Surface Characterization of New Azulene-Based CMEs for Sensing

Films of 2-(azulen-1-yldiazenyl)-5-phenyl-1,3,4-thiadiazole (T) were successfully deposited on glassy carbon surfaces to prepare chemically modified electrodes (CMEs). Their surface characterization was analyzed by electrochemical impedance spectroscopy (EIS), atomic force microscopy (AFM), and scanning electron microscopy (SEM). This complexing monomer has been deposited through direct electropolymerization in conditions established during the electrochemical characterization of T performed by cyclic voltammetry (CV), differential pulse voltammetry (DPV) and rotating disk electrode voltammetry (RDE). These methods put in evidence the high degree of asymmetry of oxidation and reduction curves, which is due to the irreversible processes occurring at opposite potentials. The film formation was confirmed by ferrocene redox assay probe. The properties of the electrodes modified with T (T-CMEs) were investigated for sensing heavy metal (HM) ions in water solutions, with promising results for Pb(II) among Cd(II), Cu(II), and Hg(II) ions.

Recognition of Heavy Metal Ions by Using E-5-((5-Isopropyl-3,8-Dimethylazulen-1-yl) Dyazenyl)-1H-Tetrazole Modified Electrodes

Chemically modified electrodes (CMEs) based on polymeric films of E-5-((5-isopropyl-3,8-dimethylazulen-1-yl) diazenyl)-1H-tetrazole (L) deposited on the surface of the glassy carbon electrode have been used for the recognition of heavy metal (Me) ions. The electrochemical study of L was done by three methods: differential pulse voltammetry (DPV), cyclic voltammetry (CV), and rotating disk electrode voltammetry (RDE). The CV, DPV, and RDE studies for L were performed at different concentrations in 0.1 M tetrabutylammonium perchlorate solutions in acetonitrile. The polymeric films were formed by successive cycling or by controlled potential electrolysis (CPE). The film formation was proven by recording the CV curves of the CMEs in ferrocene solution. The CMEs prepared at different charges or potentials were used for detection of heavy metal ions. Synthetic samples of heavy metal ions (Cd(II), Pb(II), Cu(II), Hg(II)) of concentrations between 10−8 and 10−4 M were analyzed. The most intense signal was obtained for Pb(II) ion (detection limit of about 10−8 M). Pb(II) ion can be detected by these CMEs in waters at such concentrations. The ability of the ligand L to form complexes with Pb(II) and Hg(II) ions was also tested by UV-Vis spectrometry. The obtained results showed the formation of Me(II)L2 complexes.

Electrochemical Comparison on New (Z)-5-(Azulen-1-Ylmethylene)-2-Thioxo-Thiazolidin-4-Ones

Three (Z)-5-(azulen-1-ylmethylene)-2-thioxo-thiazolidin-4-ones are electrochemically characterized by cyclic voltammetry, differential pulse voltammetry, and rotating disk electrode voltammetry. The electrochemical investigations revealed that the redox potential is influenced by the number and position of the alkyl groups, and the possible oxidation mechanism is proposed. These compounds, after their immobilization on glassy carbon electrodes during oxidative electropolymerization, were examined as complexing ligands for heavy metal ions from aqueous solutions through adsorptive stripping voltammetry.

Chemically Modified Electrodes Based on 4-(azulen-1-yl)-2,6-bis ((e)-2-(thiophen-2-yl)vinyl) Pyrylium Perchlorate

The electrochemical behavior of 4-(azulen-1-yl)-2,6-bis((E)-2-(thiophen-2-yl)vinyl) pyrylium perchlorate (L) was studied by cyclic voltammetry, differential pulse voltammetry, and rotating disk electrode voltammetry. The electrochemical polymerization of L was studied. Modified electrodes covered by polyL films were obtained by successive scanning or by controlled potential electrolysis (CPE) at different charges and potentials. The new electrodes obtained by CPE were applied for sensing the following heavy metals ions: Cu(II), Pb(II), Cd(II), Hg(II). The best results have been registered for Pb(II) ion with a detection limit of 10-8 M.

A Benchmarking Approach for Routine Determination of Flow Battery Kinetics

This work focusses on improved precision and reproducibility in the study of redox flow battery (RFB) kinetics. We measured the electron-transfer reaction rates of the Fe(III/II) redox couple at polycrystalline Pt and Au electrodes in aqueous HCl supporting electrolyte using rotating disk electrode voltammetry. We made considerable effort to implement a systematic electrode preparation protocol, which was necessary for reproducibility. We found the reaction to be quasi-reversible at both electrodes and Pt to be a slightly more effective catalyst than Au. We further discuss some of the benefits and challenges of applying classical electroanalysis to RFB device design.

A Benchmarking Approach for Routine Determination of Flow Battery Kinetics

This work focusses on improved precision and reproducibility in the study of redox flow battery (RFB) kinetics. We measured the electron-transfer reaction rates of the Fe(III/II) redox couple at polycrystalline Pt and Au electrodes in aqueous HCl supporting electrolyte using rotating disk electrode voltammetry. We made considerable effort to implement a systematic electrode preparation protocol, which was necessary for reproducibility. We found the reaction to be quasi-reversible at both electrodes and Pt to be a slightly more effective catalyst than Au. We further discuss some of the benefits and challenges of applying classical electroanalysis to RFB device design.

The Heavy Metals Sensing Based on 2,6-Bis(-2-(Thiophen-3-yl)Vinyl)-4-(4,6,8-Trimethylazulen-1-yl)Pyrylium Modified Electrodes

This paper focuses on electrochemical characterization of new azulene compound 2,6-bis((E)-2-(thiophen-3-yl)vinyl)-4-(4,6,8-trimethylazulen-1-yl)pyrylium (L) by cyclic voltammetry (CV), differential pulse voltammetry (DPV), rotating disk electrode voltammetry (RDE) on glassy carbon disk working electrodes. The character of redox processes was established by CV and RDE using increasing scan rates at different scan domains. PolyL modified electrodes have been prepared by scanning or controlled potential electrolysis (CPE). The complexing properties of L and polyL have been investigated towards detection of heavy metal ions by anodic stripping technique. The voltammetric curves present well defined peaks for Pb2+, Cd2+, Cu2+ and Hg2+, which can be used as analytical signals for their determination. The performances of the modified electrodes obtained at different potentials and charges have been evaluated. The best results have been obtained for Pb2+ and Cd2+ with the achievement of detection limits of 10-7 M.

Polyazulenes Based Materials for Heavy Metal Ions Detection

Azulene is a special monomer used to functionalize electrodes due to its high polarizability, because it makes possible spontaneous electron drift from the five-membered ring to the seven-membered ring. Our study concerns the electrochemical characterization by cyclic voltammetry, differential pulse-voltammetry and rotating disk electrode voltammetry of a new azulene monomer, 4-(5-isopropyl-3,8-dimethylazulen-1-yl)-2,6-bis((E)-2-(thiophen-2-yl)vinyl) pyridine (L). It has been used to obtain complexing modified electrodes by electrochemical polymerization. PolyL films modified electrodes have been characterized by cyclic voltammetry in ferrocene probe solution. The complexing properties of polyL based functional materials have been investigated towards heavy metals (Pb, Cd Hg, Cu) by preconcentration � anodic stripping technique.

Electrochemical Behavior and Convoluted Voltammetry of Carbon Nanotubes Modified with Anthraquinone

The validity of convolution voltammetry for determination accurate values of diffusion coefficient (D) and electrons number (n) consumed in electrochemical reaction has been explained by applying the technique to a carbon nanotubes chemically modified using func-tional groups of anthraquinone(AQ). The analysis with macrodisk electrode was facilitated due to the presence of minor contribution of nonfaradaic current, so moderate values of sweep speed can be used without subtraction of residual current to quantify the diffusivity of electro-active species.The values of D and nCb were determined simultaneously and demonstrated using convoluted procedure. The ob-tained results indicate that the convolution voltammetry provides advantages over constant state methods (plateau) such as micro-disk electrode voltammetry and rotating disk electrode voltammetry, as it is not limited by the method of diffusion (planar or radial), which remove the limitations of solvent viscosity, geometry of electrode, and voltammetric sweep speed.