Electrochemical detection of kynurenic acid in the presence of tryptophan with the carbon paste electrode modified with the flower-like nanostructures of zinc oxide doped with terbium.

With the help of a hydrothermal approach in this study, we could provide flower-like nanostructures (NSs) of zinc oxide (ZnO) doped with Tb (FL-NS Tb3+/ZnO). Then, FL-NS Tb3+/ZnO morphology was investigated by energy-dispersive X-ray spectroscopy (EDX), scanning electron microscopy (SEM), X-ray powder diffraction (XRD), and map analysis. The results revealed higher activity centers and porosity of this nanocomposite, which were followed by acceptable electrochemical function. Hence, it can be utilized for fabricating an electrochemical sensor with an appropriate response for the simultaneous determination of kynurenic acid (KYN) and tryptophan (TRP). However, as compared with the modified carbon paste electrode (FL-NS Tb3+/ZnO/CPE), the bare carbon paste electrode (BCPE) exhibited a weak response toward KYN and TRP but the modified electrode was followed by a high current response for KYN and TRP at a potential 0.35 and 0.809 V. Therefore, cyclic voltammetry (CV) was applied in optimal experimental conditions to study the electrochemical behaviors of KYN and TRP over the surface of the proposed modified electrode. Moreover, we used differential pulse voltammetry (DPV) for quantitative measurements. It was found that this new modified electrode linearly ranged from 0.001 to 700.0 µM, with detection limits of 0.34 nM and 0.22 nM for KYN and TRP, respectively. In addition, KYN and TRP in real samples can be analyzed by this sensor, with a recovery of 97.75%-103.6% for the spiked KYN and TRP in real samples.

A study on synergistic effect of chloride and sulfate ions on copper corrosion by using electrochemical noise in asymmetric cells.

The current study includes a systematic examination of copper corrosion initially in each of NaCl and Na2SO4 solutions separately and then in the mixture solution of Cl- and SO42- ions as aggressive ions. Electrochemical current noise (ECN) signals resulting from asymmetric (Asy) as well as symmetric (Sym) cells have been interpreted using wavelet transform (WT) along with statistical procedures. The signals have been detrended and the decomposition of every signal has been carried out into 8 crystals. Then the standard deviation of every crystal has been illustrated with the standard deviation of partial signal (SDPS) plots. The Asy electrodes increased the pitting detection on copper compared with the Sym ones, indicating higher efficiency of the Asy electrodes. Asymmetric-copper electrodes have been studied using SDPS plots at different temperatures (40, 60, as well as 80 °C). Finally, in order to partly understand the effect of Cl- and SO42- ions on the corrosion of copper, the stabilization of Cu2+ cations by Cl- and SO42- ions in aqueous solutions have been modeled by DFT calculations. The derived results are in accordance with the experimental data.

Green and facile microwave solvent-free synthesis of CeO2 nanoparticle-decorated CNTs as a quadruplet electrochemical platform for ultrasensitive and simultaneous detection of ascorbic acid, dopamine, uric acid and acetaminophen.

This study designed a simplistic, efficient, and greener procedure to synthesize CeO2-CNTs. The analysis of structural and morphological characteristics of nano-composites has been done with regard to different procedures (e.g., EDX, XRD, & FESEM). In addition, simultaneous detection of ascorbic acid (AA), dopamine (DA), uric acid (UA) and acetaminophen (AC) has been examined at the modified glassy carbon electrode with CeO2-CNTs nano-composites. The surface area and electron transfer speed of the interplay between neuro-transmitters and electrode may be efficiently enhanced due to the existence of CeO2 nano-particles on CNTs surfaces. Moreover, electro-chemical behavior of electrodes has been dealt with by differential pulse voltammetry (DPV), impedance analysis (EIS), and cyclic voltammetry (CV). Acceptable linear response of AA, DA, UA and AC respectively have been ranged 0.01-900.0 µM, 0.01-700.0 µM, 0.01-900.0 µM, and 0.01-900.0 µM with determination limits (S/N = 3) of 3.1 nM, 2.6 nM, 2.4 nM and 4.4 nM. Ultimately, this procedure was used with successful results for determining AA, DA, UA and AC in real specimens, which suggested probable uses in other sensing studies.