Film-modified Electrode Research Articles

A facile poly(allura red) film for signal-amplified electrochemical sensing of dopamine and uric acid in human plasma and urine

A novel and facile sensing platform based on poly(allura red) film, synthesized via a one-step cyclic voltammetry scanning, was used for determining dopamine and uric acid in human plasma and urine. The signal was amplified thanks to the good π–π and electrostatic interaction of the allura red polymer film, and thus the superior electron transfer rate. The electrochemical determination of dopamine and uric acid, alone and in the presence of each other, was investigated and the oxidation peaks at 190 mV for dopamine and 320 mV for uric acid were used as the analytical response. Characterization measurements for the fabricated platform were performed with various techniques including cyclic voltammetry, electrochemical impedance spectroscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy. The poly(allura red) film-modified electrode exhibits a remarkable limit of detection values of 10.5 nM for dopamine and 30.1 nM for uric acid with wide linear ranges of 0.03–20 µM and 25–70 µM µM for dopamine, 0.09–110 µM for uric acid, 0.48–80 µM and 90–290 µM for dopamine in the presence of uric acid, and 0.35–200 µM for uric acid in the presence of dopamine. The proposed method was applied to the human plasma and urine samples, the results were statistically compared with those obtained from the titrimetric method, and no significant difference at a 95 % confidence level was found.

A three-dimensional composite film-modified electrode based on polyoxometalates and ionic liquid-decorated carbon nanotubes for the determination of L-tyrosine in food.

A stable and innovative composite film-modified electrode based on Dawson polyoxometalates H8P2Mo16V2O62 (P2Mo16V2) and ionic liquid (BMIMBr)-decorated carbon nanotubes, annotated as PEI/(P2Mo16V2/BMIMBr-CNTs)8, has been constructed by using the layer-by-layer self-assembly (LBL) method for the determination of L-tyrosine. The combination of three active components not only offers higher conductivity to facilitate rapid electron transfer, but also avoids the accumulation of P2Mo16V2 to expand the contact area and increase the reactive active sites. The modified electrode exhibits outstanding sensing performance for determination of Tyr with wide linear determination range of 5.8×10-7 M ~ 1.2×10-4 M, low determination limit of 1.7×10-7M (S/N=3), high selectivity for common interferences, and excellent stability at the potential of +0.78 V (vs. Ag/AgCl (3 M KCl)). The relative standard deviation (RSD) of 4.3% for five groups of parallel experiments shows the satisfactory repeatability of PEI/(P2Mo16V2/BMIMBr-CNTs)8. In addition, for determination of Tyr, the PEI/(P2Mo16V2/BMIMBr-CNTs)8 shows good recoveries of 98.8-99.8% in meat floss, which can be feasible in practical application.

Evaluation of antioxidant performance of economic crops by electrochemical sensors using guanine as a probe

The evaluation of antioxidant performance in economic crops is of significant importance due to their potential health benefits and increasing demand for functional foods. In this study, we developed an electrochemical sensor based on guanine binding technology to assess the antioxidant capacity of common economic crops, including tomatoes, blueberries, spinach, grapes, and oranges. The guanine oxidation peak current, measured using square wave voltammetry on a composite film-modified electrode (RGO/G/GCE), served as an indicator of antioxidant activity. Statistical analysis, including one-way analysis of variance (ANOVA) and post-hoc tests, revealed significant differences (p < 0.05) in the guanine oxidation peak currents among the tested crops, highlighting variations in their antioxidant activities. Blueberries exhibited the highest guanine oxidation peak current, indicating the strongest antioxidant capacity, followed by spinach and grapes with significant antioxidant activity. Tomatoes and oranges displayed relatively lower antioxidant capacity. The working/linear range for the electrochemical sensor was determined to be 0.5–4.0 mg/L of ascorbic acid (AA), and the limit of detection (LOD) was calculated as 0.35 mg/L. The proposed electrochemical sensor provides a rapid, sensitive, and cost-effective approach for assessing antioxidant capacity, offering potential applications in quality control, nutraceutical analysis, and functional food development.

Ultrasensitive Electrochemical Detection of Cr(VI) in the Air of Workplace Using the Bismuth Film Modified Electrode

Ultrasensitive Electrochemical Detection of Cr(VI) in the Air of Workplace Using the Bismuth Film Modified Electrode

Constructing combinational and sequential logic devices through an intelligent electrocatalytic interface with immobilized MoS2 quantum dots and enzymes

Stable molybdenum disulfide quantum dots (MoS2 QDs) were synthesized using a simple method and embedded into chitosan (Chit) films with glucose oxidase (GOD) on the surface of a polyaniline (PANI) pre-electrodeposited ITO electrode, designated as Chit-MoS2-GOD/PANI. At the prepared film electrode, the fluorescence property of MoS2 QDs as well as the catalytic properties of MoS2 QDs and GOD were well maintained and could be reversibly regulated by external stimuli, such as pH, potential, and the concentrations of glucose and ascorbic acid (AA) in the solution. By controlling the redox state of PANI with an externally applied voltage, the color of the film electrode switched between violet blue and nearly transparent, simultaneously quenching/dequenching the fluorescence signals from MoS2 QDs through Fӧster resonance energy transfer (FRET). The electrocatalytic signals toward hydrogen peroxide (H2O2), a product formed by biocatalysis between glucose and GOD, could be tuned through the catalytic capacity of MoS2 QDs in the films. Thus, an intelligent platform was built based on the film electrode with pH, potential, glucose and AA as inputs and UV–vis extinction (E), photoluminescent intensity (PL), and amperometric current (I) as outputs. Combinational logic operations such as a 4-input/5-output logic network and sequential logic operations such as a keypad lock and a reprogrammable delay/data (D) flip flop was first simulated in a biocomputing system with the film-modified electrode. This work demonstrated the construction of a multiple stimulus-responsive system with dual-functional nanomaterials and provided a new approach for sequential logic operations for further applications in the information storage.

Graphene and Chitosan Composite Film Modified Electrode as a Sensitive Voltammetric Sensor for Tyrosine Detection in Food and Biological Samples

In this paper, a voltammetric sensor made from a graphene and chitosan modified glassy carbon electrode (GR-CTS/GCE) was fabricated for accurate analysis of tyrosine (Tyr) in both food and in biological samples. The surface morphology of the electrode and the properties of the electrode-electrolyte interface were determined by scanning electron microscopy (SEM) and cyclic voltammetry (CV). Compared with a bare glassy carbon electrode (GCE), the synergistic effect of GR and CTS is obvious. The peak current increases by 35.6 times. The experimental conditions were optimized by second derivative linear sweep voltammetry (SDLSV) and Tyr was quantitatively analyzed on the electrode. The study shows that the oxidation peak current of Tyr obtained in 0.1 M pH 2.7 phosphate buffer is proportional to its concentration between 0.006–0.8 μM and 0.8–10.0 μM, with the low detection limit being 4.0 nM (signal/noise = 3). The excellent anti-interference ability was demonstrated by investigating the voltammetric response of Tyr in mixtures containing other biomolecules. In addition, the sensor exhibited good stability and repeatability. Through the detection of Tyr in milk and serum samples, the effectiveness of the sensor is studied, and the results are satisfactory.

An unprecedented dumbbell-shaped pentadeca-nuclear W-Er heterometal cluster stabilizing nanoscale hexameric arsenotungstate aggregate and electrochemical sensing properties of its conductive hybrid film-modified electrode

An unprecedented dumbbell-shaped pentadeca-nuclear W-Er heterometal cluster stabilizing nanoscale hexameric arsenotungstate aggregate and electrochemical sensing properties of its conductive hybrid film-modified electrode

Establishment of PPy-derived carbon encapsulated LiMn2O4 film electrode and its performance for efficient Li+ electrosorption

Improving the cycle stability and Li+ electrosorption rate of the LiMn2O4 (LMO) film electrode in the selective Li+ electrosorption process is still a considerable challenge. In this work, a novel polypyrrole (PPy) - derived carbon encapsulated material LiMn2O4@Carbon/Nitrogen-4 (LMO@CN-4) was prepared by the three-dimensional in-situ polymerization and high-temperature annealing of PPy on the LMO surface. The LMO@CN-4 film electrode showed a faster Li+ electrosorption rate, higher lithium-ion selectivity, and higher stability than the LMO film electrode. The maximum capacity of the LMO@CN-4 film electrode for Li+ could reach 34.57 mg/g within 40 min in 0.05 mol/L LiCl solution. Even in the simulated concentrated seawater with a low Li+ concentration (0.17 g/L), it could quickly reach adsorption equilibrium and maintain the high selectivity of Li+. The adsorption capacity was about 37.14 mg/g and the separation coefficient of α (Li+/Mg2+), α (Li+/Na+), and α (Li+/Ca2+) was about 228.25, 2110.64, and 1381.89. The carbon encapsulation served as a conductive layer to enhance charge and ion transport. It also provided a buffer layer to prevent the volume collapse of the crystal and the dissolution of Mn. Therefore, the charge and discharge capacity of the LMO@CN-4 film electrode could be maintained at about 80% after 50 cycles at the 1C (148 mAh/g) rate, which was 20% higher than that of the bare LMO. What’s more, the high cycle stability and Li+ electrosorption rate of the modified film electrode also suggested its potential for lithium electrosorption from concentration seawater.

A bifunctional electrochemical aptasensor based on AuNPs-coated ERGO nanosheets for sensitive detection of adenosine and thrombin

A simple and sensitive bifunctional electrochemical aptasensor for detection of adenosine and thrombin has been developed using gold nanoparticles–electrochemically reduced graphene oxide (AuNPs-ERGO) composite film-modified electrode. Firstly, the reduced graphene oxide film and AuNPs were sequentially immobilized on glassy carbon electrode (GCE) surface. Secondly, thrombin aptamer was immobilized on the modified electrode. Finally, adenosine aptamer was hybridized with it to serve as a recognition element and methylene blue (MB) as electrochemical signal indicator. In the presence of adenosine or thrombin, the sensor recognized it and a conformational change was induced in aptamer, resulting in decrease of the peak current of MB. The linear relation between concentration of adenosine or thrombin and peak current of MB allowed quantification of them. Thanks to the special electronic characteristic of AuNPs-ERGO composite film, sensitivity of sensor was greatly improved. Under optimal conditions, the proposed aptasensor presented an excellent performance in a linear range of 25 nM to 750 nM for adenosine and 0.5 nM to 10 nM for thrombin. Detection limits were estimated to be 8.3 nM for adenosine and 0.17 nM for thrombin, respectively. Moreover, dual-analyte detection of adenosine and thrombin was achieved without potentially increasing the complexity and cost of the assay.

Enhanced Electrocatalytic Activity of Thiophene-Substituted Asymmetric Porphyrin Film for Electrochemical Determination of Dopamine

Thiophene substituted porphyrin derivative was synthesized and investigated. The porphyrin derivative was characterized via MALDI-MS, 1H NMR, FT-IR, and cyclic voltammetry methods. The poly-porpyrin (PPor) film was electrochemically deposited on a glassy carbon electrode (GCE) via cyclic voltammetry in phosphate buffer solution (PBS). The electrocatalytic activity of the polymeric porphyrin film-modified electrode (GCE-PPor) was investigated towards dopamine through differential pulse voltammetry (DPV) method. The electrochemical results revealed that GCE-PPor exhibited a better catalytic activity towards dopamine in PBS when compared to an unpolymerized porphyrin-modified electrode. The PPor-modified electrode shows a sensitivity of 5.82 μA μM–1 cm–2 and low detection limit of 0.42 μM with high selectivity in the presence of ascorbic acid (AA) and uric acid (UA) as interferents. The enhancement of the electrocatalytic activity can be explained by the enhanced π-conjugation after polymerization.

Determination of mercury in cosmetics on electropolymerized film-modified electrodes

Electropolymerized film-electrodes modified with a film consisting of N-ethyl-N-(p-hydroxyphenethyl) amine, tyramine and tri-n-octylphosphine oxide, in a 0.5% Nafion or 0.02% poly(vinyl chloride) matrix were used for an anodic stripping determination of mercury in cosmetics. The most important parameters include thickness of the modifying film, the modifier-to-matrix ratio in the modifying film and the base electrolyte composition. These parameters were investigated in this study. Comparison with results obtained from atomic absorption spectrophotometric analysis (AAS) showed good agreement.

Fabrication of bacteriochlorin shell/gold core nanoparticles for the sensitive determination of trichlosan using differential pulse voltammetry

The triclosan contamination in daily life has attracted great attention, and there is rare electroanalytical assay based on π-system dyes. In this work, a facile preparation and electroanalytical application of an organic dispersion containing bacteriochlorin dyes (LS11) and gold nanoparticles (AuNPs) was proposed. The organic-inorganic hybrid nanocomposites were characterized by transmission electron microscope (TEM) showing a core–shell structure with a uniform layer of dye molecules. The as-prepared nanocomposites were successfully coated onto glassy carbon electrodes, and the surface characteristics of the top most layer of the modified electrodes were examined by atomic force microscopy (AFM), field emission scanning electron microscopy (FE-SEM) and water contact angle experiments. The nanocomposite film-modified electrodes exhibited good electrochemical activity towards oxidation of triclosan. The oxidation of adsorbed triclosan occurred at a reduced overpotential, and the anodic current responses under a pre-concentration step prior to the potential scan were used for quantitative analysis. A good linear relationship from 0.01 μM to 0.5 μM was obtained using differential pulse voltammetry. The sensitivity and detection limit (S/N = 3) were 23.69 μA μM−1 and 0.03 μM, respectively. The proposed assay was applied to detect triclosan in two personal hygiene products using standard addition method, and the results showed good recoveries that ranged from 96.6% to 101.5% and from 99.3% to 103.8% for a toothpaste sample and a hand wash sample, respectively. A reference HPLC-UV method was used to evaluate the proposed electroanalytical method, and a good agreement was achieved.

Square-wave adsorptive stripping voltammetric approaches at two in situ modified electrodes as first analytical methods for the quantitative determination of a new anticancer drug candidate

The two adsorptive stripping voltammetric approaches for detection and quantitative determination of diethyl (2E)-2-{(2E)-[1-(4-methylphenyl)imidazolidin-2-ylidene]hydrazinylidene}butanedioate (DIB)—a novel molecule of medical importance—using two sensitive sensors based on modified glassy carbon electrodes as reusable sensors, were developed for the first time. The proposed electrochemical methods are based on adsorptive/reductive behaviour of DIB at two modified carbonic electrodes: a bismuth film-modified glassy carbon electrode (BiF/GCE) and a lead film-modified glassy carbon electrode (PbF/GCE). The electron gain mechanism for the electrochemical reduction of DIB on both developed sensors was proposed for the first time. To achieve the highest sensitivity in adsorptive stripping determinations, various experimental variables (e.g. the composition and pH of the supporting electrolytes, deposition conditions of bismuth and lead films, concentrations of plating solutions, accumulation times and potentials of DIB, etc.) were extensively examined. The comparison of validation parameters obtained during the determination of DIB at two sensors was presented. The excellent linear correlation was found between the monitored adsorptive stripping voltammetric peak current and the DIB concentration in the range of 15–600 μg L−1 at an accumulation time of 30 s (with LOD = 4.2 μg L−1 and LOQ = 14.0 μg L−1) using the BiF/GCE as a sensor. Furthermore, the excellent linear relationship was confirmed between the monitored adsorptive stripping voltammetric peak current and the DIB concentration in the range of 9–900 μg L−1 at an accumulation time of 10 s (with better LOD = 1.5 μg L−1 and LOQ = 5.0 μg L−1), employing the PbF/GCE as a sensor. The two optimized adsorptive stripping voltammetric approaches—as facile, sensitive, reliable and inexpensive—were successfully used as first methods for the quantitative analysis of a novel anticancer agent (DIB) in its pure pharmaceutically acceptable form. However, the practical applicability of square-wave adsorptive stripping voltammetric determination of the electroactive DIB molecule at a PbF/GCE, as the modified electrode of higher sensitivity, was presented after its successful solid phase extraction from a real serum sample.

Synthesis of semicarbazide catechol derivative as a potential electrode modifier: application in electrocatalysis of catechol amine drugs

2-(1-(3,4-Dihydroxyphenyl)ethylidene)hydrazine-1-carboxamide was synthesized as a precursor for generation of redox polymer. In acidic media, the opposite charge on the surface of this monomer and graphene quantum dots make feasible monomer electrodeposition. Fourier transform infrared spectroscopy and field-emission scanning electron microscopy were used for chemical band identification and morphological characteristics of coated film at electrode. Polymer-modified electrode enhances electron-transfer process of catechol amines such as dopamine and dobutamine selectively. Graphene quantum dots/polymer film-modified electrode produce more oxidation current compared to polymer-modified electrode alone. Under optimized condition, the concentration of dobutamine and its oxidation signal was well fitted to the linear regression function in the range of 0.05–35.0 µM with the detection limit of 0.01 µM. The accuracy evaluation of modified electrode was determined by measuring concentration of dobutamine in serum samples.

Poly(amido amine) dendrimer and silver nanoparticle–multi-walled carbon nanotubes composite with poly(neutral red)-modified electrode for the determination of ascorbic acid

A new film containing poly(amido amine) dendrimer, silver nanoparticles and multi-walled carbon nanotubes composite with poly(neutral red) was prepared on a paraffin wax impregnated graphite electrode. The PAMAM / AgNPs–MWCNT / PNR film exhibited promising electrocatalytic oxidation of ascorbic acid (AA) in acetate buffer solution of pH 4.0. The PAMAM / AgNPs–MWCNT / PNR film-modified electrode enhanced the sensitivity of detection of AA. The PAMAM / AgNPs–MWCNT / PNR film-modified electrode was characterized by cyclic voltammetry, chronoamperometry, hydrodynamic voltammetry (HDV) and difference pulse voltammetry. These experiments confirmed the electrocatalytic oxidation of AA by PAMAM / AgNPs–MWCNT / PNR film-modified electrode. The PAMAM / AgNPs–MWCNT / PNR-modified electrode has been found to possess good electrocatalytic activity towards AA oxidation which has been observed at a lower oxidation potential of around 0.26 V with a higher current response. The electrochemical oxidation of AA by PAMAM / AgNPs–MWCNT / PNR-modified electrode involved a two proton and two electron process. A linear relationship between the catalytic current and AA concentration was obtained in the range from 0.16 to 2500 \(\upmu \)M with a detection limit of 0.053 \(\upmu \)M.

Ultrathin Phthalocyanine-Conjugated Polymer Nanosheet-Based Electrochemical Platform for Accurately Detecting H2O2 in Real Time.

As a vital biological mediator and a widely used industrial oxidant, the accurate detection of hydrogen peroxide (H2O2) is of significance for both academic purpose and practical applications. Herein, we report a novel approach for the development of a high-performance electrochemical H2O2 sensor constructed by iron phthalocyanine (FePc)-based diyne-linked conjugated polymeric nanosheets (NSs), FePc-CP NSs. The FePc-CP NSs were delaminated from the bulk material via a defect- and disorder-induced synthetic strategy. By the quasi-Langmuir-Shäfer method, the prepared FePc-CP NSs were self-assembled into multilayer films with controllable thickness on electrodes. Owing to the highly exposed active centers on the surfaces, the FePc-CP NS film-modified electrodes exhibited excellent H2O2 determination performance with a wide linear detection range (0.1-1000 μM), a short response time (the response current approached the maximum value within 0.1 s), a low limit of detection (0.017 μM), and excellent sensitivity (97 μA cm-2 mM-1), which are comparable to the best results reported so far for electrochemical H2O2 sensors. In addition, the fabricated electrochemical H2O2 sensor also displayed satisfactory stability, reproducibility, and selectivity. Furthermore, the obtained FePc-CP NS film sensor can be applied in real-time monitoring of H2O2 in commercial orange juice and beer as well as H2O2 secreted from A549 live cells, revealing its application potential toward the accurate detection of H2O2 in real-sample analysis.

Graphite/SiO2 film electrode modified with hybrid organic-inorganic perovskites: Synthesis, optical, electrochemical properties and application in electrochemical sensing of losartan

Hybrid organic-inorganic semiconductors (HOIS) still remain as research focus due to their exceptional optoelectronics properties, placing them as ideal candidates for use in the field of light emitting diodes and photovoltaics. In the present work, HOIS have been synthesized, characterized as well as adsorbed onto graphite/silica film electrodes (GSiHE), the latter used as simple, low cost, yet sensitive, electrochemical sensors. These composite electrodes have been specifically characterized with electrochemical methods and have been applied in the development of prototype electrochemical drug sensors; a paradigm is provided for simple, efficient, sensitive and relatively specific sensing of an antihypertensive drug, losartan (LOS). The electrochemical behavior of GSiHE film modified with HOIS was examined by cyclic voltammetry, while its morphology, structural and spectroscopic properties were investigated by field emission scanning electron microscopy, X-ray diffraction, porosimetry, optical and luminescence spectroscopies. Under optimized conditions, the modified film electrode demonstrated excellent electrocatalytic activity towards oxidation of LOS in the linear response range for concentrations from 4 × 10−5 M to 3.2 × 10−4 M (correlation coefficient 0.989) with the limit of detection computed at 3 × 10−6 M. The sensor takes advantage of the ability of ions to interact with the HOIS lattice on the GSiHE film; this type of sensor has demonstrated good repeatability, reproducibility and stability and was found to be applicable for use in determining pharmaceutical tablet sample concentrations.

A novel electrochemical assay for aspartame determination via nucleophilic reactions with caffeic acid ortho-quinone

Cyclic voltammetry (CV) in a pH 7.0 phosphate buffer solution containing aspartame (ASP) and caffeic acid (CAF) was studied. In sharp contrast to untreated electrodes, two distinct redox peaks were observed at preanodized screen-printed carbon electrodes (SPCE*) due to the formation of a homopolymer poly(CAF) and a copolymer poly(CAF-ASP). The characteristics of the polymer film-modified electrodes were well-characterized by atomic force microscopy (AFM), scanning electron microscopy (SEM), photoelectron spectroscopy (XPS) and the water contact angle technique. Electrochemically induced polymerization mechanisms were discussed. Current responses from poly(CAF-ASP) were employed for ASP determination, and a linear dynamic range from 0.05 μM to 10 μM was obtained using differential pulse voltammetry (DPV). The limit of detection (LOD, S/N = 3) was 0.0076 μM, the limit of quantification (LOQ, S/N = 10) was 0.0256 μM, and sensitivity was 12.067 μA μM−1. The relative standard deviation (RSD) was less than 5%, indicating good precision. Common additives in soft drinks do not interfere with the ASP analysis. The proposed assay was applied for the determination of ASP in two soft drinks using the standard addition method, and recoveries in the range of 103.0–106.7% and 97.3–106.4% were obtained for Coca-Cola and Coke Zero, respectively. A reference high-performance liquid chromatography (HPLC) was applied to validate the proposed method, and good agreement was obtained.

A direct and selective electrochemical hydrogen sulfide sensor

Continuous, in situ detection of hydrogen sulfide (H2S) in biological milieu is made possible with electrochemical methods, but direct amperometry is constrained by the generation of elemental sulfur as an oxidative byproduct. Deposition of a sulfur layer passivates the working electrode, reducing sensitivity and causing performance variability. Herein, we report on the use of a surface preconditioning procedure to deposit elemental sulfur on a glassy carbon electrode prior to measurement and evaluate performance with common analytical metrics. The lack of traditional anti-poisoning techniques (e.g. redox mediators, cleaning pulses) also allowed for facile surface modification with electropolymerized films. For the first time, a series of electropolymerized films were characterized for their H2S permselective behavior against common biological interferents. Highly selective, film-modified electrodes were then evaluated for their anti-biofouling ability in simulated wound fluid. The final optimized electrode was capable of measuring H2S with a low detection limit (i.e., <100 nM) and ∼80% of its initial sensitivity in proteinaceous media.

Polypyrrole entrapped 18-molybdodisulphate anion for the detection of hydrogen peroxide

Dawson-type 18-molybdodisulphate anion [S2Mo18O62]4-has been immobilized within polypyrrole film by means of electrochemical polymerization. The polymer modified electrodes have been characterized with voltammetry and surface based techniques. The noticeable change in electrochemical properties of [S2Mo18O62]4- has been observed with immobilization, which is favours its electrocatalytic performance. Hydrogen peroxide reduction in neutral pH as a standard system for electrocatalytic properties assessment has been studied on composite film-modified electrodes and showed the sensitivity of 127 mAM−1cm−2. Developed system showed high stabilities towards redox switching and peroxide reduction.