Simple Electrochemical Method Research Articles

Electrochemical determination of diethylstilbestrol in livestock and poultry meats by L-cysteine/gold nanoparticles modified electrode

A fast and simple electrochemical method for the determination of diethylstilbestrol (DES) was developed. Gold nanoparticles stabilized by chitosan (AuCS) were prepared and used in combination with L-cysteine (L-Cys) by self-assembly for fabricating the electrochemical sensors. Compared with unmodified electrode, the oxidation peak current of DES could be increased greatly by using the L-Cys/AuCS modified GCE (L-Cys/AuCS/GCE), indicating L-Cys/AuCS had excellent ability to promote electron transfer. Under the optimal conditions, the oxidation peak current was linear to the concentration of DES in the range from 5 × 10−7 to 1 × 10−4 mol/L (r = 0.997) with the detection limit of 1.7 × 10−7 mol/L (S/N = 3). The proposed method was successfully used for the determination of DES in livestock and poultry meats with the satisfying recovery results (75.3–91.9%). The method not only exhibited good accuracy and reproducibility for DES detection, but also had the advantages of low cost, simple preparation method and convenient for batch preparation.

Synthesis, Characterization, Semiconductor-Assisted Photocatalysis and Antibacterial Activity of Electrochemically Synthesized SnS and NiS/SnS Nano Photocatalysts

In present study, SnS and NiS/SnS nano-photocatalysts have been synthesized by simple electrochemical method and their photocatalytic activity and bacterial inactivation were investigated. The size, morphology, chemical composition and optical properties were investigated by X-ray diffraction (XRD), scanning electron microscope (SEM), energy dispersive X-ray analysis (EDAX) and optical absorption spectroscopy. The XRD analysis confirmed the crystalline SnS phase. The band gap estimated from Tauc’s plot was 2.9 eV for SnS and 2.7 eV for NiS/SnS nanoparticles shows that they are photoactive under UV light radiation. The photocatalytic activity of nanoparticles was studied by degradation of textile dye Indigo carmine under ultraviolet radiation and the photocatalytic decolourization of the dye follows the first order kinetics. The antibacterial susceptibility of SnS and NiS/SnS nanoparticles was evaluated by disc diffusion Kirby-Bauer method using Staphylococcus aureus and Escherichia coli.

A hybrid design of Ag-decorated ZnO on layered nanomaterials (MgAC) with photocatalytic and antibacterial dual-functional abilities.

In this work, Ag@ZnO and Ag@ZnO/MgAC photocatalysts were synthesized using a simple two-step electrochemical method by the addition of magnesium aminoclay (MgAC) as a great stabilizer and a Lewis base, which could donate electrons for reduction of Ag+ and Zn2+ ions, facilitating uniform formation as well as effective inhibition of aggregation of Ag@ZnO nanoparticles (NPs) on the MgAC matrix. Ag@ZnO and Ag@ZnO/MgAC were investigated for photocatalytic degradation of MB and their antibacterial efficiencies. Ag@ZnO/MgAC showed excellent photocatalytic MB degradation with a performance of 98.56% after 80 min of visible-light irradiation and good antibacterial activity against Salmonella (Sal) and Staphylococcus aureus (S. aureus) bacterial strains, providing promising high application potential. Herein, different from the bare ZnO NPs, for Ag@ZnO/MgAC nanocomposites, Ag@ZnO NPs functioned as an effective photocatalyst under visible light illumination, in which, incorporated Ag atoms in the ZnO crystal structure caused the increase in a larger number of lattice defect sites. Benefiting from the strong surface plasmon resonance (SPR) effect of Ag and energy band matching between ZnO and Ag, the visible light absorption capacity and the separation of the photogenerated charge carriers were promoted. Therefore, the MB degradation efficiency of Ag@ZnO/MgAC was considerably accelerated in the presence of produced radicals from visible light illumination.

Electrochemical growth of metallic zinc and its crystallographic study using Rietveld

We have used a simple electrochemical method of synthesizing metallic zinc. X-ray diffraction was carried out for detailed crystallographic study. We carried out Rietveld analysis for comparing the observed diffraction data with that for ideal structure. The unit cell was found to be wurtzite with lattice parameters a=b=2.660183 Å and c=4.934607. Å as calculated from the Rietveld analysis. The crystallite size and strain were also calculated from Scherrer and Williamson-Hall method. The results suggest the existence of small microstrain in the crystal. The dislocation density is an important parameter in determining the crystalline quality of a crystal and was also estimated from the XRD pattern. The other parameters like degree of orientation, d-values and figure of merit were also calculated from the diffraction pattern to understand the detailed crystallographic properties.

A simple method to assay tumor cells based on target-initiated steric hindrance.

We have proposed a simple electrochemical method in this work for the assay of tumor cells through their own steric hindrance effect. Specifically, tumor cells can block the catalysis of terminal deoxynucleotidyl transferase to the aptamer previously immobilized on the electrode surface. By making use of the hindrance effect, cancer cells can be quantitatively analyzed in the range from 1.6 × 102 to 1.6 × 106 cells per mL without complicated design or cumbersome operation, while the detection limit can be about 53 cells per mL. This method can also show satisfactory performance in complex environments, indicating its potential in clinical application.

Simultaneous Quantification of Antioxidants Paraxanthine and Caffeine in Human Saliva by Electrochemical Sensing for CYP1A2 Phenotyping.

The enzyme CYP1A2 is responsible for the metabolism of numerous antioxidants in the body, including caffeine, which is transformed into paraxanthine, its main primary metabolite. Both molecules are known for their antioxidant and pro-oxidant characteristics, and the paraxanthine-to-caffeine molar ratio is a widely accepted metric for CYP1A2 phenotyping, to optimize dose–response effects in individual patients. We developed a simple, cheap and fast electrochemical based method for the simultaneous quantification of paraxanthine and caffeine in human saliva, by differential pulse voltammetry, using an anodically pretreated glassy carbon electrode. Cyclic voltammetry experiments revealed for the first time that the oxidation of paraxanthine is diffusion controlled with an irreversible peak at ca. +1.24 V (vs. Ag/AgCl) in a 0.1 M H2SO4 solution, and that the mechanism occurs via the transfer of two electrons and two protons. The simultaneous quantification of paraxanthine and caffeine was demonstrated in 0.1 M H2SO4 and spiked human saliva samples. In the latter case, limits of detection of 2.89 μM for paraxanthine and 5.80 μM for caffeine were obtained, respectively. The sensor is reliable, providing a relative standard deviation within 7% (n = 6). Potential applicability of the sensing platform was demonstrated by running a small scale trial on five healthy volunteers, with simultaneous quantification by differential pulse voltammetry (DPV) of paraxanthine and caffeine in saliva samples collected at 1, 3 and 6 h postdose administration. The results were validated by ultra-high pressure liquid chromatography and shown to have a high correlation factor (r = 0.994).

Rapid Determination of 5-Nitrofuran Ring Antibiotics in Complex Samples Using a Boron-Doped Diamond Electrode and Differential Pulse Voltammetry

A rapid, simple, and precise electrochemical method was developed for the determination of the total content of antibiotics containing a 5-nitrofuran ring with antibacterial activity including furazolidone, nitrofurazone, nitrofurantoin, and furaltadone in several samples. Boron-doped diamond electrode was used as the working electrode. The electrochemical properties of these compounds were evaluated by cyclic voltammetry. A differential pulse voltammetric method based on the cathodic reduction at high potentials was used for the determination of the total nitrofuran content in a mixture at pH 6.47. The voltammetric measurements showed that the proposed electrochemical method was able to identify the nitrofurazone from a mixture of antibiotics based on its anodic oxidation in alkaline medium (pH 10.6). This method presented good accuracy (between 94.5 and 102.5%) and precision (less than 3.94%), with calibration graphs starting from 50 nmol L−1. The method was applied with success for the determination of total content of compounds with 5-nitrofuran ring and for the selective determination of nitrofurazone in pharmaceutical tablets and food products (milk and honey) without pretreatment of the samples.

Simultaneous electrochemical detection of ciprofloxacin and Ag(I) in a silver nanoparticle dissolution: Application to ecotoxicological acute studies

The combination of the indiscriminate use of antibiotics such as ciprofloxacin (CIP) and the recent use of biocides such as silver nanoparticles (AgNPs) that are eventually disposed of in the environment can negatively impact on aquatic biota. This work aims to develop a simple electrochemical method to detect CIP, AgNPs, and their mixtures (CIP–AgNPs) concentrations and to correlate them with the ecotoxicological effects in acute toxicity bioassays (48 h) using the microcrustacean Ceriodaphnia dubia as a test organism. The simultaneous electrochemical detection of CIP and Ag(I) in AgNP dissolution was performed by square wave anodic stripping voltammetry (SWASV) using a bismuth film electrode (BiFE). The analytical performance in the linear range was from 8 to 200 ng L−1 (R2 = 0.993) for CIP and from 104 to 3300 ng L−1 (R2 = 0.995) for Ag(I). The limits of detection (LODs) were 3 and 34 ng L−1 for CIP and Ag(I), respectively. The method was applied to the measurements of Ag(I) in the supernatant of AgNP suspensions and the study of the stability of CIP and Ag(I) from AgNPs during acute tests of C. dubia at 48 h. The median lethal concentration (LC50) of C. dubia in the presence of CIP, AgNPs, and CIP–AgNPs was calculated, and the toxicity decreased as follows: AgNPs > CIP–AgNP mixture > CIP. The lower toxicity of AgNPs in mixture with CIP could be explained by the complexation of metal ions with quinolones, decreasing their interaction with the test organisms. The stabilities of CIP and Ag(I) from AgNPs in ecotoxicology assays were estimated by measuring their concentrations by SWASV, and their values ranged from 80% to 120% from the nominal values, according to the OECD recommendation. As a perspective, the results of the work showed that the simultaneous use of stripping voltammetry and toxicity tests could be applied to the study of natural water samples and potentially to the monitoring of environmental quality. The relevance of electrochemical and ecotoxicology approaches as useful tools to contribute knowledge to preserve environmental health is highlighted.

Tailoring molecular permeability of vertically-ordered mesoporous silica-nanochannel films on graphene for selectively enhanced determination of dihydroxybenzene isomers in environmental water samples

Herein we demonstrate a simple and rapid electrochemical method for selectively enhanced determination of catechol (CC) or hydroquinone (HQ) isomers in environmental water samples by tailoring the molecular permeability of vertically-ordered mesoporous silica-nanochannel films on electrochemically reduced graphene oxide (VMSF/ErGO). Such VMSF/ErGO composite film was fabricated on the gold electrode (AuE) surface using electrochemically assisted self-assembly approach. The as-prepared electrodes with surfactant micelles (SM) template inside silica nanochannels, designed as SM/VMSF/ErGO/AuE, possess hydrophobic hydrocarbon cores and show preferential response to CC via hydrophobic effect. After removing SM from silica nanochannels, the obtained VMSF/ErGO/AuE displays more sensitive response to HQ, which is due to the hydrogen bond effect between the silanol groups of silica walls and HQ. Given the potential-resolved and high electrocatalytic ability of ErGO, and molecular permeability and anti-fouling ability of VMSF, these two present sensors could detect CC and HQ in lake water with a low limit of detection (18 nM for CC and 16 nM for HQ), and a high sensitivity (0.33 μA/μM for CC and 0.37 μA/μM for HQ), without complicated sample pretreatment. Moreover, the proposed sensors provide a convenient, rapid and economic way for direct analysis of environmental water samples, exhibiting excellent long-term stability.

Fast Detection of Beta Galactosidase and Enzyme Kinetics with 4-Aminophenyl-β-D-Galactopyranoside as Substrate

Beta-galactosidase (β-Gal) is an important enzyme utilized to determine cell senescence and understand disease pathology, among being utilized for several biosensing applications. This key biomarker can be measured indirectly using electrochemical methods by detecting the electroactive p-aminophenol (PAP) produced from the enzymatic conversion of a substrate. Here, we present a quick electrochemical method based on cyclic voltammograms (CVs) to quantify the amount of β-Gal in aqueous solution in under 5 minutes. Using timed CVs, the enzyme kinetics of β-Gal versus 4-aminophenyl-β-D-galactopyranoside (PAPG) was estimated. The detection limit for β-Gal was 40 ng ml−1 using the timed quick CV method. KM was found to be 18.7 ± 0.7 µM, and Vmax 10.1 ± 0.6 µmol min−1 mg−1, for β-Gal with PAPG as a substrate. By adding divalent salts Mg2+ and Ca2+, KM was lowered to nearly half, and Vmax increased by 20%. The electrochemical protocol utilized neutral pH and ambient room temperature benchtop conditions, making it amenable to scanning electrochemical microscopy and lab-on-chip detection platforms. In addition to cell senescence, this quick and simple electrochemical method can be used in broad biosensing applications, including the detection of water and foodborne pathogens and the identification of toxic contaminants.

The storage mechanism difference between amorphous and anatase as supercapacitors

Although TiO2 nanotubes is a promising electrode as supercapacitors due to its high energy density, easy synthesis and chemical stability, there are draw backs such as low conductivity and capacitance. Many studies concentrated on improving its electrochemical performance itself but little attention was payed to the reason of capacitance differences caused by its different crystal structures. Herein, we prepare amorphous and anatase TiO2 nanotubes and hydrogenated them by a simple electrochemical hydrogenation method to improve their conductivity and capacitance. And then study and compare their morphology and structure differences by SEM, TEM, XRD and BET. The results show that the pore size distribution, internal structure order and internal carrier concentration are the main reasons for their electrochemical performance differences. The microporous structure less than 2 nm in amorphous nanotubes act as a trap of electrolyte ions at current density larger than 0.1 μA cm−2, leading to small charge and discharge capacitance. The long-range ordered crystal structure of anatase is more favorable for the orderly diffusion of carriers, reducing the inelastic scattering of carrier diffusion process and the electron hole-complexing probability, making anatase nanotubes exhibit higher coulomb efficiency and cycle stability than that of amorphous ones.

Gold-Deposited Nickel Foam as Recyclable Plasmonic Sensor for Therapeutic Drug Monitoring in Blood by Surface-Enhanced Raman Spectroscopy.

A sensitive and recyclable plasmonic nickel foam sensor has been developed for surface-enhanced Raman spectroscopy (SERS). A simple electrochemical method was used to deposit flower-shaped gold nanostructures onto nickel foam substrate. The high packing of the gold nanoflowers onto the nickel foam led to a high enhancement factor (EF) of 1.6 × 1011. The new SERS sensor was utilized for the direct determination of the broad-spectrum β-lactam carbapenem antibiotic meropenem in human blood plasma down to one pM. The sensor was also used in High Performance Liquid Chromatography (HPLC)-SERS assembly to provide fingerprint identification of meropenem in human blood plasma. Moreover, the SERS measurements were reproducible in aqueous solution and human blood plasma (RSD = 5.5%) and (RSD = 2.86%), respectively at 200 µg/mL (n = 3), and successfully recycled using a simple method, and hence, used for the repeated determination of the drug by SERS. Therefore, the new sensor has a strong potential to be applied for the therapeutic drug monitoring of meropenem at points of care and intensive care units.

Facile synthesis of hierarchically self-assembled dandelion-like microstructures of bimetallic-MOF as a novel electrode material for high-rate supercapacitors

Metal–organic frameworks (MOFs) have gained immense attention as electrode materials for energy storage applications, because of their large porosity as well as high surface area. In this work, a novel needle-like bimetallic MOF (metal = bismuth and molybdenum; BM-MOF) self-assembled in dandelion structure is successfully prepared through a one-pot cathodic electrodeposition route onto nickel foam and directly used as supercapacitor electrode. The fabricated BM-MOF showed a high specific capacity of 476 C g−1 at 10 A g−1, proper rate capability of 43% (from 10 to 100 A g−1) as well as superior cycling performance of 95.1% capacity retention after 8000 cycles at high discharging load of 10 A g−1. These data verified that the fabricated BM-MOF is suitable candidate for charge storage aims. The simple developed electrochemical method is suggested as green synthesis method for fabrication of various bimetallic metal organic frameworks.

Electrodeposition of micro-nano hierarchically structured fluoridated hydroxyapatite coating on AZ31B alloy

ABSTRACT In this study, a novel micro-nano hierarchically structured fluoridated hydroxyapatite (FHAp) coating on AZ31B substrate was successfully synthesized via a simple one-step electrochemical deposition method. And the formulation of the electrodeposition solution is simple and environment-friendly without any harmful additives. The FHAp coating consists of a large amount of nanorods and some micro-structured spherical aggregates composed of nanorods. Electrochemical tests demonstrated that the FHAp coating exhibited higher anti-corrosion property and lower degradation rate than that of pure HAp coating. Moreover, the FHAp coating with micro-nano hierarchically structured surface displayed good cell biocompatibility. The addition of fluorine ion into HAp coating can further promote the cell adhesion and proliferation. This work provides a simple, environment-friendly, and efficient way to prepare FHAp coating on AZ31B alloy with improved corrosion resistance and biocompatibility.

Preparation and evaluation of a new solid-phase microextraction fiber based on polythionine for analysis of phthalate esters in aqueous samples

Polythionine was prepared by a simple electrochemical method and used as solid-phase microextraction coating for headspace extraction and analysis of four phthalate esters (dioctyl phthalate, benzyl butyl phthalate, di-n-butyl phthalate, and di-iso-butyl phthalate) by gas chromatographic-flame ionization detector. The thionine polymerization was performed at pH of 9 on a Pt wire. Made ready coating displayed a good thermal stability (up to 280 °C). The effects of three extraction parameters, containing salt effect, temperature and extraction time, on the extraction efficiencies of phthalate esters were evaluated. Under the optimized conditions, limits of detection were among 0.34–1.67 µg L−1. The inter-day and intra-day deviations of relative standard, attained at 50 µg L−1, were 7.64–10.62% and 10.14–12.84%, respectively. The method capability for analysis of the phthalates in real samples of cheese water and wastewater was evaluated and relative recoveries were between 82.63 and 119.50%.

Direct electrochemical detection of 4-aminophenol in pharmaceuticals using ITO electrodes modified with vertically-ordered mesoporous silica-nanochannel films

Abstract 4-Aminophenol (4-AP) served as the drug intermediates has been widely used or found in pharmaceutical preparations. Therefore, direct and rapid determination of 4-AP content in pharmaceuticals is highly important for human health. In this work, we demonstrate a simple and fast electrochemical method for direct analysis of 4-AP in pharmaceuticals by using the indium tin oxide (ITO) electrode modified with vertically-ordered mesoporous silica-nanochannel films (VMSF). Arising from the vertically-aligned nanochannels and high porosity of VMSF, 4-AP could permeate the VMSF and transfer to the underlying electrode surface, ultimately giving rise to the electrochemical signal. By using the differential pulse voltammetry (DPV) method, the VMSF/ITO sensor was able to detect 4-AP in a wide linear range from 0.5 μM to 400 μM. The obtained limit of detection was calculated as 0.32 μM. Owing to the good anti-fouling and anti-interference ability of VMSF, direct analysis of 4-AP in pharmaceuticals was achieved, without any complex sample pretreatments.

Simple electrochemical method for monitoring the time-dependent dissolution behavior of layers deposited by atomic layer deposition

Spectroscopic and microscopic techniques are not suitable for the rapid monitoring of time-dependent dissolution behavior (particularly, pinhole changes) of a layer deposited by atomic layer deposition (ALD). Here, we present a simple electrochemical method that provides information on the dissolution mechanism including pinhole generation and thickness change. Because indium tin oxide (ITO) electrodes exhibit flat capacitive currents and good (electro)chemical stability, they are selected as ideal underlying substrates for the electrochemical monitoring of the ALD layers even under harsh conditions. Two ALD layers (Al 2 O 3 and TiO 2 layers) that exhibit opposite dissolution behaviors are chosen as model layers because the as-deposited Al 2 O 3 layers are pinhole-free but unstable in aqueous solutions, whereas the as-deposited TiO 2 layers are not pinhole-free but stable in aqueous solutions. The combination of capacitive current level (in an electrolyte solution containing no redox-active species) and electrochemical blocking behavior (in an electrolyte solution containing a redox-active species such as Ru(NH 3 ) 6 3+ and ferrocenemethanol) obtained from cyclic voltammograms enables us to verify whether the dissolution of an ALD layer occurs, to evaluate the dissolution rate, and to identify the plausible dissolution mechanism. The electrochemical results reveal that the Al 2 O 3 layers are dissolved in biological buffers, along with pinhole generation, and that the TiO 2 layers are stable with no pinhole generation. The difference in electrochemical blocking behavior between Ru(NH 3 ) 6 3+ and ferrocenemethanol provides information on the approximate size of the pinholes. The present method is appealing for practical use because even an ALD layer with a thickness of only a few nanometers can be tested to monitor the dissolution behavior and because any ALD layer that can be readily deposited on ITO electrodes can be easily examined using this method. • Stability comparison of Al 2 O 3 and TiO 2 layers deposited by atomic layer deposition. • Indium tin oxide electrodes are ideal underlying substrates for the comparison. • The combination of capacitive current level and electrochemical blocking behavior allows for evaluating dissolution. • Al 2 O 3 layers are dissolved in biological buffers, along with pinhole generation.

Facile electrochemical synthesis of dilute AuCu alloy nanostructures for selective and long-term stable CO2 electrolysis.

Electrochemical CO production from CO2 electrolysis has been considered the most economically viable approach among various candidate products. AuCu bimetallic alloys are currently receiving attention for their potential to tailor catalytic activity. Here, we synthesized a dilute AuCu alloy nanostructure with an AuCu atomic composition ratio of 3% by using a simple electrochemical treatment method on a 200 nm-thick Au thin film. The dilute AuCu alloy catalyst shows an exceptional CO2 reduction activity in terms of selectivity and overpotential for CO production. In addition, the stability property is more significantly enhanced as compared to pure Au nanostructures. In addition, we describe an in situ tailoring method of catalytic activity for Au nanostructures by repeating an electrochemical treatment process that is performed for forming the Au nanostructure. This approach will be a promising and facile strategy not only for reactive Au catalysts but also to increase the stability activity simultaneously by utilizing Cu impurities existing in an aqueous electrolyte for CO2 reduction.

A High‐sensitivity and Enzyme‐free Clenbuterol Sensor using SWCNT Arrays Prepared with a One‐pot Method Comprising Gold Nanoparticles and Cl−

AbstractWe describe a novel enzyme‐free sensor for clenbuterol (CLE) prepared by a simple electrochemical method. A new method to detect clenbuterol hydrochloride was developed by single‐walled carbon nanotubes (SWCNTs) arrays and gold nanoparticles (AuNPs)‐Cl− complex. SWCNT arrays modified glass carbon electrode (GCE) was first prepared by one‐pot method with cyclic voltammetry.Then AuNPs were deposited on the SWCNT arrays and complexed with a high concentration of chloride ions (0.1 mol/L). The as‐fabricated SWCNT arrays/AuNPs senor have showed an excellent sensitivity in CLE detection with lower detection limit (0.5 ng/L) and wider linear range (1–800 ng/L). Its high performance can be attributed to the high catalytic activity of SWCNT arrays and the special absorption of CLE on AuNPs. The surface morphology of the electrode was analyzed by atomic force microscopy, X‐ray photoelectron spectroscopy and SEM. This work offers a new method for the synthesis of SWCNT arrays and a novel avenue for CLE detection. The modified electrode was stable with 98.5 % of its initial current response after remained one month, it was used to detect CLE in human urine, animal tissues and food with satisfactory results.

Simple electrochemical method for the quantification of chlorite in aqueous and non-aqueous media

The recent recommendation of the WHO for a limit of chlorite of 0.7 mg L−1 calls for reliable and fast analysis methods. Here, we present a robust differential pulse voltammetry (DPV) method for the quantification of chlorite (ClO2−) well below this limit. Different working electrode materials and electrolytes were evaluated, of which the combination of glassy carbon with bis(trifluoromethylsulfonyl)azanide (NTf2−) salts turned out to be highly advantageous. It was found that for aqueous samples the lithium salt of NTf2− was most suitable, while for organic systems solutions of the ionic liquid N‑butyl‑N-methylpyrrolidinium bis(trifluoromethylsulfonyl)azanide ([BmPyrr][NTf2]) in methanol were the most robust ones. Neither the other chlorooxo anions (hypochlorite OCl−, chlorate ClO3−, perchlorate ClO4−) nor the standard ions, except iodide, interfere with the method. To demonstrate the feasibility of the method, a broad range of samples were investigated for their chlorite content, such as commercial disinfectants, bleaches, chlorinating agents, organic acid chlorides, as well as products of the Pinnick reaction, for which chlorite is used as a reagent.