, 4) in which 5-nitro-2-(2′,4′-difluorophenyl)pyridyl (dFNppy) is used as the main ligand are synthesized and characterized. The crystal structures of 3 and 4 are determined by X-ray diffraction analyses. Photoluminescence spectra of 1–4 in CH2Cl2 solutions at room temperature show the maximum emission wavelengths (λmax) in the range from 586 to 627nm, corresponding to red-orange luminescence. HOMO–LUMO energy levels of 1–4 are estimated by cyclic voltammetry measurements. Compared with corresponding 2-phenylpyridyl (ppy)-containing Ir(III) complexes having same ancillary ligands, 1–4 have obviously smaller HOMO–LUMO energy gaps (Eg). Simultaneously, 1–4 show relatively bigger Eg compared with 2-phenyl-5-nitropyridyl (5-NO2-ppy)-containing Ir(III) complexes possessing same ancillary ligands. Methods of Eg adjustment are also discussed.

Optical properties of ion-doped ZnO(Se) layers in the context of band anticrossing theory

The study of the optical properties of ZnO(Se) is a continuation of previous studies of ZnS(O), ZnSe(O), and CdS(O) systems in the context of band anticrossing theory. Selenium ions are implanted into high-purity zinc oxide crystals to a concentration of 1020 cm–3. The microcathodoluminescence spectra recorded with a scanning electron microscope at a temperature of 100 K provide information from the bulk of the implanted layer. The origin of the orange-red luminescence of ZnO(Se)–Zn layers is clarified. Orangered luminescence is thought to be a result of the formation of a highly mismatched alloy system, in which ZnSe(O) is formed during implantation and radiation annealing. Data suggesting that the green luminescence of pure self-activated ZnO–Zn is the self-activated (SA) emission studied in detail for other II–VI compounds (ZnS(O), ZnSe(O)) and defined by intrinsic defect complexes (A centers) are reported.

Structure and Luminescence Characteristics of Eu3+‐Activated Trigonal Layered Perovskite Ba2La2ZnW2O12

Eu3+‐doped tungstate Ba2La2ZnW2O12 phosphors with perovskite‐structure were prepared by the high temperature solid‐state reaction. The X‐ray powder diffraction (XRD) patterns and structure refinements indicate that the phosphors crystalized in the trigonal layer‐perovskite. The luminescence properties of the phosphors were investigated such as photoluminescence (PL) excitation and emission spectra, decay lifetimes, and color coordinates. It was found that the pure host shows self‐activated emission excited by the UV light. Moreover, Ba2La2ZnW2O12 also shows scintillation characteristics under the X‐ray irradiation. The near‐UV and blue light can efficiently excite Eu3+‐doped Ba2La2ZnW2O12 phosphors inducing the strong orange–red luminescence. The optimal Eu3+ doping concentration in this host is 40 mol%. The luminescence spectra and the luminescence color of the phosphors strongly depend on the doping levels and excitation wavelength. The different luminescence features were discussed on the base of crystal structure. Eu3+ ions have two possible substitutions on A or B sites in this trigonal layered perovskite. The phosphor could act as a candidate for the potential application in near‐UV excited white‐LEDs lighting.

Synthesis and luminescence properties of highly uniform SiO2@LaPO4:Eu3+ core–shell phosphors

Abstract SiO 2 @LaPO 4 :Eu 3+ core–shell phosphors have been successfully synthesized by a one-step and economical wet-chemical route at low temperature. The as-obtained products were characterized by means of photoluminescence spectroscopy (PL), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED), scanning electron microscopy (SEM), X-ray diffraction (XRD), energy-dispersive spectrometer (EDS) and X-ray photoelectron spectroscopy (XPS). The SEM, EDS and XPS analysis indicate that SiO 2 @LaPO 4 :Eu 3+ core–shell phosphors can only be synthesized in a pH range of 8–11 and the possible mechanism has been proposed. The XRD results demonstrate that the structure of LaPO 4 :Eu 3+ layers is transferred into monoclinic phase from hexagonal phase after annealing at 800 °C for 2 h. The SiO 2 @LaPO 4 :Eu 3+ phosphors show strong orange–red luminescence under ultraviolet excitation. The relative emission intensity of Eu 3+ increases with increasing the annealing temperature and the number of coating cycles, and the optimum concentration for Eu 3+ was determined to be 5 mol% of La 3+ in SiO 2 @LaPO 4 phosphors.

Photoluminescence characteristics of Sm3+ doped Sr2P2O7 as new orange-red emitting phosphor

A series of Sr2P2O7: Sm3+ phosphors and Sr2P2O7: Sm3+ doped with different charge compensator (co-doping Li+, Na+, K+) phosphors were prepared by the high temperature solid-state reaction process at 1100 °C in air. The phase structure, photoluminescence properties and thermal stability were of the as prepared powders were investigated. Sr2-xP2O7: xSm3+ phosphors can be efficiently emitted an orange-red luminescence under ultraviolet and blue light irradiation due to 4G5/2-6H7/2 transition of Sm3+. The emission spectrum with three emission peaks is located at 562, 600 and 641 nm. The emission intensity can be enhanced by introducing the charge compensator R+ (R = Li, Na, K) into Sr2P2O7: Sm3+ phosphors. The results indicate that Sr2-xP2O7: xSm3+ is a promising orange red-emitting phosphor that can be used in the LED's and other optical devices in the visible region.