Electrocatalytic oxidation of methanol on a glassy carbon modified electrode by bis(1,2-phenylenediamine) nickel(II) complex

Electrocatalytic oxidation of methanol on a glassy carbon electrode coated with Ni(II)-(1,2-phenylendiamine)₂ (GC/NiOPD), conditioned by the potential recycling in a potential range of 100–650 mV (vs. SCE) is studied by cyclic voltammetry in an alkaline medium (0.10 M NaOH). The results show that the NiOPD layer formed at the surface of the electrode behaves as an efficient electrocatalyst for the oxidation of methanol in the alkaline medium via the Ni(III) species with a cross exchange reaction occurring throughout the layer at a low concentration of methanol. The effects of various parameters such as potential scan rates, methanol concentration and NiOPD surface concentration on the electro-oxidation of methanol are also investigated.     

Kinetic-Spectrophotometric Determination of Trace Quantities of Thiocyanate Based on Its Landolt Effect on the Reaction of Bromate with Hydrochloric Acid1

A new method for the rapid and sensitive determination of trace quantities of thiocyanate based on its Landolt effect on the bromate-hydrochloric acid reaction was developed. The induction period of the reaction is proportional to the SCN^– concentration. The decolorization of methyl orange by the reaction products was used to monitor the reaction spectrophotometrically at 525 nm. We were able to determine thiocyanate in the range 2 × 10^–7–4 × 10^–5 M by this method. The relative standard deviation for 10 determinations of 1.5 × 10^–6 M thiocyanate ion is 0.19% and the detection limit of the method was 7.00 × 10^–8 M. The method was applied to the determination of thiocyanate in human blood serum and of saliva samples with satisfactory results.     

Electrocatalytic oxidation of methanol on a Nickel(II)-1-(2-pyridylazo)-2-naphthol complex modified glassy-carbon electrode in alkaline medium

Electrocatalytic oxidation of methanol on a glassy carbon disc electrode modified with Ni(II)-1-(2-pyridylazo)-2-naphthol (Ni-PAN) complex and conditioned by potential recycling in a limited range (between 100–600 mV) in 0.1 M NaOH solution, abbreviated as NiPANME, is studied by cyclic voltammetry in alkaline medium. The results are compared with those obtained for a NiO modified glassy-carbon electrode, NiOME, prepared in similar conditions. The findings show that the NiPAN film behaves as an efficient electrocatalyst for the oxidation of methanol in alkaline medium via Ni(III) species with the cross-exchange reaction occurring throughout the layer at a low concentration of methanol and for a thin film of modifier. Effects of the scan rate and methanol concentration on the methanol oxidation are investigated. The cyclic voltammetry and amperometry methods are used to investigate the methanol electrooxidation at the modified electrode. Published in Russian in Elektrokhimiya, 2006, Vol. 42, No. 2, pp. 196–202. The text was submitted by the authors in English.     

Adhesion and interfacial interactions of BaO–SiO<Subscript>2</Subscript>–B<Subscript>2</Subscript>O<Subscript>3</Subscript>-based glass-ceramic seals and AISI430 interconnect for solid oxide fuel cell applications

In the present work, adhesion, leak rate, and chemical compatibility of a series of borosilicate-based glasses, belonging to the ternary BaO–SiO₂–B₂O₃ system, with AISI 430 alloys as interconnect were investigated for solid oxide fuel cell applications. Wetting angle and deformation behavior of the selected glasses with temperature and time were initially characterized with the hot-stage microscope. It was observed that the temperature ranges of wetting for all combinations were greater than 1000 °C. Significant deformation did not appear in the samples over soaking time at sealing temperature. In the next step, the leakage tests of AISI430/glass-ceramic couples were performed. The sample containing 32 % molar BaO (Ba32) had no gas leakage; a low leak rate of 10^?7to 10^?8 Pam³ s^?1 was obtained for the glass with 37 % molar BaO (Ba37) and big leak of the system (10^?3to 10^?4 Pam³ s^?1) for Ba42. Possible interfacial reactions between the as-received glass and cell ingredients and aging up to 100 h were studied by scanning electron microscopy in conjunction with energy-dispersive X-ray spectroscopy and X-ray dot mapping. The results showed that the Ba32 and Ba37 glasses coupled with AISI had fine adhesion, which remained stable under these conditions and were compatible with the interconnect. So, the use of these glass-ceramics will probably be successful in joining the ceramic electrolytes to the metallic interconnect.     

Copper Salt Catalyzed Synthesis of Functionalized 2H‐Pyranes

A copper‐catalyzed reaction between terminal alkynes, oxiranes, and malonitrile has been described. In this transformation, copper acetylide was attacked on oxiranes to form homopropargyl alkoxy‐copper intermediate that was further transferred to 2H‐pyrane skeletons by reaction with malonitrile. We found that the reaction was not productive without hexafluoroisopropanol.     

The reaction of N-isocyaniminotriphenylphosphorane (NICITPP) with some of cyclic ketones and a primary amine in the presence of 3-phenyl-2-propynoic acid

The 1:1 imine intermediate generated by the addition of a primary amine to a cyclic ketone is trapped by N-isocyaniminotriphenylphosphorane in the presence of 3-phenyl-2-propynoic acid and the corresponding iminophosphorane intermediate was formed. Disubstituted 1,3,4-oxadiazole derivatives are formed via intramolecular aza-Wittig reaction of the iminophosphorane intermediate. The reactions were completed in neutral conditions at room temperature (18–26°C). The disubstituted 1,3,4-oxadiazole derivatives were produced in excellent yields.     

NMR Studies of Drugs: Antipyrine and Analogs. I. Use of Achiral and Chiral Lanthanide Shift Reagents to Examine Hindered Rotation.

The 200 MHz ¹H NMR spectra of the analgesic, antipyrine, 1, have been studied in CDC1₃ solution at ambient temperatures with the achiral lanthanide shift reagent (LSR) tris (6, 6, 7, 7, 8, 8, 8-heptafluoro-2, 2-dimethyl-3, 5-octanedionato) europium (III), Eu(FOD)₃, 2, and with the chiral LSR, tris[3-(heptafluoropropylhydroxymethylene)-(+)-camphorato]europium(III), Eu(HFC)₃, 3., Lanthanide-induced shift (LIS) magnitudes and broadening of selected signals are consistent with predominant LSR binding at the carbonyl oxygen with either 2 or 3. Of the different possible conformational regimes for the N-phenyl group of 1, our results appear to rule out a slow exchange limit (SEL) system with the N-phenyl coplanar with the heterocyclic ring. Perpendicular rings in an SEL regime can not be ruled out. A rapidly-rotating N-phenyl (fast exchange limit, FEL system) would also be consistent with observed results. Accurate chemical shifts for the aryl protons (overlapped in the 200 MHz spectrum of unshifted 1) are determined from spectra with added LSR by extrapolation to zero molar ratios of [LSR]:[1]. Relative slopes in the plots of chemical shift versus [LSR]:[1] molar ratios are calculated for each proton signal of 1.     

DFT calculations of <Superscript>14</Superscript>N, <Superscript>17</Superscript>O,and <Superscript>2</Superscript>H NQR parameters: Investigation of hydrogen bond interactions in sulfapyridine crystalline structure

DFT calculations of electric field gradient (EFG) tensors at the sites of ¹⁴N, ¹⁷O, and ²H nuclei are carried out to characterize the hydrogen bond (HB) interactions in the sulfapyridine crystal structure. One-molecule (monomer) and hydrogen-bonded hexameric cluster models of sulfapyridine are constructed according to available X-ray coordinates where the proton positions are optimized. Then, EFG tensors are calculated for both monomer and target molecule in the hexameric cluster of sulfapyridine to show the effect of HB interactions on the tensors. The calculated EFG tensors are converted to the experimentally measurable nuclear quadrupole resonance (NQR) parameters: quadrupole coupling constant (C _Q ) and asymmetry parameter (η _Q ). The results reveal different contribution of various nuclei to N-H⋯N and N-H⋯O HB interactions in the cluster where the N2 and O1 have major contributions. The computations are performed with B3LYP and B3PW91 functionals DFT method and 6-311+G* and 6-311++G** standard basis sets using the Gaussian 98 package.     

Recent advances in electrochemical and electrochemiluminescence based determination of the activity of caspase-3

Caspases, especially caspase-3, play a critical role in the intrinsic and extrinsic pathways of apoptosis. In addition, caspase-3 is involved in mental disorders like Alzheimer disease. Any up and down regulation of caspase-3 activity may cause cancer. This review (with 58 references) summarizes recent advances in electrochemical and electrochemiluminescent quantitation of the activity of caspase-3 based on the use of nanomaterials. The nanomaterials and nanolabels are classified in three main subgroups, namely electrochemical signal amplification strategies, amplification based on modified electrodes, and the combination of both modes. The potential of various electrochemical and electrochemiluminescence bioassays is discussed, and methods to circumvent certain limitations are oresented. Finally, current trends in the detection of caspase-3 such as system integration and the application of advanced nanomaterials are discussed.

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Graphical abstract The review summarizes electrochemical methods for the quantitation of caspase-3 activity based on the use of nanomaterials and of nanomaterial based labels. It contains subsections on electrochemical signal amplification strategies, amplification based on modified electrodes, and the combination of both modes.

     

A facile method for dye and heavy metal elimination by pH sensitive acid activated montmorillonite/polyethersulfone nanocomposite membrane

Modified clay/polyethersulfone (PES) mixed matrix membranes (MMMs) were prepared by acid activated montmorillonite (AA-MMT) with different concentrations and used to eliminate dyes and remove heavy metals from aqueous solution.The morphology and physiochemical properties of prepared clay nanoparticles and MMMs were characterized using X-ray diffraction (XRD),Fourier transform infrared (FTIR) spectroscopy,scanning electron microscopy (SEM),enegy dispersive X-ray (EDX) spectroscopy,Brunauer-Emmett-Teller (BET) analysis,atomic force microscopy (AFM),contact angle measurement and fouling studies.The filtration study showed that removal of dyes and heavy metals was strongly dependent on pH so that dyes with positive and negative charges showed different separation efficiency in acidic and alkaline conditions.The modified membranes possessed better heavy metal removal in acidic and alkaline pHs.When the rejection of heavy metals was measured in an alkaline environment,it was observed that the rejection had a great increase compared to the neutral values for Zn2+ and Ni2+ ions,while rejection of Cu2+ and Cd2+ did not undergo significant changes.So it can be concluded that modified membranes show good selectivity for elimination of Zn2+ and Ni2+ ions with respect to other cations.