Search

Several new derivatives of 2,2′‐bipyridines with a spacer group separated from the 2,2‐bipyridine fragment, namely, an ethynyl fragment, were obtained using the Sonagashira cross‐coupling reaction. The resulting derivatives were physically adsorbed on platinum electrode and were then used as activators of the catalytic activity of a platinum electrode in the reaction of cholesterol electrooxidation in an acetonitrile medium. Sensitivity, limit of detection and detectable concentration range were calculated, and the best results was established as 6.2±0.6 μA/mM, 0.08 mM and 0–0.3 mM, respectively. These results show that the prepared compounds adsorbed on platinum electrode are perspective systems for developing of new enzymeless cholesterol sensor based on them. [ABSTRACT FROM AUTHOR]

A novel electrochemical sensing platform based on Fe3O4-antibody conjugate was developed for the rapid and sensitive determination of Salmonella typhimurium antigen in model suspensions. The conjugates Fe3O4-antibody were synthesized via carbodiimide cross-linking and characterized by infrared spectroscopy and cyclic voltammetry. The electrochemical properties of Fe3O4 magnetic nanoparticles in water were investigated; the possible mechanism of direct electrochemical reduction was proposed and justified as an analytical signal. The design of an electrochemical sensing platform with magnetically controlled flows has been proposed. Under the most appropriate conditions, the developed portable device was provided the linear response as I (µA) = (7.20 ± 0.35) × (–lg CAg) − (23.77 ± 1.95) in the concentration range 1 × 10−7–1 × 10−4 mg/mL. The detection limit was 390 ng/mL and was comparable to other works. [ABSTRACT FROM AUTHOR]

The present work is devoted to the electrochemical reduction study of presumably biologically active 2-substituted quinoxaline derivatives. In this work, two new quinoxaline derivatives are presented. The electrochemical behavior of this compound in an aprotic medium and while its protonating was investigated via a voltammetric method. Using computational methods, the localization of the reduction centres depending on the compound’s structure was determined. The EPR spectra data obtained by electrochemical generation reduction product proved that the studied quinoxaline’s electroconversion occurs with radical anion formation. The linear correlation between the reduction potential of studied compounds and energy of their affinity to the electron was found (R2 = 0.933). This confirms the single reduction mechanism of radical nature for the entire series of studied 2-substituted quinoxaline derivatives. Based on that, the electron-accepting ability of these compounds was compared in order to evaluate their possible bioactivity and to select the most perspective ones among them for further research. [ABSTRACT FROM AUTHOR]

AbstractFor the first time, Neutral Red (NR) has been used as a redox probe for comparative evaluation of the electrochemical performance of screen-printed carbon electrodes (SPCEs) modified with bismuth under different potentiostatic pre-plating conditions (Bi/SPCEs). It was shown that protonated NR undergoes quasi-reversible redox transformations at bare-SPCE and Bi/SPCEs in the pH range 5–6 in phosphate buffer solutions (PBS) in the potential range of (−0.2)–(−0.8) V, where bismuth is not electroactive. Bi/SPCEs have been characterized morphologically by scanning electron microscopy (SEM) and electrochemically by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) employing NR as a redox probe. The obtained SEM, CV, and EIS data are in good agreement. The highest charge transfer resistance (Rct) values (3.9 and 3.3 kΩ) were obtained at bare-SPCE and Bi/SPCE having low degree of bismuth coverage. Contrarily, the lowest Rct value (8 Ω) was recorded at Bi/SPCE, with the highest degree of bismuth coverage. CV experiments showed a significant increase in the electrochemical performances of Bi/SPCEs, whose surface is half or more covered with bismuth, in comparison to the bare-SPCE. Nickel (II) ions and formaldehyde (FM), in the form of formaldehyde hydrazone (FAH), were used as model analytes to determine the electroanalytical performance of Bi/SPCEs. A comparison of roughness factor and sensitivity toward both analytes for Bi/SPCEs with two-tailed Pearson’s criterion showed a high degree of correlation between their electrochemical and electroanalytical characteristics. The data acquired indicates that the use of NR as a redox probe may be quite helpful to control modification processes when developing novel bismuth-containing sensors. [ABSTRACT FROM AUTHOR]