Diphenylamine‐Substituted Cruciform Oligo(phenylene vinylene): Enhanced One‐ and Two‐Photon Excited Fluorescence in the Solid State

1,4‐di(4′‐N,N‐diphenylaminostyryl)benzene (DPA‐DSB) is a well known compound with a large two‐photon absorption (TPA) section and strong fluorescence in solution. However, the ease with which it crystallizes results in the formation of discontinuous crystalline phases during vacuum deposition processes, thereby greatly limiting its applicability in solid‐state devices. A cruciform dimer of DPA‐DSB, 2,5,2′,5′‐tetra(4′‐N,N‐diphenylaminostyryl)biphenyl (DPA‐TSB) is reported, wherein two DPA‐DSB molecules are linked through a central biphenyl bond. The DPA‐TSB molecules take on a cruciform configuration because of the steric crowding around the central biphenyl core, which has the effect of efficiently suppressing crystalline and intermolecular interactions. The neat DPA‐TSB solid shows strong green–blue fluorescence because of both steady‐state absorption as well as TPA. The DPA‐TSB solid exhibits a photoluminescence (PL) efficiency (η_solid) of 29 % and a solid‐state two‐photon action cross section (δη_solid) of 954 GM (1 GM = 1 × 10^–50 cm⁴ s photon^–1 molecule^–1), which is much greater than for the model compound DPA‐DSB (η_solid = 16 % and δη_solid = 150 GM, where δ is the TPA cross section and η is the fluorescence quantum yield). Based on its high PL efficiency, good film‐forming ability, and strong TPA, DPA‐TSB seems to be a good candidate for applications in solid‐state optical devices.     

Structural Changes in the BODIPY Dye PM567 Enhancing the Laser Action in Liquid and Solid Media

In the search for more efficient and photostable solid‐state dye lasers, newly synthesized analogs of the borondipyrromethene (BODIPY) dye PM567, bearing the polymerizable methacryloyloxypropyl group at position 2 (PMoMA) or at positions 2 and 6 (PDiMA), have been studied in the form of solid copolymers with methyl methacrylate (MMA). The parent dye PM567, as well as the model analogs bearing the acetoxypropyl group in the same positions, PMoAc and PDiAc, respectively, have been also studied both in liquid solvents and in solid poly(MMA) (PMMA) solution. Although in liquid solution PMoAc and PDiAc have the same photophysical properties as PM567, PDiAc exhibited a photostability up to 10 times higher than that of PM567 in ethanol under 310 nm‐irradiation. The possible stabilization factors of PDiAc have been analyzed and discussed on the basis of the redox potentials, the ability for singlet molecular oxygen [O₂(¹Δ_g)] generation, the reactivity with O₂(¹Δ_g), and quantum mechanical calculations. Both PMoAc and PDiAc, pumped transversally at 532 nm, lased in liquid solution with a high (up to 58 %), near solvent‐independent efficiency. This enhanced photostabilization has been also observed in solid polymeric and copolymeric media. While the solid solution of the model dye PDiAc in PMMA showed a lasing efficiency of 33 %, with a decrease in the laser output of ca. 50 % after 60 000 pump pulses (10 Hz repetition rate) in the same position of the sample, the solid copolymer with the double bonded chromophore, COP(PDiMA‐MMA), showed lasing efficiencies of up to 37 %, and no sign of degradation in the laser output after 100 000 similar pump pulses. Even under the more demanding repetition rate of 30 Hz, the laser emission from this material remained at 67 % of its initial laser output after 400 000 pump pulses, which is the highest laser photostability achieved to date for solid‐state lasers based on organic polymeric materials doped with laser dyes. This result indicates that the double covalent linkage of the BODIPY chromophore to a PMMA polymeric matrix is even more efficient than the simple linkage, for its photostabilization under laser operation.     

多组分气体检测与识别技术进展

介绍了国内外气体检测技术的分类与发展现状,论述了当前主要气体检测技术的原理、用途及优缺点,并对不同的气体检测方法进行了比较,通过分析认为红外光谱气体检测技术具有检测精度高、检测范围广的特点,在气体检测领域,是一种发展前景极为广阔的新技术,因此应用与开发红外光谱气体检测技术应该会成为气体检测领域发展的一种趋势.     

Fluorescence properties and energy transfer mechanism of Sm ion in lead telluroborate glasses

We report the fluorescence properties of Sm³⁺-doped lead telluroborate glasses of composition PbF₂.TeO₂.H₃BO₃.Sm₂O₃ as a function of Sm³⁺ concentration. A Judd-Ofelt scheme was used to determine the intensity parameters and radiative properties of Sm³⁺ ion. The emission and decay measurements were carried out at 402 nm excitation. Beyond 1.0 mol% Sm³⁺ concentration, the luminescence quenching is observed. The decay curves of ⁴G_5/2 level are well fitted to a single exponential function. The evaluated radiative properties suggest that the ⁴G_5/2 → ⁶H_7/2 transition is responsible for reddish-orange luminescence which might be used in the development of visible lasers.     

Zwitterionic diaminodicyanoquinodimethanes with enhanced blue-green emission in the solid state

Diaminodicyanoquinodimethane molecules which show strong solid state emission in the blue-green region are developed. The new materials are structurally characterized; extended supramolecular assemblies mediated by H-bond interactions are observed in the crystal lattice. Spectroscopic studies including life-time and fluorescence quantum yield measurements in the solution and solid states are carried out. Emission in the solid state is ∼400 times stronger than that in solution; this can be attributed to the inhibition of the excited state geometry relaxation to a non-radiative state, in the solid. Impact of the molecular structure in the crystals on the solid state light emission is discussed. Semiempirical computational studies provide useful insight into the various structural and spectroscopic features of the new materials. The present observations serve as a pointer to further design strategies for realizing novel blue photoluminescent molecular materials based on the diaminodicyanoquinodimethane framework.     

Facile synthesis and characterization of novel coronene chromophores and their application to LCD color filters

New coronene derivatives, diphenylcoronene tetracarboxdiimide and monophenylbenzoperylene tetracarboxdiimide, were synthesized from N,N′-bis(2,6-diisopropylphenyl)-1,7-dibromoperylene-3,4,9,10-tetracarboxdiimide via a one-step reaction. The suggested synthetic route is the simplest and most economical among the methods to extend the aromatic systems along the short molecular axis of perylene. The synthesized molecules exhibited superior stability and color strength as yellow chromophores. They were characterized by significant hypsochromic shifts of the absorption compared to perylene tetracarboxdiimide and high fluorescence quantum yields.     

Growth and spectroscopic investigation of new promising laser crystal chromium (IV) doped germanoeucryptite Cr:LiAlGeO4

Single crystals of germanoeucryptite doped by chromium (IV) have been grown for the first time. Spectroscopic properties of grown crystals have been investigated. The intensive broadband fluorescence of Cr⁴⁺-ions in the range between 1070 and 1600 nm was observed with lifetime 10 μs. Preliminary investigations show that this material is promising for use as an active medium for new tunable solid-state laser of near IR-region.     

Use of fluorescence fingerprints for the estimation of bloom formation and toxin production of Microcystis aeruginosa

The development of methods facilitating the detection of cyanobacterial blooms in drinking water reservoirs at an early stage is of great importance. Fluorescence spectroscopy could meet these requirements. The study contains the examination of possible correlations between the different maxima of a fluorescence excitation-emission matrix and the amount of produced and excreted toxins of a lab culture of Microcystis aeruginosa at different stages of growth. Various fluorescence signals (protein-like and humic-like substances, pigments) are suited for an estimation of cell density and actual intra- and extracellular toxin concentration. One signal at 315 nm/396 nm presumably originating from protein-like substances might be useful as a tool for the prediction of increasing cyanobacterial toxin concentrations. As the measurement of fluorescence matrices is still time consuming, synchronous scans with Δλ = 80 nm were tested as a potential alternative. They accurately depict the course of protein-like and humic-like fluorescence during the different stages of growth although especially the latter one is not captured at its maximum. However, due to insufficient separation of chlorophyll a and phycocyanin, the image of the matrix maxima by synchronous scans with Δλ = 80 nm can only be used with minor restrictions. Nevertheless, fluorescence spectroscopy seems to be a powerful tool for the evaluation of cyanobacterial blooms.     

Molecular recognition of DNA–protein complexes: A straightforward method combining scanning force and fluorescence microscopy

Combining scanning force and fluorescent microscopy allows simultaneous identification of labeled biomolecules and analysis of their nanometer level architectural arrangement. Fluorescent polystyrene nano-spheres were used as reliable objects for alignment of optical and topographic images. This allowed the precise localization of different fluorescence particles within complex molecular assemblies whose structure was mapped in nanometer detail topography. Our experiments reveal the versatility of this method for analysis of proteins and protein–DNA complexes.