A Reliable Cyclic Voltammetry Technique for the Degradation of Salicylaldehyde: Electrode Kinetics

Salicylaldehyde (SA) is used in numerous biological, pharmaceutical, and industrial applications. Releasing effluents from these industries contaminates water. So the degradation of salicylaldehyde is necessitated. The electrochemical degradation of salicylaldehyde in buffered media was studied using the eco-friendly cyclic voltammetry (CV) technique on a platinum electrode at different scan rates. Kinetic and electrochemical parameters were evaluated for the reaction such as standard heterogeneous rate constant (k0,2.468×103 s-1 ), anodic electron transfer rate constant (kox,2.507×103 s-1), electron transfer coefficient of reaction (?,0.673), and formal potential (E0, 1.0937) under the influence of scan rate. The nature of the reaction is found to be diffusion controlled. The concentration study in the range of 1 mM to 4 mM was calibrated. The limit of detection and the limit of quantification were calculated to be 0.0031 mM and 0.0103 mM respectively.

Investigate and Calculation Electron Transfer Rate Constant in the N749 Sensitized Dye Contact to ZnSe Semiconductor

The dye–semiconductor interface between N749 sensitized and zinc semiconductor (ZnSe) has been investigated and studied according to quantum transition theory with focusing on the electron transfer processes from the N749 sensitized (donor) to the ZnSe semiconductor (acceptor). The electron transfer rate constant and the orientation energy were studied and evaluated depended on the polarity of solvents according to refractive index and dielectric constant coefficient of solvents and ZnSe semiconductor. Attention focusing on the influence of orientation energies on the behavior of electron transfer rate constant. Differentdata of rate constant was discussion with orientation energy and effective driving energy for N749-ZnSe system. Furthermore, the electron transfer rate constant is increased with less orientation energy at less effective driving energy while the electron transfer rate constant increased with large orientation energy with large effective driving energy, as seen as the electron transfer rate reach to 1.3109 × 1011 with less orientation energy has 0.188708eV at effective driving energy E=0.22eV comparing the rate reach to 9.7207× 10−96 with driving energy E=1.89eV and same orientation energy. In general, the electron transfer rate constant increases with increases the coupling coefficient of system, its indicate that alignment of energy levels are very good between N749 sensitized metal and ZnSe semiconductor.

Enhanced Performance of Bioelectrodes Made with Amination-Modified Glucose Oxidase Immobilized on Carboxyl-Functionalized Ordered Mesoporous Carbon

This research reveals the improved performance of bioelectrodes made with amination-modified glucose oxidase (GOx-NH2) and carboxyl-functionalized mesoporous carbon (OMC-COOH). Results showed that when applied with 10 mM EDC amination, the functional groups of NH2 were successfully added to GOx, according to the analysis of 1H-NMR, elemental composition, and FTIR spectra. Moreover, after the aminated modification, increased enzyme immobilization (124.01 ± 1.49 mg GOx-NH2/g OMC-COOH; 2.77-fold increase) and enzyme activity (1.17-fold increase) were achieved, compared with those of non-modified GOx. Electrochemical analysis showed that aminated modification enhanced the peak current intensity of Nafion/GOx-NH2/OMC-COOH (1.32-fold increase), with increases in the charge transfer coefficient α (0.54), the apparent electron transfer rate constant ks (2.54 s−1), and the surface coverage Γ (2.91 × 10−9 mol·cm−2). Results showed that GOx-NH2/OMC-COOH exhibited impressive electro-activity and a favorable anodic reaction.

MXene/Ag2CrO4 Nanocomposite as Supercapacitors Electrode

MXene/Ag2CrO4 nanocomposite was synthesized effectively by means of superficial low-cost co-precipitation technique in order to inspect its capacitive storage potential for supercapacitors. MXene was etched from MAX powder and Ag2CrO4 spinel was synthesized by an easy sol-gel scheme. X-Ray diffraction (XRD) revealed an addition in inter-planar spacing from 4.7 Å to 6.2 Å while Ag2CrO4 nanoparticles diffused in form of clusters over MXene layers that had been explored by scanning electron microscopy (SEM). Energy dispersive X-Ray (EDX) demonstrated the elemental analysis. Raman spectroscopy opens the gap between bonding structure of as-synthesized nanocomposite. From photoluminence (PL) spectra the energy band gap value 3.86 eV was estimated. Electrode properties were characterized by applying electrochemical observations such as cyclic voltammetry along with electrochemical impedance spectroscopy (EIS) for understanding redox mechanism and electron transfer rate constant Kapp. Additionally, this novel work will be an assessment to analyze the capacitive behavior of electrode in different electrolytes such as in acidic of 0.1 M H2SO4 has specific capacitance Csp = 525 F/g at 10 mVs−1 and much low value in basic of 1 M KOH electrolyte. This paper reflects the novel synthesis and applications of MXene/Ag2CrO4 nanocomposite electrode fabrication in energy storage devices such as supercapacitors.

Characterization of graphite-epoxy composite electrodes for free electrochemical detection of adenine and guanine in DNA

Graphite-epoxy composites (GECs) are alternative construction materials for electro­chemical sensors. For these materials, the electron transfer rate constant of some redox reaction depends additionally on the stoichiometric relationship between the insulating and conducting phases of the composite. In this work, the influence of dif­fe­rent ratios of araldite/hardener/graphite on the electrochemical properties of GEC electrodes is evaluated for the simultaneous determination of adenine and guanine in the single chain DNA, using the square wave voltammetry technique. Six GEC electro­des were prepared with different ratios of components, and electrochemically charac­terized by cyclic voltammetry in the presence of ferri/ferrocyanide redox couple as a redox probe. GEC electrodes that showed the best electrochemical responses of redox probe were characterized by thermogravimetric analysis (TGA) and used for the simul­taneous determination of free adenine and guanine in a solution, and DNA oligonu­cle­otides. The best results were obtained for GEC electrodes containing twice higher volu­me of araldite resin with respect to the hardener. TGA analysis revealed presence of 15-26 % of resin for these GEC electrodes. The obtained results revealed potential appl­ication of these GEC electrodes as DNA sensors based on the oxidation signal of guanine.

Disposable stencil-printed carbon electrodes for electrochemical analysis of sildenafil citrate in commercial and adulterated tablets

Forensic studies are extremally important to investigate suspected adulterations of consumable products, such as Viagra®. This report describes the determination of sildenafil citrate (SC) in commercial and adulterated tablets based on square-wave voltammetry (SWV) measurements using disposable stencil-printed carbon electrodes. The conductive ink used for the manufacture of integrated electrodes was produced by combining graphite powder and glass varnish. To promote a reusable strategy for limiting the geometric area of the electrodes, a 3D-printed holder was constructed. Detailed morphological and electrochemical characterization studies revealed well-defined graphite flakes incorporated on the polymeric substrate and a faster heterogeneous electron-transfer rate constant (Ks = 1.3 × 10–3 cm s–1). Based on the analytical performance, a linear behavior was observed in a SC concentration range from 1 to 20 µmol L–1 with limit of detection equal to 0.2 µmol L–1. The selectivity of the proposed method was evaluated and the presence of potentially interfering compounds like phosphate, lactose, paracetamol and tadalafil and no difference higher than 15% was observed. The analysis of SC was performed in commercial and seized tablets and the achieved values were 50 ± 1 mg for Viagra® tablet, 54 ± 1 mg for generic formulations 38 ± 1 mg for seized tablet. In addition, the proposed method offered satisfactory accuracy (98.2 – 102.0%) no noticeable matrix effect. Lastly, considering the achieved results, the use of stencil-printed carbon electrodes and SWV has demonstrated to be a powerful and robust analytical tool for forensic investigations.

Electrochemical implications of modulating the solvation shell around redox active organic species in aqueous organic redox flow batteries

Organic and organometallic reactants in aqueous electrolytes, being composed of earth-abundant elements, are promising redox active candidates for cost-effective organic redox flow batteries (ORFBs). Various compounds of ferrocene and methyl viologen have been examined as promising redox actives for this application. Herein, we examined the influence of the electrolyte pH and the salt anion on model redox active organic cations, bis((3-trimethylammonio) propyl)- ferrocene dichloride (BTMAP-Fc) and bis(3-trimethylammonio) propyl viologen tetrachloride (BTMAP-Vi), which have exhibited excellent cycling stability and capacity retention at ≥1.00 M concentration [E. S. Beh, et al. ACS Energy Lett. 2, 639–644 (2017)]. We examined the solvation shell around BTMAP-Fc and BTMAP-Vi at acidic and neutral pH with SO42-, Cl−, and CH3SO3− counterions and elucidated their impact on cation diffusion coefficient, first electron transfer rate constant, and thereby the electrochemical Thiele modulus. The electrochemical Thiele modulus was found to be exponentially correlated with the solvent reorganizational energy (λ) in both neutral and acidic pH. Thus, λ is proposed as a universal descriptor and selection criteria for organic redox flow battery electrolyte compositions. In the specific case of the BTMAP-Fc/BTMAP-Vi ORFB, low pH electrolytes with methanesulfonate or chloride counterions were identified as offering the best balance of transport and kinetic requirements.

Biological and Electrochemical Studies of Macrocyclic Complexes of Iron and Cobalt

In this work, we synthesized two tetraaza [N4] macrocyclic complexes of FeIII and CoII metal ions. The synthesized macrocyclic complexes were fully characterized by using various analytical techniques IR, UV-Vis, and MS. The spectral analysis indicated an octahedral geometry for both macrocyclic complexes. The electrochemical behavior was carried out using cyclic voltammetry on the Pt dish (0.031 cm2) electrode. The complexes were shown to have unusual oxidation states for the metal ions. The “heterogeneous electron transfer rate constant” (Ko) was also calculated using “Nicholson and Kochi’s method” and observed in the order: KoCoII > KoFeIII. The antimicrobial activities of two complexes were computed against E. coli, P. aeruginosa, B. cereus, S. aureus, whereas antifungal activities against C. Albicans and were contrasted with the standard drug “Gentamycin”.