ZnS:Mn摩擦发光特性的研究

本文报道了ZnS:Mn具有良好摩擦发光性能。研究了ZnS:Mn发光中心Mn^2 及其含量以及样品的灼烧温度、灼烧时间等条件对样品发光特性的影响。优化浓度配比和制备条件制备出了较高摩抢擦发光效率的ZnS:Mn摩擦发光材料。摩擦发光机理可能是由于机械能使ZnS:Mn的电子从基态激发到激发态所致,而具有较高的摩擦发光效率可能来源于ZnS:Mn具有较宽的激发能量范围。     

Effects of ZnS:Mn concentrated vinyl ester matrices under flexural loading on the triboluminescent yield

This paper investigates the feasibility of using zinc sulfide manganese (ZnS:Mn) concentrated vinyl ester resin as a photon emitter for damage monitoring of polymer composites under flexural loading. Unreinforced vinyl ester resins doped with optical emitting materials (ZnS:Mn phosphors) in ratios of 5–50% by weight were cast, and subjected to flexural loading using standard 3-point bend tests. The intent of this work was to observe the transient response of triboluminescence (TL) throughout the failure cycle. Results indicate TL crystals emit light at various intensities corresponding to crystal concentration and imminent matrix fracture. Consequently, concentrated samples showed nearly 50% reductions of mechanical moduli. Scanning electron microscopy (SEM) revealed particulate inclusions with shearing bands and semblance of particle to resin adhesion. Despite significant parasitic effect to mechanical properties, the triboluminescent properties occur at yielding and point of matrix fracture.     

Syntheses and electroluminescent properties of two europium ternary complexes Eu(DBM)3(PBO) and Eu(DBM)3(PBT)

Two europium complexes, Eu(DBM)₃(PBO) and Eu(DBM)₃(PBT) (DBM=dibenzoylmethanato, PBO=2-(2-pyridyl)benzoxazole, PBT=2-(2-pyridyl)benzothiazole), were prepared and used as emitting materials in organic electroluminescent (EL) devices. The devices with the structures ITO/TPD/Eu(DBM)₃(PBO) (or Eu(DBM)₃(PBT)/BCP/Alq₃/Mg:Ag/Ag emit red light originating from the europium complexes.     

Rationally Designed Fluorescent pH Sensors for Measurements in Extremely Alkaline Media

We investigated the pK_a increasing effects on meso-phenol BODIPY to achieve fluorescent pH sensors working in extreme alkalinity. We demonstrated the effects of substituents on meso, α, γ and position of the hydroxyl group on pK_a. By considering these parameters, we developed pH sensors working above 11.0 in aqueous medium (ethanol/water 1:1). One of these sensors had a pK_a of 12.0 and enabled the measurement of pH up to 13.6. This highly photostable and bright sensor compound could be synthesized easily from cheap starting materials.     

Decay dynamics of Eu/Tb in solution-processed Y2O3

As new synthesis techniques are developed to create phosphors with smaller particles the physical processes that govern luminescence behaviors, like efficiency and decay rates, are influenced by the large surface-to-volume ratios of the nano-structured materials. Decay of lanthanide excited states, following pulsed laser excitation, is used to probe the affect of size-induced decay channels on the luminescent properties. We report results on the decay dynamics of europium and terbium excited states in solution-produced yttrium oxide. Radiative decay from the Eu³⁺⁵D₀ state is found to be well described by a single exponential function over a range of concentrations (0.01-2.0%). The Tb³⁺⁵D₄ decay exhibits a distribution of decay rates over the concentration range 0.01-5.0%. The distribution of decay rates is discussed using a probability density function based on the Kohlrausch decay function.     

Progress in triboluminescence-based smart optical sensor system

Extensive research work has been done in recent times to apply the triboluminescence (TL) phenomenon for damage detection in engineering structures. Of particular note are the various attempts to apply it in the detection of impact damages in composites and aerospace structures. This is because TL-based sensor systems have a great potential for wireless, in-situ and distributed (WID) structural health monitoring when fully developed. This review article highlights development and the current state-of-the-art in the application of TL-based sensor systems. The underlying mechanisms believed to be responsible for triboluminescence, particularly in zinc sulfide manganese, a highly triboluminescent material, are discussed. The challenges militating against the full exploitation and field application of TL sensor systems are also identified. Finally, viable solutions and approaches to address these challenges are enumerated.     

The kinetics of the triboluminescence of zinc sulphide I

The paper proposes a two-stage model of the time dependence of triboluminescence as a function of the magnitude of the applied exciting pressure; it is confirmed by the results of measuring the time dependence of triboluminescence. The decay of triboluminescence excited by a blow and by friction is measured. The spectral dependence of triboluminescence in ZnS-Mn was found. It has the same form as in photoluminescence and in addition contains maxima corresponding to the electric discharge in air.     

Structural stability and conductivity of cubic (WO3)x - (Dy2O3)y-(Bi2O3)1−x−y

Isovalent rare earth oxide cubic stabilized bismuth oxides undergo an order-disorder transition of the oxygen sublattice ∼600 °C. Annealing below this temperature leads to a decay in conductivity due to ordering. We recently discovered a high conductivity Bi₂O₃ electrolyte doped with both Dy₂O₃ and WO₃ (DyWSB). The dopants were selected based on their polarizability and its effect on both structural stability and conductivity. Electrical conductivity results of the stabilized bismuth oxide system as function of temperature and time are presented. By manipulating the composition ratio of the dopants, the structural stability was enhanced resulting in a more stable conductivity.     

Selective processing of semiconductor nanowires by polarized visible radiation

Semiconductor nanowires have attracted intense interest due to potential applications in electronics, sensors and photonics. Introduction of dopants and their subsequent activation are essential for exploiting the electronic properties of semiconductor materials. In this work, we demonstrate pulsed laser annealing of silicon nanowires by visible radiation to be an efficient way for activating incorporated dopants and repairing implantation damage in a process that is compatible with sensitive flexible substrates. In situ electrical monitoring was used to study the laser annealing process. The absorption of laser light in SiNWs was shown to be strongly dependent on the light polarization and nanowire diameter based on finite difference time domain simulations. PACS 42.62.-b; 64.70.Nd; 78.67.n; 81.16.c     

Features of the doping effect on YAlO3 phase sequences during synthesis from an amorphous precursor state

Using X-ray diffraction methods, it has been shown that small lanthanum (La) dopants during solid-phase synthesis of YAlO₃ from an amorphous precursor state initiate the formation of the high-temperature hexagonal modification of yttrium aluminate in the first crystallization stages, whereas the equilibrium perovskite phase has an orthorhombic cell. At the same time, during YAlO₃ synthesis without dopants, yttrium-aluminum garnet Y₃Al₅O₁₂ is formed in the first crystallization stages, rather than the perovskite modification, as it follows from the precursor stoichiometry. The effect of lanthanum dopants on YAlO₃ phase sequences during synthesis from the amorphous precursor state is qualitatively explained.     

Spontaneous luminescence of Eu<Superscript>3+</Superscript> ions in porous Y<Subscript>2</Subscript>O<Subscript>3</Subscript> nanospheres

A study of the luminescence of Eu³⁺ ions in Y₂O₃ nanospheres indicates a significant influence of the porous structure of nanoparticles on the luminescence of dopant ions. It is shown that filling the nanopores of initially porous Y₂O₃ nanospheres shortens the decay time of the spontaneous luminescence of doping europium ions. The change in the decay time is associated with the change in the effective refractive index of the porous nanospheres.     

Luminescence decay kinetics of Eu<Superscript>3+</Superscript> ions in phosphate glasses of different composition under photo- and electron excitations

The influence of matrix composition, coactivators, and excitation method on the luminescence kinetics of Eu³⁺ ions in lithium–phosphate and lithium–phosphate–borate glasses activated by Eu, Eu/Tb, and Eu/Dy is studied. Luminescence is excited by a high current electron beam and a xenon lamp. It is found that, under photoexcitation, the europium luminescence decays more slowly than under electronic excitation. Depending on the content of cation modifiers ZnO and Li₂O, the decay time decreases with increasing amount of ZnO. The decay time weakly depends on the europium concentration. The decay of the luminescence of europium ions is well described by the Inokuti–Hirayama model.     

Photoluminescence analysis of α-Al2O3 powders doped with Eu and Eu ions

Alumina (Al₂O₃) powders doped with europium trivalent (Eu³⁺) were prepared by a low-temperature (∼280 °C) combustion synthesis technique. When the powder was heat treated at 1200 °C for 2 h in the presence of flowing ammonia (NH₃), α-Al₂O₃ crystalline ceramic powders was obtained. The analysis of the luminescence showed that Eu³⁺ was reduced to europium divalent (Eu²⁺) after the heat-treatment process. Under ultraviolet (UV) lamp excitation (λ=254 nm) these powders containing sub-microcrystalline structures present bright red (Al₂O₃:Eu³⁺) and green (Al₂O₃:Eu²⁺) luminescence indicating that this material is a potential candidate for applications in phosphor technology.     

Preparation of photoluminescent PMMA doped with tris(pyrazol-1-yl)borate lanthanide complexes

The neutral homoleptic Ln(III) complex Ln(Tp)₃ (Ln=Sm, Eu, Tb, Yb; Tp=hydrotris(pyrazol-1-yl)borate) were used as dopants for the preparation of novel photoluminescent poly(methyl methacrylate) glasses indicated as Ln(Tp)₃@PMMA. The doped polymers containing samarium, europium and terbium derivatives showed emission associated to f–f transitions in the visible range upon excitation with UV light, while a NIR emission was obtained from Yb(Tp)₃@PMMA. The maximum incident wavelength able to induce emissions from the Ln(Tp)₃-doped polymers depends upon the choice of the lanthanide ion. No meaningful antenna-effect was instead observed using dysprosium as metal centre.     

Eu2+掺杂硼硅酸镁玻璃的发光性能

利用高温固相法合成了Eu2+掺杂的新型蓝色硼硅酸盐发光玻璃,讨论了不同掺杂浓度下硼硅酸镁玻璃体系中Eu-O键共价性的变化以及氧原子周围不同配位环境对MgO-SiO2-B2O3玻璃发光性能的影响.利用X射线衍射仪和荧光光谱仪对该玻璃体系进行了结构表征和性能测试.在紫外-可见光激发下,Eu2+掺杂硼硅酸镁玻璃的荧光发射光谱...     

Incorporation of AsSe centers in ZnSe far from equilibrium

An experimental technique employing nuclear transmutation to probe the effects of arsenic doping in ZnSe is presented. ZnSe epitaxial layers are grown from elemental Zn and elemental Se that contains the ⁷⁵Se isotope. Arsenic dopants are incorporated in ZnSe through the decay of ⁷⁵Se to ⁷⁵As which proceeds via electron capture. The 118.5 day half-life of the decay allows ZnSe epitaxial layers to be deposited prior to significant arsenic formation so that As_Se dopants are incorporated after all crystal growth processes are complete. Also, the temperature at the time of dopant incorporation is under investigator control. Because the decay process produces nuclear recoils that are far too small to displace the arsenic dopants from their substitutional selenium sites, no post-growth thermal annealing is required. This experimental technique permits a limiting case of far-from-equilibrium doping, and the long half-life of ⁷⁵Se results in the gradual incorporation of As_Se so that time-resolved studies can be performed. In the experimental work reported here, As_Se centers are introduced in ZnSe homoepitaxial layers in concentrations greater than 1.5×10¹⁸ cm⁻³. Time-resolved low temperature photoluminescence is employed to observe the effects of As_Se doping of ZnSe.     

Photoluminescence properties of Li6CaB3O8.5: M3+ (M3+: Dy and Sm)

Li₆CaB₃O_8.5: M³⁺ (M³⁺: Dy and Sm) phosphors were synthesized by a solution combustion synthesis. The synthesized materials were characterized by using the powder XRD. The emission and excitation spectra of these materials were measured at room temperature with a spectrofluorometer. Both Li₆CaB₃O_8.5: Dy³⁺ and Li₆CaB₃O_8.5: Sm³⁺ phosphors emit red, yellow and green light. Consequently, these materials are promising phosphors for white LEDs.     

Crystal Structure,Luminescence and Triboluminescence of the Complex [Eu(NO<Subscript>3</Subscript>)<Subscript>2</Subscript>3hmpa] NO<Subscript>3</Subscript>·HQuin

The atomic structure of crystals of the complex [Eu(NO₃)₂3hmpa] NO₃·HQuin , (hmpa – hexamethylphosphortriamide, HQuin – quinaldic acid) characterized by intensive luminescence and triboluminescence has been determined by the X-ray method. The noncentro-symmetric crystals of the compound are rhombic : a = 16.8193(3), b = 12.2877(2), c = 27.6516(5) Å, пр. гр. Pca2(1), Z = 4, ρ _{calc. .} = 1.427 g/сm³. The crystals have a structure of the insular type which is presented by the isolated complex molecules, outer-sphere NO₃ ^? – groups, and neutral molecules of quinaldic acid. Some structural aspects of formation of the luminescent and triboluminescent properties of the compound were discussed: the role of break planes in the crystal destruction was revealed.     

Luminescent europium(III) and terbium(III) nicotinate complexes covalently linked to a 1,10-phenanthroline functionalised sol-gel glass

Sol-gel glasses with covalently linked lanthanide complexes are luminescent materials which can be processed at ambient temperatures, which have a good solubility and uniform distribution of the complexes in the host matrix. In this study, a luminescent terbium(III) complex was covalently coupled to an organic-inorganic hybrid material prepared by the sol-gel process. This was realised by use of nicotinate groups as the ligands for the terbium(III) ion. The [Tb(C₅H₄NCO₂)₃(phen)(H₂O)₂] complex was immobilised on the sol-gel glass matrix and showed a green photoluminescence upon irradiation with ultraviolet light. The nicotinate groups act as an antenna to absorb the incident light and channel the excitation energy to the terbium(III) ion. The sol-gel glass was also prepared for the corresponding europium(III) complex. In this case, excitation of the europium(III) ion was possible via both the nicotinate ligands and the 1,10-phenanthroline ligands. High-resolution luminescence and excitation spectra were recorded and the radiative lifetimes were measured.     

(CaO · Al2O3 · SiO2): Eu phosphors for violet/ultraviolet-to-white radiation conversion

(2CaO · 0.5Al₂O₃ · 5SiO₂): Eu and (CaO · 0.2Al₂O₃ · SiO₂): Eu phosphors doped with B₂O₃ in an amount of 3 wt % are obtained by direct solid-phase synthesis at 1350°C. When excited by LED radiation with a maximum at 380 nm, these phosphors emit white light with color coordinates, which are close to those in the EBU and NTSC TV standards and fall into the field of white light corresponding to light warning systems according to the International Commission on Illumination (CIE).