Effect of Liquid-Phase Oxidative Treatments on the Purity,Hydrophilicity, and Structure of Single-Wall Carbon Nanotubes and on the Electrical Conductivity of Their Arrays

Russian Journal of Applied Chemistry - A study using a set of physicochemical methods has shown that treatment of single-wall carbon nanotubes synthesized by the electric arc method with an aqueous...     

Generation and detection of gaseous W12O 41 −· and other tungstate anions by laser desorption ionization mass spectrometry

The presence of a peak centered near m/z 2862, observed for the first time for the caged dodecatungstate radical-anion, [W₁₂O₄₁]^−·, enables distinguishing WO₂ from WO₃ by Laser Desorption Ionization mass spectrometry (LDI-MS). In addition to WO₂, laser irradiation of dry deposits made from aqueous ammonium paratungstate, and calcium and lead orthotungstate also produce the [W₁₂O₄₁]^−·. In contrast, spectra recorded from deposits made from aqueous Na₂WO₄, sodium metatungstate, and WO₃, or non-aqueous calcium and lead orthotungstate, and ammonium paratungstate, failed to show the m/z 2862 peak cluster. These observations support the hypothesis that polycondensation reactions to form [W₁₂O₄₁]^−· occur solely in the presence of water. Although dry spots are irradiated for ionization, the solvent used for sample preparation plays an important role on the chemical composition endowed to ions detected. For example, the m/z 2862 peak seen from deposits made from aqueous ammonium paratungstate, and calcium and lead orthotungstate, is absent in the spectra recorded either from pristine deposits or those derived from solutions made with organic solvents such as acetonitrile or ethanol.     

Analytical Applications of Enzymatic Growth of Quantum Dots

We have developed an analytical assay to detect the enzymatic activity of acetylcholine esterase and alkaline phosphatase based on the generation of quantum dots by enzymatic products. Acetylcholine esterase converts acetylthiocholine into thiocholine. The latter enhances the rate of decomposition of sodium thiosulfate into H₂S, which in the presence of cadmium sulfate yields CdS quantum dots showing a time dependent exponential growth, typical of autocatalytic processes. This assay was also applied to detect acetylcholine esterase inhibitors. Alkaline phosphatase hydrolyzes thiophosphate and yields H₂S, which instantly reacts with Cd²⁺ to give CdS quantum dots. The formation of CdS quantum dots in both reactions was followed by fluorescence spectroscopy and showed dependence on the concentration of enzyme and substrate.     

Electrooptical and Conformational Properties of Poly(1-Trimethylsilyl-1-Propynes) with Different Chain Microstructures

The methods of the Kerr effect and solution hydrodynamics were applied to study the electrooptical and hydrodynamic properties of samples of disubstituted polyacetylenes, poly(1-trimethylsilyl-1-propynes), prepared by polymerization of 1-trimethylsilyl-1-propyne with NbCl₅ and TaCl₅/BuLi as catalysts. The experimental electrooptical characteristics of polymers were compared with those calculated by PM3 semiempirical quantum-chemical method.     

Synthesis,X-ray and DFT Studies of 6-halo-3-(hydroxymethyl)cinnolin-4(1H)-ones

Chemistry of Heterocyclic Compounds - The Richter cyclization was used for the synthesis of 6-halo-3-(hydroxymethyl)cinnolin-4(1H)-ones. X-ray analysis revealed that these compounds exist as dimers...