A novel biosurfactant, 2-acyloxyethylphosphonate, isolated from waterblooms of Aphanizomenon flos-aquae

A novel biosurfactant, 2-acyloxyethylphosphonate, was isolated from waterblooms of Aphanizomenon flos-aquae. Its structure was elucidated by chemical degradation and HRFABMS, GC/EI-MS and 1D- and 2D-NMR spectral analyses. The surfactant contained one mole of 2-hydroxyethylphosphonate and one mole of fatty acid, with hexadecanoic acid accounting for 84.1% of the total fatty acid content. The structure was confirmed by synthesis of 2-oleoyloxyethylphosphonate from ethylene oxide, phosphorus acid and oleic acid chloride. Considering the isolated surfactant molecule as hexadecanoyloxyethylphosphonic acid (mw. 364), the critical micelle concentration (CMC) was about 22 mM.     

Arching a bay area of triphenyleno[1,12-bcd]thiophene with group 14 functionalities: Synthesis of the first triphenylene derivatives having thiophene and metallafluorene moieties

Arching a bay area of triphenyleno[1,12-bcd]thiophene with group 14 functionalities gave the first triphenylene derivatives whose two pairs of bay carbons are connected by two different heteroatom functionalities. Triphenyleno[1,12-bcd:4,5-b′c′d′]dithiophene, which had been only accessible through the very severe reaction conditions, was synthesized under the mild reaction conditions. Photophysical properties of newly-obtained heterolotriphenylene derivatives are discussed with theoretical calculations.     

Flow injection fluorometric determination of ascorbic acid using perylenebisimide-linked nitroxide

A simple and sensitive flow injection fluorometric method for the determination of ascorbic acid is described. Perylenebisimide-linked nitroxide (PBILN) is used as a fluorescent reagent, which permits the selective determination of ascorbic acid. The fluorescence of the perylenebisimide moiety in PBILN is quenched by the nitroxide moiety, which is linked to the perylenebisimide. When a stream of a solution of ascorbic acid is merged with a stream of PBILN, the ascorbic acid reacts with the nitroxide moiety of PBILN to form hydroxylamine, and the fluorescence properties of the perylenebisimide moiety are recovered. As a result, a peak-shaped fluorescence signal is produced, which can be observed by a fluorescence detector located downstream. Under optimized conditions, a good linear relationship between the concentration of ascorbic acid and peak height in the concentration range from 0.5 to 10 μmol L⁻¹ was found and the detection limit (S/N = 3) was 0.28 μmol L⁻¹. The relative standard deviation for the determination of 4.0 μmol L⁻¹ ascorbic acid samples was 1.0% (n = 5). The proposed method was applied to the determination of ascorbic acid in several soft drink beverages and the analytical results were in good agreement with those obtained using a conventional method.     

Synthesis, structures and optical properties of trisilasumanene and its related compounds

Novel trisilasumanenes that have no substituents on the exo carbon atoms, silicon analogues of sumanene, were prepared via repetitive lithiations of triphenylene followed by introduction of silicon functionalities. The optical properties of these trisilasumanenes and their related compounds were investigated by UV-vis and fluorescence spectroscopy.     

Engineering control over the conformation of the alkyne-aryl bond by the introduction of cationic charge

A novel arylene-ethynylene molecule has been synthesized. This molecule is more stable in a coplanar form than in a twisted form as in the cases of typical arylene-ethynylene molecules. When the cationic charge was introduced into the pi-conjugated system, the perpendicularly twisted form became more stable than the coplanar state. The conformational change was controlled by introduction and removal of cationic charge, confirmed by the absorption and fluorescence spectroscopy and DFT calculation.     

Simple and effective 3D recognition of domoic acid using a molecularly imprinted polymer

We have developed a simple and effective molecular imprinting technique to target compounds with flexible structure. Domoic acid (DA), an amnesic shellfish poison, was used as the target compound while many acidic compounds (mono-, di-, and tricarboxylic acids) were used as template molecules for molecularly imprinted polymers (MIPs). Evaluation of selective recognition abilities using liquid chromatography revealed that the highest selective recognition ability for DA was found when pentane-1,3,5-tricarboxylic acid (1,3,5-PeTA) was used as the template. Computer modeling studies of the DA structure suggested that the observed selective recognition depended on the structural changes in DA at the recognition site of the MIPs as well as spatial distance between the COOH groups in DA and 1,3,5-PeTA. Using the 1,3,5-PeTA-MIP, we could easily purify DA from blue mussel extracts by solid-phase extraction.     

Experimental comparison of a Kerr nonlinearity figure of merit including the stimulated Brillouin scattering threshold for state-of-the-art nonlinear optical fibers

We introduce a new figure of merit (FOM) including the input pump power limit associated with stimulated Brillouin scattering (SBS) for evaluation of the Kerr nonlinearity efficiency of optical fibers. The new FOM is expressed as gammaL(eff)P(SBS) (gamma is a nonlinearity parameter, L(eff) is effective length, and P(SBS) is the SBS threshold), while the conventional FOM is given by gammaL(eff). Using the new FOM, we perform an efficiency comparison among four types of state-of-the-art nonlinear optical fiber: a Bi2O3-based nonlinear fiber, a silica-based holey fiber, a highly nonlinear dispersion-shifted fiber, and a conventional dispersion-shifted fiber. The Bi2O3-based nonlinear fiber is found to have the best Kerr nonlinearity efficiency owing to the superior nonlinear property of the Bi2O3 glass compared with that of the silica.     

Design and fabrication of bismith-silicate photonic crystal fiber

The process of design and fabrication of bismuth-silicate photonic crystal fiber (Bi-PCF) is reported. The Bi-PCF was fabricated by stack and draw method. This is the first trial of the fabrication of photonic crystal fiber made of bismuth-based glass with stack and draw method. The Bi-PCF structure was designed to reduce group-velocity-dispersion (GVD) in a plausible process. Thermal properties of the glass are investigated to establish the fabrication process. The applying pressure and pumping in fiber preform preparation were effectively utilized to control the air-hole diameter and arrangement. The fabricated Bi-PCF shows the well reduced GVD as the numerical calculation predicted. Fusion splicing between Bi-PCF and SMF-28 was also demonstrated.