Photophysical property and photostability of J-aggregate thin films of thiacyanine dyes prepared by the spin-coating method

By use of electrostatic interactions of dye molecules and poly(diallyldimethylammonium chloride) (PDDA), the spin-coating technique has been successfully applied to the preparation of stable J-aggregate thin films of thiacarbocyanine dyes on a polycarbonate or quartz plate. The J-aggregate thin films were prepared by the spin-coating of PDDA aqueous solution on dye thin films prepared on a substrate by the spin-coating of 2,2,3,3-tetrafluoro-1-propanol solution of dyes. Photophysical properties of the dye thin films and J-aggregate thin films were studied by measuring the fluorescence spectra, quantum yields, and lifetimes. Coherent size of the J-aggregates was estimated to be 3-12 by means of the absorption bandwidth (full width at half maximum) or radiative lifetime. Photostability of the J-aggregate thin films was also studied in terms of photodegradation efficiency under argon and oxygen in comparison with the dye thin films, and J-aggregate thin films were found to be more stable than the corresponding dye thin films.     

Formation and characterization of water-soluble hetero capsules derived from multiple ionic interactions

We now report the formation and characterization of water-soluble hetero-capsules 1·2 resulting from the ionic interactions between positively charged flexible aniline hydrochloride 1 and negatively charged phosphonate 2 having rigid homooxacalix[3]arene units. The formation of the molecular capsules was studied by NOESY, DOSY NMR spectroscopy and ESI-Mass spectrometry. The water solubility of the capsules is improved by the introduction of mono- or triethylene glycol substituents in the homooxacalix[3]arene-based phosphonate units 2.     

Characterization of microbial poly (ε-l-lysine) by FT-IR, Raman and solid state C NMR spectroscopies

The molecular structure and conformation of microbial poly(ε-l-lysine) (M-ε-PL) produced by a variant of Streptomyces albulus were studied by means of FT-IR, FT-Raman and solid-state ¹³C NMR spectroscopies. Vibrational results indicate that M-ε-PL assumes a β-sheet conformation in the solid state. Solid state ¹³C NMR spectra of the crystalline and the amorphous components were observed separately and the degree of crystallinity was estimated to be 63%. A plausible conformation model was proposed.     

Determination of thallium in soils by flame atomic absorption spectrometry

A method is described for the determination of Tl in soils by FAAS, involving extraction of Tl from 5 g of soil by digestion with HClO₄/HNO₃ followed by separation of the extracted Tl into 5 mL of diisopropylether from HBr solution, including Ce(SO₄)₂. Tl in the organic phase is determined by direct aspiration into the spectrophotometer. The percentage relative standard deviation (% RSD) for 5 replicate samples is about 1%. The detection limits (S/N = 3) of this method are 0.001 mg/L for aqueous solution and 0.02 mg/kg DW for soil, when 50 mL of soil solution corresponding to 2.5 g soil are used. The Tl concentration even of unpolluted soils can be determined. The method was shown to be unaffected by the presence of various ions in soil and was able to recover nearly 100% Tl added to soils. The arithmetic mean (range) of 18 Japanese unpolluted surface soils was 0.33 (0.10–0.56)mgTl/kg DW.     

New approach to the first-order phase transition of Lennard-Jones fluids

The multicanonical Monte Carlo method is applied to a bulk Lennard-Jones fluid system to investigate the liquid-solid phase transition. We take the example of a system of 108 argon particles. The multicanonical weight factor we determined turned out to be reliable for the energy range between -7.0 and -4.0 kJ/mol, which corresponds to the temperature range between 60 and 250 K. The expectation values of the thermodynamic quantities obtained from the multicanonical production run by the reweighting techniques exhibit the characteristics of first-order phase transitions between liquid and solid states around 150 K. The present study reveals that the multicanonical algorithm is particularly suitable for analyzing the transition state of the first-order phase transition in detail.     

Multicolor fluorescence of a styrylquinoline dye tuned by metal cations

A styrylquinoline dye with a dipicolylamine (DPA) moiety (1) has been synthesized. The dye 1 in acetonitrile demonstrates multicolor fluorescence upon addition of different metal cations. Compound 1 shows a green fluorescence without cations. Coordination of 1 with Cd(2+) shows a blue emission, while with Hg(2+) and Pb(2+) exhibits yellow and orange emissions, respectively. The different fluorescence spectra are due to the change in intramolecular charge transfer (ICT) properties of 1 upon coordination with different cations. The DPA and quinoline moieties of 1 behave as the electron donor and acceptor units, respectively, and both units act as the coordination site for metal cations. Cd(2+) coordinates with the DPA unit. This reduces the donor ability of the unit and decreases the energy level of HOMO. This results in an increase in HOMO-LUMO gap and blue shifts the emission. Hg(2+) or Pb(2+) coordinate with both DPA and quinoline units. The coordination with the quinoline unit decreases the energy level of LUMO. This results in a decrease in HOMO-LUMO gap and red shifts the emission. Addition of two different metal cations successfully creates intermediate colors; in particular, the addition of Cd(2+) and Pb(2+) at once creates a bright white fluorescence.     

In‐situ Fabrication of Functional Materials inside Porous Fiber using Microwave Selective Heating

We developed a simple fabrication method, which can emplace functional materials inside porous fibers. In contrast to conventional impregnation methods or surface coating, various functions can be included inside of natural or synthetic fibers. This fabrication method has three steps. First, the raw material solution is absorbed to the fiber. Then the fiber is immersed and pressurized in immiscible liquids with the raw material solution. Finally, the functional particles are fabricated in‐situ inside of the fiber by a chemical reaction such as microwave selective heating. As a model reaction, we fabricated silver‐nanoparticle‐containing cotton fiber. The elemental silver was distributed inside of the fiber in a cross‐sectional distribution as confirmed by SEM‐EDS. Furthermore, we fabricated fibers with zeolite particles inside of porous PTFE fibers.     

Cu(II)-selective fluorescence of a bis-quinolylimine derivative

A new bis-quinolylimine ligand containing an azadiene moiety, 1,4-bis(2-quinolyl)-2,3-diaza-1,3-buthadiene (1), was synthesized by one-step facile condensation. This simple ligand, when dissolved in acetonitrile, shows a Cu²⁺-selective fluorescence enhancement. Coordination of 1 with Cu²⁺ produces two kinds of complexes with 1:1 and 1:2 stoichiometries. The 1:2 complex shows a strong fluorescence (Φ_F = 0.37), while the 1:1 complex does not (Φ_F < 0.01). Ab initio molecular orbital calculation reveals that the 1:1 complex has a distorted structure, while the 1:2 complex has a planar structure. The planar configuration of the 1:2 complex, therefore, allows an extended π-conjugation over the entire molecule and, hence, results in fluorescence enhancement.     

Fluorescence properties of polyamines bearing two terminal quinoline fragments in water

Fluorescence properties of polyamines bearing two terminal quinoline fragments with different polyamine chain length, such as ethylenediamine (L0), diethylenetriamine (L1), and triethylenetetramine (L2), have been studied in water. These ligands show Zn²⁺-induced fluorescence enhancement, while showing almost no enhancement with other cations. However, stability constants for Zn²⁺ coordination and fluorescence response against Zn²⁺ depend strongly on the polyamine chain length. The chain length also affects the fluorescence wavelength. The Zn²⁺-L1 and Zn²⁺-L2 complexes show emission at 410 nm, while Zn²⁺-L0 complexes show a blue-shifted emission at 375 nm due to the partial charge transfer from the excited state quinoline to the Zn²⁺ center.     

Optimum observation conditions of emission spectra from laser induced plasmas evaluated by using a two-dimensionally imaging spectrograph.

A two-dimensionally imaging spectrometer system was employed to measure spatial variations in the intensities of emission lines in a Cu-Mn-Ni alloy sample when they were excited from a laser-induced plasma with krypton gas. The emission zone of these lines shrank and had greater emission intensities with increasing gas pressure, and the intensities of their background also became more intense. It was thus found that the optimum observation zone for the analytical application varied with the pressure of the plasma gas. The two-dimensional distribution of the signal-to-background ratio for each analytical line was investigated to determine the measuring conditions for the emission analysis, indicating that the spatially-resolved measurement was generally superior to the conventional spatially-integrated measurement over the plasma region.