Cyclic Voltammetric Studies Research Articles

Facile green synthesis of silver oxide nanoparticles and their electrochemical, photocatalytic and biological studies

In the recent times, cost-effective and eco-friendly processes of synthesizing nanoparticles (NPs) have emerged as a substitute to conventional synthetic methods. Several research groups in the past have synthesized silver oxide (Ag2O) nanoparticles from various plant extracts and have been extensively reported. A first of its kind facile green combustion method has been adopted here to synthesize Ag2O NPs using Centella Asiatica and Tridax plant powder. The unique pentacyclic and triterpene constituents of Centella Asiatica and tridax powder has kindled our curiosity to explore their electrochemical, photocatalytic and biological activities that may contribute to various environmentally benign industrial applications. The cyclic voltammetric studies show that the cathodic and anodic peak potentials for the synthesized Ag2O NPs exhibit hysteresis in the range of 0.3 V to −0.1 V. A high percentage of degradation of acid orange 8 (AO8) dye by the synthesized Ag2O NPs offers new hope on its potential photocatalytic activity. Finally, their anti-bacterial and anti-fungal activities carried out against S. epidermidis and S. aureus and A. fumigates and A. aureus respectively, have shed new light on the ability of the synthesized Ag2O NPs to inhibit the growth of various disease-causing pathogens. Hence, it is believed that this research work will act as a fundamental basis to various researchers and industrialists working in the energy, water and biological fields to carry out advanced studies in the aforementioned domains.

Microstructural, optical and electrochromical properties of W-doped Nb2O5 thin films prepared by dip-coating process using sols obtained by the chloroalkoxide route

Undoped and W-doped Nb2O5 thin films have been characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and atomic force microscopy (AFM) in order to study the influence of W doping on their structural and morphological properties. The synthesized Nb2O5 thin films have been found to possess an orthorhombic crystal structure having crystallite sizes 10–31 nm. The UV–visible spectroscopy shows the optical bandgap ~ 3.60 eV. The cyclic voltammetric studies show that the colouration efficiency of the films improves upon W doping with the optimum value of 68.7 cm2/C at 600 nm for the 3 at.% W-doped film. The chronoamperometric studies reveal that the switching response of the films becomes better upon W doping. The electrochemical impedance spectroscopy (EIS) data has been analyzed by fitting it to the equivalent electrical circuit (EEC) using Nova software.

Design and synthesis new colorimetric receptors for naked-eye detection of biologically important fluoride and acetate anions in organic and arsenite in aqueous medium based on ICT mechanism: DFT study and test strip application.

Novel three colorimetric anion receptors R1, R2 and R3 have been designed and synthesized via condensation reaction and characterized using IR, MS, and NMR spectroscopic techniques. Anion sensing properties were studied using colorimetric, UV-vis titration, 1H NMR titration, and Cyclic Voltammetric Studies. Comparing the UV-visible titration data of the receptors R1 and R2, R2 showed high redshift (∆λmax) in the mixed competitive solution (DMSO: H2O, 9: 1; v/v) of about 155 nm, 157 nm, 169 nm for Na+F-, Na+AcO-, and Na+AsO2- ions with LOD of 0.23 ppm, 0.18 ppm, and 0.30 ppm, respectively. The observed spectral change of receptor R2 is due to the anion-induced deprotonation of the OH proton, which is confirmed by UV-vis titration, 1HNMR titration, and cyclic voltammetric studies. Theoretical studies via DFT calculation were carried for R1 and R2 to optimize the structure and to explain the anion-binding mechanism. The application of designed receptor R2 was successfully demonstrated for the detection of F- and AsO2- ions using a test strip. The receptors R1 and R2 proved itself to be potentially useful for real-life application by sensing F- and AcO- ions in real samples like toothpaste, mouthwash, vinegar and seawater in a complete aqueous medium.

Cyclic Voltammetric and Electrical Impedance Spectroscopy Studies of Graphene- and Conductive Polymer-based Enzyme Electrodes

Screen-printed carbon electrodes (SPCEs), modified with graphene oxide and poly(3,4-ethylenedioxythiophene):polystyrenesulfonic acid (GO-PEDOT:PSS/SPCEs), and SPCEs modified with partially reduced GO and PEDOT:PSS (prGO-PEDOT:PSS/SPCEs) were studied for electrochemical transduction. Randles-Sevcik analysis showed that the prGO-PEDOT:PSS/SPCE has a higher effective surface area of 219.3 µm2in comparison to the unreduced GO-PEDOT:PSS/SPCE (87.0 µm2) and the bare SPCE (71.7 µm2). Using electrical impedance spectroscopy (EIS), we determined that the prGO-PEDOT:PSS/SPCE has a lower charge-transfer resistance (Rct) of 163.82 Ω in comparison to the GO-PEDOT:PSS/SPCE (427.87 Ω) and the bare SPCE (13.31 kΩ). Glucose oxidase (GOx) was immobilized on all electrode types, including GO/SPCE as additional control and tested with low (0.2 mM), intermediate (0.6 mM), and high (1 mM) glucose concentrations. GOx/GO/SPCEs showed the largest change in anodic peak current (Ipa), 8.5, 7.5 and 4.9 µA for low, intermediate, and high glucose concentrations, respectively. Interestingly, GOx/prGO-PEDOT:PSS/SPCEs have no change in both anodic and cathodic peak current, although they exhibit better redox capability, while GOx/SPCEs have very low Ipa. The results show that the high effective surface area and low charge-transfer resistance (Rct) of prGO-PEDOT:PSS/SPCEs do not necessarily result in a sensitive glucose sensor in cases where immobilization of enzymes on the material can affect electron transfer.

Variations of Mass-Transport and Heterogeneous Electron-Transfer Rate with the Temperature in Ionic Liquids

Ionic liquids are molten salts with a melting point under 100°C. They are of growing interest due to their outstanding properties and appear to be good candidates for many electrochemical applications. However, ionic liquids represent a huge category of compounds and an electrochemical reference is needed to be able to make comparison of their behavior. For this purpose, the ferrocene/ferrocenium redox couple is considered as the reference of choice because it has a kinetically facile and rapid process. Moreover, this redox couple usually described as a nearly "solvent independent" formal potential system.1 However, a quick look at the literature shows important discrepancies in the heterogeneous electron-transfer rate constant (k°).1, 2 In this work, we chose to study two ionic liquids (1-butyl-1-methylpyrrolidium bis(trifluoromethanesulfonylimide), C4mpyrTFSI and 1-butyl-3-methyl-midazolium bis(trifluoromethanesulfonylimide), C4mimTFSI) in the temperature range between 20°C to 60°C for which several physicochemical properties (conductivity, density, viscosity) were measured. Then, the electrochemical behavior of ferrocenemethanol was examined by different techniques (linear sweep voltammetry, cyclic voltammetry, electrochemical impedance spectroscopy, chronoamperommetry) in the same temperature range with a gold and carbon microelectrodes of 25 µm and 11 µm of diameter, respectively. Modifying the temperature leads to a variation of the conductivity and viscosity implying a change in the mass transport of the redox species to the electrode but also in the rate constant k°. From the linear sweep voltammetry, the rate constant of the redox reaction of ferrocenemethanol was determined by the analysis of steady-state voltamogram3 and compared to results obtained from impedance spectroscopy. Additionally, the variations of the diffusion coefficient of the reduced species and the rate constant with the temperature were also analysed in term of viscosity of the solvent. Bentley, C. L.; Li, J.; Bond, A. M.; Zhang, J., Mass-Transport and Heterogeneous Electron-Transfer Kinetics Associated with the Ferrocene/Ferrocenium Process in Ionic Liquids. J. Phys. Chem. C 2016, 120 (30), 16516-16525. Siraj, N.; Grampp, G.; Landgraf, S.; Punyain, K., Cyclic Voltammetric Study of Heterogeneous Electron Transfer Rate Constants of Various Organic Compounds in Ionic Liquids: Measurements at Room Temperature. Zeitschrift Fur Physikalische Chemie-International Journal of Research in Physical Chemistry & Chemical Physics 2013, 227 (1), 105-119. Mirkin, M. V.; Bard, A. J., Simple analysis of quasi-reversible steady-state voltammograms. Anal. Chem. 1992, 64 (19), 2293-2302. Figure 1

Design, Synthesis and Biological Evaluation of Novel Piperidinyl Chalcones

Aim/Background: Chalcones are one of the important class of compounds possessing a wide range of biological properties [Dinmock 1999, Go 2005]. One of the extensive area in research on chalcones is expressed in terms of their ability to act on various cancer cell lines by a variety of molecular mechanisms. Chalcones possessing methoxy groups, a trimethoxy substituted chalcone (PGHSD 234) is the most potent chalcone with cytotoxicity comparable to the standard drugs. Materials and Methods: The antioxidant potential in terms of their free radical scavenging ability and antiproliferative activities were evaluated. Log P value and cyclic Voltammetric studies were carried out to assess their hydrophobicity and to determine their anti-oxidant potential. MTT (methyl tetrazolium) assay was performed on two cell lines including Vero and MCF-7 cell lines. Molecular docking studies were performed to assess the binding pattern of synthesized chalcones into the ATP binding site of CDK2/Cyclin A protein target. Results: The MTT assay results showed the effect of various substituents on the chalcone template that could influence their cytotoxic effect. The hydrophobicity of the synthesized compounds were reported as distribution coefficient (Log D) and all the compounds showed Log D values in the range of 1.45–4.0. The cyclic voltammetric studies revealed their irreversible oxidation potential and were found in the range of -0.400 to -0.654. Conclusion: The present study provides insight for the better understanding of mechanistic studies of N-methyl piperidinyl chalcones against anticancer targets such as CDK and aromatase identified in breast cancer.

Results on the microstructural, optical and electrochromic properties of spray-deposited MoO3 thin films by the influence of W doping

Undoped and W-doped MoO3 thin films were prepared onto the glass and fluorine doped tin oxide coated glass substrates by the spray pyrolytic decomposition of molybdenum (V) chloride (MoCl5) precursor solution. X-ray diffraction analyses confirm that all the films are polycrystalline possessing an orthorhombic phase of MoO3. Surface morphological analyses reveal that the films have intermixed irregular shaped flakes-like morphology. Cyclic voltammetric studies reveal that the colour-bleaching kinetics, coloration efficiency, and electrochemical stability of the MoO3 thin films are strongly dependent upon the microstructural features of the films which, in turn, are influenced by W doping. Maximum coloration efficiency and optimum electrochemical stability have been found for the film doped with 3 at% W. Chronoamperometry analyses reveal that the 1 at% W-doped film exhibits optimal reversibility as well as good switching response. Impedance spectroscopy studies have been carried out by analyzing the Nyquist impedance plots and the Bode plots by fitting it to the equivalent electrical circuit (EEC) model using Nova software.

Photoinduced electron transfer upon supramolecular complexation of (porphyrinato)Sn-viologen with cucurbit[7]uril.

The synthesis of (porphyrinato)Sn-viologen, 1, and its supramolecular complexation with cucurbit[7]uril (CB[7]) were studied. 1H NMR spectroscopic studies obviously reveal that 1 forms a 1 : 2 supramolecular complex with CB[7] through the inclusion of viologen moieties of 1 into the cavity of CB[7]. The cyclic voltammetric study supports that the binding affinity of the radical cation forms is comparable to that of the di-cation viologen toward CB[7]. The fluorescence arising from the porphyrin moiety is significantly quenched upon the complexation of 1 with CB[7]. The ps-time-resolved fluorescence and ns-transient absorption spectroscopic studies reveal that the photoinduced electron transfer (PET) between viologen and Sn(iv) porphyrin of 1 takes place from the first excited singlet (S1) state and the second excited triplet (T2) state of the porphyrin moiety upon complexation with CB[7], while the PET from the S1 state is negligible in the absence of CB[7].

DNA Binding Properties and Antibacterial Activity of Heterolyptic Transition Metal Complexes with 2,2-Bipyridyl and 2-Acetylthiophene Thiosemicarbazone

Metal complexes having the composition M(Bipy)Cl2 (where, M = Cu(II), Ni(II) and Co(II); Bipy = 2,2-bipyridyl) are reacted with 2-acetylthiophene thiosemicarbazone (ATT) to produce heteroleptic transition metal complexes with molecular formula [M(Bipy)ATT]. The complexes are characterized by mass spectra, molar conductivity, infrared and electronic spectra. Electrochemical behaviour of these metal complexes was investigated by cyclic voltammetric studies. The metal complexes show quasi reversible cyclic voltammetric responses for the Cu(II)/Cu(I) couple. The binding properties of these complexes with calf-thymus DNA have been investigated by using absorption spectrophotometry. Metal complexes are screened for their antibacterial activity by using agar well diffusion method against pathogenic bacterial strains viz. Escherichia coli and Staphylococcus aureus. Antibacterial activity of the present complexes are comparable with the activity of ciprofloxacin. The Cu(Bipy)Cl2 complex inhibits bacteria more strongly than any other complex. The Ni(Bipy)ATT complex shows more activity than the parent complex, Ni(Bipy)Cl2.

Platinum decorated polythiophene modified stainless steel for electrocatalytic oxidation of benzyl alcohol

Platinum nanoparticles were electrochemically deposited on conducting polymer polythiophene (PTh)-coated stainless steel (SS) substrate. A thin layer of PTh on the steel substrate facilitates uniform deposition of Pt nanoparticles on the substrate, thereby improving the surface area to a great extent. The electrochemical properties of the modified electrodes were analyzed by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The physicochemical properties of the modified electrodes were investigated by Scanning electron microscopy (SEM), Transmission electron microscopy (TEM), X-ray diffraction spectroscopy (XRD), Raman spectroscopy, and Fourier transform infrared spectroscopy (FTIR). The proposed method has been applied for the electrocatalytic oxidation of benzyl alcohol in the presence of a mediator, 2,2,6,6-tetramethylpiperidine 1-oxyl (TEMPO). Cyclic voltammetric studies reveal that the electrocatalytic activity of Pt–PTh/SS electrode is higher than that of PTh/SS electrode toward the conversion of benzyl alcohol to benzaldehyde.

Controllable Synthesis of V2O5/Mn3O4 Nanoflakes and rGO Nanosheets: To Investigate the Performance of All Solid‐State Asymmetric Supercapacitor Device

AbstractDifferent nanostructured/composite materials are considered as a promising electrode material which enhances the electrochemical activity of the individual substances. V2O5/Mn3O4 composite material is synthesized using hydrothermal method at different reaction time ranging from 12 h to 24 h. Obviously, by varying the reaction time, the morphology of composite changes from individual flakes to agglomerated flakes. The change in surface morphology of the material is observed from the SEM images. Electrochemical performance of V2O5, Mn3O4, V2O5 /Mn3O4‐1, V2O5 /Mn3O4‐2 V2O5 /Mn3O4‐3, V2O5 /Mn3O4‐4 and rGO is studied using cyclic voltammetric, charge/discharge, and electrochemical impedance spectroscopic studies. At a current density of 5 A g−1, V2O5, Mn3O4, V2O5 /Mn3O4‐3, and rGO nanosheet exhibit the maximum specific capacitance of 441, 190, 1008 and 464 F g−1 respectively. Moreover, the asymmetric supercapacitor device is constructed using V2O5 /Mn3O4‐3and rGO nanomaterials. At 2 A g−1, the asymmetric V2O5 /Mn3O4‐3and rGO device obtains the highest energy density of 44.9 W h kg−1 and the corresponding power density is 1.76 kW kg−1.

The influence of the tertiary butyl group in the ligand frame on the catalytic activities, DNA cleavage ability and cytotoxicity of dinuclear nickel(II) complexes

Dinuclear phenoxo-bridged nickel complexes [Ni2(L1)H2O(CH3COO)](1) and [Ni2(L2)H2O(CH3COO)](2) (where L1H3° = 2-(2′-hydroxyphenyl)-1,3-bis[4-(2-hydroxyphenyl)-3-azabutenyl]-3-enyl]-1,3-imidazolidine and L2H3° = 2-(3,5-di-tert-butyl-2-hydroxyphenyl)-1,3-bis[4-(3,5-di-tert-butyl-2-hydroxyphenyl)-3-azabutenyl]-1,3-idazolidine, and H stands for dissociable protons) have been synthesized and characterized by different spectroscopic methods. Molecular structure of 2 was determined by X-ray crystallography. Redox properties of complexes 1 and 2 were investigated by cyclic voltammetric studies. As functional mimic of active site of galactose oxidase enzyme, complexes 1 and 2 were utilized for the oxidation of primary alcohol. Both the complexes exhibited catecholase activity. DNA interaction studies on complexes 1 and 2 were also investigated. Self-activated DNA cleavage activity of complex 2 was observed. The cytotoxicity of the complexes 1 and 2 was measured using a standard MTT assay and IC50 values for of 1 and 2 were found to be 21.92 µM and 20.69 µM on MCF-7 breast cancer cell line respectively.

Facile preparation of three-dimensional NiO nanosheets array on carbon sphere and its high-performance nonenzymatic glucose detection

An ultrathin NiO nanosheets array loaded on carbon spheres were prepared by coprecipitation method and calcination approach. The as prepared NiO nanosheets contain high surface specific area due to their cross-sectional NiO three-dimensional structure which leads to more susceptible contacting between nanosheets and electrolyte. As the results, the reversible redox reaction should be accelerated. Moreover, NiO nanosheets array@carbon sphere (NiO@C) nanocompounds were mixed with Nafion solution and loaded onto glassy carbon electrodes (GCEs) to form a high performance non-enzymatic electrochemical glucose sensor. Cyclic voltammetric (CV) and Amperometric studies indicated NiO@C nanocompounds demonstrated excellent electrocatalytic activities for glucose detection.

Flow injection amperometric determination of NADH at a calmagite-modified pencil graphite electrode

In this study, an aromatic sulfonic dye, Calmagite (Calm) was electropolymerized on a pencil graphite electrode (Poly-Calm/PGE) to investigate the electrocatalytic oxidation and flow injection (FI) amperometric detection of NADH. Cyclic voltammetric studies show that Poly-Calm/PGE exhibits a high electrocatalytic activity towards the oxidation of NADH. Then, determination of NADH was performed at Poly-Calm/PGE using FI-amperometric technique with a homemade flow cell which was fabricated for PGEs. FI-amperometric measurements showed that linear response of NADH was found between 0.10 and 100.0 µM. Detection limit was found as 0.03 µM (based on 3 Sb/m) at Poly-Calm/PGE. This study is the first one for FI-amperometric analysis of NADH using Poly-Calm/PGE which provides a simple, low cost, and sensitive determination of NADH. The proposed sensor can be a good alternative method for determination of NADH and construction of a biosensor based on dehydrogenase enzyme in future.

Initializing the commercial viability of ionic liquids for the electrodeposition techniques: A detailed procedure for preparing CdTe thin films with high photo-absorption

In this paper, we have shown a complete methodology to scrutinize the electrodeposition of stoichiometric and nanostructured CdTe thin films from an ionic liquid bath, namely 1-butyl-3-methylimidazolium chloride ([Bmim]Cl). A detailed cyclic voltammetric study using paused potentials has been carried out to identify various redox processes of an unknown complex system. As-deposited 1μm CdTe films possessed spindle like nanostructures of cubic phase and very high absorption coefficient of 6×104cm−1. Looking at the cost of ionic liquids, we have suggested a way-out procedure to reuse the ionic liquid without any recycling. A miniature ionic liquid bath of 5mL having only 1:10 (Te:Cd) precursor concentration can be utilized for fabricating four identical 0.5cm2 CdTe thin films of 1μm thickness by applying −1.65V (vs. Fc/Fc+) at 80°C. The reuse of ionic liquid decreases deposition time in 4th run to only 555s, which is the shortest deposition time from any electrolytic bath till date. The bottleneck in adopting ionic liquids for commercial use lies in their cost and this crucial issue was dealt with a simple idea proposed in the present work. This study will be important to open up a new era of “Green” and low cost alternatives to develop nanostructured thin films of any compound material for their utilization in modern photoelectric devices.

Nanomolar detection of 4-aminophenol using amperometric sensor based on a novel phthalocyanine

Novel cobalt (II) tetra-β-[N(2-(1,3-benzothiazole))carboxamide] phthalocyanine (CoTBTCAPc) has been synthesized for the first time. The dark green colored complex was characterized by different physicochemical and analytical techniques. Cyclic voltammetric studies revealed that the synthesized complex is redox-active nature. The CoTBTCAPc modified glassy carbon electrode (GCE/CoTBTCAPc) showed a stagnant charge transfer behavior for the redox probe whereas, composite hybrid of CoTBTCAPc with carbon nanoparticles (CNP) coated on GCE (GCE/CNP-CoTBTCAPc) showed facile and better charge transfer compared to the bare GCE. The GCE/CoTBTCAPc and GCE/CNP-CoTBTCAPc fabricated electrodes exhibited a decrease in over potential with the increase in oxidation peak current. Electrochemical oxidation of 4-aminophenol (4-AP) at nanomolar concentration was obtained in phosphate buffer pH 7.0 electrolytic media. The modified electrodes showed linear electrochemical response in the concentration range of 40–800 nM and the detection limit (LOD) was found as 13 and 11 nM (S/N = 3) for GCE/CoTBTCAPc and GCE/CNP-CoTBTCAPc electrodes respectively. Differential pulse voltammetric (DPV) technique showed linear response for the 4-AP oxidation in the concentration range of 100–1000 nM with sensitivity of 0.0328 and 0.4179 μA nM−1 cm−2 for the phthalocyanine and CNP-phthalocyanine modified electrodes respectively. In contrast, the amperometric sensor displayed linear response in the concentration range of 100–900 nM with sensitivity values of 0.4008 and 0.8887 μA nM−1 cm−2 and LOD of 40 and 30 nM for GCE/CoTBTCAPc and GCE/CNP-CoTBTCAPc electrodes respectively. The GCE/CNP-CoTBTCAPc showed selectivity for 4-AP even in the presence of interfering organic and inorganic species. This stable and simple sensor offers an opportunity for the electrochemical sensing of 4-aminophenol in real sample analysis like 4-AP in paracetamol tablets.

Synthesis and characterization of hetero-metal oxide nano-hybrid composite on pectin scaffold

Abstract Hetero-metal oxides play a vital role in the development of electrochemical sensors, energy storage devices etc., based on their electro-catalytic activity. To get better efficiency, agglomeration of the hetero-metal oxides has to be prevented. Moreover, the synergistic reinforcement of the properties of the metal oxides result in efficient shuttling of electrons at the hetero-metal oxide/liquid interface for sensing applications. In the current work a novel strategy is proposed which focuses on the growth of Copper oxide and Iron oxide nanoparticles on Pectin- a carbohydrate polymer scaffold. Copper oxide nano-particles and iron oxide nano-particles were synthesized by co-precipitation method. Both were ultrasonicated separately and were added to the acid extract of musk melon (Cucumis melo) peels, which is the source of pectin. The solution was heated and sonicated for 6 h and extracted with alcohol by solvent casting method. The blending of both metal oxides with pectin was uniform since the process occurs along with the formation of pectin. It was observed that the hetero-metal oxides disperse well in pectin with reduction in particle size where pectin acts as a scaffold by which the metal oxide nano-particles bind via the - OH linkage. The metal oxide nano-particles and hetero-metal oxide hybrid nanocomposite were characterized by SEM, EDX, UV–Visible, FT-IR, Raman, and XRD studies. The electrocatalytic activity was tested with cyclic voltammetric studies with potassium ferricyanide as the standard and it was observed that pectin scaffolded hetero-metal oxide composite has high electrocatalytic activity.

Hydrothermally Synthesized Cobalt Borophosphate as an Electrocatalyst for Water Oxidation in the pH Range from 7 to 14

AbstractThe synthesis of earth‐abundant‐metal‐based, robust, efficient and cost‐effective water oxidation electrocatalysts is necessary for renewable energy conversion processes. In this study, a crystalline cobalt borophosphate (CoBP) was synthesized by reacting CoCl2.6H2O with B2O3 and (NH4)2HPO4 and evaluated as an electrocatalyst for water oxidation catalysis. The electrochemical and electrocatalytic performance of the catalyst towards water oxidation has been investigated by catalyst coating on fluorine doped tin oxide (FTO) electrode in different pH solution. Cyclic voltammetric and chronoamperometric studies were performed for the investigation of pH effect on the catalytic activity. Post‐catalytic studies indicate that CoBP acts as a pre‐catalyst yielding an active phase during the course of electrolysis in the alkaline conditions. The catalyst demonstrated catalytic activity at pH 13.6 with onset potential of 1.46 V (vs. RHE) and Tafel slope of 57 mV dec−1. Electrochemical studies show that catalyst exhibits a current densities of 1 and 10 mA cm−2 at 384 and 441 mV. The catalyst showed a turnover frequency (TOF) of 1.1×10−2 s−1 at overpotential of 300 mV.

Catalytic oxidation of ethanol by a nanostructured Ni-Co/RGO composite: Electrochemical construction and investigation

Electrocatalysis of ethanol was performed by a nanocomposite which was fabricated by carbon paste electrode modified with reduced graphene oxide supported bimetallic NiCo nanoparticles (Ni-Co/RGO/CPE). It was characterized by scanning electron microscopy, energy dispersive spectroscopy, X-ray diffraction spectroscopy and cyclic voltammetry. The cyclic voltammetric studies in different conditions showed redox activity of the Ni nanoparticles in the form of Ni(OH)2/NiOOH couple. This redox activity was improved by the presence of Co nanoparticles and reduced graphene oxide nanosheets. The oxidation of ethanol was investigated in alkaline media at the Ni-Co/RGO/CPE. The anodic peak potential of ethanol oxidation was decreased and its current was greatly enhanced at the surface of the suggested electrocatalyst. Also, the chronoamperometry technique was employed for obtaining the catalytic rate constant for the electro-oxidation reaction of ethanol and a value of 2150cm3mol−1s−1 was obtained.

Role of the newly synthesized brightener in modification of surface properties of Zn-Ni alloy electrodeposited on steel substrate

In the present study, a new brightener was synthesized by condensation of salicylaldehyde and cysteine hydrochloride (SC). To examine the influence of SC on the nucleation mechanism of Zn-Ni alloy, electrodeposition, cyclic voltammetric and chronoamperometric studies were carried out. The model of Schariffker and Hills was used to analyze current transients which explained the electrocrystallization process of Zn-Ni alloy. It is revealed that Zn-Ni electrocrystallization process in presence of SC is regulated by instantaneous nucleation mechanism. The corrosion studies were done for the bright and dull zinc-nickel alloy coatings in 3.5 wt.% NaCl solution, using potentiodynamic polarization and electro­chemical impedance spectroscopic techniques. The phase structure, surface morphology and brightness of the deposit were characterized by means of X-ray diffraction (XRD) analysis, scanning electron microscopy (SEM) and reflectance studies. These studies revealed the role of SC in producing a bright Zn-Ni alloy coating on mild steel substrate and also showed its improved corrosion resistant nature.