Donor-π- acceptor styryl chromophores based on indole core were synthesized by Knoevenagel condensation of N-ethyl indole-3-carbaldehyde and different active methylene compounds. The absorption and emission properties of these dyes in different solvents were studied. The dyes displayed a broad absorption maximum in the UV and visible region between 397 and 469 nm with FWHM, 50 to 75 nm. Due to the extended π – conjugated systems this styryl chromophores shows strong intramolecular charge transfer characteristics. The dyes showed solid state emission and emission in solid state was red shifted as compared to their emission in less polar solvents. Density Functional Theory [B3LYP/6–311 + G(d)] computations were used to correlate the structural, molecular, electronic and photo physical parameters of styryl dye with experimental study. Synthesized dyes were confirmed by using FT-IR, 1H NMR, 13C NMR and HRMS spectral analysis. 相似文献
A group of structurally rigid analogues of 2,6-distyrylpyridine was synthesised. Molecular geometry of the synthesised dyes in solutions was studied by 1H-NMR, electronic absorption and fluorescence spectrometry. The spectral data testify all the compounds exist in E-configuration of their styryl residues. The most planar molecular conformation is typical for the compounds with five-membered side aromatic moieties. In the case of pyridines with six-membered aromatic residues steric hindrance results in turning the above mentioned cyclic groups out of the plane of the central pyridine moiety. The violation of planarity in this case is not significant and saves the possibility of -electronic conjugation in the molecules. The synthesised compounds are characterized by high fluorescence quantum yields in solutions. The electronic absorption spectra of titled pyridines demonstrate low sensitivity to the nature of the substituents introduced into the side aromatic rings. In contrast to this, the fluorescence bands considerably change their position under the influence of electron donor substituents. The fluorescence spectra display substantial positive solvatofluorochromism only in the cases of the dialkylamino-derivatives, especially on going from aprotic solvents to proton donor ones. Generally, the synthesised structurally rigid distyrylpyridine derivatives have prospects for their application as multi-purposes fluorescent probes. 相似文献
A novel series colorimetric and off–on fluorescent chemosensors (2a, 2b, 2c) were designed and synthesized, which showed reversible and highly selective and sensitive recognition toward Fe3+ over other examined metal ions. Upon addition of Fe3+, sensors (2a, 2b) exhibit remarkably and 2c exhibits moderate enhanced absorbance intensity and color change from colorless to pink in CH3OH–H2O(1:1, v/v). The three compounds (2a, 2b, 2c) may therefore be applicable as rhodamine-based turn-on type fluorescent chemosensors. 相似文献
Quasi-one-dimensional Fe3O4 nanowires in diameter of about 200nm were assembled into anodic aluminium oxide templates via electrodepositing and heat-treating processes. The nanowires have a polycrystalline spinel structure with α=8.317А, and each nanowire is composed of fine Fe3O4 crystallites with size of about 30nm. 相似文献
Novel Dy^3+-doped GdPO4 white light phosphors with a monoclinic system are successfully synthesized by the hydrothermal method at 240℃. The strong absorption at around 147nm in the excitation spectrum is assigned to the host absorption. It is suggested that the vacuum ultraviolet excited energy is transferred from the host to the Dy^3+ ions. The f - d transition of the Dy^3+ ion is observed to be located at 182nm, which is consistent with the calculated value using Dorenbos's expression. Under 147nm excitation, Gd0.92PO4:0.08Dy^3+ phosphor exhibits two emission bands located at 572 nm (yellow) and 478 nm (blue), which correspond to the hypersensitive transitions ^4 F9/2-^6 H13/2 and ^4 F9/2-^6 H15/2. The two emission bands lead to the white light. Because of the strong absorption at about 147nm, Gd0.92PO4:0.08Dy^3+ under vacuum ultraviolet excitation is an effective white light phosphor, and has promising applications to mercury-free lamps. 相似文献
Physics of the Solid State - The Y0.4Bi0.6VO4 and Y0.6Bi0.4VO4 solid solutions two-phase at xBi = 0.95, 0.90, and 0.80 have been formed by the solid-phase synthesis from the initial Y2O3, Bi2O3,... 相似文献
Novel ESIPT inspired benzimidazole, benzoxazole and benzothiazole were synthesized from 2,4-dihydroxy benzoic acid and 1,2-phenelenediamine, 2-aminophenol, and 2-aminothiophenol respectively. The synthesized 2-(2′,4′-dihydroxyphenyl) benzimidazole, benzoxazole and benzothiazole are fluorescent and the emission characteristic are very sensitive to the micro-environment. They show a single absorption and dual emission with large Stokes shift originating from excited state intramolecular proton transfer. The absorption-emission characteristics of all these compounds are studied as a function of pH. The change in the electronic transition, energy levels, and orbital diagrams of synthesized compounds were investigated by the molecular orbital calculation and were correlated with the experimental spectral emission. Experimental absorption and emission wavelengths are in good agreement with those predicted using the Density Functional Theory (DFT) and Time-Dependent Density Functional Theory (TD-DFT) [B3LYP/6-31G(d)].
Figure
Novel ESIPT inspired benzimidazole, benzoxazole and benzothiazole were synthesized from 2,4-dihydroxy benzoic acid and o- amino aromatics. Single absorption and dual emission are the interesting properties of the synthesized compounds. 相似文献
Fluorescent quinazolinones were synthesized form ethyl 2-methyl-4-oxo-3,4-dihydroquinazoline ?5-carboxylate intermediate. The photophysical properties of the compounds were evaluated in DMF solvent. The experimental absorption and emission of the compounds were compared with the vertical excitation and emission obtained Density Functional Theory (DFT) and Time Dependent Density Functional Theory (TD-DFT) computation. Application of the fluorescent compounds as a fluorescent brightening agent was tested on polyester fiber. Changes in the electronic transition, energy levels, and orbital diagrams of quinazolin-4(3H)-one analogues were investigated using the DFT computations and were correlated with the experimental spectral data. The experimental absorption and emission wavelengths are in good agreement with those predicted using the DFT and TD-DFT. 相似文献
A new rhodamine-based derivative bearing a naphthyridine group (compound 1) was synthesized as a colorimetric and fluorescent “off-on” chemosensor for Cu2+ in aqueous solutions. The sensing behaviors of 1 toward various metal ions in neutral aqueous solutions were investigated by absorption and fluorescence spectroscopies. Compound 1 is found to exhibit a significant increase in absorbance at 561 nm and an amplified fluorescence at 590 nm toward Cu2+ in a selective, sensitive and rapid manner. The quantification of Cu2+ by 1 using an absorption spectroscopy method was satisfactory in the linear working range 0.9–10 μM, with a detection limit of 5.4?×?10?8?M for Cu2+ and good tolerance of other metal ions. Upon addition of Cu2+, the spirolactam ring (colorless and nonfluorescent) of 1 was opened to ring-opened amide (red color and fluorescent) and a 1:1 stoichiochemetry for the 1-Cu2+ complex was formed with an association constant of 1.57?×?104?M?1. 相似文献
In this article, water-soluble graphene–cadmium telluride quantum dot nanocomposites were fabricated through the synthesis of cadmium telluride quantum dots in the presence of graphene aqueous dispersion. It was found that pyrene could remarkably quench fluorescence of graphene–cadmium telluride quantum dot nanocomposites. On this basis, a novel method for the determination of pyrene was developed. Factors affecting the pyrene detection were investigated, and the optimum conditions were determined. Under the optimum conditions, a linear relationship could be established between the quenching of fluorescence intensity of graphene–cadmium telluride quantum dot nanocomposites and the pyrene concentration in the range of 6.00 × 10?8–2.00 × 10?6 mol L?1 with a correlation coefficient of 0.9959. The detection limit was 4.02 × 10?8 mol L?1. Furthermore, the nanocomposites were applied to practical determination of pyrene in different water samples with satisfactory results. 相似文献
The possibility of obtaining scintillators with a high effective atomic number of the element Zef based on Lu3Al5O12:Ce3+ singlecrystal films (SCF) on doping with La3+ and Sc3+ ions on Y3Al5O12 substrates has been investigated. It is established that the SCF of (LuLaY)3Al5O12:Ce3+ (Zef = 58.9 and = 6.67 g/cm2) does not rank below those of Y3Al5O12:Ce3+ (Zef = 29 and = 4.52 g/cm2) in the conversion efficiency of radiation at the band with max = 515 nm. This allows their use as screens of xray images with a space resolution of 0.75–1.00 m. It is suggested that in the SCF of Lu3Al5O12 the isoelectronic impurities of lanthanum and scandium form radiative recombination centers of the type LaLu, ScLu, and ScAl as well as the centers Lu as a consequence of the effect of replacement of some Lu3+ ions by the La3+ ions to octanodes of the garnet lattice. The low efficiency of Ce3+ radiation in the SCF of (LuSc)3(AlSc)5O12:Ce is explained by substantial losses due to excitation of the recombination luminescence in the UV region of the centers formed by the isoelectronic impurities of scandium and to the possible existence of the channel of energy excitation dissipation related to the transitions between extrema of the allowed energy bands and activator levels. 相似文献
Polymer–clay nanocomposites have been prepared by melt blending of commercial organoclay Cloisite 15A with blends of polyethylenes (PE) and maleic-anhydride-grafted PE (PE/PE-g-MA) with wide range of composition. Three types of PE/PE-g-MA blends with different molecular structure, namely blends of high-density PE (HD) with HD-g-MA (HDMA), blends of low-density PE (LD) with LD-g-MA (LDMA), and blends of linear low-density PE (LL) with LL-g-MA (LLMA) were used. The influence of the molecular structure of the PE matrixes and the compatibility between the blend components on the morphology of the nanocomposites was studied. The thermal properties, microhardness, and transparency of the nanocomposites were investigated. The influence of the degree of exfoliation/intercalation on the materials characteristics is discussed. 相似文献
In this paper, the organic ligands TTA and TAA are grafted onto the coupling agent to achieve the organic precursors (TTA-Si,
TAA-Si) as first ligand and the organic 4-(4-nitrostyryl)pyridine (Nspy) is synthesized as the second ligand. Both of them
are coordinated to the rare ions with the carbonyl group and nitrogen atom respectively. After the hydrolysis and copolycondensation
between the teraethoxysilane (TEOS) and the ternary rare earth organic complex via the sol–gel process, the chemical bonded
hybrid materials are constructed and characterized in detail. The obtained hybrid materials present superior thermal stabilities
and regular and homogenous square blocks microstructure. Among the hybrids Eu(TTA-Si)3Nspy shows a more strong characteristic emission and longer lifetime than the hybrids Eu(TAA-Si)3Nspy, while hybrids Tb(TAA-Si)3Nspy exhibits the stronger characteristic emission and longer lifetime than the hybrids Tb(TTA-Si)3Nspy. For Sm3+ hybrid materials, the photoluminescence of Sm(TAA-Si)3Nspy is too weak to find in the characteristic emission spectra, meanwhile, Sm(TTA-Si)3Nspy has the excellent luminescent intensity. 相似文献
Samples of composites with polytetrafluoroethylene as the matrix and a powder of 0, 1, 2, 4, 8, 16, and 32 vol % Al–Cu–Fe quasi-crystal as the filler are prepared. Electron microscopy studies of the sample structure are carried out, the influence of the filler on the degree of crystallinity and the melting and destruction temperatures of the samples is investigated; mechanical tensile tests and tribological tests are performed. The composite samples with filler contents of 4, 8, 16, and 32 vol % show ultralow wear with the coefficient K < 5 × 10–7 mm3/N m. The highest wear resistance exceeding that of unfilled polytetrafluoroethylene by 2200–3100 times is recorded in composites with 16 vol % filler. An increase in the wear resistance is associated with formation on the friction surface of a thin crust containing quasi-crystal particles 0.2–0.3 μm in size, revealed by scanning electron microscopy in combination with energy dispersive analysis. 相似文献
Maleic anhydride was modified by long chain alcohol (1-hexadecanol, 1-octadecanol and 1-eicosanol) to a novel sort of corresponding
long monoester mono-L cis-butene dicarboxylate (L = hexadecyl, octadecyl and eicosyl), i.e. monohexadecyl cis-butene dicarboxylate
(MAH), monooctadecyl cis-butene dicarboxylate (MAO), and monoeicosyl cis-butene dicarboxylate (MAE), respectively. Then the
some novel ternary lanthanide (Eu3+, Tb3+) complexes with the as-derived long chain monoester and assistant nitrogen-heterocyclic ligands (2,2’-bipyridyl (bipy) and
1,10-phenanthroline (phen)) were synthesized and characterized by elemental analysis and IR spectra. The photophysical properties
of these complexes were studied in detail with ultraviolet absorption spectra, luminescent excitation and emission spectra
and luminescent lifetimes, indicating that the intramolecular energy transfer mechanism runs smoothly within these ternary
complexes in terms of sensitized functions of bipy and phen and strong characteristic red or green emissions of Eu3+ or Tb3+ have been achieved. 相似文献
Technical Physics - Ferroelectric ceramic LixNa1 –xTayNb1 –yO3 (x = 0.17, y = 0–0.5) solid solutions with perovskite structure are synthesized for the first time by the... 相似文献
Alginic acid–Fe3O4 nanocomposite is synthesized by the precipitation of Fe3O4 in the presence of alginic acid (AA). Structural, surface, morphological, thermal and electrical transport properties of the nanocomposite were performed by XRD, FT-IR, TEM-SEM, TGA and conductivity measurements respectively. FT-IR analysis revealed that Fe3O4 NPs are strongly capped with AA and TGA analysis showed that nanocomposite have 80% of Fe3O4 content. TEM analysis of Fe3O4 NPs show an average particle size of 9.5 nm, and upon nanocomposite formation with AA these particles are observed to form aggregates of ~150 nm. The frequency-dependency of the AC conductivity show electrode polarization effect. Analysis of electrical modulus and dielectric permittivity functions suggest that ionic and polymer segmental motions are strongly coupled. DC electrical conductivity is strongly temperature dependent, and is classified into three regions over a limited temperature range of up to 100 °C. 相似文献
Epitaxial ZnO films are grown on Al2O3 (0001) by the MOCVD method. These films are high quality wurtzite crystals with (0001) orientation. Big hexagonal crystallites (diameter from several decades to 100 μm) are found on the surface. Inside these crystallites, a stronger luminescence is observed compared with the plain area. Transmission electronic microscopy reveals that the film is thicker inside the hexagonal crystallites than the plain area, and some crystallites are not connected with each other and are slightly rotated with respect to their neighbours. 相似文献
Blue emitting cyano substituted isoquinoline dyes were synthesized by one-pot multicomponent reactions (MCRs) of aldehydes, malononitrile, 6-methoxy-1,2,3,4-tetrahydro-naphthalin-1-one and ammonium acetate. Results obtained from spectroscopic (FT-IR, 1H-NMR, 13C-NMR, EI-MS) and elemental analysis of synthesized compounds was in good agreement with their chemical structures. UV–vis and fluorescence spectroscopy measurements proved that all compounds are good absorbent and fluorescent. Fluorescence polarity study demonstrated that these compounds were sensitive to the polarity of the microenvironment provided by different solvents. In addition, spectroscopic and physicochemical parameters, including electronic absorption, excitation coefficient, stokes shift, oscillator strength, transition dipole moment and fluorescence quantum yield were investigated in order to explore the analytical potential of synthesized compounds. The anti-bacterial activity of these compounds were first studied in vitro by the disk diffusion assay against two Gram-positive and two Gram-negative bacteria then the minimum inhibitory concentration (MIC) was determined with the reference of standard drug chloramphenicol. The results displayed that compound 3 was better inhibitors of both types of the bacteria (Gram-positive and Gram-negative) than chloramphenicol.