钡-磷酸盐玻璃中Cr~(3+)离子发光特性

在室温和低温(80K)下,对磷酸盐玻璃中 Cr~(3+)离子的吸收光谱、激发光谱、荧光光谱及荧光寿命进行了测量。根据配位场理论对实验结果进行了分析。不同波长激发下,观测到荧光峰值的移动和线宽的变化,对玻璃中 Cr~(3+)离子的浓度猝灭效应进行了讨论。     

Enhanced optical properties of heterostructured ZnO/CeO2 nanocomposite fabricated by one-pot hydrothermal method: Fluorescence and ultraviolet absorption and visible light transparency

Many researchers investigated the properties of either discrete metal oxide CeO₂ or ZnO materials. However, less attention has been paid to the various nanostructure and performances of CeO₂ and ZnO nanocomposite up to now. In this paper, a facile and low cost one-pot hydrothermal synthesis method has been adopted to obtained directly precursors of CeCO₃OH and Zn₅(CO₃)₂(OH)₆ with different Ce atom molar ratios to Zn, which are transformed into their corresponding metal oxide to form the ZnO/CeO₂ heterostructure nanocomposites (HSNCs) by pyrolysis. The heterostructure is composed of ZnO and CeO₂ monocrystals, simultaneously, CeO₂ monocrystals are well dispersed on the surface of ZnO monocrystal for cosmetics. Bing dependent on the analysis results of XRD and TEM for the obtained precursors before and after pyrolysis, the formation mechanism of HSNCs was proposed. To the best of our knowledge, the paper first reported heterostructured ZnO/CeO₂ nanocomposite grown in one-pot mixed aqueous solution of cerium nitrate, zinc acetate and urea without other extra surfactant. Additionally, the influence of various Ce/Zn molar ratios on the heterostructure, fluorescence emission and UV–visible absorption properties of HSNCs was investigated in detail. ZnO/CeO₂ HSNCs display higher fluorescence emission with the increasing Ce/Zn molar ratio. Meanwhile, the larger Ce/Zn molar ratio of ZnO/CeO₂ HSNCs, the stronger transparency in the visible light region and the weaker UV absorption. The results are due to the fact that the band gap of ZnO/CeO₂ HSNCs will decrease from 3.25 to 3.08 eV when Ce/Zn atom molar ratio is increased from 0 to 0.08. By the comprehensive analysis on the optical performances of HSNCs with the different Ce/Zn atom molar ratios, ZnO/CeO₂-0.04 HSNCs could become UV absorber materials and transparent material in the visible region. ZnO/CeO₂-0.04 HSNCs with the UV-filtering and Vis-transparent properties is appropriate for personal-care cosmetics.     

Optical absorption and fluorescence spectra of novel annulated analogues of azafluoranthene and azulene dyes

Paper reports optical absorption and fluorescence spectra as well as basic photophysical characteristics of newly synthesized 1,3-diphenyl-3H-indeno[1,2,3-de]pyrazolo[3,4-b]quinoline (DPIPQ) and 6-phenyl-6H-5,6,7-triazadibenzo[f,h]naphtho[3,2,1-cd]azulene (PTNA) dyes being recorded in organic solvents of different polarity. The experimental results are compared with the quantum chemical calculations performed within the semiempirical method PM3. While the solvent polarity changes from cyclohexane to acetonitrile both dyes exhibit the hypsochromic (blue) shift of the absorption spectra and the bathochromic (red) shift of the fluorescence spectra. This fact is found to be consistent with the Lippert–Mataga solvatochromic model and is explained by a specific orientation of the ground and excited state dipole moments. Quantitative evaluations of the solvatochromic shifts give quite well agreement with the experimental data only for optical absorption spectra of both dyes. In the case of the fluorescence spectra the experiment suggests much larger dipole moment of the excited state comparing to the one which follows from the semiempirical calculations. Corresponding discrepancy is especially strong for DPIPQ dye and is assumed to be related with an enhanced mixing of the lowest LE state with the lowest ICT states due to lowering of their energies in a polar solvent environment. Both dyes reveal substantial quantum yield thus may be considered as candidates for the luminescent or electroluminescent applications. Depending on solvent polarity they emit light in the green-yellow range of the visible spectra.     

Control of electron–phonon dynamics by quantum confinement in isolated Y2SiO5:Pr nanocrystal

The fluorescence spectrum and decay of isolated Y₂SiO₅:Pr³⁺nanocrystals at the glass-air interface were investigated using the confocal fluorescence microscopy and time-resolved techniques. Intense fluorescence from the upper crystal field components of the split ¹D₂ term of Pr³⁺ was observed. The fluorescence decay is characterized by the non-exponential law t^-1/2 which is caused by the back-to-back energy exchange between Pr³⁺ electronic states and long-lived nanocrystal phonons. The observed effect is very sensitive to the cluster–substrate interaction and opens a new spectroscopic way to explore the excited states of J-manifolds of RE ions directly.     

甲醇溶液的荧光光谱特性

应用SP-2558多功能光谱测量系统,由Xe灯通过激发光谱仪获得不同波长的紫外光,对不同浓度甲醇溶液在不同波长紫外光激励下产生荧光光谱的特性进行了实验研究。结果表明,甲醇溶液在波长220nm左右的紫外光激励下能产生较强的荧光。荧光峰是310nm至370nm范围的宽谱峰;荧光峰值波长在337nm附近,并随激励光波长增大而产生红移;在同一紫外光激励下,荧光强度随甲醇溶液浓度的增大发生先增强再减弱的变化。根据分子光谱理论,经分析提出,该荧光是由甲醇分子中-OH基团的孤对电子跃迁产生的,荧光光谱的上述特性由电子的跃迁情况决定。研究结果为甲醇作为常用溶剂和重要有机化工原料的应用、检测提供依据。     

一种高能X光转换屏的荧光光谱实验研究

X光转换屏的强度 -谱线曲线对闪光照相具有重要意义。本实验对 4号高能 X光转换屏在 X光照射下所发荧光光谱作了分析 ,文中给出了谱线图 ,以及扫描出的强度 -谱线曲线 ,并对实验结果作了分析     

Comparison of fluorescence spectra of Yb:Y3Al5O12 and Yb:YAlO3 single crystals

Yb:Y₃Al₅O₁₂ (Yb:YAG) single crystals with Yb doping concentration 0.5 at.%, 5 at.%, 15 at.%, 25 at.%, 50 at.%, 100 at.% and Yb:YAlO₃ (Yb:YAP) single crystals with Yb doping concentration 0.5 at.%, 5 at.%, 15 at.%, 30 at.% were grown by the Czochralski process. The fluorescence spectra of these crystals and the effects of self-absorption on the shape of the fluorescence spectra were studied. Through comparing the fluorescence spectra of Yb:YAG and Yb:YAP, all results indicate that the effects of self-absorption on the fluorescence spectra of Yb:YAP are remarkably stronger than that of Yb:YAG at the same Yb concentration.     

EU:Y2O3纳米晶的光谱特性与微结构

采用均相共沉淀法制备了不同粒径的Y2O3：Eu^3＋和Y2O3粉体材料,根据红外光谱和荧光光谱,探讨了纳米Y2O3：Eu^3＋粉体的微观结构与同质体微米材料相对变化.发现纳米粉体的Y（Eu）-O键吸收峰校正高度和面积随着颗粒的减小而减小,而对于同质微米材料却相反.分析认为：Y（Eu）-O键红外吸收峰校正高度和面积由Y（Eu）-O键的平均键长和Y（Eu）-O键振动态的数目两个因素决定,对于微米粉Y（Eu）-O键长起主要作用.由于纳米粉体的比表面积随粒径的减少呈指数的增加,不饱和键和悬空键的数目随粒径减小而指数增加,Y（Eu）-O键振动态的数目起主要作用.计算了纳米粉体相对微米粉的跃迁强度参量Ωt/Ωt＇值,发现Ω2和Ω4均增加,说明粉粒内部跃迁几率增加.纳米荧光粉比微米粉荧光强度减少的实验事实应是纳米粉粒表面效应引起的,与红外光谱实验的结果相符.     

Photoluminescence and laser behavior of Yb:YAG ceramic

Yb:YAG transparent ceramics with different doping concentration were fabricated by the traditional solid-state diffusion route, and their fluorescence properties and laser behavior were investigated. It is found that both the fluorescence intensity and lifetime depend deeply on both the doping concentration of Yb ions and the annealing treatment. The continuous wavelength (C.W.) laser performance for 10 at.% Yb:YAG ceramic suggests that both the threshold pump power and slope efficiency increase with increasing transmittance of the output couple (T_oc). For T_oc = 15%, the threshold pump power is about 6.1 W, the slope efficiency is 25%, and the maximum output power of 2.2 W is achieved when pumped by 14.9 W.     

Observation of Non-Radiative Recombination Enhanced Point Defect Reaction in Semiconductors

IntroductionWide-bandgapcompoundsemiconductorsforblue-greenlaserdiodesandlight-emittingdiodeshavebeenintensivelystudiedinrecentyears.Ithasbeenrecognizedthatpre-existingdefectsplayasignificantroleinthedevicedegradation.Reductionofthesedefectshasbeentheprimaryeffortinachievingalonglifetimeoflight-emittingdevices.Inthispaper,wepresentourmainexperimentalresultsonthenonradiativerecombinationenhancedpointdefectreactioninsemiconductorsbydirectlymonitoringtheprocessofradiativeelectron-holerecombinatio…