Variation of crystal structure and defect luminescence in Ca3−xSrxAl2O6 phosphors

Ca_3−xSr_xAl₂O₆(x=0, 1.07, 1.88, 1.98, 3) phosphors were prepared through solid state reaction route under different atmospheres and two kinds of oxygen-defects were identified in Ca_3−xSr_xAl₂O₆ by means of X-ray photoelectron and electron spin-resonance spectra. Their defect luminescence behavior was discussed based on photoluminescence spectra as well as the calculation of bond volume polarizability of chemical bonds. Interstitials oxygen O_i is easily formed by the lattice oxygen (O1) with increasing Sr²⁺ content and air atmosphere may also provide O_i(O_i=1/2O₂). Besides, emission intensities of samples regularly changed by accommodating more O_i in air. By selecting proper excitation energy (276/355 nm), emission occurred from different O_i defect centers, with Spectral regions from 350 nm to 600 nm. Analysis suggested that the tunable emission characteristic at different excitation energies was linked with abnormal O_i, which was located in the interior of [AlO₄] six-member rings and the capacity of accommodating O_i is related to the size of six-member rings. Based on the theoretical and experimental results, a model was proposed to explain the mechanisms related to emission tunability accordingly. This research may help elucidate emission induced by an oxygen defects system.     

F−-Eu3+ charge transfer energy and local crystal environment in Eu3+ doped calcium fluoride

A series of CaF₂:xEu³⁺ (x = 0.01–0.05) phosphors were synthesized by coprecipitation and high temperature solid-state method. Three different F^--Eu³⁺ charge transfer (CT) bands in CaF₂:xEu³⁺ (x = 0.01–0.05) were detected through the PL spectra. Three local crystal environments (deformed O_h octahedron, C_3V, C_4V) were proposed in Eu³⁺ doped CaF₂. The broad peak at 277 nm is F^- → Eu³⁺ CT peak, in which Eu³⁺ ions located deformed O_h octahedron sites, the broad peak at 312 nm is due to Eu³⁺ ions situating at C_4v sites, also, Eu³⁺ ions with C_3v sites can make the F^- → Eu³⁺ CT produce a 38-nm redshift to 315 nm. Density functional theory (DFT) was performed to calculate the energy band gap(Eg) according to the three models. The calculation results consist with the experiment. The excitation peaks can be tuned in the same host through changing the local structure of Eu³⁺.     

Crystal structure and luminescence properties of green-emitting Sr1−xAl12O19:xEu2+ phosphors

In this paper, a series of novel luminescent Sr_1−xAl₁₂O₁₉:xEu²⁺ phosphors were synthesized by a high temperature solid-state reaction. The phase structure, photoluminescence (PL) properties, as well as the decay curves were investigated. The quenching concentration of Eu²⁺ in SrAl₁₂O₁₉ was about 0.15 (mol). Upon excitation at 378 nm, the composition-optimized Sr_0.85Al₁₂O₁₉:0.15Eu²⁺ exhibited strong broad-band green emission at 530 nm with the CIE chromaticity (0.2917, 0.5736). The results indicate that Sr_1−xAl₁₂O₁₉:xEu²⁺ phosphors have potential applications as green-emitting phosphors for UV-pumped white-light LEDs.     

Influence of Bi2O3 flux in the structural and photoluminescence properties of SrAl2O4:Eu2+ phosphors

SrAl₂O₄:Eu²⁺ phosphors with various content of Bi₂O₃ flux were synthesized and analyzed. It was observed that the crystallinity and the particle size of the phosphors were increased with the addition of Bi₂O₃ flux. These phenomena are considered to be caused via the melting of the Bi₂O₃ flux particles during the synthesis of the phosphors. The melted Bi₂O₃ flux increased the mobility and homogeneity of solid reactants, thereby enhancing the photoluminescence intensity of the phosphors. SrAl₂O₄:Eu²⁺ phosphors with Bi₂O₃ as the flux exhibited a broad green emission with a peak at 520 nm. The highest photoluminescence emission intensity was observed when 5 mol% Bi₂O₃ flux was added into the phosphors. The emission is due to 4f⁶5d→4f⁷ (⁸S_7/2) transitions of the Eu²⁺ ions. Moreover, Bi₂O₃ flux extended the application of the ultraviolet excited phosphors toward the blue-light excited phosphors. Nevertheless, the influence of Bi₂O₃ on the afterglow and the emission color of SrAl₂O₄:Eu²⁺ phosphors were not significant. This research indicated that Bi₂O₃ flux is effective flux for synthesizing SrAl₂O₄:Eu²⁺ phosphors.     

Study of Eu3+–Gd3+ co-doped Ba–Bi–B glasses for red-laser applications: Physical,structural, photoluminescence and time-resolved spectral characteristics

A series of Eu³⁺ and Eu³⁺/Gd³⁺ co-doped barium-bismuth-borate (Ba–Bi–B) glasses were prepared by melt-quench technique. And deliberated the physical, structural, and spectroscopic properties of all glasses and explored the energy transfer process from Gd³⁺ to Eu³⁺ ions. The density of glasses increased with increasing of Gd³⁺ concentration in co-doped glasses. Characteristics of steady-state and time-resolved photoluminescence (PL) of Eu-doped and Eu³⁺-Gd³⁺ co-doped glasses under different excitation wavelengths suggested the prospects of the investigated glass system for display device applications. PL spectrum displays a strong red emission peak centered at 612 nm due to the Eu³⁺: ⁵D₀→ ⁷F₂ transition. Less intense emissions centered at 577 nm (⁷F₀), 590 nm (⁷F₁), 651 nm (⁷F₃) and 700 nm (⁷F₄) are also observed from the radiative transitions of the excited state ⁵D₀ of Eu³⁺ions. The values of radiative parameters such as transition probability, branching ratios, and stimulated emission cross-sections were obtained from Judd–Ofelt theory analysis and indicated the aptness of the Ba–Bi–B glasses for optical devices. A 5-fold enhancement in the PL intensity was observed in 1.0 mol% Eu³⁺ and 3.0 mol% Gd³⁺ co-doped glass under λ_Exci. = 394 nm excitation. The calculated commission Internationale de l'eclairage color coordinates and correlated color temperature values show that the Ba–Bi–B glasses are useful for red-laser and display device applications.     

One novel 3D tetranuclear cadmium coordination polymer based on 2,3′,4,5′-biphenyltetracarboxylic acid: Synthesis,crystal structure and luminescence

One novel 3D cadmium coordination polymer, namely, {[Cd₂(bptc^4 −)(ox^2 −)_0.5(H₂O)₂] · 4.5H₂O}_n (1), has been hydrothermally synthesized through a reaction of 2,3′,4,5′-biphenyltetracarboxylic acid (H₄bptc) with divalent cadmium salt in the presence of a second ligand (ox = oxalic acid). X-ray single crystal structure analysis reveals that tetranuclear cadmium clusters are formed by linking two Cd1 and two Cd2 ions with carboxyl groups. Each ox^2 − ligand, with a bidentate chelating mode, connects two Cd2 ions from two adjacent tetranuclear clusters to afford 1D zigzag cadmium cluster chains. Furthermore, 1D chains are connected by bptc^4 − ligands to extend a 3D framework with one-dimensional channels along the [001] direction. From a topology view, complex 1 exhibits an unprecedented 2-nodal 4, 10-connected net with the Schläfli symbol of {4⁶}₂{4⁹. 5¹².6²².7²}. The luminescence analyses reveal that complex 1 shows an emission maximum at 437 nm, which may be attributed to the intra-ligand transition. A red shift of 31 nm compared with H₄bptc ligand was observed and the luminescent decay lifetime is 2.74 ns, which indicates that it might be a potential blue light-emitting candidate. In addition, it was also characterized by elemental, IR spectra, PXRD and TG analyses.     

Effect of M3+ (M = Bi,Al) co-doping on the luminescence enhancement of Ca2ZnSi2O7:Sm3+ orange-red−emitting phosphors

In this paper, the luminescence properties of Ca₂ZnSi₂O₇:Sm³⁺ phosphors were improved by co-doping with M³⁺ (M = Bi, Al) via the sol-combustion method. The structure and luminescence properties of the Ca₂ZnSi₂O₇:Sm³⁺, M³⁺ samples were investigated in detail, especially the luminescence enhancement effect of Bi³⁺/Al³⁺ co-doping. XRD results indicated that moderate Bi³⁺/Al³⁺ co-doping in the host structure did not change the tetragonal structure of Ca₂ZnSi₂O₇. The series of Ca₂ZnSi₂O₇:Sm³⁺, M³⁺ phosphors could be excited by 402 nm near-ultraviolet light and several significant emission peaks were obtained at 567, 604 and 650 nm, which originated from the electron transitions of Sm³⁺ from ⁴G_5/2 to ⁶H_5/2, ⁶H_7/2 and ⁶H_9/2 levels, respectively. The luminescence intensity of Ca₂ZnSi₂O₇:Sm³⁺ was markedly enhanced through Bi³⁺/Al³⁺ co-doping, which could be explained by Al³⁺ decreasing the crystal field symmetry and greatly increasing the red luminescence intensity, and Bi³⁺ functioning as a sensitizer to increasing the luminescence intensity through energy transfer from Bi³⁺ to Sm³⁺ ions. In conclusion, the excellent Ca₂ZnSi₂O₇:Sm³⁺, M³⁺ phosphors have potential application as red phosphors in white light emitting diodes.     

Red-emitting double perovskite phosphors Sr1−xCaxLaMgSbO6:Eu3+: Luminescence improvement based on composition modulation

Crystal structures of Sr_1-xCa_xLaMgSbO₆:Eu³⁺ phosphors were studied in detail. Both the SrLaMgSbO₆ and the CaLaMgSbO₆ have a monoclinic (P2₁/n) structure. With increasing the Ca²⁺ concentration, the peaks gradually divided and the phase changed from SrLaMgSbO₆ to CaLaMgSbO₆. The symmetry of La³⁺ in SrLaMgSbO₆ is lower than that in CaLaMgSbO₆. Eu³⁺ ions, as the structural probes, were selected to study the structure. Lifetimes and intensity ratio were used to study the symmetry in the structure. Thermal quenching of the phosphors was discussed from 323 K to 473 K. The emission intensities of ⁵D₁→⁷F_J and ⁵D₀→⁷F_J damped in different ratios while increasing temperature. The configurational coordinate diagram was used to explain this interesting phenomenon.     

Effect of Sr/Ca substitution on phase structure and photoluminescence properties of micro-SrxCa1−xAlSiN3: Eu2+ phosphor for high CRI white LEDs

Sr_xCa_1−xAlSiN₃: Eu²⁺ phosphors were prepared by using the high temperature solid state reaction in a 1.1 Mpa N₂ atmosphere. The phase structures, photoluminescence (PL) properties, and chromaticity properties of the phosphors affected by Sr/Ca Substitution have been investigated in detail. With increasing Sr content (x value), the crystal grain became bigger and the average grain size increased from 5 µm to 10 µm. PL emission bands of Sr_xCa_1−xAlSiN₃: Eu²⁺ showed a blue-shift from 660 (x=0) to 617 nm (x=0.8), the shoulder of the excitation spectra around 550 nm showed a slightly blue-shift and decay lifetime shortened from 776.96 (x=0.2) to 642.35 ns (x=0.8). Both the emission and excitation intensity of peak position increased with Sr content increased. The ideal white light with high CRI (Ra>88) can be obtained by mixing the Sr_xCa_1−xAlSiN₃: Eu²⁺ phosphors and commercial green phosphors with appropriate proportion of the components.     

Abnormal upconversion luminescence induced by defects and Er3+–Yb3+ distance change in Cs3GdGe3O9:Er3+/Yb3+ phosphors

A series of Er³⁺/Yb³⁺ co-doped Cs₃GdGe₃O₉ (CGG) phosphors were prepared by solid-phase sintering method, and the microstructure and upconversion luminescence (UCL) properties were tested by variable-temperature X-ray diffractometry and variable-temperature spectrometer. Abnormal UCL phenomena were found, which include UCL intensity continuously increasing under 980 nm laser continuous irradiation and UCL thermal enhancement. After 10 min of continuous irradiation by 980 nm laser at 513 K, the UCL intensity increased 2.91 times compared with the initial UCL intensity. The phenomenon is due to the electron releasing of host defects. The green UCL intensity of CGG:0.1Er³⁺/0.2Yb³⁺ decreases at 303–423 K and increases at 423–723 K, which reaches 13.23 times compared with that at 423 K. The phenomenon is due to Er³⁺–Yb³⁺ distance change by temperature and phonon-assisted transitions. In addition, the absolute temperature sensitivities of samples are calculated by luminescence intensity ratio technology, the maximum absolute sensitivity of CGG:0.1Er³⁺/0.4Yb³⁺ is 0.00691 K⁻¹ at 546 K, and the maximum relative sensitivity of CGG:0.1Er³⁺/0.1Yb³⁺ is 0.01224 K⁻¹ at 303 K. These results indicate that CGG:Er³⁺/Yb³⁺ phosphors can be used as a high-temperature optical thermometer.     

Investigation on the preparation and luminescence property of (Gd1−xDyx)2O3 (x=0.01–0.10) spherical phosphors

Uniform spheres of (Gd_1−xDy_x)₂O₃ (x=0.01–0.10) have been converted from their colloidal precursor spheres synthesized via homogeneous precipitation. The synthesis, particle size control, luminescent properties and energy transfer of the (Gd_1-xDy_x)₂O₃ were systematically studied by the combined techniques of fourier transform infrared (FT-IR) spectroscopy, x-ray diffractometry (XRD), field emission scanning electron microscopy (FE-SEM), photoluminescence excitation/ photoluminescence (PLE/PL) spectroscopy, and fluorescence decay analysis. The precursor exhibit mono-dispersed spherical morphology and its size can be efficiently controlled by adjusting the urea content. The phase pure (Gd_1−xDy_x)₂O₃ oxides can be obtained by calcining precursor at 600 °C, and the spherical morphology remained at even high temperature of 1000 °C. The (Gd_1−xDy_x)₂O₃ phosphors display strong yellow emission at 575 nm (⁴F_9/2→⁶H_13/2 transition of Dy³⁺) and weak blue emission at 486 nm (⁴F_9/2→⁶H_15/2 transition of Dy³⁺) upon ultraviolet (UV) excitation of Gd³⁺ at 275 nm (⁸S_7/2→⁶I_J transition of Gd³⁺). The optimal content of Dy³⁺ was found to be ~2 at% (x=0.02) due to the concentration quenching. Owing to the efficient Gd³⁺→Dy³⁺energy transfer, the fluorescent property of the phosphor was significantly improved. The emission intensity of (Gd_1−xDy_x)₂O₃ increased with calcination temperature and particle size increasing, while the lifetime for the 575 nm emission gradually decreased. The (Gd_1−xDy_x)₂O₃ spheres developed in the present work is expected to be a promising yellow phosphor widely used in the lighting and display areas.     

Effects of ionic polarizability and crystal structure on microwave dielectric properties of RE2O3 (RE = La,Eu) ceramics with opposite τf and high Q

Hexagonal La₂O₃ and monoclinic Eu₂O₃ ceramics were prepared, and their microwave dielectric properties were investigated. La₂O₃ sintered at 1400 °C exhibited promising microwave dielectric properties of ε_r = 18.6, Q×f = 71,400 GHz, and a negative τ_f of − 35.1 ppm/°C, while Eu₂O₃ sintered at 1500 °C possessed relative lower ε_r and Q×f values of 17.9 and 35,000 GHz, respectively, with an abnormally positive τ_f of + 19.6 ppm/°C. The difference in their microwave dielectric properties is mainly due to lattice-induced strain, which can be characterized by bond valence. To investigate the degradation of RE₂O₃ (RE = La, Eu) ceramics in air, a series of La_2−xEu_xO₃ (x = 0.5, 1, and 1.5) ceramics were prepared. The results of the present study suggest that the introduction of Eu³⁺ effectively prevents the decomposition of La₂O₃.     

Effects of Ni2+ substitution on the crystal structure,bond valence,and microwave dielectric properties of BaAl2–2xNi2xSi2O8–x ceramics

BaAl_2?2xNi_2xSi₂O_8?x (x = 0, 0.005, 0.01, 0.02, 0.03) ceramics were prepared using traditional solid phase reaction method. The microwave dielectric properties, including permittivity (ε_r), quality factor (Q × f), and temperature coefficient of resonant frequency (τ_f), were discussed based on the bond valence theory. The first-principle calculation was adopted to determine the site (Ba, Al, and Si) where doping element (Ni²⁺) would be inclined to occupy. The substitution of Ni²⁺ for Al³⁺ contributed to the breaking of Al-O and Si-O bonds and then facilitated the BaAl₂Si₂O₈ (BAS) hexacelsian-celsian transformation. Moreover, this substitution could change the bond strength between cation and oxygen anion due to the variation of the bond valence, which reasonably explained the variation of ε_r, Q × f, and τ_f values. Well-sintered and completely transformed celsian ceramics can be obtained after doping with Ni²⁺. When x = 0.01, compact BaAl_1.98Ni_0.02Si₂O_7.99 ceramic exhibited highly promising microwave dielectric properties: ε_r = 6.89, Q × f = 53, 287 GHz and τ_f = -25.31 × 10^?6 /°C.     

Effects of Sr2+/Zn2+ co-substitution on crystal structure and properties of nano-β-tricalcium phosphate

The incorporation of therapeutic ions like Sr²⁺, Si⁴⁺, Zn²⁺ and Li⁺ into biomaterials has become a promising approach to promote bone regeneration. However, the effects of Sr²⁺ and Zn²⁺ co-substitution on the crystal structure and properties of β-tricalcium phosphate (β-TCP) have not been elucidated well. In this study, Sr²⁺/Zn²⁺ co-substituted β-tricalcium phosphate (SrZnTCP) nano-powders with different extents of substitution (0–4.8 mol%) were synthesized by poly(ethylene glycol)-assisted co-precipitation and subsequent heat treatment. The as-synthesized SrZnTCP nano-powders were characterized by x-ray diffraction, Fourier transform infrared spectroscopy, elemental analysis, Rietveld refinement and differential scanning calorimetry. The results showed that the conversion of calcium-deficient apatite to β-TCP was achieved after heat-treatment above 800 °C. The a-axis and c-axis lattice parameters gradually decreased with increasing level of Sr²⁺/Zn²⁺ co-substitution in β-TCP lattice. Sr²⁺ and Zn²⁺ preferentially occupied the ninefold coordinated Ca (4) sites and the sixfold coordinated Ca (5) sites, respectively. The co-substitution of Sr²⁺ and Zn²⁺ for Ca²⁺ significantly improved the thermal stability of β-TCP. The release rate of Zn²⁺ from SrZnTCP depended on Ca²⁺ concentration over 63-day immersion in PBS solution while that of Sr²⁺ was not affected by Ca²⁺ concentration. The amount of Sr²⁺ released increased with increasing Sr²⁺ content in SrZnTCP. Collectively, SrZnTCP showed great promise as a Sr²⁺/Zn²⁺-releasing biomaterial for bone repair, although no obvious mineralization was observed on β-TCP and SrZnTCP disc samples during 56 days of immersion in simulated body fluid.     

A unique 3D Co(II)-MOF based on [Co6(μ3-OH)4]8 +n chains: Synthesis,crystal structure,and magnetic property

A novel metal-organic framework, [Co₆(μ₃-OH)₄(ndc)₄(bip)₂(H₂O)₂]_n (1)[H₂ ndc = 1,4-naphthalenedicarboxylic acid, bip = 1,5-bis(imidazole-1-yl)pentane], constructed from unique [Co₆(μ₃-OH)₄]^8 +_n chains containing alternate [Co₄(OH)₂]^6 + and [Co₂(OH)₂]^2 + subunits, was reported, which has a new (3,3,8,12)-connected or 12-connented fcu/cubic network and shows weak antiferromagnetic interaction between the adjacent Co(II) ions mediated through the carboxylate and hydroxyl groups.     

Citrate-based sol–gel synthesis and luminescent properties of Y6WO12:Eu3+, Dy3+ phosphors for solid-state lighting applications

The rare-earth ions (Eu³⁺, Dy³⁺) doped Y₆WO₁₂ phosphors were prepared by a citrate-based sol–gel method. The morphologies and structural properties of the as-prepared and doped samples were analyzed by scanning electron microscope images and X-ray diffraction patterns. The luminescent properties were studied by examining the excitation and emission spectra of the samples. The Eu³⁺ and Dy³⁺ ions doped samples exhibited their characteristic emission bands in the visible region under ultraviolet light excitation. The temperature-dependent photoluminescence (PL) properties of the samples were also investigated. The PL spectra of the synthesized samples by the sol–gel method were compared with those of the bulk sample prepared by a solid-state reaction. Similarly, the Commission International de I’Eclairage chromaticity coordinates and the decay times of Y₆WO₁₂:Eu³⁺ (3 mol%) and Y₆WO₁₂:Dy³⁺ (2 mol%) phosphors were studied.     

Fabrication and characterization of La2O3–Fe2O3–Bi2O3 nanopowders: Effects of La2O3 addition on structure,optical, and radiation-absorption properties

In this study, we fabricated and characterized six new nanopowders representing variations of La₂O₃–Fe₂O₃–Bi₂O₃, i.e., 100Bi₂O₃, 30Fe₂O₃–70Bi₂O₃, 3La₂O₃–27Fe₂O₃–70Bi₂O₃, 7La₂O₃–23Fe₂O₃–70Bi₂O₃, 10La₂O₃–20Fe₂O₃–70Bi₂O₃, and 20La₂O₃–10Fe₂O₃–70Bi₂O₃ (represented by 100B, 30F70B, 3L27F70B, 10L20F70B, and 20L10F70B, respectively). These nanopowders were prepared by the microwave-assisted hydrothermal synthesis method. Saponin extract from soapnuts was used as the nanoparticle capping agent. The structural, optical, and gamma radiation characteristics were measured, calculated, and analysed, respectively. The chemical structures of the nanocomposites influenced their optical and radiation shielding characteristics. The optical bandgaps of the 100B, 30F70B, 3L27F70B, 7L23F70B, 10L20F70B, and 20L10F70B nanopowders were 3.16, 3.13, 3.43, 3.45, 3.46, and 3.58 eV, respectively. The ranges of the mass attenuation coefficients of the nanopowders were computed, using XCOM, to be 0.0412–5.1624, 0.0401–4.5406, 0.0401–4.5285, 0.0401–4.5129, 0.0401–0.5015, and 0.0400–4.4156 cm²/g, respectively, and the ranges of mass energy absorption coefficients were found to be 0.0232–1.7525, 0.0228–1.5484, 0.0228–1.5598, 0.0288–1.5746, 0.0228–1.5853, and 0.0227–1.6192 cm²/g, respectively, for photon energies in the range of 0.1–10 MeV. The order of the dose rate trend was as follows: 30F70B < L27F70B < 7L23F70B < 10L20F70B < 20L10F70B. Analysis of the photon interaction parameters showed that the synthesized nanopowders could function well as fillers in radiation-shielding matrices.     

Synthesis,crystal structure,and anti-thermal quenching performance of Lu2Sr(1−x)Al4SiO12:xEu2+ phosphors

With high-temperature solid-state reaction method, a series of Lu₂Sr_(1−x)Al₄SiO₁₂:xEu²⁺ phosphors have been synthesized. With Rietveld refinement method, the crystal structure of Lu₂SrAl₄SiO₁₂ has been refined. Under the excitation of the ultraviolet and violet band light, Lu₂Sr_(1−x)Al₄SiO₁₂:xEu²⁺ emits the Eu²⁺ characteristic blue broadband light. The photoluminescence properties of concentration quenching, emission peak shift, reflectance spectra, and luminescence decay have been investigated. With the structure analyses, the corresponding physical mechanisms have been discussed. With the increased temperature, this phosphor shows well thermal stabilities. For the x_Eu = 0.06, 0.08, and 0.1 phosphors, the strong anti-thermal quenching performance has been observed. The reason for the anti-thermal quenching of this phosphor has been discussed. The trap capture mechanism may be the suitable physical mechanism to explain the anti-thermal quenching of this phosphor. This phosphor shows the potential applications in the white LED lighting fields.     

Phase composition,microstructure and luminescent property evolutions in “light-scattering enhanced” Al2O3-Y3Al5O12: Ce3+ ceramic phosphors

Classic transparent ceramics for laser gain medium and window materials may benefit from their distinctive features of structural homogeneity and high transparency at large scales. However, this has restricted the ability of the ceramics for local light management. Herein, a strategy for ceramic-phosphor design was conducted in the present work via introducing light-scattering centers into single phased YAG: Ce³⁺ transparent ceramics, and an enhancement of light extraction was experimentally realized through the control of Al₂O₃ grain size. UV–vis-NIR diffuse reflectance spectra further confirmed the important roles of the excrescent Al₂O₃ grains. More importantly, PL characterization shows orange-white light emission with high brightness at high temperature. The results highlight that the unique configuration enables simultaneous control of light propagation, luminous efficiency and thermal stability of luminescence, and the design strategy may create great opportunities for laser lighting and displays with high laser power density.     

A 3D cadmium coordination polymer with 2-fold interpenetration structure and helical chains based on biphenyl-4-hydroxyl-3,3′-bicarboxylic acid: Synthesis and crystal structure and properties

One cadmium coordination polymer with 2-Fold parallel Interpenetration Structure and Helical Chains based on biphenyl-4-hydroxyl-3,3′-bicarboxylic acid (H₂L) and μ-4,4′-bipyridine (bpy) {[Cd(L) (bpy)_1/2(H₂O)]₂}_n (1), has been obtained by hydrothermal synthesis and characterized by elemental analysis, powder X-ray diffraction (PXRD), IR spectra, thermal gravimetric analyses (TGA) and also by single-crystal X-ray diffraction. It crystallizes in the monoclinic, space group P2₁/c. The L^2 − anions of complex 1, as a bridging ligand, connect Cd(II) ions to form two-dimensional (Cd₂(L)₂)_n layer in which the 1D (Cd–L)_n helical chains are alternately arranged in a right- and left-handed sequence. These layers are further linked to build a three-dimensional network by the bpy ligands. In addition, the photochemical property of compound 1 has also been investigated.