Fabrication of a sensitive amperometric sensor for NADH and H2O2 using palladium nanoparticles-multiwalled carbon nanotube nanohybrid

Palladium nanoparticles decorated multiwalled carbon nanotubes (PdNPs-MWCNTs) were synthesized and simply cast on the surface of a glassy carbon electrode (GCE) to prepare an amperometric sensor. The fabricated sensor (PdNPs-MWCNTs/GCE) showed excellent electrocatalytic activity towards NADH and H2O2 oxidation and H2O2 reduction. A fast, linear and highly sensitive response was observed for NADH in the concentration range between 0.1 and 200 μM with a detection limit (S/N = 3) of 32 nM. Also, the sensor exhibited fast and sensitive responses (< 2 s) towards H2O2. The sensitivity and detection limit for H2O2 at the operating potential of + 0.35 V were 167 nA μM− 1 cm− 2 and 1.2 μM, respectively and better than those obtained at the operating potential of − 0.25 V (68 nA μM− 1 cm− 2 and 14 μM). Moreover, further modification of the proposed sensor by glucose oxidase led to the fabrication of a glucose biosensor with satisfactory performance

Flow injection chemiluminescence determination of isoniazid using luminol and silver nanoparticles

The effect of silver colloidal nanoparticles (AgNPs) on the luminol-isoniazid system was investigated. It was found that AgNPs could act as a nanocatalyst on the luminol-isoniazid system to generate chemiluminescence (CL). The CL emission spectrum of the luminol-isoniazid-AgNPs system showed a peak with a maximum at 425 nm. It was suggested that the luminophor species was the excited state 3-aminophthalate. The reduction of dissolved O2 to H2O2 by isoniazid and decomposition of H2O2 to the oxygen-related radicals were attributed to the catalytic effect of AgNPs. Under optimized conditions, the CL signal intensity was linear with the isoniazid concentration in the range of 10-1000 ng mL- 1, with the correlation coefficient of 0.9996. The limit of detection was 2.7 ng mL- 1 isoniazid. The relative standard deviations for seven repeated measurements of 60 and 200 ng mL- 1 isoniazid were 1.4 and 2.4%, respectively. The effect of potent interfering compounds on the CL signal intensity of the proposed luminol-isoniazid-AgNPs system was investigated. The proposed method was successfully applied to the determination of isoniazid in a pharmaceutical sample

Formation of a robust and stable film comprising ionic liquid and polyoxometalate on glassy carbon electrode modified with multiwalled carbon nanotubes: Toward sensitive and fast detection of hydrogen peroxide and iodate

A robust and stable film comprising n-octylpyridinum hexafluorophosphate ([C8Py][PF6]) and 1:12 phosphomolybdic acid (PMo12) was prepared on glassy carbon electrodes modified with multiwall carbon nanotubes (GCE/MWCNTs) by dip-coating. The cyclic voltammograms of the GCE/MWCNTs/[C8Py][PF6]-PMo12 showed three well-defined pairs of redox peaks due to the PMo12 system. The surface coverage for the immobilized PMo12 and the average values of the electron transfer rate constant for three pairs of redox peaks were evaluated. The GCE/MWCNTs/[C8Py][PF6]-PMo12 showed great electrocatalytic activity towards the reduction of H2O2 and iodate. The kinetic parameters of the catalytic reduction of hydrogen peroxide and iodate at the electrode surface and analytical features of the sensor for amperometric determination of hydrogen peroxide and iodate were evaluated

Second-order data obtained from differential pulse voltammetry: Determination of tryptophan at a gold nanoparticles decorated multiwalled carbon nanotube modified glassy carbon electrode

Three-way data obtained from different pulse heights of differential pulse voltammetry (DPV) was analyzed using multivariate curve resolution by alternating least squares (MCR-ALS) algorithm. Differential pulse voltammograms of tryptophan were recorded at a gold nanoparticles decorated multiwalled carbon nanotube modified glassy carbon electrode (GCE/MWCNTs-nanoAu). The determination of tryptophan was performed even in the presence of unexpected electroactive interference(s). Both the simulated and experimental data were non-bilinear. Therefore a potential shift algorithm was used to correct the observed shift in the data. After correction, the data was augmented and MCR-ALS was applied to the augmented data. A relative error of prediction of less than 8% for the determination of the simulated analyte of interest and tryptophan in synthetic samples indicated that the methodology employing voltammetry and second-order calibration could be applied to complex analytical systems

Nano-Size Layered Manganese-Calcium Oxide as an Efficient and Biomimetic Catalyst for Water Oxidation Under Acidic Conditions: Comparable To Platinum

Inspired by Nature's catalyst, a nano-size layered manganese-calcium oxide showed a low overvoltage for water oxidation in acidic solutions, which is comparable to platinum.Institute for Advanced Studies in Basic Sciences and the National Elite FoundationUS Department of Energy, Office of Basic Energy Sciences, Division of Chemical, Geochemical and Biological Sciences DE-FG02-86ER13622, DE-FG0209ER16119Russian Foundation for Basic Research 11-04-01389a, 12-0492101a, 13-04-92711aMolecular and Cell Biology Programs of the Russian Academy of SciencesCenter for Electrochemistr

Insights into the Wnt Signaling Pathway Evolution

Animals’ Wnt signaling pathways are highly preserved signal transduction pathways, which play a crucial role in embryogenesis and adult tissue homeostasis. This chapter reviews the three major Wnt pathways, focusing on some critical proteins in the Wnt/β-catenin path in terms of their evolution and role in homeostasis. Wnt proteins act as a gateway between extracellular, cytoplasmic, and nuclear components to transmit signaling pathways. The Frizzled (FZD) family as G-protein-coupled receptors activates the signaling pathways by binding to Wnt ligands. LRP5/6, members of the family of low-density lipoprotein receptors (LDLR), associate with FZD receptor and Wnt ligands as co-receptors to initiate the Wnt/β-catenin pathway. The Wnt/β-catenin pathway is regulated by antagonists such as the Dickkopf and secreted Frizzled-related protein (SFRP) families

Nano-size layered manganese–calcium oxide as an efficient and biomimetic catalyst for water oxidation under acidic conditions: comparable to platinum

This is the published version. ©Copyright Royal Society of Chemistry 2015Inspired by Nature's catalyst, a nano-size layered manganese–calcium oxide showed a low overvoltage for water oxidation in acidic solutions, which is comparable to platinum

Pair interaction potential energy function for some practically important refrigerants from the viscosity in the limit of zero density

483-488An iterative inversion procedure is used to obtain the effective isotropic part of the pair-interaction potential for some pure refrigerants from the proposed correlation function for the zero density collision integrals of viscosity. The Lennard-Jones (LJ12-6) potential energy function is used as the initial model potential required by the method. Over a range of reduced temperature extending from 1 to 100, this measured potential can be used in the calculation of the orientation-averaged viscosity collision integrals and the dimensionless ratios which are essential to calculate other transport properties

<span style="font-size:16.0pt;mso-bidi-font-size:12.0pt" lang="EN-IN">Determination of pair-interaction potential function for <span style="mso-bidi-font-style:italic">O₂-O₂ from viscosity data of gases </span></span>

687-691A direct inversion procedure is used to obtain the effective isotropic part of the pair-interaction potential for O2-O2 from the corresponding states viscosity over a range of reduced temperature extending from 1 to 100. We have used the experimentally reduced orientational average viscosity collision integrals obtained from the corresponding-states correlation and performed INVERT to determine the reduced potential energy curve corresponding to the collision integral. This directly determined potential is in excellent agreement with the ESMSV-type independently known potential of Brunett etal. This accurate inverted potential can be used to obtain the orientation averaged viscosity collision integrals and the dimensionless ratios which are essential to calculate of her transport properties. The advantages of the in version method are that, the technique represents a distinct advance over the traditional methods for force filling data to potential functions of primitive forms and lengthy multiparameter filling procedure is largely removed. </span