Voltammetric Results Research Articles

A green and efficient synthesis of novel caffeic acid derivatives with Meldrum’s acid moieties as potential antibacterial agents

Electrochemical oxidation of caffeic acid (1) has been studied in the presence of methyl and phenyl Meldrum's acids (3a–3b) as nucleophiles in water/acetonitrile (90/10) solutions using cyclic voltammetry and controlled-potential coulometry methods. The cyclic voltammetric results indicate that a one‐pot two‐step sequential reaction occurs between Meldrum's acids and the electrochemically derived o‐benzoquinone from the oxidation of caffeic acid and new caffeic acid derivatives with Meldrum's acid moieties (5a–5b) is formed. The mechanism of this reaction was suggested as an EC pathway using cyclic voltammetry, controlled-potential coulometry and spectroscopic data. In this work, we introduced the synthesis of new compounds with good yields and enhanced antibacterial activity through a catalyst‐free, environmentally friendly method at room temperature under green conditions. Furthermore, the antibacterial evaluation of caffeic acid (1), methyl and phenyl Meldrum's acids compounds (3a–3b) (as primary substances) in comparison with synthesized compounds (5a–5b) was performed by broth micro-dilution (or micro-dilution) method. Compounds (5a–5b) were found to be more effective against Gram ( −) and Gram ( +) bacteria than primary substances (1, 3a–3b).

Photoelectrochemical reduction rate of ferricyanide at different TiO2 forms: comparison of SECM and cyclic voltammetric results

Photoelectrochemical reduction rate of ferricyanide at different TiO2 forms: comparison of SECM and cyclic voltammetric results

Electroseparation of uranium from lanthanides (La, Ce, Pr, Nd and Sm) on liquid gallium electrode

The aim of this work is to explore the electroseparation of uranium from lanthanides (La, Ce, Pr, Nd and Sm) on a liquid gallium electrode. Cyclic voltammetric results showed that in multi-component melt systems (U/Nd, U/La-Ce-Nd, and U/La-Ce-Pr-Nd-Sm), the reduction potentials of each lanthanides on the Ga cathode are identical and cannot be distinguished and resolved. The peak potential differences between the lanthanides and uranium are all at about 250 mV. The practical electroseparations in U/Nd, U/La-Ce-Nd and U/La-Ce-Pr-Nd-Sm systems were carried out by applying different electrochemical techniques as galvanostatic, potentiostatic and current pulse electrolysis. After electrolysis, the ICP-AES technique was used to determine the composition of molten salt and alloy deposits, and the actual separations factor of U over lanthanides in these multi-component systems were calculated and compared. The results showed that the separation factors of U/La and U/Sm can be both up to 1000, whilst that of U/Nd is relatively low with an average value of about 350. In addition, the separation factor obtained by the current pulse electrolysis is larger than that of galvanostatic and potentiostatic method, and the potentiostatic electrolysis provides the lowest one.

Voltammetric detection of arsenic (III) using gold nanoparticles modified carbon screen printed electrodes: Application for facile and rapid analysis in commercial apple juice

This paper describes a voltammetric method and data analysis program developed for the detection of arsenic(III) in commercial apple juice. Arsenic(III) was detected using square wave stripping voltammetry with gold nanoparticle modified screen printed electrodes. The only sample pretreatment performed was the addition of a 100 mM phosphate buffer with a pH of 7. To compensate for interference from high ascorbic acid concentrations, a data analysis program was developed in MATLAB to fit a non-linear baseline, allowing for accurate peak height measurement. With this data analysis program, the developed methodology had a sensitivity of 0.1007 µA (µg L−1)−1 and a limit of detection of 16.73 µg L−1. A comparison between the voltammetric method and graphite furnace atomic absorption spectroscopy showed no bias in the voltammetric results and a good correlation between the two sets of predicted concentrations, with an R2 of 0.939.

Al2O3 microparticles immobilized on glassy‑carbon electrode as catalytic sites for the electrochemical oxidation and high detectability of naproxen: Experimental and simulation insights

This work demonstrates that Al2O3 microparticles immobilized on a glassy‑carbon electrode (GCE) anticipate the electrochemical oxidation of naproxen in 150 mV and increases its oxidation current, resulting in a highly sensitive sensor. Considering their non-conducting nature, we suggest that Al2O3 microparticles act as adsorption sites that alter the electrochemical oxidation pathway of naproxen by adsorbing its intermediate(s) and facilitating the electron transfer at the GCE surface. Interestingly, the voltammetric results obtained for ibuprofen (presents similar chemical structure and electrochemical oxidation mechanism) indicated the same facilitated electron transfer that suggests that the interaction between naproxen (or ibuprofen) with Al2O3 microparticles occurs via the carboxylic group, which is removed after the first electron transfer according to the proposed mechanism. Molecular dynamics simulations showed stronger interaction of naproxen than ibuprofen with alumina sites which may explain the respective facilitated electron transfer. Moreover, a stronger interaction of a major electrochemical oxidation product of naproxen with alumina was confirmed by simulation and explains the electrode fouling occurred when more positive potentials (+1.4 V instead of +1.0 V vs. Ag/AgCl/KClsat) were applied for the naproxen amperometric detection. The alumina-modified GCE surface presented a detection limit of 12 nmol L−1 with a linear range between 50 and 500 nmol L−1 for naproxen determination (Edet = +1.0 V). These sensing characteristics are superior in comparison with electrodes modified with carbon nanotubes and their composites. Hence, a simpler protocol for electrode modification using a non-conducting material can provide a highly sensitive sensor for naproxen due to its catalytic properties facilitating the electron transfer between naproxen (or ibuprofen) and GCE.

Guanine-Based DNA Biosensor Amplified with Pt/SWCNTs Nanocomposite as Analytical Tool for Nanomolar Determination of Daunorubicin as an Anticancer Drug: A Docking/Experimental Investigation

Daunorubicin is a famous anthracycline anticancer chemotherapy drug with many side effects that is very important to measure in biological samples. A daunorubicin electrochemical biosensor was fabricated in this study using ds-DNA as the biorecognition element and glassy carbon electrode (GCE) amplified by Pt/SWCNTs as a sensor. The synthetization of Pt/SWCNTs was done by the polyol method, and their characterization was accomplished via XRD, EDS, and TEM methods. The results showed a diameter of about 5.0 nm for the Pt nanoparticle decorated at the surface of SWCNTs. The morphological and conductivity properties of Pt/SWCNTs/GCE were investigated by EIS and AFM methods, and the results confirmed that Pt/SWCNTs/GCE had a high surface area and high conductivity. ds-DNA/Pt/SWCNTs/GCE showed an oxidation signal relative to that of the guanine base at the potential of 847 mV and a positive shift after interaction with the daunorubicin anticancer drug. This point confirms the intercalation reaction between the guanine base in the ds-DNA structure and the drug that could be used as an analytical factor for the determination of daunorubicin. Furthermore, molecular docking study is used to predict the interaction site of daunorubicin with DNA. It is found that daunorubicin interacts with guanine bases of DNA via an intercalative mode. Kinetic investigation showed an association equilibrium constant (Ka) of about 5.044 × 103 M–1 between ds-DNA and daunorubicin. The differential pulse voltammetric results showed a linear dynamic range of 4.0 nM to 250.0 μM with a detection limit of 1.0 nM for determination of daunorubicin on the surface of ds-DNA/Pt/SWCNTs/GCE. Finally, ds-DNA/Pt/SWCNTs/GCE was successfully used for the determination of daunorubicin in injection samples with a recovery range of 98.27–10313%.

Density Functional Theory and Voltammetric Study of Niclosamide Adsorption Behavior On Carbon Nanotubes

Adsorption of niclosamide (NA) on zigzag carbon nanotubes was studied utilizing electrochemical techniques and density functional theory calculations to understand the capability of these carbon nanotubes for detecting NA molecules. Voltammetric results revealed that NA molecules interact with carbon nanotubes and are physically adsorbed on the surface of a working electrode modified with a thin layer of carbon nanotubes. The redox reaction of NA is facilitated at the modified electrode which leads to an increase in peak current. The results show that the electronic properties of zigzag carbon nanotubes with semiconducting properties are sensitive to the presence of NA. The NA adsorption energy on carbon nanotubes is about—33.76 kJ/mol revealing good interaction between target analyte and modifier surface, while the conductivity of the electrode does not change. Hence, these carbon nanotubes are proper for use as sensors for sensitive determination of trace levels of NA concentration.

Modification of screen-printed gold electrode with 1,4-dithiothreitol: application to sensitive voltammetric determination of Sudan II

AbstractObjectivesThe aim of this study is to investigate the electrochemical behavior of Sudan II (SuII) using a screen-printed gold electrode (SPGE) modified with 1,4-dithiothreitol (DTT) and to determine the amount of Sudan II by voltammetry.Materials and MethodsA DTT-modified screen-printed gold electrode (DTT/SPGE) was fabricated and its application for differential pulse voltammetric (DPV) determination of SuII was reported. Fourier transform infrared spectroscopy (FT-IR), cyclic voltammetry and electrochemical impedance spectroscopy were used for the characterization of the modified electrode. The effects of instrumental and chemical parameters were optimized for the determination of SuII. The fabricated electrode was used for the analysis of SuII in fortified and real samples. High-performance liquid chromatography was preferred as a reference method for the evaluation of the obtained voltammetric results.ResultsThe electrochemical studies and FT-IR demonstrated that the SPGE was modified with DTT. The obtained peak current at DTT/SPGE was 6.67 times higher than that recorded with SPGE. At the optimized conditions of DPV in pH = 2.5 of H2SO4, the oxidation peak current of SuII was proportional to its concentration in range: 0.001–1.500 μmol l–1 with a detection limit of 0.0002 μmol l–1 (S/N = 3). For the analysis of SuII, 101.67%–104.33% of recovery percentage was obtained.ConclusionsA new electrode was successfully improved for the determination of SuII. This highly selective and sensitive electrode supplied the fast determination of SuII in ketchup, chili sauce and salsa dip sauce. In addition, voltammetric and chromatographic results are found to be consistent.

Preparation and Assessment of a Polysafranin/Multiwall Carbon Nanotube-Nafion Hybrid Film–Modified Carbon Paste Electrode and Its Performance as an Easy Sensing Probe for H2O2 and Cu2+

A polysafranin/multiwall carbon nanotube-Nafion hybrid film was prepared by electropolymerizing safranin on the surface of a MWCNT-Naf/CPE. The modified electrode was evaluated as an electrochemical sensor for hydrogen peroxide (H2O2) and Cu2+ in the presence of H2O2, in 0.1 M Tris buffer (pH 6.0) using cyclic and differential pulse voltammetric methods. The electrode showed a pair of well-defined and quasi-reversible redox peaks with formal potential (E°΄) = 0.290 ± 0.005 V versus Ag/AgCl corresponding to the polysafranin redox couples. The effects of the experimental variables on the electrode behavior regarding polymerization conditions, electrolyte pH, and MWCNT concentration were investigated to obtain optimum experimental conditions. The investigation of differential pulse voltammetric results showed that the polysafranin film at the modified electrode surface acts as an effective catalyst for H2O2 r and Cu2+ reduction in the presence of H2O2. Under optimum conditions, the modified electrode exhibited a linear dynamic range of 4.5–23.0 mM and a sensitivity of 17.4 ± 0.4 μA mM-1 cm‑2 toward H2O2 with a detection limit of 0.6 mM (3Sbl/m). In the presence of 17.0 mM H2O2, the electrode showed a linear response range of 1.0–80.0 μM and a sensitivity of 7.6 ± 0.2 μA μM‑1 cm‑2, with a detection limit of 0.1 μM (3Sbl/m) for Cu2+. In the next step, using differential pulse voltammetry, the response of the electrode to Cu2+ was studied in the presence of interfering metal ions that can promote Fenton’s reaction. The results showed that Fe2+, Co2+, and Al3+ produce interference at more than 5-, 2- and 10-fold ratios ([cation]/[Cu2+]) respectively.

Development of Novel 3d Printable Graphene-based Composite Towards Fabrication of Thin Film Electrode Material

Graphene/polymer composite thin film electrodes have many important applications, but the fabrication of these electrodes is often difficult because of poor processability of graphene. This paper presents the primary results on using 3D printing technique for thin film electrode preparation from graphene-based composite ink. The printing ink was synthesized from graphene oxide (GO), polyvinyl alcohol (PVA) as a binder and stabilizer, and ascorbic acid (AA) as a reducing agent. The measured zeta potential value showed that PVA can make GO ink more stable, the absolute value of zeta potential increased from 10.1 mV (without PVA) to 31.4 mV (with 12 wt. % PVA). The thin film electrodes can be easily printed using GO/PVA/AA composite ink, and obtained voltammograms recorded on the surface of these electrodes in 5 mM K3[Fe(CN)6]/K4[Fe(CN)6] solution clearly indicated the GO reduction by AA. The best electrochemical properties of printed electrodes were founded in the case of composite ink with wt/wt ratio GO:PVA:AA = 80:12:8. The cyclic voltammetric results demonstrated the linear dependence of the anodic and cathodic signals of redox couple [Fe(CN)6]4-/K3[Fe(CN)6]3- with the square root of scan rate, indicating a reversible redox reaction on the electrode surface. The thin films printed from GO/PVA/AA composite ink can be used as electrode material for diverse applications in electrochemistry.

Fast and enhanced electrochemical sensing of dopamine at cost-effective poly(DL-phenylalanine) based graphite electrode

In the present study, a sensitive and a low-priced electrochemically polymerized DL-phenylalanine graphite electrode (Poly(DLPA)-GE) wasdesigned for Dopamine (DA) sensing. The redox activity of DA was inspected at this developed electrode via cyclic voltammetry (CV) and differential pulse voltammetry (DPV) in a phosphate buffer (PB) with pH 6.5. The achieved voltammetric result presents that Poly(DLPA)-GE exposes a significant enrichment in DA redox currents with the declining of overpotential than the bare graphite electrode (BGE). In the optimal operating conditions, Poly(DLPA)-GE describes a fine linear enhancement for DA oxidation in the concentration range of 2.0 μM to 45.0 μM with an estimated lower limit of detection (LOD) of 28 nM and limit of quantification (LOQ) of 93 nM. The proposed electrode shows fine selectivity and sensitivity for DA analysis in the presence of interfering moieties such as Ascorbic acid (AA), Uric acid (UA) and organic dyes. Finally, the sensor was effectively verified for the actual DA detection in the madicinal sample.

New aryl Schiff bases of thiadiazole derivative of ibuprofen as DNA binders and potential anticancer drug candidates

The work presented in this paper describes the synthesis of two new aryl Schiff bases [(E)-N-(4-(benzyloxy)-3-methoxybenzylidene)-5-(1-(4-isobutylphenyl)ethyl)-1,3,4-thiadiazol-2-amine] (ASB-1) and [(E)-N-(4-(benzyloxy)benzylidene)-5-(1-(4-isobutylphenyl)ethyl)-1,3,4-thiadiazol-2-amine] (ASB-2). These compounds were characterized by different analytical techniques and then studied for DNA binding. Binding studies were carried out at neutral pH (7.0) and at 37 °C by theoretical and experimental methods including DFT, molecular docking, spectroscopy (UV-visible, fluorescence), cyclic voltammetry (CV) and viscometry. Further investigations of these compounds were done on hepatocellular carcinoma; Huh-7 cancer cell line. Binding constant, free energy change and binding site size, i.e. Kb, ΔG and n were evaluated which indicated that both ASB-1 and ASB-2 bind significantly and spontaneously with the DNA. However, data revealed relatively greater binding of ASB-1 with DNA. Spectral and voltammetric results were found supportive of each other. Binding site sizes and viscosity measurements verified the mixed binding mode of interactions as observed in molecular docking analysis, i.e. intercalation with groove binding. DNA binding studies were very well correlated with the in-vitro studies performed on Huh-7 cell line as well as normal HEK-293 cell lines. The compound ASB-1 not only showed greater binding affinity toward DNA but also showed greater anticancer potency with least IC50 value as compared to ASB-2.

Selective Formation of Ce-Ni Hydrogen Storage Alloys By Electrodeposition in LiCl-KCl-CeCl3 Melts Using Ni As Cathode

Cerium-nickel based hydrogen storage alloys are one of the important new rare earth-based hydrogen storage alloys due to their high discharge capacities, easy activation and good hydrogen pressure. Cerium-nickel based alloy compound, CeNi5, is usually used as the hydrogen storage alloy in Ni/MH battery, due to their favorable electrochemical activation, improved discharge and charge kinetic properties. CeNi2 and CeNi3, are also used as hydrogen storage alloys. The electrochemical way in molten salts is more economic for the metallurgical industry, because it has simpler in operation and lower in energy consumption than many existing industrial technologies. However, the electrochemical formation of Ce-Ni hydrogen storage alloys by selective electrodeposition has not been reported on a Ni cathode in LiCl-KCl molten salts. In this study, the electrochemical behavior of Ce(III) ions was explored in molten LiCl-KCl salts using nickel as working electrode to produce the Ce-Ni hydrogen storage alloys. Cyclic voltammetric and square wave voltammetric results indicated that the electrochemical reduction of Ce (III) appeared at a less negative value than that recorded on a W electrode because of the formation of Ce-Ni alloy compounds by the electro-deposition of Ce on a Ni electrode. The nucleation mechanism of Ce deposited on a Ni electrode based on the Scharifker-Hill non-dimensional theoretical model was found to be the progressive nucleation. The change of electrode surface morphology with the deposited time was observed by SEM, which clearly indicated that the nucleation and growth of Ce follows the mechanisms of dendritic growth. Based on the studies of the above electrochemical behavior, Ce-Ni alloys were prepared using potentiostatic electrolysis, five kinds of Ce-Ni intermetallic compounds, CeNi5, Ce2Ni7, CeNi3, CeNi2 and CeNi were formed under our experiment conditions in LiCl-KCl-CeCl3 melts. XRD and SEM-EDS analysis results showed that the hydrogen storage alloys of CeNi5, CeNi3 and CeNi2 could be selectively prepared using potentiostatic electrolysis by controlling applied potential. Furthermore, The thermodynamic properties of Ce-Ni compounds, such as Gibbs free energy(ΔG), enthalpy(ΔH) and entropy(ΔS) of formation for each Ce-Ni alloy compound as well as activity and partial molar Gibbs energy of Ce in Ce-Ni alloy were computed employing open circuit chronopotentiometry measurement. Therefore, this work presents a promising method for the preparation of the Cerium-nickel based hydrogen storage alloys. Keywords: Electrochemical behaviour; Electrochemical formation; Ce-Ni intermetallic compounds; Thermodynamic properties References [1] Y. Zhang, H.Y. Yin, S.D. Zhang, D.Y. Tang, Z.W. Yuan, T.H.Yan, W.F. Zheng, D.H. Wang,Preparation of CeNi2 intermetallic compound by direct electroreduction of solid CeO2-2NiO in molten LiCl,J. Rare Earth.3(9)(2012) 923-927.[2] B.J. Zhao, L. Wang, L. Dai, G.H. Cui, H.Z. Zhou, R.V. Kumar, Direct electrolytic preparation of cerium/nickel hydrogen storage alloy powder in molten salt,J. Alloys Compd. 468 (2009) 379-385.[3] B.J. Zhao, X.G. Lu, Q.D.Zhong, C.H. Li, S.L. Chen, Direct electrochemical preparation of CeNi5 and LaxCe1-xNi5 alloys from mixed oxides by SOM process,Electrochim. Acta 55 (2010) 2996-3001.Fig.1 Square wave voltammogram for Ni electrode in LiCl-KCl-CeCl3 melts at 873 K. Pulse height: 0.1 V; potential step: 0.002 V; frequency: 20 Hz. Figure 1

Interaction between Amorphous Zirconia Nanoparticles and Graphite: Electrochemical Applications for Gallic Acid Sensing Using Carbon Paste Electrodes in Wine.

Amorphous zirconium oxide nanoparticles (ZrO2) have been used for the first time, to modify carbon paste electrode (CPE) and used as a sensor for the electrochemical determination of gallic acid (GA). The voltammetric results of the ZrO2 nanoparticles-modified CPE showed efficient electrochemical oxidation of gallic acid, with a significantly enhanced peak current from 261 µA ± 3 to about 451 µA ± 1. The modified surface of the electrode and the synthesised zirconia nanoparticles were characterised by scanning electrode microscopy (SEM), Energy-dispersive x-ray spectroscopy (EDXA), X-ray powdered diffraction (XRD) and Fourier-transform infrared spectroscopy (FTIR). Meanwhile, the electrochemical behaviour of GA on the surface of the modified electrode was studied using differential pulse voltammetry (DPV), showing a sensitivity of the electrode for GA determination, within a concentration range of 1 × 10−6 mol L−1 to 1 × 10−3 mol L−1 with a correlation coefficient of R2 of 0.9945 and a limit of detection of 1.24 × 10−7 mol L−1 (S/N = 3). The proposed ZrO2 nanoparticles modified CPE was successfully used for the determination of GA in red and white wine, with concentrations of 0.103 mmol L−1 and 0.049 mmol L−1 respectively.

Development of transition metal based electrolyzer for efficient oxygen evolution reaction

The greatest challenge of the 21st century is to develop renewable systems of energy, which are efficient, environmentally friendly, and scalable. In this context, production of hydrogen and oxygen from electrolysis of water is a smart approach. Its inputs are only water and potential. However, oxygen evolution reaction (OER) via water splitting is a sluggish reaction. So, herein, we report the synthesis of a novel OER hybrid tetrametallic electrocatalyst (Co–Ni–Fe–Zn) that is cost affordable as compared to the traditional precious noble-metal-based catalysts. It was grown over the surface of fluorine doped tin oxide by a facile potentiodynamic method, and the surface modification was ensured from XRD, scanning electron microscopy, and energy dispersive x-ray spectroscopy analyses. The OER catalytic activity of the designed electrocatalyst was examined through electrochemical techniques. Linear scan voltammetric results revealed that the as-prepared catalyst generates a signal of OER with a current density of 10 mA/cm2 at an overpotential of just 90 mV under alkaline conditions. To the best of our knowledge, this is the first report on an OER catalyst that demands the lowest overpotential. Hence, the synthesized catalyst is a promising candidate for realizing the dream of rapidly producing sustainable and environmentally friendly fuel.

A novel high performance Ti/Ti–W- reinforced polyaniline functionalized Ni–P electrode for high sensitive detection of dopamine from urine sample

We, in our previous work, detailed the new design technology for the synthesis of novel TiO2/TiO2-WO3 core/shell composite (Ti/Ti–W) via the application of titanium turnings. Herein, we exploited the strategy with appropriate alternations to broaden the industrial significance of the method as well as the material. The work embodies a polyaniline assisted modification of Ti/Ti–W (0.1 g Ti metal/1:2 Ti–W) to develop a novel hybrid composite that has not yet been synthesized and studied. The composite was used to fabricate a sensing electrode for dopamine detection by electroless deposition from Ni–P bath. Cyclic voltammetric results revealed the sensing performance of Ni–P/PANI/Ti/Ti–W electrode towards dopamine detection. Further, differential pulse voltammetry (DPV) was employed to detect the sensing potential and sensing current, and the detection limit was found to be as low as 0.0037 μM with a sensitivity of 44.7 μA/μM cm2. The linear range of the optimized sensing electrode was 0.1–50 μM. Moreover, the electrode offered a remarkable detection of dopamine even in presence of other electroactive species such as AA, UA, NaCl and glucose. The real sample analysis explored Ni–P/PANI/Ti/Ti–W as a potential sensing electrode and can detect dopamine from urine sample with high sensitivity and accuracy. The obtained electroanalysis results confirm a 2H+/2e− mechanism of sensing in the developed electrode.

A New Redox Mediator (Cupric‐Neocuproine Complex)‐ Modified Pencil Graphite Electrode for the Electrocatalytic Oxidation of H2O2: A Flow Injection Amperometric Sensor

AbstractThis paper introduces the cupric‐neocuproine complex ([Cu(Nc)2]2+) as a new redox mediator for the electrocatalytic oxidation of H2O2. For this purpose, [Cu(Nc)2]2+ was modified onto a disposable pencil graphite electrode (PGE) surface by using Nafion (Nf) as a cation‐exchange membrane for the effective adsorption of complex. The modified electrode was prepared by immersing Nf‐adsorbed PGE into [Cu(Nc)2]2+ complex solution (0.40 mM of Cu2+ and 0.80 mM of Nc prepared at pH 4.76 in 0.10 M acetate buffer). SEM images and EDX spectra of electrodes were presented for the elucidation of their surface morphologies. Cyclic voltammetric results showed that H2O2 was electrocatalytically oxidized at [Cu(Nc)2]2+/Nf/PGE, because both the increase in current and the potential shift to a more negative direction were observed for oxidation of H2O2 at [Cu(Nc)2]2+/Nf/PGE in comparison to bare PGE. Then, the electrocatalytic activity of [Cu(Nc)2]2+/Nf/PGE toward H2O2 oxidation was utilized for amperometric determination of H2O2 in flow injection analysis (FIA) system. Flow injection (FI) amperometric studies showed two linear calibration ranges (1.0‐1000.0 μM (R2=0.9958) and 1000.0‐10000.0 μM (R2=0.9902) with a detection limit of 0.4 μM H2O2 which is considered good for electroanalytical determinations, especially for electrocatalytic oxidation. To test the applicability of the developed FI amperometric hydrogen peroxide sensor, H2O2 contents of some relevant samples were determined.

Facile fabrication of a novel 3D rose like lanthanum doped zirconia decorated reduced graphene oxide nanosheets: An efficient electro-catalyst for electrochemical reduction of futuristic anti-cancer drug salinomycin during pharmacokinetic study

An innovative electrochemical nanoprobe, for analysis of salinomycin (SAL), was proposed. The nanoprobe based on decoration of glassy carbon electrode (GCE) with 3D rose like La3+@ ZrO2 supported on reduced graphene oxide (RGO) nanosheets. The 3D rose like La3+@ ZrO2 was synthesized via sintering process. The successful decoration of 3D rose like La3+@ ZrO2 on the surface of RGO was characterized using different spectroscopic and analytical techniques. The obtained voltammetric results confirmed the good electrochemical performance of 3D rose like La3+@ ZrO2 in terms of lower peak potential (Epc) and higher cathodic current (Ipc). Moreover, the modified nanoprobe showed wide linearity range (0.34–115 × 10−8 M), lower detection limit (0.11 × 10−8 M) and higher selectivity. Besides, the nanocomposite showed good applicability for analysis of SAL in biological fluids and during pharmacokinetic evaluation in rabbit plasma. The obtained results opens a new venue for the determination of futuristic drug, SAL, during pharmacokinetic and pharmacodynamics studies.

Zinc oxide nanoparticles modified-carbon paste electrode used for the electrochemical determination of Gallic acid

Zinc oxide nanoparticles (nano-ZnO) was used to modify carbon paste electrode (CPE) for a fast and sensitive electrochemical determination of gallic acid (GA). The study was carried out using cyclic voltammetry (CV and differential voltammetry (DPV) techniques, where the nano-ZnO-modified electrode exhibited an efficient and sensitive oxidation of GA. The cyclic voltammetric result showed a significant enhancement of the peak current from 250μA to about 410μA. The electrochemical behaviour of GA on the nano-ZnO modified carbon paste electrode was studied using DPV, showing a sensitivity of the electrode in a concentration range of 1 x 10−6 to 5.0 x 10−5 mol L−1, with a correlation coefficient R2 of 0.9968 and a limit of detection of 1.86 x 10−7 mol L−1 (S/N =3). The proposed electrode was used successfully for the determination of GA in red wine with recoveries of 103%.

Carboxyl hydrogel particle film as a local pH buffer for voltammetric determination of luteolin and baicalein

Electrochemical determination of luteolin and baicalein always needs acidic supporting electrolyte to guarantee good sensitivity. Therefore, most of the reported electrochemical sensors of luteolin and baicalein are unsuitable for detection of neutral actual samples. It is necessary to design a highly sensitive sensor for direct determination of them in neutral conditions. In this study, poly(N-isopropylacrylamide-acrylic acid) hydrogel particles (NIPA/AA) and multiwall carbon nanotubes (MWCNTs) composite modified glassy carbon electrode (GCE) was fabricated by a simple casting method. The voltammetric results showed that the NIPA/AA particle film provided acidic environment for proton-electron coupled reaction in neutral mediums. The near-surface pH of the electrode was related on the loaded amount of the NIPA/AA particles in pH range from 4.2 to 5.9. The voltammetric behaviors of luteolin and baicalein at the NIPA/AA-MWCNTs-GCE were studied by cyclic voltammetry. The peak separations between cathodic and anodic peaks were decreased and peak currents were increased because of decrease in pH and increase in ion conductivity at the local electrode surface. The sensitivity of the electrode was investigated by differential pulse voltammetry. Even under neutral conditions, the plots of the oxidation currents of luteolin and baicalein were dependent linearly on their concentration with detection limit of 14.5 pM and 44.4 pM, respectively. Moreover, the proposed NIPA/AA-MWCNTs-GCE was also successfully applied for determination of luteolin and baicalein in peanut shell, Huang-qin and tomato samples.