Flow injection spectrophotometric determination of sub-mg dm(-3) silver(I) in a strongly acidic solution containing concentrated copper(II) using a pyridylazo reagent

A novel spectrophotometric flow injection method for determination of silver(I) in a strongly acidic solution containing concentrated copper(II) was developed using a coloring ligand, 4-(3,5-dibromo-2-pyridylazo)-N-ethyl-N-(3-sulfopropyl)aniline (3,5-diBr-PAESA). The method was first investigated by batch method. The interference from copper(II) chelate could be eliminated by the masking effect of EDTA. By utilizing the large formation constant (K = 12.3) of AgBr, one could determine silver(I) as a decrease of absorption by silver(I) chelate due to formation of AgBr by addition of KBr. Based on the results of batch experiments, two types of flow injection analysis (FIA) systems were constructed. Sub-mg dm(-3) determination of silver(I) was attained without interference from excess copper(II). The proposed method was successfully applied to determination of silver in a copper plating solution used in a plant to manufacture copper printed circuit boards, where the concentration of silver was critically important in the process control.     

The beam properties of high-power InGaAs/AlGaAs quantum well lasers

The vertical beam quality factor of the fundamental TE propagating mode for InGaAs/AlGaAs SCH DQW lasers emitting at 940 nm is investigated by using the transfer matrix method and the non-paraxial vectorial moment theory for non-paraxial beams. An experimental approach is given for the measurement of the equivalent vertical beam quality factor of an InGaAs/AlGaAs SCH DQW laser. It has been shown that the vertical beam quality factor M_x² is always larger than unity, whether the thickness of the active region of LDs is much smaller than the emission wavelength or not.     

Integrated photonic decoder with complementary code processing and balanced detection for two-dimensional optical code division multiple access

We propose a novel integrated photonic decoder for two-dimensional (time spreading, wavelength hopping) optical code division multiple access. The decoder is composed of multiplexers-demultiplexers, variable delay lines, and a coupler, which processes complementary codes and utilizes balanced detection to reduce unwanted cross-correlation interference. We successfully carried out a 10 Gbit/s transmission that demonstrated its effectiveness.     

Effect of chiral diene ligands in rhodium-catalyzed asymmetric addition of arylboronic acids to α,β-unsaturated sulfonyl compounds

Asymmetric addition of arylboronic acids to α,β-unsaturated sulfonyl compounds proceeded in the presence of a rhodium catalyst coordinated with a chiral diene ligand to give high yields of the addition products with high enantioselectivity (96->99.5% ee). The diene ligand was proved to be essential for the formation of the addition products, while the use of a bisphosphine ligand mainly gave the cine-substitution product.     

Observation of low-frequency fluctuations in vertical-cavity surface-emitting lasers

Low-frequency fluctuations, which are typical irregular oscillations in edge-emitting semiconductor lasers, are experimentally observed for the y-polarization mode (y is the direction along the optical axis of a laser material) in a vertical-cavity surface-emitting laser with optical feedback.     

Effect of underlying coronene and perylene adlayers for [60]fullerene molecular assembly

Supramolecularly assembled layers of C60 on coronene- and perylene-modified Au(111) surfaces were investigated and the structure of the C60 adlayer was found to be strongly influenced by the underlying organic layers, suggesting that the latter underlying organic adlayers play an important role in the process of formation of the C60 molecular adlayer.     

Oxidative electrochemical switching in dithienylcyclopentenes, part 1: effect of electronic perturbation on the efficiency and direction of molecular switching

The electro- and spectroelectrochemical properties of dithienylhexahydro- and dithienyhexafluorocyclopentenes are reported. The large effect of variation in the central cyclopentene moieties on the redox properties of the dithienylcyclopentenes is in striking contrast to the minor effect on their photochemical properties. The electronic properties of the oxidised compounds in the +1 and +2 oxidation state are reported, and the possibility of electrochemical cyclisation and cycloreversion were explored by UV/Vis spectroelectrochemistry. The efficiency of electrochemical switching is found to be dependent both on the central cyclopentene unit and on the nature of the substituents at C5 of the thienyl rings. For the hexahydrocyclopentene-based compounds oxidative ring closure of the ring-open form is observed, while for the hexafluorocyclopentene-based compounds oxidative ring opening of the ring-closed form is observed. However, the introduction of electroactive groups such as methoxyphenyl allows oxidative ring closure to occur in the hexafluoro compounds. The effect of electrolyte, solvent and temperature on the spectroelectrochemical properties were examined, and the switching process was found to be sensitive to the donor properties of the solvent/electrolyte system employed. In addition, thermally activated reversible isomerisation of the dicationic closed form was observed. The driving force for electrochemical ring opening and closure appears to be dependent on the relative stabilisation of the dicationic ring-open and ring-closed states. This study provides insight into the factors which determine the direction of cyclisation.     

Syntheses of aromatic polyketones and aromatic polyamide

High molecular weight aromatic polyketones were prepared from p- and m-phenoxybenzoic acid in polyphosphoric acid by heating the reaction mixture at 100°C. High molecular weight aromatic polyamide was derived from the polyketone obtained through Schmidt reaction or Beckmann rearrangement. The polyamide obtained by Schmidt reaction was found to have some regularity in an arrangement of its repeating units. The thermal stability of the polyketone and the polyamide were good.