All-solid-state planar miniature ion-selective chloride electrode

All-solid-state ion-selective electrodes with plastic membrane (poly(vinyl chloride) (PVC), bis(2-ethylhexyl) sebacate (DOS), methyltri-n-tetradecylammonium chloride (MTTACl)), a conducting poly(pyrrole) (PPy) film doped either with chloride ions (PPyCl) or hexacyanoferrate(II) ions (PPyFeCN), and glassy carbon (GC) or screen-printed graphite layer (S-PG) as an inner electric contact were investigated. All the electrodes show close to Nernstian response, but their lifetimes vary. The at least 2-months lifetime of screen-printed electrodes is only achieved for the electrodes containing PPyFeCN (cation-exchanging film). Shorter lifetime of other screen-printed electrodes, i.e. without PPy, or with PPyCl (anion-exchanging film), was attributed to the diffusion of anionic products of the hydrolysis of organic components of the graphite paste used to prepare the electric contact. The properties of miniature, screen-printed electrodes comprising PPyFeCN solid contact, were comparable to those ion-selective electrodes with PPy solid contact (regardless the ion-exchanging characteristic of the polymer) deposited on GC electric contact.     

Immobilization of Pd Catalysts on Mesoporous Silica for Amine- and Copper-Free Sonogashira Coupling Reactions

Immobilization of catalysts on solid supports is a promising approach to combine the advantages of heterogeneous and homogeneous catalysts. Pd(PPh₃)₂Cl₂, known as an extremely active homogeneous catalyst for the Sonogashira coupling reaction, has been immobilized on high-surface-area MCF (mesocellular foams)–type mesoporous silica powder modified with 3-aminopropyltriethoxysilane and subsequently with diphenylphosphine. The functionalized MCF-type silica and supported catalysts have been characterized by x-ray photoelectron spectroscopy (XPS), fourier transform infrared spectroscopy (FTIR), elemental analysis, nitrogen sorption porosimetry, and scanning electron microscopy (SEM). Such supported Pd catalysts have proven to be useful recyclable reagents for copper- and amine-free Sonogashira coupling reactions of haloaromatic compounds with terminal alkynes.     

Development and Optimization of Twenty-Four Hour Manual Methods for the Collection and Colorimetric Analysis of Atmospheric NO2

Abstract

Manual twenty-four hour colorimetric procedures for the determination of atmospheric NO₂ are described. The methods are based on collecting NO₂ by bubbling ambient air for twenty-four hours through reagents that form stable nitrite solutions. The reagents described have a 93 % collection efficiency over the range of 20 to 750 μg/m³ NO₂ with no apparent interferences. The inadequacies' of the former reference or alkaline method¹ are also described.     

Measurement of the neutron capture cross-section of 238U using the neutron activation technique

The ²³⁸U(n, ??)²³⁹U reaction cross-section at average neutron energy of 3.7?±?0.3?MeV from the ⁷Li(p, n)⁷Be reaction has been determined using activation and off-line ??-ray spectrometric technique. The ²³⁸U(n, ??)²³⁹U and ²³⁸U(n, 2n)²³⁷U reaction cross-sections at average neutron energy of 9.85?±?0.38?MeV from the same ⁷Li(p, n)⁷Be reaction have been also determined using the above technique. The experimentally determined ²³⁸U(n, ??)²³⁹U and ²³⁸U(n, 2n)²³⁷U reaction cross-sections were compared with the evaluated data of ENDF/B-VII, JENDL-4.0, JEFF-3.1 and CENDL-3.1. The experimental values were found to be in general agreement with the evaluated value based on ENDF/B-VII, and JENDL-4.0 but not with the JEFF-3.1 and CENDL-3.1. The present data along with literature data in a wide range of neutron energies were interpreted in terms of competition between different reaction channels including fission. The ²³⁸U(n, ??)²³⁹U and ²³⁸U(n, 2n)²³⁷U reaction cross-sections were also calculated theoretically using the TALYS 1.2 computer code and were also found to be in agreement experimental data.     

Synthesis of ethyl furfuryl ether (potential biofuel) by etherification of furfuryl alcohol with ethanol over heterogenized reusable H1Cs2PW12O40 catalyst

Research on Chemical Intermediates - Ethyl furfuryl ether (EFE) considered as potential biofuel can replace petroleum diesel up to 100%. EFE also has efficient blending properties with biodiesel to...     

Bismuth-Oxide-Decorated Graphene Oxide Hybrids for Catalytic and Electrocatalytic Reduction of CO2

Global warming challenges are fueling the demand to develop an efficient catalytic system for the reduction of CO₂, which would contribute significantly to the control of climate change. Herein, as-synthesized bismuthoxide-decorated graphene oxide (Bi₂O₃@GO) was used as an electro/thermal catalyst for CO₂ reduction. Bi₂O₃@GO is found to be distributed uniformly, as confirmed by scanning electron and transmission electron microscopic analysis. The X-ray diffraction (XRD) pattern shows that the Bi₂O₃ has a β-phase with 23.4 m² g⁻¹ BET surface area. Significantly, the D and G bands from Raman spectroscopic analysis and their intensity ratio (I_D/I_G) reveal the increment in defective sites on GO after surface decoration. X-ray photoelectron spectroscopic (XPS) analysis shows clear signals for Bi, C, and O, along with their oxidation states. An ultra-low onset potential (−0.534 V vs. RHE) for the reduction of CO₂ on Bi₂O₃@GO is achieved. Furthermore, potential-dependent (−0.534, −0.734, and −0.934 vs. RHE) bulk electrolysis of CO₂ to formate provides Faradaic efficiencies (FE) of approximately 39.72, 61.48, and 83.00 %, respectively. Additionally, in time-dependent electrolysis at a potential of −0.934 versus RHE for 3 and 5 h, the observed FEs are around 84.20 % and 87.17 % respectively. This catalyst is also used for the thermal reduction of CO₂ to formate. It is shown that the thermal reduction provides a path for industrial applications, as this catalyst converts a large amount of CO₂ to formate (10 mm ).     

Polyimides from diisocyanates and dianhydride

Polyimides soluble in polar solvents such as dimethylacetamide (DMAC) and dimethylformamide (DMF) were synthesized by reacting 3,3′,4,4′-benzophenonetetracarboxylic dianhydride (BTDA) and three different diisocyanates with the following general structure: where R is ethyl, propyl, or phenyl. Thermal properties of these polymides have been compared with that obtained by reacting 2,2-bis(4-isocyanatophenyl)propane and BTDA.     

Synthesis and Cation Recognition Study of Novel Benzo Crown Ether Functionalized Enamine Derivatives

A novel series of benzo crown ether (dibenzo 18-crown-6 ether, benzo 18-crown-6 ether, and benzo 15-crown-5 ether) functionalized enamines derivatives from amino benzo crown ether (4-amino dibenzo 18-crown-6 ether, 4-amino benzo 18-crown-6 ether, 4-amino benzo 15-crown-5 ether) and substituted 3-(dimethylamino)-1-phenylprop-2-en-1-one compounds have been synthesized. All the synthesized compounds were characterized by infrared, ¹H NMR, ¹³C NMR, distortionless enhancement polarization transfer, and mass and elemental analysis techniques. The cation recognition property for benzo crown ether enamine 8a was studied by absorption and fluorescence spectroscopy.