Electrochemical Synthesis and Structural Characterization of a Novel Mixed-valence Copper (I)-copper (II) Complex: {[Bis(ethylenediamine) Copper (II)] Bis[diiodocuprate (I)]}

A novel, mixed-valent copper(I)-copper(II) complex, {[bis(ethylene-diamine)copper(II)] bis[diiodocuprate(I)]} (1), has been prepared by electrochemicaldissolution of a sacrificial copper anode in a solution of ethylenediamine (en), I2 andtetraethylammoniumperchlorate (TEAP) as supporting electrolyte in acetonitrile (AcN)and characterized by single-crystal X-ray structure determination. The crystal structure ofthe complex 1 shows that it consists of a CuI2 polymer formed from I- ligands bridgingCu(I) ions, with a nearly square planar geometry of bivalente Cu(II) atoms chelated by twoethylenediamine ligands. The results also show that direct electrosynthesis of the complexhad high current efficiency, purity and electrolysis yield

Electrosynthesised CdS@ZnS quantum dots decorated multi walled carbon nanotubes for analysis of propranolol in biological fluids and pharmaceutical samples

Quantum dots (QDs) based electrochemical assays have received a great deal of attention. They preserve the outstanding characteristics of electrochemical methodologies with respect to simplicity, ease-of-use, and costeffective instrumentation. In this work, a new challenge was opened up to explore the electrochemical features of CdS@ZnS as two well-known semiconductors for analytical utilizations. Here, CdS@ZnS core-shell QDs have been prepared electrochemically and applied for electrochemical sensor development in this approach. An activated glassy carbon electrode modified with a thin film of multi walled carbon nanotube was coated with CdS@ZnS QDs (activated GCE/MWCNTs/CdS@ZnS) as a thin uniform layer for analysis and monitoring of propranolol (PRO), a non-selective beta-blocker drug. Field emission scanning electron microscopy (FESEM) and energy-dispersive X-ray spectroscopy (EDX) were used to characterize the surface morphology of the developed electrodes. The results demonstrated that CdS@ZnS QDs were well-dispersed on the activated GCE/MWCNTs surface and were able to enhance the number of adsorbed analyte molecules. The electrochemical behavior of the PRO was studied at the modified electrode surface. The kinetic parameters of electron transfer coefficient (alpha) and the catalytic rate constant (kcat) for the electron transfer between PRO and the modified electrode were calculated. The electrochemical oxidation mechanism of PRO was also investigated by square wave voltammetry (SWV). Under optimal conditions, the proposed sensor demonstrated a linear response towards propranolol in the range of 0.06-27 mu mol L-1 and a detection limit of 12 nmol L-1. Furthermore, the analytical performance of the developed sensor was evaluated for measuring propranolol in biological fluids and pharmaceutical samples. The observed promising results confirm the suitability of the developed sensor for applications in measuring complex materials

Electrochemical Study of Iodide in the Presence of Phenol and o-Cresol: Application to the Catalytic Determination of Phenol and o-Cresol

Abstract: The electrochemical oxidation of iodide in the presence of phenol and o-cresol was investigated at a glassy carbon electrode in buffered media by cyclic voltammetry, linear sweep voltammetry and controlled–potential coulometry. The experimental results indicate that the phenol and o-cresol convert to their derivatives after participating in a halogenation coupled reaction (quasi-catalytic reaction) following the oxidation of iodide to iodine. The concentrations of phenol and o-cresol have been determined in aqueous solutions according to the linear dependence of quasi-catalytic peak currents with the concentration. The calibration graphs show two linear sections of 0.0 to 1.0×10-4 M and 2.0×10-4 to 1.0 ×10-3 M for phenol and 4.2×10-5 to 1.0×10-4 M and 2.0×10-4 to 1.0×10-3 M for o-cresol. The theoretical detection limits and the relative standard deviations for ten measurements of phenol and o-cresol are 1.125×10-5 M, 1.06 % and 4.201×10-5 M, 1.44%, respectively

Cobalt sulfide flower-like derived from metal organic frameworks on nickel foam as an electrode for fabrication of asymmetric supercapacitors

Abstract Metal–organic frameworks, as a kind of advanced nanoporous materials with metal centers and organic linkers, have been applied as promising electrode materials in energy storage devices. In this study, we are successfully prepared cobalt sulfide nanosheets (CoS) derived from the metal–organic framework on nickel foam (NF). The prepared electrodes are characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, energy-dispersive X-ray spectroscopy, Brunauer–Emmett–Teller and Barrett-Joyner-Halenda and electrochemical methods like voltammetry, galvanostatic charge–discharge curve and electrochemical impedance spectroscopy. The CoS/NF electrode demonstrates a high specific capacity of 377.5 mA h g−1 (1359 C g−1) at the current density of 2 A g−1, considerable rate performance and excellent durability (89.4% after 4000 cycles). A hybrid supercapacitor is assembled using CoS/NF as the positive electrode and activated carbon as the negative electrode, it shows a high energy density of 57.4 W h kg−1 at a power density of 405.2 W kg−1. The electrochemical results suggest that the CoS nanosheet arrays would possess excellent potential for applications in energy storage devices

An amplified electrochemical sensor employing a polymeric film and graphene quantum dots/multiwall carbon nanotubes in a deep eutectic solvent for sensitive analysis of paracetamol and 4-aminophenol

Herein, a nanocomposite consisting of graphene quantum dots, a deep eutectic solvent and carboxyl functionalized multiwall carbon nanotubes (GQDs + DES + MWCNTs-COOH) was prepared. After electropolymerization of l-arginine on the surface of a glassy carbon electrode modified with the GQDs + DES + MWCNTs-COOH nanocomposite, an electrochemical sensor was fabricated. The morphology of the GQDs + DES + MWCNTs-COOH/PARG surface was characterized via field emission electron microscopy. The sensor allowed excellent performance to be obtained for the analytical monitoring of paracetamol and its metabolite 4-aminophenol. Under the optimal conditions, the prepared electrochemical sensor exhibited wide linear dynamic ranges from 0.030 to 110 μmol L-1 and 0.050 to 100 μmol L-1 for paracetamol and 4-aminophenol, respectively. Moreover, the detection limits were 0.010 μmol L-1 and 0.017 μmol L-1, for paracetamol and 4-aminophenol, respectively. The practical applicability of the constructed sensor was explored by the determination of both compounds in human fluid samples and acceptable results were obtained

Electrochemical Synthesis and Structural Characterization of a Novel Mixed-valence Copper (I)-copper (II) Complex: {[Bis(ethylenediamine) Copper (II)] Bis[diiodocuprate (I)]}

A novel, mixed-valent copper(I)-copper(II) complex, {[bis(ethylene-diamine)copper(II)] bis[diiodocuprate(I)]} (1), has been prepared by electrochemicaldissolution of a sacrificial copper anode in a solution of ethylenediamine (en), I2 andtetraethylammoniumperchlorate (TEAP) as supporting electrolyte in acetonitrile (AcN)and characterized by single-crystal X-ray structure determination. The crystal structure ofthe complex 1 shows that it consists of a CuI2 polymer formed from I- ligands bridgingCu(I) ions, with a nearly square planar geometry of bivalente Cu(II) atoms chelated by twoethylenediamine ligands. The results also show that direct electrosynthesis of the complexhad high current efficiency, purity and electrolysis yield

Lipase and Laccase Encapsulated on Zeolite Imidazolate Framework: Enzyme Activity and Stability from Voltammetric Measurements

Lipase (Pseudomonas fluorescens) and laccase (Trametates versicolor) were encapsulated on two zeolite imidazolate framework, ZIF‐8 and ZIF‐zni, materials using a one‐pot synthesis‐immobilization method in aqueous solution at room temperature. The synthesized immobilized biocatalysts (Lip@ZIF‐8, Lip@ZIF‐zni, Lac@ZIF‐8, and Lac@ZIF‐zni) were characterized by X‐ray diffraction, scanning electron microscopy, Fourier transform infrared spectroscopy, and thermogravimetric analysis. The enzymatic activities of the four immobilized biocatalysts were characterized via the electrochemical detection of the substrates, p‐nitrophenyl butyrate and 2,2‐azinobis‐3‐ethylbenzthiazoline‐6‐sulfonic acid. For Lip@ZIF‐8 the specific activity was 91.9 U mg−1 and 123.1 U mg−1 for Lip@ZIF‐zni, while for Lac@ZIF‐8 and Lac@ZIF‐zni, the activity was 51 U mg−1 and 163 U mg−1, respectively, confirming that laccase retains a higher level of activity when immobilized onto ZIF‐zni than on ZIF‐8. Lac@ZIF‐8 was the most stable system on storage (15 days at 5 °C), retaining 94 % of initial activity, while Lip@ZIF‐zni biocatalyst had the optimal level of reusability, retaining 40 % of initial activity after five reaction cycles