Electrochemical Behavior of Hybrid Films Composed of Copper Hexacyanoferrate and Conducting Polymer

Hybrid organic / inorganic films, composed of poly 4-aminoquinolidine (PAQ) matrix and Prussian blue – like copper hexacyanoferrate (CuHCFe) redox centers were prepared. Platinum disk (Pt) was used as a conductive substrate onto which the hybrid films (Pt/PAQ/CuHCFe) were electrodeposited by potential cycling. Electrochemical behavior of the modified electrode was well characterized using cyclic voltammetry technique. The hybrid film modified electrode showed improvement in the electrochemical response in aqueous and non aqueous media compared with the polymer film (PAQ) single layer. Moreover a good electrocatalytic activity towards the oxidation of hydroquinone (H2Q) was observed. In addition, the electrode exhibited a distinct advantage of good chemical and mechanical stability. (doi: 10.5562/cca1920

Electrooxidation of Iodide Ion at Poly 8-(3-acetylimino-6-methyl-2,4- dioxopyran)-1-aminonaphthalene Modified Electrode in Aqueous Solution

Poly 8-(3-acetylimino-6-methyl-2,4-dioxopyran)-1-aminonaphthalene (PAMDAN) films were electrodeposited on platinum electrode (Pt), forming PAMDAN/Pt modified electrode, to study its utility in electrooxidation of iodide ion. The electrooxidation process was investigated by cyclic voltammetry. The effects of different factors e.g. scan rate, iodide ion concentration, film thickness and acid concentration have been studied to improve the redox response of PAMDAN/Pt modified electrode during the oxidation process. (doi: 10.5562/cca1843

Ceftriaxone as an Inhibitor for Corrosion of Al in Formic Acid Solutions

The inhibiting effect of ceftriaxone on the corrosion of Al in HCOOH solution was studied by means of weight loss, thermometry, hydrogen evolution and potentiodynamic polarization techniques, complemented with surface examination using scanning electron microscopy (SEM). The obtained results showed that ceftriaxone are excellent inhibitor in HCOOH solution. The inhibition efficiency increases with inhibitor concentration. Polarization curves indicate that ceftriaxone was acted as a mixed-type inhibitor. The adsorption of the inhibitor on Al surface was found to obey Langmuir isotherm and showed a physisorption mechanism. The thermodynamic activation and adsorption parameters were calculated and discussed. Keywords: Ceftriaxone, aluminum, corrosion inhibitor, potentiodynamic polarization, adsorption, gravimetry and gasometr

Voltammetric and impedimetric determinations of selenium(iv) by an innovative gold-free poly(1-aminoanthraquinone)/multiwall carbon nanotube-modified carbon paste electrode

Selenite (Se4+), a significant source of water pollution above the permissible limits, is considered a valuable metal by environmentalists. In this study, we described a novel electrochemical sensor that utilized a carbon paste electrode (CPE) that was modified using multiwall carbon nanotubes (MWCNTs) and poly(1-aminoanthraquinone) (p-AAQ) for finding Se4+ in water samples. Electrochemical quantification of Se4+ depends on the formation of a selective complex (piaselenol) with p-AAQ. In this work, we prepared a CPE modified by physical embedding of MWCNTs and 1-aminoanthraquione (AAQ), while the polymer film was formed by anodic polymerization of AAQ by applying a constant potential of 0.75 V in 0.1 M HCl for 20 s followed by cyclic voltammetry (CV) from -0.2 to 1.4 V for 20 cycles. The modified CPE was used for differential pulse voltammetry (DPV) of Se4+ in 0.1 M H2SO4 from 0 to 0.4 V with a characteristic peak at 0.27 V. Further, the proposed sensor was characterized by scanning electron microscopy, energy-dispersive X-ray spectroscopy, and electrochemical impedance spectroscopy (EIS). The analytical conditions regarding the electrode performance and voltammetric measurements were optimized, with the accumulation time and potential, supporting electrolyte, differential-pulse period/time, and amplitude. The EIS results indicated that the p-AAQ/MWCNTs-modified CPE sensor (p-AAQ/MWCNTs/CPE) that also exhibited low charge-transfer resistance (R-ct) toward the anodic stripping of Se4+, exhibited good analytical performance toward different concentrations of Se4+ in a linear range of 5-50 mu g L-1 Se4+ with a limit of determination (LOD) of 1.5 mu g L-1 (3 sigma). Furthermore, differential-pulse voltammetry was employed to determine different concentrations of Se4+ in a linear range of 1-50 mu g L-1 Se4+, and an LOD value of 0.289 mu g L-1 was obtained. The proposed sensor demonstrated good precision (relative standard deviation = 4.02%) at a Se4+ concentration of 5 mu g L-1. Moreover, the proposed sensor was applied to analyze Se4+ in wastewater samples that were spiked with Se, and it achieved good recovery values

Modified electrode decorated with silver as a novel non-enzymatic sensor for the determination of ammonium in water

Abstract Ammonium is an essential component of the nitrogen cycle, which is essential for nitrogen cycling in ecosystems. On the other hand, ammonium pollution in water poses a great threat to the ecosystem and human health. Accurate and timely determination of ammonium content is of great importance for environmental management and ensuring the safety of water supply. Here we report a highly sensitive electrochemical sensor for ammonium in water samples. The modified electrode is based on the incorporation of silver nitrate (AgNO3) into a carbon paste embedded with 1-aminoanthraquinone and supported by multi-walled carbon nanotubes, which are commercially available. A potential of 0.75 V is applied to the modified electrode, followed by activation in hydrochloric acid. The modified electrode was used for square wave voltammetry of ammonium in water in the potential range of − 0.4–0.2 V. The performance of ammonium analysis was determined in terms of square wave frequency, square wave amplitude and concentration of electrolyte solution (sodium sulphate). The calculation of the surface area according to the Randles–Sevcik equation resulted in the largest surface area for the Ag/pAAQ/MWCNTs/CPE. The modified electrode exhibited a linear range of 5–100 µM NH4 + in 0.1 M Na2SO4 with a detection limit of 0.03 µM NH4 + (3σ). In addition, the modified electrode showed high precision with an RSD value of 9.93% for 10 repeated measurements. No interfering effect was observed at twofold and tenfold additive concentrations of foreign ions. Good recoveries were obtained in the analysis of tap and mineral water after spiking with a concentration of ammonium ions

Ultrasensitive Platform for Electrochemical Sensing of Copper and Antimony Based on Poly(1,5-Diaminoanthraquinone)/Multiwalled Carbon Nanotubes/Carbon Paste Electrode

A new sensor for the detection of copper (II) (Cu2+) and antimony (III) (Sb3+) metal ions is described herein. The sensor is based on multi-walled carbon nanotubes mixed with a carbon paste electrode modified by poly(1,5-diaminoanthraquinone) (p-1,5-DAAQ). The Cu2+ and Sb3+ ions were effectively detected by square wave anodic stripping voltammetry (SWASV) both individually and simultaneously. The proposed modified electrode was characterized by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM), and atomic force microscopy (AFM). Poly(1,5-diaminoanthraquinone)/multi-walled carbon nanotubes/carbon paste electrode (p-1,5-DAAQ/MWCNT/CPE) was utilized for electrochemical determination of Cu2+ and Sb3+ under pre-optimized conditions (i.e., deposition potential, deposition time, square wave frequency, and concentration of HCl). For simultaneous detection, a linear range of 1-180 μ l-1 was employed with a limit of determination (LOD) of 1.3 and 1.4 ng l-1 for Cu2+ and Sb3+, respectively. Moreover, for individual detection, a linear range of 2-30 μg l-1 was used for Sb3+, while for Cu2+ it was set at 0.5-25 μg l-1, with a limit of detection of 205.7 ng l-1 and 1.9 ng l-1 for Cu2+ and Sb3+, respectively. The effects of Tween 80 (nonionic surfactant) and humic acid on the metal peak current were also studied. Water samples spiked with both Cu2+ and Sb3+ were analyzed utilizing the proposed method as well as by inductively coupled plasma-mass spectroscopy (ICP-MS). Overall, good recovery values were achieved, demonstrating the applicability of the described approach for the detection of metal ions in real water samples

Biosynthesized silver nanoparticles for electrochemical detection of bromocresol green in river water

In this study, silver nanoparticles (AgNPs)-based electrochemical sensor has been reported for assessing bromocresol green (BG) in river water. Firstly, AgNPs were greenly produced using the aqueous extract of Ficus sycomorus leaves. Then, the AgNP-modified glassy carbon (GC) electrode was prepared using the sticking method. AgNPs were characterized using transmission electron microscope (TEM), X-ray diffraction (XRD), square wave voltammetry (SWV) and scanning electron microscope (SEM). TEM and SEM were used for determining the size of AgNPs before and after adsorption, respectively. The results show that there was an increase in AgNP size from 20 to 30 nm. Additionally, XRD was used for characterizing the crystal nature of AgNPs, while SWV exhibited a characteristic oxidation peak of AgNPs at 0.06 V. Moreover, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were used for characterizing the catalytic effect of AgNPs. BG as a targeted pollutant was detected at AgNPs/GC based on its oxidation through proton and electron transfer. Two peaks corresponding to the monomer and polymer oxidation were detected. The monomer- and polymer-based sensors have revealed a linear range of 2.9 × 10−5 to 2.1 × 10−4 mole l−1 and low detection limits (LODs) of 1.5 × 10−5 and 1.3 × 10−5 mole l−1, respectively