Colorimetric response of spiropyran derivative for anions in aqueous or organic media

We previously found that a simple spiropyran derivative (1:1′,3′,3′-trimethyl-6-nitro-spiro-[2H-1-benzopyran-2,2′-indoline]) behaves as a selective and sensitive cyanide anion (CN⁻) receptor in aqueous media under UV irradiation¹³. The receptor, when irradiated by UV light in a water/MeCN mixture, creates a CN⁻-selective absorption band via a nucleophilic addition of CN⁻ to 1 (formation of the 1-CN⁻ species) and allows quantitative determination of very low levels of CN⁻. In the present work, effects of pH and water content on the response of 1 to anions were studied to clarify the detailed properties of 1. In aqueous media, 1 reacts selectively with CN⁻regardless of pH and water content, but the reaction is suppressed by a decrease in pH and an increase in water content due to the protonation of CN⁻. In contrast, in pure MeCN, addition of F⁻ also creates a new absorption band, as does CN⁻. This is promoted via a nucleophilic interaction between 1 and F⁻ in a 1:2 stoichiometry (formation of the 1-2F⁻ species). The 1-CN⁻ and 1-2F⁻ species have different photochemical properties; the 1-CN⁻ species is stable upon UV irradiation, while the UV irradiation of the 1-2F⁻ species leads to a decomposition of the spiropyran platform.     

Influence of plasticizer content on the transition of electromechanical behavior of PVC gel actuator

The actuation performance of plasticized poly(vinyl chloride) (PVC) gel actuators in an electric field depends on their chemical composition and electrical and mechanical properties. The influence of plasticizer (dibutyl adipate) content on electromechanical behavior of PVC gels was investigated by impedance spectroscopy and space charge measurement. By plasticizing the PVC, the dielectric constant and space charge density of PVC gel were drastically increased at 1:2 w/w ratio of PVC to plasticizer. To apply the results obtained from the impedance spectroscopy and space charge measurement, electrostatic adhesive forces generated between the PVC gel and the anode were measured. The electrostatic adhesive force at the anode was also dramatically increased at the same plasticizer content. All of the results indicated a transition of electromechanical behavior of PVC gel in the electric field, which was considered to originate from the orientation of polarized plasticizer molecules and dipole rotation of PVC chains. By using the electrostatic adhesive force of PVC gel derived from the electromechanical transition, a new electroactive actuator can be developed for novel applications.     

Liquid phase separation of polyaromatics on [Cu2(BDC)2(dabco)

The porous coordination polymer (PCP) [Cu(2)(BDC)(2)(dabco)] is capable of selectively adsorbing up to 25 wt % of either 1-methylnaphthalene or 2-methylnaphthalene. Uptakes of unsubstituted naphthalene and 1,4-dimethylnaphthalene are significantly lower (7-13 wt %), suggesting that monomethyl substituted polyaromatics can be separated from the other fractions. Furthermore, this PCP can perform the difficult separation of 1-methylnaphthalene from 2-methylnaphthalene with separation factors as high as 2.6, proving that specific interactions of the methyl group with the lattice play an important role in determining the adsorption selectivity.     

A BODIPY-based fluorescent chemodosimeter for Cu(II) driven by an oxidative dehydrogenation mechanism

A boradiazaindacene (BODIPY) derivative containing a simple NO bidentate ligand shows a Cu(2+)-selective fluorescence in aqueous media. This is promoted via a coordination of Cu(2+) followed by oxidative dehydrogenation of an amine moiety, leading to a formation of a fluorescent Cu(+)-Schiff base complex.     

Gelled droplet vitrification improves recovery of cryopreserved potato germplasm

The droplet vitrification method was improved for maneuverability by embedding shoot tips in gelled droplets before osmoprotection. This newly modified cryopreserving method -gelled droplet vitrification - was compared with other PVS2-based cryopreservation methods using potato shoot tips. Survival rates of each cryogenic procedure held at 25 degree C were about 40 percent by cryotube-vitrification procedures (vitrification and encapsulation vitrification methods) and about 70 percent by PVS2-droplet procedures (droplet vitrification and gelled droplet vitrification methods). Much higher cooling rates of PVS2-droplet procedures than cryotube- vitrification procedures increased their survival rates. The gelled droplet vitrification method was applied to shoot tips of 26 potato cultivars and six wild potatoes. After a little modifications of the conditions for preculture, osmoprotection and dehydration, all cultivars and wild potatoes produced high enough survival rates to be of value to genebanks and all surviving shoot tips developed normal shoots within 3 weeks.     

A two dimensional liquid crystal simulation for thin film transistor liquid crystal displays

Abstract

A two-dimensional liquid crystal simulation, whose electrode configuration corresponds to that in a thin film transistor liquid crystal display (TFT-LCD), was carried out. Simulation results show that the lateral field between buslines and pixel electrode forms a reverse tilt domain. This reverse tilt domain leads to the disclination on the pixel electrode. The distance from the pixel electrode edge to this disclination location depends on the dielectric anisotropy and elastic constant for the liquid crystal. A small dielectric anisotropy or large elastic constant makes this distance small.     

Formation of a porphyrin/fullerene light-harvesting system from self-assembly of porphyrin-end-functionalized polycyclohexane and [6,6]-phenyl-C61-butyric acid methyl ester: Effects of microphase separation and π–π interactions

Thin films composed of zinc tetraphenylporphyrin-end-functionalized polycyclohexane (ZnTPP-PCHE) and [6,6]-phenyl-C₆₁-butyric acid methyl ester (PCBM) blends were prepared to investigate their potential as light-harvesting systems within polymer solar cells (PSCs). Both the microphase separation characteristics and the extent of π–π interactions in these ZnTPP-PCHE/PCBM blends had significant effects on the optical properties of the films. The extent to which the absorption bands of the films overlapped the terrestrial solar spectrum was increased considerably when the blends formed a co-continuous structure, even though films of pure ZnTPP-PCHE or PCBM exhibited only weak absorption over that wavelength region. We conclude that these polymer blend films may be considered as viable candidates for light-harvesting systems within PSCs. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2013     

Preparation of Colloidal Rhodium in Poly(vinyl Alcohol) by Reduction with Methanol

Refluxing of a solution of poly(vinyl alcohol) and rhodium(III) chloride in methanol-water gives a colloidal dispersion of rhodium which is an effective catalyst for hydrogenation of cyclohexene in methanol at 30°C under atmospheric hydrogen pressure. Formaldehyde is produced quantitatively with the reduction of rhodium(III) chloride to metallic rhodium. The rhodium particles in the colloidal dispersion are found to consist of two kinds of particles, about 8 and 40 Å in diameter by electron microscopy. The sizes of the small (8 Å) and large (40 Å) particles are almost constant during the course of refluxing. The number of small particles, which is the great majority of particles at the early stage of refluxing, gradually decreases; concurrently the number of large particle increases on prolonged refluxing. An absorption peak appears at 260 nm at the early stage of refluxing. The presence of the 260 nm peak, which indicates the coordination of poly(vinyl alcohol) to rhodium(III) ion, is indispensable for the formation of a homogeneous colloidal dispersion of rhodium. The addition of ethylenediamine inhibits the formation of colloidal rhodium in refluxing. The catalytic activity of colloidal dispersion of rhodium is dependent upon the concentration of rhodium(III) chloride charged and is independent of that of poly(vinyl alcohol). The formation mechanism of colloidal rhodium is discussed.     

Preparation of Colloidal Transition Metals in Polymers by Reduction with Alcohols or Ethers

Colloidal dispersions of rhodium, palladium, osmium, iridium, and platinum are prepared by refluxing the methanol-water solutions of rhodium(III) chloride, palladium(II) chloride, osmium(VIII) oxide, sodium chloroiridate, and chloroplatinic acid, respectively, in the presence of poly(vinyl alcohol) as a protective colloid. The preparations of colloidal dispersions of rhodium are successful in the presence of vinyl polymer with polar group such as poly(vinyl alcohol), polyvinylpyrrolidone, or poly(methyl vinyl ether). Polyethyleneimine, gelatin, polyethylene glycol), and dextran are ineffective as the protective colloid. Water-soluble primary alcohols such as methanol and ethanol, water-soluble secondary alcohols such as 2-propanol, and water-soluble diethers such as 1,4-dioxane are available as reductants for preparation of the colloidal dispersion of rhodium. The average diameters of metal particles in the colloidal dispersions of palladium, rhodium, platinum, iridium, and osmium in poly(vinyl alcohol) are determined by electron microscopy to be 53, 40, 27, 14, and < 10 Å, respectively. The particle size distribution in each colloidal dispersion is sharp within 50 Å wide. The particles in the colloidal dispersions of both iridium and osmium are highly dispersed with no aggregation, while in the colloidal dispersions of rhodium, palladium, and platinum, there exist aggregates of 5-15, 5-30, and 100-200 particles, respectively. Colloidal dispersions of rhodium, palladium, osmium, and platinum are effective as catalysts for hydrogenation of cyclohexene at 30.0°C under atmospheric hydrogen pressure.