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71.
采用高温固相反应法,合成了一系列不同组份的磷光体,测定了它们的振动光谱.结果表明,随着Al/B比的减小,在1100~1000cm-1的区域内的振动光谱没有明显变化,铕离子不可能进入Al18B4O33的晶格中;振动光谱的背底升高,非晶相逐渐增加.研究了Al2O3-B2O3-Eu2O3中Eu3+离子的光谱特性,发现随着Al/B比的减少,Eu3+离子的存在相由晶相逐渐向非晶相转化。在非晶相中,Eu3+离子的声子伴带表明电子与声子的耦合强度随着Al/B比的减少而减小,Eu3+离子的发射强度相应的增加,这与多声子弛豫的理论一致. 相似文献
72.
Maja Nendel Bernd Goldfuss K. N. Houk Klaus Hafner Udo Grieser 《Theoretical chemistry accounts》1999,102(1-6):397-400
B3LYP/6-31G* calculations on bis-periazulene (cyclohepta[def]-fluorene) predict a triplet ground state for this molecule. The singlet has an aromatic 14π-electron periphery but is 2 kcal/mol
higher in energy. The results agree with earlier predictions by Heilbronner.
Received: 19 August 1998 / Accepted: 6 October 1998 / Published online: 23 February 1999 相似文献
73.
74.
Emission properties and applications of nanostructured luminescent oxide nanoparticles 总被引:2,自引:0,他引:2
D. Giaume V. Buissette K. Lahlil T. Gacoin J.-P. Boilot D. Casanova E. Beaurepaire M.-P. Sauviat A. Alexandrou 《Progress in Solid State Chemistry》2005,33(2-4):99-106
Rare earth doped oxide materials are well known for their numerous applications in light emitting devices. An interesting issue is to study the emission properties of nanoparticles, with the aim to understand the influence of small size and surface effects on the emission processes. These particles could furthermore be used in new applications such as the elaboration of transparent emitting devices or new biological labels. The work presented here concerns highly luminescent rare earth doped yttrium vanadates (YVO4:Eu) and lanthanum phosphate LaPO4:Ce,Tb·xH2O nanoparticles. Simple aqueous colloidal syntheses are used for the elaboration of concentrated colloids based on the progressive decomposition of polymeric precursors at moderate temperature (60–90 °C). Both types of particles exhibit strong emission (quantum yields of 25% and 45% for vanadates and phosphates, respectively), but significantly lower than that for the equivalent bulk materials. The alteration of the emission processes is discussed in terms of surface quenching effects. Improvements are obtained through the elaboration of core/shell nanostructures. Surface derivatization has been achieved through the controlled growth of an organically modified silica shell using a functionalized silane precursor. Two examples are given concerning the applications of those particles. The first one is the elaboration of transparent and highly luminescent thin films, obtained by the dispersion of the functionalized particles in a sol–gel silica matrix. The other one is the use of guanidine functionalized particles as biological labels for the single particle detection of sodium channels in cardiac cells. 相似文献
75.
A nanometer-sized Al2O3 powder was prepared by calcination of the nanometer-sized boehmite powder at different temperatures for 3 h in air. The main absorption bands located at about 200, 236, 255, 334 and 348 nm always occur in any phase of nanometer-sized alumina powder, and also do not change with the particle size. The luminescence bands at 404 nm in nanometer-sized alumina powder are presented under 236 and 254 nm excitation, respectively. The luminescence intensity of peak located at 404 nm decreases quickly with the increasing alumina powder size. It is suggested that the defect level in the nanometer alumina powder should be taken into account for the mechanism of new luminescent emission bands. 相似文献
76.
《Journal of Coordination Chemistry》2012,65(16):2689-2697
Two isomorphic lanthanide complexes [Eu2(L)6(H2O)4] · 2H2O (1) and [Tb2(L)6(H2O)4] · 2H2O (2), (HL = 4-quinoline carboxylic acid) have been synthesized and structurally characterized by single-crystal X-ray diffraction. Both complexes are binuclear and each metal center adopts nine-coordination with nine oxygens from two H2O molecules and carboxylates of three ligands; L exhibits three different coordination modes. Luminescent properties of 1 and 2 at room temperature indicate that the triplet-state level of this ligand matches better with the lowest excited state level of Eu(III) than with Tb(III). 相似文献
77.
Sidath Wijesinghe Sabina Maskey Dvora Perahia Gary S. Grest 《Journal of Polymer Science.Polymer Physics》2016,54(5):582-588
The conformation of dinonyl poly para phenylene ethynylenes (PPEs) with carboxylate side chains, equilibrated in solvents of different quality have been studied using molecular dynamics simulations. PPEs are of interest because of their tunable electro‐optical properties, chemical diversity, and functionality which are essential in wide range of applications. The polymer conformation determines the conjugation length and their assembly mode and affects electro‐optical properties which are critical in current and potential uses. This study investigates the effect of carboxylate fraction on PPEs side chains on the conformation of chains in the dilute limit, in solvents of different quality. The dinonyl PPE chains are modeled atomistically, where the solvents are modeled both implicitly and explicitly. Dinonyl PPEs maintained a stretched out conformation up to a carboxylate fraction f of 0.7 in all solvents studied. The nonyl side chains are extended and oriented away from the PPE backbone in toluene and in implicit good solvent, whereas in water and implicit poor solvent, the nonyl side chains are collapsed toward the PPE backbone. Rotation around the aromatic ring is fast and no long range correlations are seen within the backbone. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016 , 54, 582–588 相似文献
78.
Hongbo Lu Qiang Zhang Junqing Sha Miao Xu Jun Zhu Guobing Zhang 《Liquid crystals》2013,40(10):1574-1583
ABSTRACTThe optical properties of luminescent molecules dissolved in liquid crystals have led to their proposed use in luminescent thin-film polarizers. These molecules are typically required to fulfil a range of criteria related to their absorption and emission properties, degree of alignment and stability; however, concurrently satisfying these requirements has proven a barrier in their practical use. We obtained highly polarized absorption and emission luminescent thin-film polarizer using reactive liquid crystalline monomers and highly dichroic luminescent dyes, both of which have polymerizable end groups. In situ photopolymerization of the liquid crystalline mixtures in the highly ordered SmB phase resulted in the formation of cross-linked polymeric networks in which the anisotropic absorption and emission of the film were fixed. The as-obtained product exhibited a high dichroic ratio (DR = 30) with a large fluorescence quantum yield (?F = 0.77). The device is both cheap and easy to fabricate and has the potential to be used in practical electro-optic applications. 相似文献
79.
We report the synthesis of pyrene‐ and carboxyfluorescein labeled Cα‐tetrasubstituted amino acids (TAAs). The fluorescent dye can be coupled to the TAA before or after its incorporation into a peptide sequence using a Suzuki‐type C? C bond formation. 相似文献
80.
Uniform and crack free polycrystalline lutetium oxide (Lu2O3:(Eu,Pr)) films were fabricated by Pechini sol-gel method combined with the spin-coating technique. X-ray diffraction (XRD) and atomic force microscope (AFM) characterizations indicated that the obtained film was composed of polycrystalline cubic Lu2O3 phase with an average grain size around 30 nm. The photoluminescence(PL) spectra and decay performances of the Lu2O3:5 mol% Eu films co-doped by 0-0.5 mol% Pr3+ with different concentrations were characterized. It was found that the afterglow was reduced obviously due to the introduction of 0-0.5 mol% Pr3+ in the Lu2O3:5 mol% Eu films coupled by decrease in the emission intensity at 612 nm. The mechanism of afterglow diminishing was discussed based on the thermoluminescence measurements. 相似文献