A green-emitting α-substituted β-diketonate Tb3+ phosphor for ultraviolet LED-based solid-state lighting

The α-substituted β-diketonate [Ln(3Cl-acac)₃(H₂O)₂] [Ln = Tb, Gd] complexes (with 3Cl-acac^– being 3-chloro-2,4-pentanedionate) were characterized by elemental analysis, infrared, ultraviolet (UV)-visible and photoluminescence spectroscopies. For comparison purposes regarding photoluminescence, the well-known [Tb(acac)₃(H₂O)₂] complex was also synthesized. By considering the phosphorescence spectra of [Gd(3Cl-acac)₃(H₂O)₂], the effect of chloride replacement of hydrogen on the triplet state energy of the 3Cl-acac ligand was revealed. To support the interpretation and rationalization of the experimental results, Time-dependent DFT calculations were performed on Tb(3Cl-acac)₃(H₂O)₂. Additionally, the possibility of Tb(3Cl-acac)₃(H₂O)₂ to be used as potential green-emitting phosphor material for solid-sate light emitting diodes was evaluated. A prototype was successfully fabricated coating a near-UV LED (370 nm) with the Tb(3Cl-acac)₃(H₂O)₂ complex.     

新型可溶性酞菁的合成和光致发光及电致发光性质

以3(4)-硝基邻苯二腈和对甲氧基苯酚为原料, 经过两步反应合成了α(β)-四(4-甲氧基苯氧基)酞菁锌, 通过谱学方法和元素分析表征了其结构. 比较研究其溶液和旋涂膜的紫外可见光谱、光致发光光谱和固体薄片的光致发光光谱. 并以其旋涂膜为发光层制备了电致发光器件, 研究其电致发光性质. 结果表明, 固态酞菁材料与其溶液的荧光发射波长相比均向长波方向移动了145 nm以上, 而且都有不同程度的宽展. 在固态下β-位取代酞菁荧光发射波长红移的程度比α-位取代酞菁大. 电致发光光谱的发射波长和其旋涂膜的光致发光光谱的发射波长基本一致, 大约在856和862 nm左右. 在固态下酞菁分子排列紧密, 分子间相互作用增强导致了荧光发射波长的巨大红移.     

Insights into photoluminescence property and photocatalytic activity of cubic and rhombohedral ZnIn2S4

Cubic and rhombohedral ZnIn₂S₄ were synthesized by thermal sulfidation of Zn-In mixed oxide precursor in H₂S atmosphere at different temperatures. Cubic ZnIn₂S₄ was obtained when Zn-In mixed oxide precursor was sulfurized at 400 °C. With sulfidation temperature increasing from 400 to 800 °C, the crystal phase of ZnIn₂S₄ gradually turned from cubic to rhombohedral, which was demonstrated by different analysis techniques such as XRD, Raman, SEM, etc. UV-vis absorption spectra indicated that cubic ZnIn₂S₄ displayed better light absorption property than rhombohedral ZnIn₂S₄, with band gaps calculated to be 2.0 and 2.5 eV, respectively. However, under visible light irradiation, rhombohedral ZnIn₂S₄ photocatalyzed H₂ evolution from aqueous sodium sulfite/sulfide solution efficiently, whereas cubic ZnIn₂S₄ was not active for this reaction. The photoluminescence property revealed the different dynamics of photogenerated carriers, which made a predominant contribution to the increasing photocatalytic performances of ZnIn₂S₄ with crystal phase turning from cubic to rhombohedral.     

Water-based Synthesis and Properties of a Scandium 1,4-Naphthalenedicarboxylate

A new scandium naphthalenedicarboxylate with the framework composition [Sc₂(1,4-NDC)₃] (H₂-1,4-NDC = 1,4-naphthalenedicarboxylic acid) was obtained under hydrothermal synthesis conditions. A structure model could be developed by a combination of 3D electron diffraction measurements and computationally assisted structure determination, which was further validated by a good agreement with the experimental powder X-ray diffraction pattern. The structure consists of isolated ScO₆ octahedra interconnected by the carboxylate groups of linker molecules to form chains. These chains are connected by the naphthalene-moieties to form a three-dimensional framework with square-shaped pores and the organic group pointing into the pores. Although very similar synthesis conditions were chosen, [Sc₂(1,4-NDC)₃] is not isostructural to aluminum naphthalenedicarboxylate [Al(OH)(1,4-NDC)], which crystallizes in a MIL-53 type structure. This can be traced back to the different inorganic building units that are observed. The compound was thoroughly characterized by elemental analysis, IR spectroscopy, sorption measurements, thermogravimetric analysis and luminescence measurements. [Sc₂(1,4-NDC)₃] exhibits a high thermal stability and a ligand-based blue luminescence in the solid state at room temperature.     

Solvo-thermal Preparation and Characterization of Two CdII Coordination Polymers Constructed From 2,6-(1,2,4-Triazole-4-yl)pyridine and 5-R-Isophthalic Acid (R = Nitro,Sulfo)

Under the solvo-thermal conditions, two novel Cd^II mixed-ligand coordination materials with 2,6-(1,2,4-triazole-4-yl)pyridine(L₁) and aromatic poly-carboxylic acid co-ligands such as 5-R-isophthalic acid (R = nitro, sulfo), namely [Cd(L₁)(NO₂-BDC)(H₂O)₂] · 2H₂O ( 1 ) and [Cd(L₁)(HSIP)(H₂O)] · 4H₂O ( 2 ) (NO₂-H₂BDC = 5-nitroisophthalic acid, H₃SIP = 5-sulfobenzene -isophthalic acid) were successfully prepared. These Cd^II mixed-ligand coordination polymers 1 – 2 have been measured by crystal X-ray analysis, FT-IR spectra and powder X-ray diffraction analyses. In 1 , these seven-coordinate Cd^II atoms (Cd1) are inter-linked by didentate 5-nitroisophthalic acid ligands forming 1D chain structures. In 2 , these L₁ and partially de-pronated HSIP^2– are inter-linked by central Cd^II centers and are arranged into the unique 2D micro-porous metal-organic framework of 2 . Side view of 2 , it is noted that numerous oxygen atoms of un-coordinated carboxylate groups and coordinated SO₃ groups protrude out and decorate the 2D framework of 2 . PXRD patterns of 1 and 2 sample is tested, which is consistent with the simulated PXRD diffraction pattern. Photoluminescence studies show that 2 is highly selective and sensitive to trace elements of Eu³⁺ with excellent K_sv value (7.86 × 10⁴ m ^–1) and low detection limit (5.56 × 10^–2 mM), which also provides a convenient method and platform for real-time detection of Eu³⁺.     

非晶碳氧化硅纳米线的合成与光致发光

利用直流电弧放电合成非晶碳氧化硅(SiCO)纳米线,不使用催化剂和模板,独立的SiCO 纳米线沉积在石墨锅的表面．通过XRD、SEM、TEM、XPS、FTIR等对SiCO纳米线进行了表征．结果表明,纳米线长度为20～100 μm,直径为10～100 nm,Si原子同C原子和氧原子分享成键组成SiCO单元．SiCO纳米线的光致发光谱在454和540 nm呈现了强而稳定的白色发光峰． SiCO纳米线的生长机制为等离子辅助气―固生长机制．     

A novel red-emitting phosphor Ca9Bi(PO4)7:Eu3+ for near ultraviolet white light-emitting diodes

Red phosphors Ca₉Bi_1-x(PO₄)₇:xEu³⁺ (x = 0.06, 0.10, 0.20, 0.30, 0.40, 0.50, 0.60, 0.70, 0.80 and 1.00) were synthesized by a conventional solid-state reaction (SSR) route. The X-ray diffraction patterns, photoluminescence spectra, ultraviolet–visible reflection spectroscopy, decay time and the International Commission on Illumination (CIE) chromaticity coordinates of these compounds were characterized and analyzed. The Eu-doped Ca₉Bi(PO₄)₇ phosphors exhibited strong red luminescence which peaks located at 615 nm due to the ⁵D₀→⁷F₂ electric dipole transition of Eu³⁺ ions after excitation at 393 nm. Ultraviolet–visible spectra indicated that the band-gap of Ca₉Bi_0.30(PO₄)₇:0.70Eu³⁺ is larger than that of Ca₉Bi(PO₄)₇. The results indicate that the phosphor Ca₉Bi_0.30(PO₄)₇:0.70Eu³⁺ can be a suitable red-emitting phosphor candidate for LEDs.     

Influence of substrate activation process on structural and optical properties of ZnS thin films

ZnS thin films were deposited on glass substrates by a chemical bath deposition method using a substrate activation process in which aluminum ions become “contaminants” that act as a nucleation center for active components within the deposition solution. The structure and morphology results demonstrate that the films have a ZnS sphalerite crystal structure with a particle size less than 15 nm, and the films consist of small homogeneous grains. The effects of the substrate activation process on the band gap energies and donor-acceptor pair luminescence process were also investigated. A green emission centered at 502 nm was produced due to donor-acceptor transitions from the aluminum acceptor to the ionized and substitution aluminum centers (Al³⁺).     

Optical and luminescence properties of Dy3+ ions in phosphate based glasses

Phosphate glasses with compositions of 44P₂O₅ + 17K₂O + 9Al₂O₃ + (30 − x)CaF₂ + xDy₂O₃ (x = 0.05, 0.1, 0.5, 1.0, 2.0, 3.0 and 4.0 mol %) were prepared and characterized by X-ray diffraction (XRD), differential thermal analysis (DTA), Fourier transform infrared (FTIR), optical absorption, emission and decay measurements. The observed absorption bands were analyzed by using the free-ion Hamiltonian (H_FI) model. The Judd–Ofelt (JO) analysis has been performed and the intensity parameters (Ω_λ, λ = 2, 4, 6) were evaluated in order to predict the radiative properties of the excited states. From the emission spectra, the effective band widths (Δλ_eff), stimulated emission cross-sections (σ(λ_p)), yellow to blue (Y/B) intensity ratios and chromaticity color coordinates (x, y) have been determined. The fluorescence decays from the ⁴F_9/2 level of Dy³⁺ ions were measured by monitoring the intense ⁴F_9/2 → ⁶H_15/2 transition (486 nm). The experimental lifetimes (τ_exp) are found to decrease with the increase of Dy³⁺ ions concentration due to the quenching process. The decay curves are perfectly single exponential at lower concentrations and gradually changes to non-exponential for higher concentrations. The non-exponential decay curves are well fitted to the Inokuti–Hirayama (IH) model for S = 6, which indicates that the energy transfer between the donor and acceptor is of dipole–dipole type. The systematic analysis of revealed that the energy transfer mechanism strongly depends on Dy³⁺ ions concentration and the host glass composition.     

Synthesis, characterization, and OLED application of oligo(p-phenylene ethynylene)s with polyhedral oligomeric silsesquioxanes (POSS) as pendant groups

Two new classes of mono- and oligo(p-phenylene ethynylene)s grafted with polyhedral oligomeric silsesquioxanes (POSS) were synthesized via ‘click’ chemistry and palladium-catalyzed Sonogashira cross-coupling. These materials with cubic silsesquioxanes are very robust with excellent thermal stability in air (T_5%loss>330 °C) and exhibited T_g>80 °C. All the compounds showed high photoluminescence with a range of blue emission and quantum yield up to 80% in the solution. Extended π conjugation molecules of oligo-pPEs POSS maintain relatively high PL quantum efficiencies in the solid state, compared to mono-pPEs POSS. A preliminary report is made of some of the materials as multilayer OLED components with active dopants PVK and PBD.