scholarly journals Homogeneous electron-transfer of chlorophyll and its derivative chlorophyllin at gold electrode

2019 ◽  
Vol 7 (1) ◽  
pp. 1-17
Author(s):  
Alhasan H ◽  
Alahmadi N ◽  
Wadhawan J
Keyword(s):  
Electron Transfer ◽  
Cyclic Voltammetry ◽  
Electrode Surface ◽  
Gold Electrode ◽  
Reference Electrode ◽  
Surface Preparation ◽  
Active Species ◽  
Bulk Solution ◽  
Photovoltaic Properties ◽  
Working Electrode

Introduction: Chlorophyll is a light harvesting pigment, which absorbs light in the visible spectrum of sunlight and promotes electron transfer, Chlorophyllin (CHL) is One of the most important derivative molecules of chlorophyll. Nowadays, chlorophyll pigment and its derivatives are utilised in organic photosynthetic solar cells for their desirable photovoltaic properties. Cyclic voltammetry (CV) is an essential technique. It is extensively used to study electroactive species to interpret the intermediates of reactions, supply information about the thermodynamics of oxidation-reduction reactions and elucidate the kinetics of electron transfer reactions. Materials and Methods: Prior to the electrochemical study, the working gold (Au) electrode surface was prepared by immersing it in the various concentrations of chlorophyllin for a period time. The electrolyte was degassed by using N2 for approximately 30 minutes inside a Faraday cage before any electrochemical experiment was performed. A three electrode system was used with, Ag/AgCl as a reference electrode, graphiteas a counter and the working electrode (Au). Results and Discussion: As a route to develop new chemical systems for artificial photosynthesis, this work reports the effectiveness of different parameters in transferring electrons between chlorophyllin (CHL) pigment and the working electrode surface (gold). These parameters such as the adsorption time, the electrolyte nature and concentration and chlorophyllin concentration are investigated. The use of chlorophyllin as a redox mediator is examined, with a gold electrode being employed. The importance of gold electrode surface preparation in determining the mechanism of redox is described, and the environment of adsorption process of the different concentrations of chlorophyllin on the surface of the gold electrode has been elucidated in this study. Conclusiones: The electrochemical method showed that the cyclic voltammetry responses of studied adsorption chlorophyllin pigment on the gold electrode were more efficient. In addition, the redox reaction was successful electrochemically in aqueous solution thanthe organic solution. It was suggested that electrons reduce to the chlorophyllin pigment by adding active species in the bulk solution homogeneous transfer. Finally, detections of chl on spinach leaves using various methods are reported.

Characterization of Mercaptoethylamine-Modified Gold Electrode Surface and Analyses of Direct Electron Transfer to Putidaredoxin

Langmuir ◽  
1995 ◽  
Vol 11 (12) ◽  
pp. 4818-4822 ◽  
Author(s):  
Ling Sang Wong ◽  
Vincent L. Vilker ◽  
William T. Yap ◽  
Vytas Reipa
Keyword(s):  
Electron Transfer ◽  
Electrode Surface ◽  
Gold Electrode ◽  
Direct Electron Transfer

scholarly journals Electrochemical reduction of artemisinin: Chromatographic identification of bulk electrolysis products

2019 ◽  
Vol 9 (3) ◽  
pp. 165-174 ◽  
Author(s):  
Faraja Ombwayo ◽  
Zahilis Mazzhichette ◽  
Amos Mugweru
Keyword(s):  
Cyclic Voltammetry ◽  
Sesquiterpene Lactone ◽  
Electrode Surface ◽  
Reference Electrode ◽  
Carbon Electrode ◽  
Naturally Occurring ◽  
Bulk Electrolysis ◽  
Electrolysis Products ◽  
Peroxide Bond ◽  
Prominent Peak

Artemisinin is a naturally occurring sesquiterpene lactone with an endo-peroxide bond. This drug is used for treatment of many diseases including malaria. The reduction of this molecule on an electrode surface was carried out by cyclic voltammetry as well as amperometry. Cyclic voltammetry of artemisinin generated one prominent peak wave at -1.0 V and another, smaller one at -0.3 V vs Ag/AgCl reference electrode. The bulk electrolysis of artemisinin on a carbon electrode generated two other irreversible peak waves at around -0.7 and -0.1 V. The concentration of the products was dependent on the time of electrolysis. LC-MS was used to determine the bulk electrolysis products of artemisinin. Initially dihydroartemisinin was generated as the main reduction product. Other reduction products were formed after further reduction of dyhidroartemisinin.

scholarly journals Cyclic voltammetry of samarium ions in the molten LiCl-KCl eutectic for diffusion coefficient analysis

2019 ◽  
Author(s):  
Vickram Singh ◽  
Christopher Bruneau ◽  
Dev Chidambaram
Keyword(s):  
Cyclic Voltammetry ◽  
Diffusion Coefficient ◽  
Surface Area ◽  
Electrode Surface ◽  
Measurement Errors ◽  
Current Response ◽  
High Concentration ◽  
Melt Temperature ◽  
Peak Current ◽  
Working Electrode

Cyclic voltammetry (CV) was used to investigate the electrochemical behavior of SmCl3 when it is solvated in the molten LiCl-KCl eutectic at 773 K. An experimental method obtained from the literature was adjusted to produce repeatable current responses attributed to the Sm3+/Sm2+ reaction couple and to determine working electrode surface area. The effect of solvating SmCl3 at high concentration was investigated as it relates to electrochemical reversibility and diffusion coefficient analysis. An electrochemically reversible region was identified using correlations between the current response and the scan rate along with peak current ratio measurements. In these, the reversibility was unaffected by increasing concentration. The correlation between current response and concentration was less linear than expected, suggesting the effects of additional modes of diffusion, solution resistance, and charge transfer kinetics may be contributing more at high concentrations. The measurement errors associated with peak current response, working electrode surface area, and melt temperature were used to estimate the associated uncertainties of the reported diffusion coefficients of Sm3+ in the molten LiCl-KCl eutectic. These diffusion coefficient values were found to be relatively consistent with values for Sm3+ reported in the literature for lower concentrations.

Electrochemical Treatment of Graphene

2019 ◽  
Vol 799 ◽  
pp. 197-202
Author(s):  
Alexander Usikov ◽  
Mike Puzyk ◽  
Sergey Novikov ◽  
Iosif Barash ◽  
Oleg Medvedev ◽  
...  
Keyword(s):  
Cyclic Voltammetry ◽  
Partial Oxidation ◽  
Electrochemical Method ◽  
Counter Electrode ◽  
Reference Electrode ◽  
Electrochemical Treatment ◽  
Complete Dissolution ◽  
Graphene Films ◽  
Working Electrode ◽  
Electrode Cell

Treatment of graphene/SiC dies in inorganic electrolytes (KOH, KCl and Na2SO4) is discussed. An electrochemical method based on the cyclic voltammetry in a conventional three-electrode cell with Ag/AgCl reference electrode, a platinum counter electrode, and the graphene/SiC dies as working electrode (anode) is used for the treatment. It was observed either partial oxidation of graphene or its complete dissolution with the formation of CO2. The treatment performed resulted in the deterioration of the graphene films and change of the graphene-die resistivity depending on the range of the scanning potential applied to the graphene/SiC dies.

Electrochemical Reduction of [Ni(Mebpy)3]2+. Elucidation of the Redox Mechanism by Cyclic Voltammetry and Steady-State Voltammetry in Low Ionic Strength Solutions.

2020 ◽  
Author(s):  
Koushik Barman ◽  
Martin A. Edwards ◽  
David P. Hickey ◽  
Christopher Sandford ◽  
Yinghua Qiu ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Cyclic Voltammetry ◽  
Steady State ◽  
Ionic Strength ◽  
Outer Sphere ◽  
Oxidation States ◽  
Bulk Solution ◽  
Redox Mechanism ◽  
Predominant Species ◽  
Low Ionic Strength

<p>Bipyridine complexes of Ni are used as catalysts in a variety of reductive transformations. Here, the electroreduction of [Ni(Mebpy)<sub>3</sub>]<sup>2+</sup> (Mebpy = 4,4’-dimethyl-2,2’-bipyridine) in dimethylformamide is reported, with the aim of determining the redox mechanism and oxidation states of products formed under well-controlled electrochemical conditions. Results from cyclic voltammetry, steady-state voltammetry (SSV) and chronoamperometry demonstrate that [Ni(Mebpy)<sub>3</sub>]<sup>2+</sup> undergoes two sequential 1<i>e</i> reductions at closely separated potentials (<i>E</i><sup>0’</sup><sub>1 </sub>= -1.06 ± 0.01 V and <i>E</i><sup>0<i>’</i></sup><sub>2 </sub>=<sub> </sub>-1.15 ± 0.01 V vs Ag/AgCl (3.4 M KCl)). Homogeneous comproportionation to generate [Ni(Mebpy)<sub>3</sub>]<sup>+ </sup>is demonstrated in SSV experiments in low ionic strength solutions. The comproportionation rate constant is determined to be > 10<sup>6</sup> M<sup>-1</sup>s<sup>-1</sup>, consistent with rapid outer-sphere electron transfer. Consequentially, on voltammetric time scales, the 2<i>e</i> reduction of [Ni(Mebpy)<sub>3</sub>]<sup>2+</sup> results in formation of [Ni(Mebpy)<sub>3</sub>]<sup>1+</sup> as the predominant species released into bulk solution. We also demonstrate that [Ni(Mebpy)<sub>3</sub>]<sup>0</sup><sub> </sub>slowly loses a Mebpy ligand (~10 s<sup>-1</sup>).</p>

scholarly journals Unmediated heterogeneous electron transfer reaction of ascorbate oxidase and laccase at a gold electrode

1998 ◽  
Vol 332 (3) ◽  
pp. 611-615 ◽  
Author(s):  
Roberto SANTUCCI ◽  
Tommaso FERRI ◽  
Laura MORPURGO ◽  
Isabella SAVINI ◽  
Luciana AVIGLIANO
Keyword(s):  
Electron Transfer ◽  
Electrode Surface ◽  
Gold Electrode ◽  
Ascorbate Oxidase ◽  
Cyclic Voltammograms ◽  
Intramolecular Electron Transfer ◽  
Redox Potentials ◽  
Catalytic Current ◽  
Heterogeneous Electron Transfer

The unmediated electrochemistry of two large Cu-containing proteins, ascorbate oxidase and laccase, was investigated by direct-current cyclic voltammetry. Rapid heterogeneous electron transfer was achieved in the absence of promoters or mediators by trapping a small amount of protein within a solid, electrochemically inert, tributylmethyl phosphonium chloride membrane coating a gold electrode. The problems typical of proteins in solution, such as adsorption on the electrode surface, were avoided by this procedure. In anaerobic conditions, the cyclic voltammograms, run at a scan rate of up to 200 mV/s, showed the electron transfer process to be quasi-reversible and diffusion-controlled. The pH-dependent redox potentials (+360 mV and +400 mV against a normal hydrogen electrode at pH 7.0 for ascorbate oxidase and laccase respectively and +390 mV and +410 mV at pH 5.5) were similar to those of the free proteins. The same electrochemical behaviour was recorded for the type 2 Cu-depleted derivatives, which contain reduced type 3 Cu, whereas the apoproteins were electrochemically inactive. Under aerobic conditions the catalytic current intensity of holoprotein voltammograms increased up to approx. 2-fold at a low scanning rate, with unchanged redox potentials. The voltammograms of type 2 Cu-depleted proteins and of apoproteins were unaffected by the presence of oxygen. This suggests that electron uptake at the electrode surface involves type 1 Cu and that only in the presence of oxygen is the intramolecular electron transfer to other protein sites rapid enough to be observed. The analogy with available kinetic results is discussed.

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