Analytical & Bioanalytical Electrochemistry
Volume:15 Issue: 11, Nov 2023

In this study, a new electroanalytical method has been developed for the determination of quercetin (Que), an important flavonoid derivative, in natural samples. Pencil graphite electrode (PGE) was used for the determination of Que in black tea and beet juice samples, these determinations were done by square wave adsorptive stripping voltammetry method (SWAdSV). When using the PGE, which has a wide and active surface, a significant increase was observed in the oxidation peak current of Que. Calibration graphs were drawn in the range from 9.67 ng mL−1 to 411 ng mL−1 (from 3.2×10-8 mol L-1 to 1.36×10-6 mol L-1) using 0.1 M PBS at the optimum parameters determined for quantitative determination of Que. Thus, the amount of Que in beet juice and black tea samples was determined as 10.33 ng mL−1 (3.42×10-8 M) and 16.0 ng mL−1 (5.3×10-8 M), respectively. As a result of these processes using the SWAdSV technique, Limit of Detection (LOD) and Limit of Quantification (LOQ) values were calculated as 0.51 ng mL-1 (1.7×10−9 M) and LOQ 1.54 ng mL-1 (15.1×10−9 M), respectively. With this study, the determination of Que in natural samples without any interference effect has been demonstrated with the method developed using the PGE, which is very easy to access renewable and also cheap.

The diversity of extractable compounds provides a potentially rich source of high-value products. The corrosion inhibition performances of seven Thymus algeriensis extracts on mild steel in 0.5 M HCl were investigated using the gravimetric method, electrochemical measurements, and surface analysis. The results indicate that the addition of all the extracts significantly decreases the corrosion rate of mild steel with efficiency proportional to the extract concentration. A maximum percentage of inhibition was obtained for the microwave-assisted aqueous extract (T = 100 °C, extraction time = 15 minutes) at a concentration of 500 ppm, which is the most phenolics-enriched extract. Potentiodynamic polarization curves show that the extracts acted as mixed-type corrosion inhibitors and slowed down the anodic and cathodic reaction kinetics. Scanning electron microscopy confirms the presence of a protective film. The inhibition properties were attributed to the synergism of the active components of the extracts, mainly flavonoids, carotenoids, chlorophylls, and phenolic compounds with functional groups such as conjugated double bonds, aromatic rings, and heteroatoms, which adsorb on the metal surface of the mild steel to form a protective layer preventing the contact of the aggressive medium.

In the present work, different concentrations of citrate (reducing agent) were used to reduce the silver precursor, and Poly Vinyl Alcohol (PVA) was used as a capping agent. The electrochemical performance of the synthesized multivalent silver oxide (AgxO)/PVA nanocomposite has been carefully examined. The well-crystalline, spherical, and aggregate-free AgxO/PVA nanocomposite was synthesized. The present findings were strengthened by structural, elemental, and morphological studies. The AgxO/PVA nanocomposite showed Surface Plasmon Resonance (SPR) and defect-related band gap mechanisms. The two oxidoreduction peaks in the cyclic voltammogram were observed for the graphite electrode coated with the as-prepared samples. The AgxO/PVA-loaded electrodes showed a maximum specific capacitance of 269 Fg-1 at a scan rate of 10 mVs-1. It was observed that the citrate can be used to produce silver oxide nanoparticles and to improve the electrochemical functionality of the silver oxide nanoparticles blended with PVA. There are potential uses for this type of nanocomposite-coated electrode in supercapacitors and high-performance energy storage systems.

The current paper revolves around the conduct of newly synthesized eco-friendly pyrazole derivative, N-((3,5 dimethyl-1H-pyrazol-1-yl)methyl)-4-nitroaniline (L5), as corrosion inhibitor for carbon steel (CS) in molar hydrochloric acid (1M HCl) solution. Both chemical and electrochemical techniques, namely weight loss measurements (WL), potentiodynamic polarization (PDP) and electrochemical impedance spectroscopy (EIS) were used to evaluate the efficiency of L5 molecule, as well as quantum-chemical methods. The organic compound was confirmed to be a good anti-corrosion compound with a maximum inhibition efficiency (IE%) of 95.1% at 10-3 M. In accordance to PDP outcomes, the inhibitor L5 acts as a mixed-type inhibitor. Assessment of the temperature influence evinces that L5 is chemisorbed on CS. The adsorption of L5 on CS surface appears to follow the Langmuir model. Scanning Electron Microscopy (SEM-EDX) and UV–visible disclose the constitution of a barrier film limiting the accessibility of corrosive ions into CS surface. Theoretical studies were executed to support the results deriving from experimental techniques (WL, PDP and EIS). Furthermore, theoretical studies were carried out utilizing density functional theory (DFT) and molecular dynamics simulation (MDS) to investigate the most reactive locations of the L5 molecule and its adsorption process.

 The initial corrosion rates of electrodeposited Zn-Ni coating under galvanostatic conditions are closely related to the current density. The NH4Cl 12-14 wt% Ni coating showed better corrosion resistance than those of the other investigated coatings due to the lower Ni content of 9 wt%. Moreover, nodular granules closely packed with capillary fissures, along with the formation of the electrochemically noble γ-Ni5Zn21 phase, were observed at the highest Ni concentration of 10 wt%. The results of electrochemical characterization on the copper substrate showed an extended testing time, indicating a nobler corrosion potential. Additionally, the grain size refines with the presence of NH4Cl, and the increase in cathodic current density can also lead to a decrease in grain size.The experimental results indicate that Zn-Ni alloy coatings obtained in the presence of NH4Cl exhibit favorable electrochemical properties, demonstrating a protective effect on steel substrates. However, the sacrificial effect is more pronounced when these coatings are applied on copper substrates.

Cu-doped ZnO nanotube arrays decorated with silver nanoparticles (ZnO NTs: Cu/Ag) were synthesized on fluorine-doped tin oxide (FTO) substrates by electrodeposition technique and used as photoanodes to investigate photoelectrochemical (PEC) water splitting efficiency under visible light irradiation. The prepared photoanodes were characterized by field emission scanning electron microscope, energy-dispersive X-ray spectroscopy, X-ray diffraction and UV-Visible absorption spectroscopy. Linear sweep voltammetry, electrochemical impedance spectroscopy and Mott-Schottky analysis were used to evaluate PEC efficiency. The ZnO NT: Cu/Ag photoanode exhibits a significant photocurrent density of about180 µA/cm2 at 1.6 V vs. RHE compared to other films. Also, the results show that the charge transfer density increases to 1.03×1022cm-3 and the charge transfer resistance decreases to 17.6 Ω. The improved PEC performance of ZnO NTs: Cu/Ag is attributed to the localized surface plasmon resonance (LSPR) effect of Ag nanoparticles, the ability of Cu to absorb visible light, efficient separation and transfer charge carriers.