Effects of Adsorbed Polyaniline on Redox Processes on As(2)O(3) Surfaces

Polyaniline deposited on As(2)O(3) surface resulted in a new material, which was characterized by infrared spectoscopy, thermogravimetry, differential scanning calorimetry, scanning electron microscopy, X-ray diffraction, and cyclic voltammetry. The mass percentage of polymer deposited on oxide surface is approximately 13%. The scanning electron microscopy images as well as the X-ray diffraction patterns provided conclusive evidence that the oxide surface is coated by the polymer. The cyclic voltammograms of the polyaniline adsorbed on As(2)O(3) surface showed that the adsorbate exerts remarkable effects on redox processes on this oxide. The pure oxide exhibited two oxidation/reduction peaks at 0.25/-0.06 and 0.47/-0.25 V attributed tentatively to the processes As(2)O(3)(s)+6H(+)+6e(-)=2As(s)+3H(2)O and As(s)+3H(+)+3e(-)=AsH(3)(g), respectively. The polyaniline-coated sample exhibited a better-defined voltammogram in which the first oxidation peak of the oxide had its intensity increased about four times. Copyright 2000 Academic Press.     

Uniformly Oriented Zeolite ZSM‐5 Membranes with Tunable Wettability on a Porous Ceramic

Facile fabrication of well‐intergrown, oriented zeolite membranes with tunable chemical properties on commercially proven substrates is crucial to broadening their applications for separation and catalysis. Rationally determined electrostatic adsorption can enable the direct attachment of a b‐oriented silicalite‐1 monolayer on a commercial porous ceramic substrate. Homoepitaxially oriented, well‐intergrown zeolite ZSM‐5 membranes with a tunable composition of Si/Al=25–∞ were obtained by secondary growth of the monolayer. Intercrystallite defects can be eliminated by using Na⁺ as the mineralizer to promote lateral crystal growth and suppress surface nucleation in the direction of the straight channels, as evidenced by atomic force microscopy measurements. Water permeation testing shows tunable wettability from hydrophobic to highly hydrophilic, giving the potential for a wide range of applications.     

Selenium-catalyzed oxidations with aqueous hydrogen peroxide. 2. Baeyer-Villiger reactions in homogeneous solution

Several diselenides were tested for catalytic activity in Baeyer-Villiger reactions with 60% aqueous hydrogen peroxide. Bis[3,5-bis(trifluoromethyl)phenyl] diselenide forms the corresponding 3,5-bis(trifluoromethyl)benzene seleninic acid in situ, which is a highly reactive and selective catalyst for the oxidation of carbonyl compounds in 1,1,1,3,3,3-hexafluoro-2-propanol, 2,2,2-trifluoroethanol, or dichloromethane.     

Two-phases Method and Branch and Bound Procedures to Solve the Bi–objective Knapsack Problem

The classical 0–1 knapsack problem is considered with two objectives. Two methods of the two–phases type are developed to generate the set of efficient solutions. In the first phase, the set of supported efficient solutions is determined by optimizing a parameterized single-objective knapsack problem. Two versions are proposed for a second phase, determining the non-supported efficient solutions: both versions are Branch and Bound approaches, but one is breadth first, while the other is depth first. Extensive numerical experiments have been realized to compare the results of both methods.     

Ion-molecule reactions of 2-methoxyethanol with some amines, carboxylic acids and amino acids under chemical ionization conditions

2-Methoxyethanol chemical ionization of amines, carboxylic acids and amino acids has been found to produce numerous adduct ions. The most intense adduct ions for amines are [M + H](+) and [M + 77](+), for carboxylic acids [M + 27](+), [M + 59](+) and [M + 77](+), and for amino acids [M + H](+), [M + 13](+), [M + 27](+) and [M + 77](+). Either the adduct ion [M + H](+) or [M + 77](+) was the most abundant ion found for amino acids. The proton affinities of amino acids are noticed to control the formation of the [M + H](+) and [M + 77](+) ions. The relative abundance of [M + 13](+) and [M + 27](+) ions varied for different amino acids being most intense for phenylalanine and aspartic acid. Copyright 1999 John Wiley & Sons, Ltd.