Determination of iron(II) with 2-nitroso-5-diethylaminophenol by thermal lens spectrophotometry using a semiconductor laser as a light source

The concentration of Fe(II) ion is determined by chelation with 2-nitroso-5-diehtylaminophenol and liquid-liquid extraction into chloroform. Light absorption at 780 nm is measured with a thermal lens spectrophotometer equipped with a semiconductor laser as a light source. The enhancement factor achieved experimentally is 47. The detection limit of Fe(II) ion is 8.1 × 10^?9 M, which is 3–4 times better than that obtained by conventional absorption spectrometry, and is governed by the background signal originating from Fe(II) impurity in the reagent.     

Effect of sulphonic acid on the aqueous solubility of disperse dyes

Summary The solubilities of the following compounds in water andp-toluenesulphonic acid aqueous solution were determined at 5, 25 and 40 C: azobenzenep-aminoazobenzene,p-hydroxyazobenzene,p-N, N-dimethylaminoazobenzene and 1-phenylazo-4-aminonaphthalene. Prom the results the thermodynamic parameters for the transfer of one mole of the compound from water top-toluenesulphonic acid aqueous solution were calculated. It was found that the process was nearly athermal: furthermore, it was invariably accompanied by a positive unitary entropy change. The solubilizing mechanism of aromatic sulphonic acids was explained in terms of an adduct-formation with the compound to be dissolved by means of hydrophobic and nonpolarvan der Waals interactions.

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Zusammenfassung Die Löslichkeiten folgender Verbindungen in Wasser und wÄ\rigerp-ToluolsulphonsÄure-Lösung wurden bei 5, 25 und 40 C bestimmt: Azobenzol,p-Aminoazobenzol,p-Hydroxyazobenzol,p-N,N-dimethylammoazobenzol undL-Phenylazo-4-aminonaphthalin. Aus den Ergebnissen wurden die thermodynamischen Parameter für den übergang eines Mols der Verbindung von Wasser zup-ToluolsulphonsÄurewÄ\rigen Lösungen berechnet. Es wurde gefunden, da\ die Prozesse nahezu athermisch sind. Au\erdem sind sie sÄmtlich durch eine positive und gleichmÄ\ig gro\e EntropieÄnderung begleitet. Der Lösungsmechanismus aromatischer SulphonsÄuren wird in den Begriffen einer Adduktbildung mit der Komponente erklÄrt, die durch die hydrophoben unpolarenvan-der-Waals-Wechselwirkungen entsteht.

     

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.     

Raman spectroscopic study of phase transitions in undoped morphotropic PbZr1−xTixO3

Several PbZr_1−xTi_xO₃ (PZT) compositions in the proximity of the morphotropic phase boundary (MPB) were examined by means of Raman spectroscopy in the 15–800 K temperature range. Previous studies performed by other researchers using various techniques evidenced that, in the phase diagram of PZT, areas with rhombohedral/monoclinic and tetragonal/monoclinic phases coexist across the MPB. For these compositions, either long‐range or short‐range symmetry ordering of the monoclinic phase should be considered, so that no true rhombohedral–monoclinic–tetragonal phase boundary exists. In addition, the onset of antiferrodistortive phase transitions between high‐T and low‐T perovskite phases has been predicted by ab initio calculations and experimentally reported. In the present work, low‐T and high‐T Raman scattering spectra were collected on undoped PbZr_1−xTi_xO₃ with compositions x = 0.42, 0.45, 0.465, 0.48 and 0.53 in an attempt to clarify the current open issues on the phase diagram of PZT. Spectra clearly belonging to the respective phases were observed in the rhombohedral, monoclinic and tetragonal areas, thus confirming that monoclinic ordering is long‐range only for a narrow range of compositions. Raman measurements at cryogenic temperatures allowed detecting all predicted low‐T phases, including the tetragonal one. These results are in good agreement with both ab initio calculations and experimental results obtained by other authors on the same compositions. Copyright © 2010 John Wiley & Sons, Ltd.     

Leucine pools in Escherichia coli biofilm discovered by Raman imaging

In structured communities of bacteria known as biofilms, a variety of biomolecules have been shown to play a unique role as signals and/or regulators in biofilm formation. Here, we report that high levels of the amino acid leucine (leucine pool) were detected, for the first time, within microcolonies in a 30‐h‐old Escherichia coli biofilm by Raman imaging. Localization of leucine revealed by multifrequency Raman images indicates leucine accumulation during the early stage of the E. coli biofilm formation, which may have resulted from physiological environment‐specific metabolic adaptation. We demonstrate that our label‐free Raman imaging method provides a useful platform for directly identifying still unknown natural products produced in biofilms as well as for visualizing heterogeneous distributions of biofilm constituents in situ. Copyright © 2011 John Wiley & Sons, Ltd.     

Mono‐, Di‐, or Triazidated Cyclodextrin‐Based Polyrotaxanes for Facile and Efficient Functionalization via Click Chemistry

As a feasible way for controlling the density of ligands in polyrotaxanes, azidated polyrotaxanes comprising PEG (MW = 3 000 and 20 000 g · mol⁻¹) and mono‐, di‐, or triazidated α‐cyclodextrins are prepared in a water/DMSO solution in a one‐pot synthesis. The azidated polyrotaxanes are then allowed to conjugate with propargyl‐modified mannose as a ligand via click chemistry. As proven by FTIR spectroscopy and ¹H NMR‐spectroscopy, mannose molecules are efficiently introduced into all of the azide moieties of the polyrotaxanes. The results verify the achievement of ligand‐density‐controlled polyrotaxanes. The functionalized polyrotaxanes can be utilized for a variety of biological applications.

     

Defensive effects of fullerene-C60/liposome complex against UVA-induced intracellular reactive oxygen species generation and cell death in human skin keratinocytes HaCaT,associated with intracellular uptake and extracellular excretion of fullerene-C60

The UVA-irradiation of 10 J/cm² on HaCaT keratinocytes increased 59.1% of the intracellular reactive oxygen species (ROS) by NBT assay and the cell viability decreased to 31.5% by WST-1 assay, comparing to the non-irradiated control. In the presence of fullerene-C60 (C60) incorporated in phospholipid membrane vehicle (LiposomeFullerene: Lpsm-Flln) of 250–500 ppm, they were restored to ?9.1% to  + 2.3% of the ROS and 83.0–84.8% of the cell viability, but scarcely restored by the liposome without C60 (Lpsm). In HaCaT cells administered with Lpsm-Flln (150 ppm), C60 was ingested at the intracellular concentrations of 1.4–21.9 ppm for 4–24 h, and, intracellular C60 was excreted by 80% at 4 h after rinsing-out, and decreased to 2–10% after 24–48 h. C60 was predominantly distributed around the outside of nuclear membrane without deterioration of intact cell morphology according to fluorescent immunostain. Thus Lpsm-Flln is found to be an effective antioxidant that could preserve HaCaT keratinocytes against UVA-induced cellular injury. Lpsm-Flln has a potential to serve as a cosmetic material for skin protection against UVA.