吡啶二甲酸类配体-EDTA-铽三元配合物的荧光性能

对几种吡啶－２,６－二甲酸类配体与ＥＤＴＡ、铽的三元配合物在溶液中的荧光性能进行了研究,溶液ＰＨ值和溶剂效应对体系荧光的影响也分别进行了探讨。４－甲氧基吡啶－２,６－二甲酸和４－乙氧基吡啶－２,６－二甲酸等配体在这种三元体系中的敏化性能比常用的吡啶－２,６－二甲酸好,其中４－乙酰氨基吡啶－２,６－二甲酸特别优异。不论在二元配合物系还是在三元配合物体系中,均具有发光强度大、寿命长的特点。     

多彩金纳米簇:从结构到生物传感和成像

金纳米簇是一种具有发光性能的“类分子”新兴纳米材料.通过调控金原子数目和配体组成性质,金纳米簇可以实现同激发光下不同波段发射,从而展现出“五彩缤纷”的发光特性,这使其被广泛应用于光催化、光学器件、传感和成像等多个领域.因此,开发和优化具有优异发光性能的金纳米簇一直是化学、材料和生物学科的研究热点.本文立足于金纳米簇的发...     

The role of isomerism and medium effects on stability of anions of formo- and thioformohydroxamic acid

The anionic forms of formo- and thioformohydroxamic acids have been analyzed for their relative stabilities and barriers for interconversion between the tautomeric forms employing ab initio and DFT methods. The deprotonation affinities and pK_a values are evaluated to differentiate the various deprotonation processes. The effect of medium on deprotonation behavior is analysed using Tomasi’s PCM model and examining free energy changes of deprotonation from isolated molecules, molecule–water aggregates and subsequently from anion–water aggregates in the gas phase and aqueous phase respectively. Variation of geometrical parameters, charges, electron delocalizations, intramolecular H-bonding and relative stabilities upon water aggregation of the anions all point towards NH deprotonation as the most favored process.     

Immobilization of pyrene on quartz plate surface via a flexible long spacer and its sensing properties to dicarboxylic acids

It is known that polycyclic aromatic hydrocar-bons (PAHs) form excimer easily, and show both monomer and excimer emission in polar medium[1]. This character comes from their hydrophobic nature and plane structures. The ratio of the intensity of ex-cimer emission to that of monomer emission is a func-tion of distance between neighbouring PAHs in a sys-tem. It is not difficult to understand that many factors, such as the concentration of PAHs, temperature, pres-ence and concentration of othe…     

Photophysical and conformation properties of luminescent-labeled star poly-2-isopropyl-2-oxazolines based on octa-<Emphasis Type="Italic">tert</Emphasis>-butylcalix[8]arene in solution

The synthesis of luminescent-labeled copolymers of octa-tert-butylcalix[8]arene with 8 poly-2-isopropyl-2-oxazoline arms is carried out. Each macromolecule involves one luminescent label of the anthracene structure located at the end of one of the arms. The luminescent properties of the copolymers in water and methanol are studied. It is shown that, in aqueous solutions, the formation of intermolecular aggregates with a hydrophobic core and a hydrophilic shell results in a new photophysical process of migration of electron excitation energy accompanied by a decrease in the solution luminescence polarization. The interaction of oxazoline arms with poly(methacrylic acid) via the mechanism of interpolymer complex formation implies a weakening of the efficiency of energy migration.     

The luminescence response of diamine-liganded europium complexes upon resonant and pre-resonant excitation

The luminescence of four europium thenoyltrifluoroacetonate complexes containing diamine ligands is studied in solutions. The compounds are resonantly excited in the ligand absorption band by means of high-power nanosecond UV laser pulses. Additionally, a continuous light source is also used for resonant, as well as pre-resonant excitation of the complexes. The luminescence response characterizes the synthesized europium coordination complexes as emissive compounds suitable for fluorometric applications. Related to the possible usefulness of the diamine-liganded Eu complexes as luminescent labels for sensing and imaging of biological molecules, the luminescence response of these compounds upon UV excitation was probed also in aqueous media.     

Influence of connectivity and porosity on ligand-based luminescence in zinc metal-organic frameworks

Applications of metal-organic frameworks (MOFs) require close correlation between their structure and function. We describe the preparation and characterization of two zinc MOFs based on a flexible and emissive linker molecule, stilbene, which retains its luminescence within these solid materials. Reaction of trans-4,4'-stilbene dicarboxylic acid and zinc nitrate in N,N-dimethylformamide (DMF) yielded a dense 2-D network, 1, featuring zinc in both octahedral and tetrahedral coordination environments connected by trans-stilbene links. Similar reaction in N,N-diethylformamide (DEF) at higher temperatures resulted in a porous, 3-D framework structure, 2. This framework consists of two interpenetrating cubic lattices, each featuring basic zinc carboxylate vertices joined by trans-stilbene, analogous to the isoreticular MOF (IRMOF) series. We demonstrate that the optical properties of both 1 and 2 correlate with the local ligand environments observed in the crystal structures. Steady-state and time-resolved spectroscopic measurements reveal that the stilbene linkers in the dense structure 1 exhibit a small degree of interchromophore coupling. In contrast, the stilbenoid units in 2 display very little interaction in this low-density 3-D framework, with excitation and emission spectra characteristic of monomeric stilbenes, similar to the dicarboxylic acid in dilute solution. In both cases, the rigidity of the stilbene linker increases upon coordination to the inorganic units through inhibition of torsion about the central ethylene bond, resulting in luminescent crystals with increased emission lifetimes compared to solutions of trans-stilbene. The emission spectrum of 2 is found to depend on the nature of the incorporated solvent molecules, suggesting use of this or related materials in sensor applications.     

Study of Interactions Between Eu(thenoyltrifluoroacetonate)<Subscript>3</Subscript> and a Photosynthetic Chlorophyllous Pigment

Eu(thenoyltrifluoroacetonate)₃(Eu(TTA)₃), an ideal model lanthanide complex which harvests ultraviolet light in high yield and emits visible light efficiently, was coordinated with a chlorophyll derivative, methyl pyropheophorbide-a (MPA). A distinct color change, from blue to deep green, in solution gives evidence for a supramolecular interaction within the binary system. Ultraviolet-visible absorption and luminescence excitation/emission spectra, as well as luminescence lifetimes and quantum yield measurements, further show that molecular interactions occur between the two components.     

Fabrication of nanoaggregates of poly(ethylene oxide)-b-polymethacrylate by complex formation with chitosan or methylglycolchitosan

Nanoaggregate formation of poly(ethylene oxide)-b-polymethacrylate (PEO-b PMA) is induced by chitosan (Ch) or methylglycolchitosan (MGC). The nanoaggregates are basically obtained by electrical charge neutralization of the anionic PMA block of the PEO-b-PMA polymer with cationic Ch or MGC, which results in insolubilization of the PMA block to form the core of the aggregates. Formation of the nanoaggregates was confirmed by dynamic light scattering, fluorescence spectroscopy, atomic force microscopy and zeta-potential measurements. The properties of the nanoaggregates depend upon the concentration of the polymer as well as the concentration of Ch or MGC. The significance of these aggregates is their ability to incorporate ionic species, leading them to potential applications as drug carriers and nanoreactors.     

Experiment and theoretical modeling of the luminescence of silver nanoclusters dispersed in oxyfluoride glass

Density functional theory (DFT) and complete active space perturbation theory (CASPT2) have been applied for modeling the configuration, charge, energy states, and spin of luminescent Ag nanoclusters dispersed within the bulk of oxyfluoride glass host. The excitation spectra of luminescence of the Ag nanoclusters have been measured and simulated by means of the DFT and CASPT2. Electron spin resonance spectra have been recorded and suggest diamagnetic state of Ag nanoclusters. The silver nanoclusters have been argued to consist mostly of pairs of Ag(2) (+) dimers, or Ag(4) (2+) tetramers, with different extent of distortion along the tetramer diagonal. The sites for the Ag nanoclusters have been suggested where the pairs of Ag ions substitute onto metal and hole cation sites and are surrounded by fluorine ions within a fluorite-type lattice.     

Some features of luminescent properties of PbS suspensions,stabilized by high‐molecular polyvinylpyrrolidone

The results of the investigations of optical and luminescent properties of PbS suspensions stabilized by high‐molecular polyvinylpyrrolidone are described. Suspensions prepared by liquid colloidal method from sodium sulfide and lead nitrate demonstrate strong luminescence in near infrared spectral range at the excitation by visual light with different wavelengths. It was proposed that Förster resonant energy transfer plays the important role in luminescence properties of closed packed PbS particles. The model, which describes the observed luminescent properties of the suspensions PbS‐stabilized high‐molecular polymer, is proposed. The combination of very wide spectral range of excitation of the luminescence with rather narrow range of light radiation in near infrared spectral range determine wide perspectives of the materials in solar luminescent concentrators and photodetectors. Copyright © 2015 John Wiley & Sons, Ltd.     

Enthalpies of mixing and apparent molar volumes of ethanol solution of chiral dicarboxylic acids

Enthalpies of mixing of R- and S-enantiomers of dicarboxylic acids such as 2-methylbutanedioic acid (MBA), 2-hydroxylbutanedioic acid (HBA), 2-methylpentanedioic acid (MPA) and 2-hydroxyl-2-methylbutanedioic acid (HMBA) in ethanol solution have been measured for a large range of mole fraction of heterochiral dicarboxylic acid at 298.15 K. Also densities of ethanol solution of the dicarboxylic acids were determined. Enthalpies of mixing were exothermic for all the concentrations. Enthalpic stabilization on mixing was increased with decreasing concentration of all dicarboxylic acids measured. Sequence of enthalpic stabilization on mixing was MBA mixing was MBA<DHBA<MPA<HMBA<HBS at 0.5 mass%.     

Two‐Component Self‐Assembly: Hierarchical Formation of pH‐Switchable Supramolecular Networks by π–π Induced Aggregation of Ion Pairs

Two‐component self‐assembly is a promising approach to construct functional nanomaterials. Interaction of a flexible guanidiniocarbonyl pyrrole tetra‐cation ( 1 ) with naphthalene diimide dicarboxylic acid (NDIDC) in aqueous DMSO leads to the formation of supramolecular networks. First, the carboxylate groups of NDIDC bind to the guanidiniocarbonyl pyrrole cations of 1 in a 1:2 stoichiometry. Further π–π induced aggregation then leads to 3D networks, as established by dynamic light scattering studies (DLS), NMR, fluorescence titration, viscosity measurements, AFM, and TEM microscopy. Due to ion pairing, the resulting aggregates can be switched between the monomers and the aggregates reversibly using external stimuli like protonation or deprotonation. At high concentration, a stable colloidal solution is formed, which shows an extensive Tyndall effect. Increasing the concentrations even further leads to formation of a supramolecular gel.     

Photo-controllable Luminescence from Radicals Leading to Ratiometric Emission Switching via Dynamic Intermolecular Coupling

The development of photoinduced luminescent radicals with dynamic emission color is still challenging. Herein we report a novel molecular radical system (TBIQ) that shows photo-controllable luminescence, leading to a wide range of ratiometric color changes via light excitation. The conjugated skeleton of TBIQ is decorated with steric-demanding tertiary butyl groups that enable appropriate intermolecular interaction to make dynamic intermolecular coupling possible for controllable behaviors. We reveal that the helicenic pseudo-planar conformation of TBIQ experiences a planarization process after light excitation, leading to more compactly stacked supermolecules and thus generating radicals via intermolecular charge transfer. The photo-controllable luminescent radical system is employed for a high-level information encryption application. This study may offer unique insight into molecular dynamic motion for optical manufacturing and broaden the scope of smart-responsive materials for advanced applications.     

The luminescence response of Eu(III)-thenoyltrifluoroacetonate complexes upon preresonant excitation with femtosecond laser pulses

The luminescence of thenoyltrifluoroacetonate (TTA) coordination complexes of trivalent europium ion (Eu(III)) in aqueous solutions and in solid-state polymeric films is probed upon single- and two-photon preresonant excitation with Ti:sapphire femtosecond laser. Particularly, diamine-liganded Eu(III)(TTA)₃ and poly(oxyethylene phosphate)tris(β-diketonate)Eu(III) complexes are examined aiming their possible applications as luminescent labels for sensing and imaging of biological molecules. Even at a pre-resonance, the excitation of these compounds with high-intensity, broadband light of frequency-doubled Ti:sapphire femtosecond laser centered around 400 nm results in a luminescence response suitable for fluorometric applications.     

Adsorption and charge transfer dynamics of bi-isonicotinic acid on Au(111)

The interaction of bi-isonicotinic acid (4,4(')-dicarboxy-2,2(')-bipyridine) with the Au(111) surface has been investigated using electron spectroscopic techniques. Near edge x-ray absorption fine structure (NEXAFS) spectra show that monolayers of the molecule lie flat to the surface and also reveal that the monolayer is sensitive to the preparation conditions employed. Core level x-ray photoelectron spectroscopy (XPS) shows that the adsorbed molecule does not undergo deprotonation upon adsorption. The "core-hole clock" implementation of resonant photoemission has been used to probe the coupling between molecule and substrate. This technique has revealed the possibility of ultrafast backtransfer from the substrate into the molecule upon resonant excitation of a N 1s core level electron. This is supported by a NEXAFS and XPS investigation of energy level alignments in the system.     

长余辉纳米材料的控制合成及在疾病诊断中的应用

长余辉纳米材料具有独特的发光性质, 能在激发光关闭后持续发光. 通过收集激发光关闭后的长余辉发光信号可以有效消除背景信号的干扰. 此外, 长余辉材料在成像时无需原位激发, 可以减少生物体系的组织自发荧光和光散射干扰, 提高生物成像和检测的灵敏度. 由于这种独特的光学特性, 长余辉纳米材料在生物传感/生物成像以及疾病治疗等领域被广泛应用. 近年来, 为满足疾病相关生物标志物的体外检测及体内生物成像的应用要求, 控制合成发光性能优异、 生物相容性好的长余辉纳米材料成为研究热点.     

New luminescent terbium complex for the determination of DNA

New terbium complexes of derivatives of 2-oxo-4-hydroxy-quinoline-3-carboxylic acid are reported, which are highly luminescent, water soluble and do not require luminescence enhancers. The triplet-state energy levels of the ligands, the relative quantum yields (QYs) and the excitation maxima of the respective terbium chelates were determined. The large luminescence enhancement of one of these complexes by nucleic acids was investigated and a mechanism of its interaction with DNA is proposed. The optimal conditions for determination of DNA are equal concentrations of Tb(3+) and ligand R(1) (C = 1 x 10(-6) M), pH 9.0. Under optimal conditions the luminescence intensity (RI) is proportional to the concentration of fish sperm DNA (fsDNA) or calf thymus DNA (ctDNA), respectively, within the range of 0.05-1.5 microg ml(-1). The detection limits were 10 ng ml(-1) for fsDNA and 12 ng ml(-1) for ctDNA.     

Luminescent sensing of dicarboxylates in water by a bismacrocyclic dinuclear Eu(III) conjugate

The design, synthesis, and characterization of a novel dinuclear Eu(III) bismacrocyclic conjugate 1.Eu2 as a delayed luminescent lanthanide sensor for dicarboxylates is discussed. The sensor was shown to bind small dicarboxylic acids such as aspartic, malonic, succinic, or glutaric acid in pH 6.5 solutions. However, only malonic acid gave rise to selective Eu(III) luminescent enhancements, as the emission was reduced for all of the other acids.     

Computational studies of semiconductor quantum dots

Light-absorption and luminescence processes in nano-sized materials can be modelled either by using computational approaches developed for quantum chemical calculations or by applying computational methods in the effective mass approximation (EMA) originally intended for solid-state theory studies. An overview of the theory and implementation of an ab initio correlation EMA method for studies of luminescence properties of embedded semiconductor quantum dots is presented. The applicability of the method and the importance of correlation effects are demonstrated by calculations on InGaAs/GaAs quantum-dot and quantum-ring samples. Ab initio and density functional theory (DFT) quantum chemical studies of optical transitions in freestanding silicon nanoclusters are also discussed. The accuracy of the optical gaps and oscillator strengths for silicon nanoclusters obtained using different computational methods is addressed. Changes in the cluster structures, excitation energies and band strengths upon excitation are reported. The role of the surface termination and functional groups on the silicon nanocluster surfaces is discussed.