Binding the hydrophobic fluorescent probe, 2-p-toluidinylnaphthalene-6-sulfonate,by polycations that contain apolar pendant groups: Equilibrium dialysis and fluorescence measurements

The thermodynamic parameters for the interaction of the hydrophobic fluorescent probe, 2-p-toluidinylnaphthalene-6-sulfonate (TNS), and polycations that contain a piperidinium cation and various nonpolar pendant groups were calculated. Binding is exothermic and involves a positive entropy gain. The contribution of the entropy term to the free energy change tends to increase with increasing hydrophobicity of the polymers. The intensity of the fluorescence of TNS is enhanced when the probe binds to the polycations. The nature and phenomena of hydrophobic fluorescent probe binding with the polymers are discussed.     

Fiber-optic calcium(II) sensor with reversible response

The fiber-optic sensor for calcium ions is based on the fluorescent chelate of chlortetracycline formed in aqueous solution at pH 7.5. The chlortetracycline is immobilized on an anion-exchange membrane, which is attached to the end of a bifurcated fiber optic. The sensor responds to calcium ions in the 0–400 mM range; the error in measurements is ± 10 mM. The response is reversible but other divalent metals interfere.     

Application of the thermal lens effect for determination of iron(II) with 4,7-diphenyl-1,10-phenanthroline disulfonic acid

A heat-induced refractive index change is used to increase the sensitivity of the spectrophotometric determination of iron(II) in a dual-beam system. An argon ion laser (514.5 nm) is used as the heating source and the intensity variation of a helium—neon laser (632.8 nm) is measured. The sensitivity is increased 7.3 times compared with spectrophotometry; the detection limit is 3 × 10^-7 M.     

Possibility of superconductivity in intercalation compound related to MgB2

We investigated the electronic structure of MgB₂ and intercalation compounds, MgBX (X = Li, Be, C), with fully relaxed crystal structure by using density functional theory. The compounds MgBLi and MgBBe could be similar two‐band superconductors to MgB₂ because the Fermi surface crosses σ and π bands. Our results indicate that changing the lattice constants, hole or electron doping, and stacking of B? X effect the energy levels of the σ and π bands in MgBX compounds. © 2003 Wiley Periodicals, Inc. Int J Quantum Chem, 2004     

Formal hydrochromination of alkynes under nickel catalysis. Regioselective reductive coupling of alkynes and aldehydes leading to allylic alcohols

Formal hydrochromation of an alkyne leading to a 1-substituted ethenylchromium reagent is accomplished by addition of the alkyne and water to a mixture of low-valent chromium(II), a catalytic amount of nickel(II), and triphenylphosphine in DMF.     

Temperature dependence on the binding of butyl orange by bovine serum albumin: The effect of urea

The effect of urea on the extent of the binding of butyl orange by bovine serum albumin has been examined by an equilibrium dialysis method. The first binding constants and the thermodynamic parameters for the formation of the first dye anion–protein complex have been calculated. Addition of urea to the binding system causes a marked decrease in the absolute magnitude of the free energy change. The enthalpy change during binding becomes more exothermic, and the entropy change tends to decrease with increasing concentration of urea. These results can be interpreted in terms of the concept that urea reduces the structure of the aqueous environment and hence lowers the tendency of apolar groups of the dye and the albumin to participate in the formation of hydrophobic interactions.     

The corrected structure of depressoside,an antioxidative iridoid glucoside extracted from the flowers of Gentiana urnula Harry Sm.

Three known iridoid glucosides (gentiournoside A, gentiournoside E and depressoside) were isolated from the flowers of Gentiana urnula Harry Sm. through activity-guided fractionations with a 1,1-diphenyl-2-picrylhydrazyl (DPPH) assay. All three compounds exhibited excellent DPPH radical scavenging activities (IC₅₀: 10–20 μmol L^?1) comparable to that of ascorbic acid and Trolox. However, examination of the NMR data revealed that the reported chemical structure of depressoside, previously isolated from the leaves of G. depressa, needed correcting due to incorrect elucidation around C-7 of the iridane skeleton, and was corrected to 6-β-(2,3-dihydroxyphenyl)-d-glucosyl 7-O-(2,3-dihydroxybenzoyl)-loganate. Depressoside exhibited a much higher scavenging activity against superoxide radicals (IC₅₀: 45.5 μmol L^?1) than the other two extracted compounds (IC₅₀: more than 900 μmol L^?1) due to the crucial presence of a pyrogallyl unit.     

A general strategy for highly efficient nanoparticle dispersing agents based on hybrid dendritic linear block copolymers

A modular approach to the synthesis of a library of hybrid dendritic‐linear copolymers was developed based on RAFT polymerization from monodisperse dendritic macroRAFT agents. By accurately controlling the molecular weight of the linear block, generation number of the dendrimer and the nature of the dendritic chains ends, the performance of these hybrid block copolymers as dispersing agents was optimized for a range of nanoparticles. For titanium dioxide nanoparticles, dispersion in a poly(methyl methacrylate) matrix was maximized with a second generation dendrimer containing four carboxylic acid end groups, and the quality of dispersion was observed to be superior to commercial dispersing agents for TiO₂. This approach also allowed novel hybrid dendritic‐linear dispersing agents to be prepared for the dispersion of Au and CdSe nanoparticles based on disulphide and phosphine oxide end groups, respectively. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 1237–1258, 2009     

Non-covalent strategy for activating separation and detection functionality by use of the multifunctional host molecule thiacalixarene

This review article proposes a non-covalent strategy for activating separation and detection functionality; this strategy acts not through extensive organic synthesis to a covalently constructed molecular receptor, but by combining a simple molecular platform with a chemical “field” or functional component. For such a platform, we employed thiacalixarenes—calixarenes in which the bridging methylene groups are replaced with sulfur—to demonstrate usefulness of the non-covalent strategy and the multifunctionality of thiacalixarene. Thiacalixarene exhibits inherent abilities to recognize metal ions by coordinating with the bridging sulfur and adjacent phenol oxygen, as well as to include organic guest molecules in the cavity. Moreover, the non-covalent coupling of thiacalixarene provides systems with functions higher than thiacalixarene by itself. The functions described in this paper are as follows: (1) a 200-fold pre-concentration of heavy metal ions such as Cu^II, Cd^II, and Pb^II; (2) a pre-column derivatization reagent for the highly selective and sensitive determination of Ni^II, Al^III, Fe^III, and Ti^IV at sub-ppb levels with reversed-phase HPLC; (3) the self-assembled formation of a luminescence receptor with Tb^III ions for the detection of 10^?10 M levels of 1-ethylquinolinium guest; and (4) a sensing system for 10^?9 M levels of Ag^I ions by the formation of the Ag^I-Tb^III-thiacalixarene ternary supramolecular complex. These examples support the non-covalent strategy as a highly promising way to obtain functions beyond that of a molecular platform. In addition, these diverse functions indicate the multifunctionality of thiacalixarene as well as its suitability to the non-covalent strategy, since the inherent functional groups—such as the bridging sulfur, phenol oxygen, p-substituent, aromatic ring, and hydrophobic cavity—synergistically perform the functions.     

New method to measure whole-wavelength transmittance of TCO substrates for thin-film silicon solar cells

High transmittance of transparent conductive oxide (TCO) substrates is one of the most important factors for achieving high efficiency in thin-film silicon solar cells. Immersion (IM) method with CH₂I₂ liquid is widely used for the evaluation of optical properties (transmittance, reflectance and absorption) for TCO substrates with textured surface in order to reduce the scattering at the TCO surface. However, in order to measure transmittance accurately, three problems have been found. (1) CH₂I₂ liquid itself absorbs the light in short wavelength region. (2) The transmittance around the absorption edge of CH₂I₂ liquids is very sensitive to its amount. (3) Scattering cannot be suppressed when the scattering surfaces are more than 2 surfaces (for example, TCO on reactive ion etching (RIE) processed glass). To overcome these problems, we proposed a new setup to measure optical properties of TCO substrates by holding the samples inside the integral sphere. As the results, we have confirmed that their absorption in all wavelength could be measured accurately and the transmittance measured by the new method was well consistent with the external quantum efficiency (EQE) of the fabricated cell while the transmittance measured with conventional IM method showed differently. Therefore, this new method could be a useful tool to evaluate TCO substrates for thin-film silicon solar cells.