The luminescence properties of pesticides. II. Non-fluorescing carbamates

The phosphorescence emission and excitation spectra of four pesticidal carbamates have been recorded. The phosphorescence decay times were determined over several half-lives. The studies were carried out in three different solvents — EPA, isopropyl alcohol, and 3-methyl pentane. The effect of solvent on the spectral properties of carbamates is discussed.     

The luminescence properties of pesticides: III. The fluorescence lifetimes of some carbamates

The fluorescence lifetimes, τ_f, of Phenmec, Metacrate, Matacil, Landrin, Sevin and Zectran have been recorded using single photon counting techniques. The τ_f values of these molecules vary by as much as two orders of magnitude but the fluorescence yields vary by at most a factor of four; thus, non-radiative processes have varying degrees of importance in the carbamates. The carbamates do not appear to follow any readily discernible Hammett relationship.     

The luminescence properties of SmD and EuTTA

The results of measuring the absorption and emission spectra, decay time and quantum yield of the luminescence of SmD and EuTTA as a function of temperature (in a 77K–300K interval) and concentration are discussed. The energy transfer from the molecule organic part to the rare earth ion and the influence of nonradiative transitions are studied.The authors express their appreciation of the careful assistance in preparing the chelates given by Miss. H. Voka'lová and Mr. J. Voráek.     

The luminescence properties of 2-isopropoxyphenyl-N-methyl carbamate

The fluorescence and phosphorescence properties of 2-isopropoxy phenyl-N-methyl carbamate, [formula (I)], have been studied in polar and non-polar solvents, at room temperature

and at 77 K. The fluorescence quantum yield of (I) in cyclohexane at room temperature, and the ratio of phosphorescence to fluorescence yield in three solvents at 77 K have been determined. Polarization studies have been carried out on both the fluorescence and phosphorescence emission. Phosphorescent lifetimes, τ_p, have been measured in various solvents and were found to be non-single exponential in all cases. The data provides an understanding of the excitation and emission processes in (I) and should be of use in the developement of spectral techniques for the detection of this molecule.     

The luminescence properties of MgUO4

The luminescence of MgUO₄ has been investigated. Emission and excitation spectra as well as the decay time and the quantum efficiency of the emission were measured at 4.2 K. The temperature dependence of the emission spectrum and the emission intensity was studied. The results show that in MgUO₄ the emission originates from uranate centres near defects. These centres act as optical traps. Even at 4.2 K about 90% of the excitation energy is lost non-radiatively by trapping at killer sites. These are most probably due to the presence of U⁵⁺ ions.     

The mechanism of disintegration of color centers and the non-stationary recombination luminescence of NaCl-Ag phosphor crystal. I

A combined method has been used to study the disintegration processes of the 355, 465, and 720 color centers of NaCl-Ag phosphor in the temperature range 100–550 ° K. The emission spectra of thermostimulated and photostimulated recombination luminescence of NaCl-Ag excited by X-rays at various temperatures were also studied. The possibility of ion-electron and ion-hole disintegration mechanisms of the color centers in the phosphor crystal at low temperatures is examined.The authors thank Doctor of Physical and Mathematical Sciences Ch. B. Lushchik for discussion of the subjects touched upon in the present paper, and also Yu. N. Evstifeev for assistance in performing the experiment.     

Ellipsometric investigations and luminescence properties of semiconductor microcavities

Il Nuovo Cimento D - Luminescence investigations on MBE-grown AlAs/AlGaAs microcavities reveal position-dependent spectra from embedded GaAs quantum wells and from the reflector material. Because...     

Carrier transport and luminescence properties of n-type GaN

The surface morphology, electrical properties and optical properties of Si doped n-type GaN were investigated. The intentional SiH₄ doped GaN films were grown by metal organic chemical vapor deposition with the electron concentration varying from 3×10¹⁶ cm⁻³ to 5.4×10¹⁸ cm⁻³. The surface morphology shows that the roughness and dislocation pits increase as the mass flow rate of SiH₄ increases, which indicates that the quality of GaN degrades gradually. The activation energy of Si in GaN with different n concentrations varies from 12 to 22 meV, which may originate from the interactions of donor wave functions. The carrier transport mechanism with increasing temperature from 100 to 420 K was concluded as the complex effect of both impurity scattering and phonon scattering. The position of the near band edge emission peak was determined by both renormalization of the band gap and B-M effect. The intensity variations of the yellow luminescence could be explained by the change of Ga vacancy concentration caused by Si doping. Supported by the National Basic Research Program of China (Grant No. 2006CB6049), the National Hi-Tech Research and Development Program of China (Grant No. 2006AA03A142), the National Natural Science Foundation of China (Grant Nos. 60721063, 60731160628 and 60676057), the Research Fund for the Doctoral Program of Higher Education of China (Grant No. 20050284004) and the Natural Science Foundation of Jiangsu Province of China (Grant No. BK2005210)     

掺Yb硼硅酸盐玻璃的光学特性及其双光子合作上转换荧光

采用高温固相反应方法制备了不同掺Yb浓度的硼硅酸盐玻璃．通过室温吸收光谱、光致荧光光谱及Raman光谱的测量，系统地研究了掺Yb激光玻璃近红外的光致荧光特性．给出了硼硅酸盐玻璃中的Yb^3＋的吸收和发射截面，计算了Yb^3＋-^2F5/2能级的自发辐射寿命，并对Yb离子对的团簇上转换荧光进行了测量和分析，给出了Yb离子团簇上转换荧光光子能量与红外荧光光子能量以及声子振动能量的关系．     

Spectral luminescence properties of hydroporphyrazine metallo complexes

We have studied the spectral luminescence properties of a zinc complex of dibenzobarreleno-substituted tetraazaisobacteriochlorin (a synthetic tetrapyrrole pigment which is the structural analog of the biologically important chromophore isobacteriochlorin) and a palladium complex of dibenzobarreleno-substituted tetraazachlorin. We have shown that despite the substantial effect of aza-substitution on the electronic structure and the electronic spectra of the tetrapyrrole molecules, the effect of hydrogenation of adjacent pyrrole rings on the spectral luminescence properties is similar in compounds with nitrogen and carbon bridges. As in the free base case, the fluorescence of the studied zinc complex is strongly quenched at 293 K but flares up at 77 K (temperature and viscosity-dependent quenching). To study the substituted Zn-tetraazaisobacteriochlorin, we determined the position of the 0-0 band of the low-intensity transition S₀ → S₂ and showed that the S₂ → S₁ energy difference increases with bridge aza substitution. For the Pd complex of dibenzobarreleno-substituted tetraazachlorin, we could not detect phosphorescence in the near IR region (to 1150 nm); we detected weak fluorescence. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 75, No. 5, pp. 700–707, September–October, 2008.     

Crystal growth and luminescence properties of CuI single crystals

Recently, much attention has been attached to the material of cuprous iodide (CuI) single crystals. In this paper, a detailed study of the variation in the nucleation density and the growth of CuI crystals in silica gel as a function of the concentration of feed solution, pH of gel, gel aging time, growth temperature and volume of the feed solution is presented. The optimum conditions for growth of large size CuI single crystals in gel are: pH 5, concentration of complex 0.244 M, gel aging 72 h, temperature 45 °C. A simple procedure for increasing the size of the crystals is adopted and the CuI single crystal with the size of 4 mm³ is obtained. Also, the photoluminescence (PL) spectrum of as-grown CuI crystals in silica gel is evaluated by comparing its PL spectra with that of CuI crystals grown by solvent evaporation method. The results could provide a useful clue to further improve the properties of CuI single crystals.     

Synthesis and luminescence properties of dye-doped deoxyribonucleic acid films

Dye-doped deoxyribonucleic acids (DNA)–tetradecyltrimethylammonium (TTA) films have been prepared. Rhodamine 6G, known as laser dyes, can be spontaneously doped by immersing the DNA–TTA film in rhodamine 6G-acetonitrile solutions. It is surmised that rhodamine 6G monomers and dimers diffuse within the hydrophobic TTA sites, and then monomers presumably intercalate between adjacent base pairs of DNA. Optical absorption spectra reveal that rhodamine 6G molecules in the sample undergo an unusual transformation from the dimer state to the monomer state with the elapse of time. Rhidamine 6G molecules doped in DNA–TTA show enhanced photostability and concentration quenching than those in PMMA. The environment, conformation and chemical stability of rhodamine 6G are different between DNA–TTA and PMMA, and are presumably modified by the intercalation.     

The luminescence properties of Er-doped and Er-Tm-co-doped phosphate glasses for white light emitting diode

Phosphate glasses and glass ceramics doped with Er³⁺ and co-doped with Er³⁺-Tm³⁺ are presented in this work. The luminescence properties have been characterized by absorption, excitation and emission spectra. All samples excited by blue light could emit a combination of blue/green/orange/red wavelength giving white light. For Er³⁺-doped glasses, a self-quenching effect has been obtained and an adjustable tune comes out after crystallization. For co-doped glasses, the red emission at 651 nm has been enhanced due to the existence of Tm³⁺, which could be relative to both the overlapped emissions and the energy transfer from Tm³⁺ to Er³⁺.     

纳米ZnO和ZnO∶Eu3+的表面效应及发光特性

纳米ZnO, ZnO:Eu3+及其添加覆盖层样品的光谱性质表明,表面有机物覆盖层具有改善发射光谱, 增强基质与Eu3+间能量传递的良好效果. 通过比较不同温度(60,800℃)处理的ZnO:Eu3+发光强度, 发现了小尺度(纳米)颗粒的特殊发光行为.