Specific features of luminescence of Q-CdS colloids with different sizes

The specific features of luminescence of colloidal solutions of Q-CdS with particles of different size and the regularities of luminescence quenching by quenchers of various nature were studied. The luminescence spectra of Q-CdS consist of several bands, which are shifted to the long-ware region as the particle size increases. The dependence of the integral quantum yield of luminescence on the particle size has a sharp maximum at a particle diameter of ?23Å. A Stem—Volmer-type equation including the adsorption isotherm of the quencher molecules on the surface of the Q-CdS colloidal particles was used to describe the regularities of luminescence quenching of Q-CdS colloidal solutions. The CdS particle size was found to affect the efficiency of luminescence quenching. The regularities of luminescence quenching depend both on the rate constant of electron transfer to the quencher molecules and on the ability of the quencher molecules to be adsorbed on the surface of the CdS colloidal particle.     

固溶体结构对Ca_(2-x)Sr_xZn_4Ti_(15)O_(36)∶Pr~(3+)发光性质的影响

0引言在绿色和蓝色长余辉发光材料达到应用程度之后,耐候性红色长余辉发光材料成为人们研究的重点。Eu3 、Sm3 激活的硫氧化物[1￣3]、Eu2 铝锶复合硫氧化物[4]和Y2O3∶Eu3 [5]等耐热耐水性红色长余辉材料被相继发现。Pr3 离子掺杂的碱土金属钛酸盐(M TiO3∶Pr,M=M g,Ca,Sr,Ba)是一种新型的红色长余辉发光材料。这种发光材料在615nm附近有很好的单色性红光发射。碱土金属钛酸盐基质化学性能稳定,已开始应用于场发射显示器(FE D)[6,7]。碱土金属钛酸盐是A BO3型化合物,具有钙钛矿结构。B all[8]曾通过在CaTiO3中掺入不同量的Sr2 …     

A multi-color and white-light emissive cucurbituril/ terpyridine/ lanthanide supramolecular nanofiber

The enhanced lanthanide white-emission in solid by cucurbituril-based supramolecular assembly may provide a new strategy for smart light-emitting materials.     

Effect of molecular orientation distribution and crystallinity on the measurement of the crystal lattice modulus of nylon 6 by x-ray diffraction

The crystal lattice modulus of nylon 6 (-type) was measured by x-ray diffraction using nylon 6 films drawn up to five times. The measured crystal lattice modulus was 173–175 GPa for all specimens whose crystallinity and the Young's modulus were beyond 46% and 3.75 GPa, respectively. These results indicate that a state of homogenous stress can be achieved. In contrast, the values were scattered for the speciments whose crystallinity and Young's modulus are less than the above values. To study the origin, a numerical calculation of the crystal lattice modulus, as measured by x-ray diffraction, was carried out by considering effects on the orientation factors of molecular chains and crystallinity. In this calculation, a previously introduced model was employed, in which oriented crystalline layers are surrounded by oriented amorphous phases so that the strains of the two phases at the boundary are identical. The theoretical results calculated by the introduced model indicated that the crystal lattice modulus by x-ray diffraction is almost equal to the intrinsic crystal modulus if the morphology of the test specimen can be represented as a series model. In contrast, if a parallel model is more appropriate, the difference between the measured modulus and the intrinsic value can be pronounced. Such morphological dependence was found to be less pronounced with increasing high degree of molecular orientation and crystallinity.     

Gd_3Al_5O_(12)∶Eu~(3+)柠檬酸盐硝酸盐燃烧法合成及其发光性能研究

采用柠檬酸盐硝酸盐燃烧法,在较低的温度(900℃)下成功地合成单一晶相Gd3Al5O12∶Eu3+发光粉体,紫外激发荧光光谱分析表明,粉体615 nm和593 nm荧光发射源于Eu3+的5D0-7F2和5D0-7F1跃迁.该方法中各工艺条件(如pH值、柠檬酸/金属离子比、煅烧温度)对Gd3Al5O12∶Eu3+发光性能均有影响,通过试验得出了获得最佳发光性能荧光粉体的工艺参数.     

Intramolecular and liquid structure of 2,2,2-trifluoroethanol by X-ray diffraction

Intramolecular and liquid structure of 2,2,2-trifluoroethanol (TFE) have been investigated by x-ray diffraction at 25°C. The structural parameters for the skeleton of the molecules in the liquid phase are similar to those in the gas phase. The conformers of TFE molecules in the liquid phase are discussed. The O...O distance at about 284 pm and additional F...O one at about 302 pm were found to be characteristic for the first neighbor interactions. Various models (dimers and trimers) have been examined for analyzing the first neighbor structure. The liquid structure was explained in terms of small clusters consisting of two to three molecules rather than of a more extended polymeric network.Central Research Institute for Chemistry of the Hungarian Academy of Sciences, Budapest, P. O. Box 17, H-1525, Hungary.     

Luminescence of Eu~(2 ) in Strontium Aluminum Oxide System with Long Decay Property

Luminescentmaterialshavinglongdecayperi0dhaveat-IIactedmuchinterestduetotheirpotentialwidespreadaPplicati0ns.Recently,alongdecayluminescentp0wderhavingthecomPositionofSrAl2O4activatedwithEu' wasreportedandregardedasthebestcandidateforpracticalaPPlicationbecauseofitsuniqueadVantages0veritsprecursors.l'2Inthispaper,wereportthesynthesisofthelongdecayluminescentpowderandtheinnuence0fthemolarratioofAlt0sr0ntheethessioncolor.Toproducethelundnescentp0wder,amixtureofSrCO3,Al2O3,Eu2O3andsomesol…     

Crystal structure of a tetrabromo derivative of cyclopropyldihydroarglabin and its antifungal activity

A tetrabromo derivative of arglabin was synthesized stereoselectively. The molecular structure of the new compound was established using PMR and 13C NMR spectra and an x-ray structure analysis. Its antifungal activity was demonstrated. __________ Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 253–254, May–June, 2006.     

Investigation on relation between TL and OSL of Li2B4O7:Cu, In

Polycrystal Li₂B₄O₇ (LBO) doped with Cu and In was prepared and then sintered at different temperatures. X-ray diffraction (XRD) was applied to get the parameters of the LBO structure, thermoluminescence (TL) and optically stimulated luminescence (OSL) were measured, and a second-order exponential decay model was fitted to the OSL decay curves. The results indicate that the original number of OSL traps that have captured electroncs is linearly related with the sum of TL decay during the OSL process. Mean decay constant of OSL is related to the sintered temperature. The possible reason is that the sintered temperature affects the crystal sizes of the polycrystal, and consequently affects the stimulating lights’s intensity and the photoionization cross-section of the electrons, which have been captured by the traps. __________ Translated from Acta Scientiarum Naturalium Universitatis Sunyatseni, 2005, 44(4) (in Chinese)     

Macromolecular crystallography research at Trombay

Neutron diffraction studies of hydrogen positions in small molecules of biological interest at Trombay have provided valuable information that has been used in protein and enzyme structure model-building and in developing hydrogen bond potential functions. The new R-5 reactor is expected to provide higher neutron fluxes and also make possible smallangle neutron scattering studies of large biomolecules and bio-aggregates. In the last few years infrastructure facilities have also been established for macromolecular x-ray crystallography research. Meanwhile, the refinement of carbonic hydrases’ and lysozyme structures have been carried out and interesting results obtained on protein dynamics and structure-function relationships. Some interesting presynaptic toxin phospholipases have also been taken up for study.