CH3OH electrooxidation by nanosized Pd loaded on porous LaMnO3

Generating the multifunctional influence by adding a promoter or employing a support for electrocatalytic particles is a remarkable approach to advance the efficiency and stability of anode electrode in the non-reforming methanol fuel cell. So, the coprecipitation assisted with ultrasonic is selected to fabricate porous LaMnO₃; and the nanosized Pd is loaded on LaMnO₃ via wetness incorporation. The samples are characterized through scanning electron microscopy, Fourier-transform infrared spectroscopy (FT-IR), vibrating sample magnetometry, Energy-dispersive X-ray spectroscopy (EDX), Transmission electron microscopy (TEM), Brunauer-Emmett-Teller and X-ray diffraction analysis. The electrochemical studies are carried out to identify the behavior and efficiency of electrocatalysts toward CH₃OH electrooxidation. Based on adsorption/desorption of hydrogen, the electrochemical surface area presented an ascending performance as nanosized Pd (76.63 m² g^?1) < Pd/LaMnO₃ (93.35 m² g^?1). The Pd/LaMnO₃ has higher electrocatalytic activity, stability, and CO-tolerance ability for the CH₃OH electrooxidation of as compared with nanosized Pd as non-supported Pd. The functions of current vs. time were determined by fitting and simulating of the experimental data. The transferred charge throughout CH₃OH electrooxidation vs. time was computed using the lower Riemann sum of plots, corresponding to experimental results and the integration of obtained functions. The introduced nanocomposite was used as anodic material in a single CH₃OH fuel cell.     

Electrochemical Detection of Interaction Between α‐Synuclein and Clioquinol

α‐Synuclein (α‐S) protein is expressed in presynaptic terminals in the central nervous system. The aggregation of α‐S is implicated in the pathogenesis of Parkinson’s disease (PD). In this report, the interaction of α‐S with clioquinol (CQ) was investigated in the presence of Cu(II) ions using electrochemistry, as well as Thioflavin T‐based fluorescence and Congo Red‐based UV‐Vis studies. In the presence of CQ, the α‐S aggregation rate was observed to decrease. The preliminary results showed promise in the future development of CQ derivatives as novel small molecule therapeutic agents with potential efficacy targeting α‐S in PD therapy.     

DNA sensing on glassy carbon electrodes by using hemin as the electrochemical hybridization label

The electrochemical behavior of hemin, an iron complex of porphyrin, on binding to DNA at a glassy carbon electrode (GCE) and in solution, is described. Hemin, which interacts with covalently immobilized calf thymus DNA, was detected by use of a bare GCE, a double-stranded DNA-modified GCE (dsDNA-modified GCE), and a single-stranded DNA-modified GCE (ssDNA-modified GCE), in combination with differential pulse voltammetry (DPV). The structural conformation of DNA was determined from changes in the voltammetric signals acquired on reduction of hemin. As a result of its large steric structure and anionic substitution on its porphyrin plane, hemin intercalates between the base pairs of dsDNA. A scan-rate study for hemin and the dsDNA-hemin complex were also performed to determine the electrochemical behavior of the complex. The partition coefficient was obtained from the peak currents measured when different concentrations of hemin were in the presence of dsDNA. By observing the oxidation signals of guanine, damage to DNA after reaction with hemin at the GCE surface was also detected. The electrochemical detection of hybridization between the covalently immobilized probe and its target sequence was detected by use of hemin. These results demonstrate the use of DNA biosensors in conjunction with hemin for electrochemical detection of hybridization and damage to DNA.     

Sensitive determination of hydrazine using poly(phenolphthalein), Au nanoparticles and multiwalled carbon nanotubes modified glassy carbon electrode

This study reports a detailed analysis of an electrode material containing poly(phenolphthalein), carbon nanotubes and gold nanoparticles which shows superior catalytic effect towards to hydrazine oxidation in Britton–Robinson buffer (pH 10.0). Glassy carbon electrode was modified by electropolymerization of phenolphthalein (PP) monomer (poly(PP)/GCE) and the multiwalled carbon nanotubes (MWCNTs) was dropped on the surface. This modified surface was electrodeposited with gold nanoparticles (AuNPs/CNT/poly(PP)/GCE). The fabricated electrode was analysed the determination of hydrazine using cyclic voltammetry, linear sweep voltammetry and amperometry. The peak potential of hydrazine oxidation on bare GCE, poly(PP)/GCE, CNT/GCE, CNT/poly(PP)/GCE, and AuNPs/CNT/poly(PP)/GCE were observed at 596 mV, 342 mV, 320 mV, 313 mV, and 27 mV, respectively. A shift in the overpotential to more negative direction and an enhancement in the peak current indicated that the AuNPs/CNT/poly(PP)/GC electrode presented an efficient electrocatalytic activity toward oxidation of hydrazine. Modified electrodes were characterized with High-resolution transmission electron microscopy (HRTEM), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and electrochemical impedance spectroscopy (EIS). Amperometric current responses in the low hydrazine concentration range of 0.25–13 µM at the AuNPs/CNT/poly(PP)/GCE. The limit of detection (LOD) value was obtained to be 0.083 µM. A modified electrode was applied to naturel samples for hydrazine determination.     

Analysis of Amyloid Beta Aggregation Kinetics Using Sym‐Triazine β‐Sheet Inhibitors

AD (Alzheimer’s disease) is a progressive neurodegenerative disorder characterized by the cerebral accumulation of fibrillar amyloid‐beta (Aβ) aggregates. Here we present the electrochemistry of two novel sym‐triazine derivatives (TAE‐1, TAE‐2) as modulators of Aβ_1–42 aggregation in vitro. Incubation studies conducted at physiological conditions demonstrated strong inhibition of β‐sheet fibril formation. Uniquely, square‐wave voltammetry indicated progressive changes in the surface‐availability of amyloid‐intercalated triazines for oxidation, mediated by competing peptide self‐assembly. Time‐resolved voltammetric analysis showed increasing anodic peak currents (≥3‐fold) and progressive shifts in redox potentials, measured over 24 h. The more potent aggregation modulator (TAE‐2) showed prolonged association during the pre‐nucleation states of Aβ.     

A convenient one-pot synthesis of new chromeno[3,4-c]chromene and chromeno[3,4-c]pyridine derivatives in the presence of high surface area of magnesium oxide

In this investigation a new strategy involves the one-pot,three-component reaction of malononitrile,salycilaldehyde and phenol derivatives in the presence of high surface area of MgO is extended to the formation of chromeno[3,4-c]chromene derivatives in good to excellent yields in a short reaction time.Also,the three component reactions of an aldehyde such as salycilaldehyde and ketones with malononitril for the formation of chromeno[3,4-c]pyridines are investigated.     

Miniaturized electrochemical system for cholinesterase inhibitor detection

The utility of a simple, low-cost detection platform for label-free electrochemical characterization of acetylcholinesterase (AChE) inhibition is demonstrated as a potential tool for screening of small-molecule therapeutic agents for Alzheimer's disease (AD). Technique validation was performed against the standard Ellman's colorimetric assay using the clinically established cholinesterase inhibitor (ChEI), Donepezil (Aricept^®). Electrochemical measurements were obtained by differential pulse voltammetry (DPV) performed using a portable potentiostat system for detection of the enzymatic product, thiocholine (TCh), by direct oxidation on unmodified gold screen-printed electrodes. The IC₅₀ profiles for Donepezil measured in vitro were found to be comparable between both colorimetric and electrochemical detection methods for the analysis of purified human erythrocyte-derived AChE (28 ± 7 nM by DPV; 26 ± 8 nM by Ellman's method). The selectivity of this unmodified electrode system was compared to a range of biological sulfur-containing compounds including cysteine, homocysteine, glutathione and methionine as well as ascorbic acid. Preliminary studies also demonstrated the potential applicability of this electrochemical technique for the analysis of Donepezil in crude cholinesterase samples from anterior cortex homogenates of C57BL/6J mice.     

Kinetico-mechanistic information about alkene hydroamination with aniline in bromide-rich ionic media: importance of solvolysis

The study of the [PtBr(4)](2-) reactivity with hexene and aniline in highly ionic (Bu(4)P)Br/CH(2)Br(2) media has been studied from a Kinetico-Mechanistic perspective. The results indicate bromide ion association to the square-planar starting material to produce a stable diamagnetic compound that can be described as an ion pair of a [PtBr(5)](3-) square-pyramidal complex stabilized by several phosphonium countercations. While this species reacts rapidly with aniline, producing the known square-planar complex [PtBr(3)(PhNH(2))](-) with release of the apical bromide of the square-pyramidal intermediate, the reaction with hexene, producing the square-planar [PtBr(3)(hexene)](-) complex, is much slower. The thermal and pressure activation parameters determined for these processes fully agree with the proposed reactivity. The gross features of the platinum-catalyzed hydroamination mechanism, occurring via much higher energy transition states, are not necessarily altered by these new findings, given the fact that all ligand exchange reactions occur with relatively low activation barriers. Nevertheless, the nature of the catalyst resting state needs revision as demonstrated. The importance of explicitly considering the solvent for reactions conducted in noninnocent highly organized media is also highlighted.