Anodic Peak Current Research Articles

An electrochemical sensor based on a pencil graphite electrode modified with poly-riboflavin for 4-nitrophenol quantification

It is essential to develop a simple and disposable electrochemical sensor for monitoring organic pollutants in water systems. This work aims in the quantification of hazardous water pollutant 4-Nitrophenol (4-NP) by electropolymerizing vitamin B complex (Vitamin B2/Riboflavin) over pencil graphite electrode (PGE). By differential pulse voltametric technique, the anodic peak current increased appreciably for 4-NP oxidation on poly-riboflavin modified pencil graphite electrode (PRB/PGE) as compared to bare PGE. The adapted sensor was characterized using scanning electron microscopy (SEM), infrared spectrometry (IR), energy dispersive X-ray analysis (EDX) and electrochemical impedance spectroscopy (EIS). The increased electroactive surface area and decreased electron transfer resistance was achieved by electropolymerisation of the electrode. A well-defined anodic peak of 4-NP was observed on the adapted electrode at a potential of +0.864 V in phosphate buffer solution of pH 7.2. Factors affecting the current response were optimized. Scan rate and pH analysis were used to study the fabricated electrode and thereby determining transfer electron and proton number. The sensor spectacled a linearity of 5.0 μM–700.0 μM with lower detection of limit (LOD) of 1.78 μM and limit of quantification (LOQ) of 5.94 μM. By using a simple single-step fabrication method, the PRB/PGEs exhibit high stability, reproducibility and repeatability making them an ideal tool to detect 4-NP in real water samples. The developed disposable sensor exhibited a recovery between 97-103%. Hence it is found to be a favorable tool for the electroanalysis of the analyte with high reliability.

Impedimetric nanoimmunosensor platform for aflatoxin B1 detection in peanuts.

This article developed a novel electrochemical immunosensor for the specific detection of aflatoxin B1 (AFB1). Amino-functionalized iron oxide nanoparticles (Fe3 O4 -NH2 ) were synthesized. Fe3 O4 -NH2 were chemically bound on self-assembly monolayers (SAMs) of mercaptobenzoic acid (MBA). Finally, polyclonal antibodies (pAb) were immobilized on Fe3 O4 -NH2 -MBA. The sensor system was evaluated through atomic force microscopy (AFM), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). A reduction in the anodic and cathodic peak currents was observed after the assembly of the sensor platform. The charge transfer resistance (Rct ) was increased due to the electrically insulating bioconjugates. Then, the specific interaction between the sensor platform and AFB1 blocks the electron transfer of the [Fe(CN)6 ]3-/4- redox pair. The nanoimmunosensor showed a linear response range estimated from 0.5 to 30 μg/mL with a limit of detection (LOD) of 9.47 μg/mL and a limit of quantification (LOQ) of 28.72 μg/mL for AFB1 identification in a purified sample. In addition, a LOD of 3.79 μg/mL, a LOQ of 11.48 μg/mL, and a regression coefficient of 0.9891 were estimated for biodetection tests on peanut samples. The proposed immunosensor represents a simple alternative, successfully applied in detecting AFB1 in peanuts, and therefore, represents a valuable tool for ensuring food safety.

Binding-Induced Folding of DNA Oligonucleotides Targeted to the Nucleocapsid Gene Enables Electrochemical Sensing of SARS-CoV-2.

In the wake of the COVID-19 pandemic, millions of confirmed cases and deaths have been reported around the world. COVID-19 spread can be slowed and eventually stopped by a rapid test to diagnose positive cases of the disease on the spot. It is still important to test for COVID-19 quickly regardless of the availability of the vaccine. Using the binding-induced folding principle, we developed an electrochemical test for detecting SARS-CoV-2 with no RNA extraction or nucleic acid amplification. The test showed high sensitivity with a limit of detection of 2.5 copies/μL. An electrode mounted with a capture probe and a portable potentiostat are used to conduct the test. To target the N-gene of SARS-CoV-2, a highly specific oligo-capturing probe was used. Based on the binding-induced "folding" principle, the sensor detects binding between the oligo and RNA. When the target is absent, the capture probe tends to form a hairpin as a secondary structure, retaining the redox reporter close to the surface. This can be seen as a large anodic and cathodic peak current. When the target RNA is present, the hairpin structure will open to hybridize with its complementary sequence, causing the redox reporter to pull away from the electrode. Consequently, the anodic/cathodic peak currents are reduced, indicating the presence of the SARS-CoV-2 genetic material. Validation of the test performance was performed using 122 COVID-19 clinical samples (55 positives and 67 negatives) and benchmarked to the gold standard reverse transcription-polymerase chain reaction (RT-PCR) test. As a result of our test, the accuracy, sensitivity, and specificity have been measured at 98.4%, 98.2%, and 98.5%, respectively.

3D printed electrodes design and voltammetric response

The limiting aspects in the voltammetric response of 3D printed electrodes is thoroughly investigated with numerical simulations and new 3D printed electrode designs. Severe diffusion limitations, resulting from a recessed electrode geometry, is found in a commonly used 3D printed electrode and electrochemical cell design, impeding the investigation of electron transfer kinetics at these electrodes by classical methods, such as Nicholson's, widely used on this and similarly mass transport-limited designs. A new 3D printed electrode design, an inlaid disk (non-recessed) geometry, is used to investigate the voltammetric response of printed electrodes in bulk solution, i.e., without mass transport limitations. At this condition, it is clear that the voltammetric response is limited by contact resistance, arising from the printed material low electrical conductivity. Gold modified electrodes, deliberately designed with different contact resistances, highlight the resistive behavior, with quasi-reversible voltammetric profiles. This contrasts with the common assumption of a voltammetric response limited by finite electron kinetics. Electron transfer rate constants (k0) and transfer coefficients (α) for electrodes with and without surface modifications are calculated from experimental data using a modified Butler-Volmer equation, incorporating ohmic losses. The reported k0 and α values are independent of electrode geometry or printing parameters, unlike the observable rate constant usually reported for 3D printed electrodes. By accounting for contact resistance and finite electron transfer kinetics, cathodic and anodic peak potentials and currents of voltammograms recorded with 3D printed electrodes are predicted before printing, allowing electrode designs to be optimized in the virtual space.

Synergistic impact of nanoarchitectured GQDs-AgNCs(APTS) modified glassy carbon electrode in the electrochemical detection of guanine and adenine

In this work, a facile green approach for the synthesis of graphene quantum dots (GQDs) embedded on silicate network silver nanocrystals (GQDs-AgNCs(APTS)) is reported. Moreover, glassy carbon-GC electrodes were modified with the prepared nanocomposite containing graphene quantum dots supported on silver nanocrystals (GQDs-AgNCs(APTS)) and applied for simultaneous detection of guanine (GA) and adenine (AD). The chemically modified electrode was assessed during the determination of purine bases by cyclic voltammetry-CV and differential pulse voltammetry-DPV. The incorporation of GQDs-AgNCs(APTS) nanocomposites over the surface of the GC electrode considerably enhances the anodic peak currents and decreases the adenine and guanine peak potentials. Compared to other electrodes, GQDs-AgNCs(APTS)/GC improved the electrochemical behavior towards the detection of adenine and guanine. At optimal conditions, calibration curves were obtained by DPV being linear in the range of 0.1–6.0 μM and 0.1–5.0 μM for guanine and adenine, respectively. The detection limits of both guanine and adenine were estimated as 0.1 μM. Additionally, interferences analyses were performed on the existence of other interferent compounds. Furthermore, the method developed for the identification of GA and AD was proved using fish sperm DNA samples.

Biogenic platinum based nanoparticles: Synthesis, characterization and their applications for cell cytotoxic, antibacterial effect, and direct alcohol fuel cells

In this study, biogenic platinum nanoparticles (Pt NPs) were obtained using the green synthesis method. The obtained Pt NPs were characterized using X-ray diffraction (XRD) and Transmission Electron Microscopy (TEM), and the plant extract was characterized using Fourier Transform Infrared Spectroscopy (FTIR). With this characterized Pt NPs, cytotoxicity tests on MIAPaCa 2, Hela, HEK 293, Thle 2 cell lines and antibacterial activities on S. Aureus, S. Mutans, E. Coli, E. Faecalis bacterial cell lines were investigated. As a result, it was observed that biogenic Pt NPs showed a cytotoxic effect on cell lines and an antibacterial effect against a series of bacteria. At the same time, in order to show the usability of Pt NPs synthesized by the green synthesis in different areas, studies for alternative clean energy production were also carried out, and in the methanol oxidation reaction study, 5.42 mA.cm−2 anodic peak current was obtained at 0.6 V potential. This showed that nanoparticles obtained by the green synthesis method can be used in alcohol oxidation studies for alternative clean energy generation.

Synthesis of LaW/Ag/GNRs nanocomposite: Application as transducer material for the simultaneous nano molar detection of synthetic dyes and as anode material for Li ion batteries

In this present research, we have synthesized the lanthanum tungstate/silver nanoparticle/graphene nanoribbons (LaW/Ag/GNRs) nanocomposite as a novel system for the simultaneous electrochemical determination of two synthetic food colorants sunset yellow (SY) and acid yellow (AY). The synthesised nanocomposite modified graphite electrode (Gr) provides the presence of more active sites for the transfer of electrons, allowing for a stronger voltametric response that is due to the faster rate of electron transfer from the analytes. The as-synthesized nanocomposite was characterized by different analytical methods. The enhanced anodic peak currents represented the excellent analytical performance for simultaneous detection of SY and AY in the range of 20 nm to 450 nM, with a low limit of detection (LOD) of 0.025 nm for SY and 0.050 nM for AY. This proposed sensor showed excellent recovery values real sample analysis. Further the nanocomposite was used as the anode material in Li ion batteries and was evaluated in an aqueous saturated Li2SO4 electrolyte. In terms of cycle performance, enhanced rate capability, and high discharge capacity, LaW/Ag/GNRs nanocomposite has made significant advancements. The lithiated LaW/Ag/GNRs nanocomposite half-cell vs. SCE offers a 227.86 mA h g−1 capacity up to 10 cycles at 0.08 mA. In the potential range of 1.0 to 0.0 V, the whole cell configuration LaW/AgNPs/GNRs|aq.saturated Li2SO4|LiMn2O4 produced a discharge capacity of 240.24 mA h g−1. With 96.95% columbic efficiency, the battery performance of the cell has greatly boosted. This excellent result clearly fits this material as an anode in future aqueous rechargeable lithium batteries for energy technology.

New electrode material GCE/AgNPs‐D3 as an electrochemical sensor used for the detection of thallium ions

AbstractOptimal working parameters for the innovative electrode GCE/AgNPs‐D3 were determined and the selectivity was assessed. The stripping anodic peak current of thallium characterized in linearity over range from 4.9 ⋅ 10−8 to 4.9 ⋅ 10−7 mol ⋅ dm−3, with LOD = 7.16 ppb (3.5 ⋅ 10−8 mol ⋅ dm−3). Furthermore, the new electrode showed more than sevenfold improvement in the thallium current signal compared to the unmodified electrode GCE. High selectivity was achieved using EDTA disodium salt as a complexing agent for other metals.

Titanium-Based Static Mixer Electrodes to Improve the Current Density of Slurry Electrodes.

Complex geometries for electrodes are a great challenge in electrochemical applications. Slurry electrodes have been one example, which use complex flow distributors to improve the charge transfer between the current collector and the slurry particles. Here we use titanium-based flow distributors produced by indirect 3D-printing to improve further the electron transfer from highly conductive flow distributors to the slurry particles for a vanadium redox flow application. The titanium static mixers are directly coated with graphite to increase the activity for vanadium redox reactions. Increasing layers of graphite have shown an optimum for the positive and negative electrolytes. The application of heat treatment on the electrodes improves the anodic and cathodic current peaks drastically. Testing the highly conductive static mixers in a self-made redox flow cell results in 110 mA cm-2 discharge polarization.

Silver nanoparticle doped graphene-based impedimetric biosensor towards sensitive detection of procalcitonin

In the early detection of sepsis, procalcitonin (PCT) appears to be a highly sensitive biomarker for severe inflammation and infection. A significant interaction between the electrode material to be used in the design of the biosensor and the material to be attached to the surface is of great importance. Here, we demonstrated a silver nanoparticle (AgNp) doped graphene-based sensitive PCT biosensor with low-cost, environmentally friendly materials. Cyclic voltammetry curves showing the reusability of the electrodes obtained were obtained and showed antibody-protein adhesion on the AgNp/SLG@ITO surface. The anodic and cathodic peak currents values after 20 cycles show that these values are suitable even after 20 measurements. Electrochemical impedance spectroscopy (EIS) studies confirmed the effects of PCT on binding events due to increasing concentration at a constant PCT-antibody concentration. The limit of detection (LOD) value of the fabricated PCT/Ab/AgNp/SLG@ITO impedimetric biosensor was determined as 0.55 ngmL−1. The low LOD value can be attributed to the uniform and large surface area of single-layer graphene (SLG) and noble AgNp. The LOD value based on the EIS studies has revealed that the PCT/Ab/AgNp/SLG@ITO impedimetric biosensor can be employed in real samples.

Application of ZnO-NRs@Ni-foam substrate for electrochemical fingerprint of arsenic detection in water.

Arsenic (As3+) is the most carcinogenic and abundantly available heavy metal present in the environment. Vertically aligned ZnO nanorod (ZnO-NR) growth was achieved on metallic nickel foam substrate via a wet chemical route and it was used as an electrochemical sensor towards As(iii) detection in polluted water. Crystal structure confirmation, surface morphology observation and elemental analysis of ZnO-NRs were conducted using X-ray diffraction, field-emission scanning electron microscopy and energy-dispersive X-ray spectroscopy, respectively. Electrochemical sensing performance of ZnO-NRs@Ni-foam electrode/substrate was investigated via linear sweep voltammetry, cyclic voltammetry and electrochemical impedance spectroscopy in a carbonate buffer solution of pH = 9 and at different As(iii) molar concentrations in solution. Under optimum conditions, the anodic peak current was found proportional to the arsenite concentration from 0.1 μM to 1.0 μM. The achieved values for limit of detection and limit of quantification were 0.046 ppm and 0.14 ppm, respectively, which are far lower than the recommended limits for As(iii) detection in drinking water as suggested by the World Health Organization. This suggests that ZnO-NRs@Ni-foam electrode/substrate can be effectively utilized in terms of its electrocatalytic activity towards As3+ detection in drinking water.

The first electrochemical evaluation and voltammetric detection of the insecticide emamectin benzoate using an unmodified boron-doped diamond electrode

This study introduces for the first time an electroanalytical investigation and novel voltammetric method for the determination of emamectin benzoate (EB) using a cathodically pretreated boron-doped diamond electrode (CTP-BDDE). The CPT-BDDE electrode exhibited a well-defined irreversible signal at ∼1.35 V (vs. Ag/AgCl) using cyclic voltammetry. Different scan rates (from 10 to 750 mV s−1) suggested that the oxidation of EB on the BDDE surface is a diffusion-controlled process. Using square wave voltammetry, the anodic peak current was linear with EB concentrations from 0.25 mg L-1 to 12.5 mg L-1, with LOD and LOQ found to be 0.079 and 0.263 mg L-1, respectively. The effect of other insecticides used to treat sea lice and inorganic ions found in seawater on the voltammetric detection of EB was negligible. The proposed method was successfully applied to the determination of EB at different concentrations in real sea water samples. To the best of our knowledge, the voltammetric behaviour of EB and the electrochemical method for EB determination is reported for the first time.

Comparison of carbon paste and boron-doped diamond electrodes for determination of cefepime in pharmaceutical dosage forms and biological samples

The electrochemical analysis of cefepime, a fourth-generation cephalosporin, was investigated in the direction of oxidation using a carbon paste (CP) electrode and a boron-doped diamond (BDD) electrode. The optimum paste composition was determined as 25 % mineral oil-75 % graphite powder for the CP electrode. The effects of different pHs and scan rates on the anodic peak potential and peak current of cefepime were investigated. Scan rate studies were carried out in the range of 5–200 mV s −1 (vs. Ag/AgCl). It was found that the CP electrode had an adsorption-controlled process and the BDD electrode had a diffusion-controlled process under some adsorption effect. The linear ranges of cefepime obtained for the CP electrode were determined as 0.08–10 μM (correlation coefficient; r = 0.998) for differential pulse stripping voltammetry with a detection limit of 3.73 nM and 0.4–10 μM ( r = 0.998) for square wave stripping voltammetry with a detection limit of 22.1 nM. For the BDD electrode, cefepime gave a linear range of 0.04–10 μM ( r = 0.999) for differential pulse voltammetry with a detection limit of 1.58 nM and 0.4–60 μM ( r = 0.998) for square wave voltammetry with a detection limit 11.0 nM. The precision of the proposed methods was examined by repeatability studies and presented by relative standard deviation (RSD) values below 1.76 %. Quantitative analysis of cefepime from pharmaceutical dosage forms and human serum samples using the developed methods was performed for both electrodes without any separation or filtering pretreatment. Recoveries were between 99.41 and 102.07 % for pharmaceutical dosage forms and between 99.79 and 100.50 % for human serum samples, with RSD ranging from 0.70 % to 0.98 %. • Sensitive detection of cefepime helps to increase the effectiveness of treatment. • Side effects in the treatment can be reduced by the determination of cefepime. • Oxidative determination of cefepime can be done using non-toxic solid electrodes. • Carbon paste and boron doped diamond electrodes offer advantages over each other. • Voltammetric methods enable determination from serum samples without pretreatment.

An evaluation of the electrochemical characteristics of 2-nitrobenzene-1,4-diamine organic monomer on gold or platinum thin film electrodes with a full-block random design in acidic environments

The randomized all-design statistical method utilized to elaborate and optimize an experimental model of the electropolymerization of 2-nitrobenzene-1,4-diamine organic monomer. Thin film synthesis was performed using electrochemical cyclic voltammetry (CV) on Micrux® single electrodes made of platinum and gold (A = 0.008 cm2) in 0.1 mol dm–3 H2SO4 at 1.2 pH. The Micrux® electrode chips proved to be reusable with a single sample size of only 10 µL. The electrode material, sampling rate, and monomer concentration were investigated using the phenomenon of electropolymerization. The interaction between these factors was analyzed. The first anodic and second current peaks were selected as the response results. In the first module, a new chip was used for each run, while a previously refurbished chip was used in the second module. The morphological features of the polymers were observed using scanning electron microscopy. A reduction of the spherical particle size was observed when an increase in the sweep scan rate occurred. The importance of the block design, the interaction between the factors, the advantages of the used techniques, and the electropolymerization process of the new polymer were assessed. In comparison with the classical sputtering process, it was demonstrated that an electropolymerization coating using a Micrux® single electrode combined with a block design can be an effective approach to coat materials in optimum conditions.

Highly sensitive detection of circulating tumour cells based on an ASV/CV dual-signal electrochemical strategy.

Circulating tumour cells (CTCs), as a tumour marker, may provide more information in early diagnosis and accurate therapy of cancer patients. Electrochemical detection of CTCs has exhibited exceptional advantages. However, single-signal electrochemical detection usually has a high probability of false positives coming from interferents, operating personnel, and nonstandard analytical processes. Herein, a dual-signal strategy using anodic stripping voltammetry (ASV) and cyclic voltammetry (CV) for highly sensitive detection of CTCs was developed. When MCF-7 cells were present, aptamer DNA (DNA1)-magnetic beads (MBs) were captured by CTCs and detached from the biosensing electrodes. Following magnetic separation, polystyrene bead (PS)-CdS QDs labelled on MCF-7 cells were dissolved by HNO3 and the intensity of the oxidation peak current of Cd2+ ions was proportional to the amount of MCF-7 cells in ASV (y = 6.8929 lg Ccells + 1.0357 (Ccells, cells per mL; R2, 0.9947; LOD, 3 cells per mL)). Meanwhile, the anodic peak currents of the remaining electrode in CV were also proportional to the amount of MCF-7 cells (y = 3.7891 lg Ccells + 52.3658 (Ccells, cells per mL; R2, 0.9846; LOD, 3 cells per mL)). An ASV/CV dual-signal biosensor for electrochemical detection of CTCs was achieved, which overcame the limitations of any single-signal mode and improved the detection reliability and precision.

Using 3D printed magnetic platform as support for screen printed electrode applied for p-toluenediamine detection in biological fluid and water samples

The present work reports the development and application of a new electrochemical sensor for the determination of low concentration levels of p-toluenediamine (PTD) in biological fluids and surface water samples. The proposed sensor was developed using a 3D-printed magnetic device as platform for carbon screen printed electrode (CSPE) modified by magnetic nanoparticles functionalized with carboxylic groups and l-cysteine (MNP-CA-CYS). The results obtained from the morphological and electrochemical characterizations of the sensing platform enabled us to confirm the success of the sensor functionalization with l-cysteine and to have a better understanding of the electrochemical behavior and preconcentration of PTD on the electrode surface. PTD oxidation occurred at 0.24V on MNP-CA-CYS and the mechanism recorded an increase of 51.0% in anodic peak current. Under optimized conditions, the square wave voltammograms obtained for the electrode modified by 40.0 μL MNP-CA-CYS suspension at 1.0 mg mL−1, with accumulation time of 3 min, presented an analytical curve with linear range of 8.00 × 10−7 to 8.00 × 10−5 mol L−1, represented by the equation Iap = (0.383 ± 0.011)[PTD] - (8.112 ± 0.07) × 10−8 (R2 = 0.9994), and detection and quantification limits of 8.53 × 10−8 and 2.56 × 10−7 mol L−1, respectively. Finally, the proposed method was validated through comparison with high performance liquid chromatography coupled to diode array detector (HPLC-DAD) technique and was successfully applied for PTD determination in samples of surface water, tap water, fetal bovine serum and artificial urine.

Sn-Doping in a Sb2Se3 Conversion-cum-Alloying Material Renders Efficient Sodium-Ion Electrochemical Performance: Facile Kinetics Achieved by Active Metal Doping

Conversion-cum-alloying anode materials have particularly been sought after as promising high-capacity Na+ anode materials owing to a double redox alkali-ion uptake offered by them. The addition of electrochemically nonactive conducting additives to enhance the sluggish kinetics of the conversion/deconversion step although instrumental in enhancing the kinetics ends up in a considerable decline in electrochemical capacity. Herein, we demonstrate an alternative strategy of doping an ultra-active Sn element in the well-known conversion-cum-alloying Na+ battery anode, Sb2Se3. The Sn-doped Sb2Se3 phase, Sn0.2Sb1.8Se3, besides depicting an enhanced capacity (reversible capacity of 520 mA h g–1) and cyclic stability, delivered an excellently improved rate performance (360 mA h g–1 at a current of 500 mA g–1) in comparison to pristine Sb2Se3 which delivers a capacity of 45 mA h g–1 at the same current density. Electrochemical techniques such as cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) lend support to improved kinetics of the conversion/deconversion process. The enhanced kinetics reflects in larger anodic peak currents (147 mA g–1 for Sn0.2Sb1.8Se3 against 32 mA g–1 for Sb2Se3) in CV plots and reduced charge-transfer resistance (RCT of 350 Ω for Sn0.2Sb1.8Se3 against 670 Ω for Sb2Se3) in EIS measurements. The electrochemical galvanostatic intermittent titration technique reveals a 3-order-magnitude increase in the diffusion coefficients (2.02 × 10–14–6.6 × 10–11 cm2 s–1) in the Sn0.2Sb1.8Se3 in comparison to pristine Sb2Se3 (2.5 × 10–17–4.2 × 10–14 cm2 s–1).

Sensitive and selective determination of vanillin in the presence of dopamine and uric acid using low-cost and trouble-free pencil graphite electrode modified with methyl orange

A simple, low-cost, and trouble-free electrochemical sensor has been developed by electropolymerization of methyl orange (MO) on a pencil graphite electrode (PGE) for the selective and sensitive voltammetric investigation of vanillin (VNL). Surface morphology of poly (methyl orange) modified pencil graphite electrode (poly (MO)/PGE) and bare pencil graphite electrode (BPGE) were examined by scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDX) and electron impedance spectroscopy (EIS). The poly (MO)/PGE shows good electrocatalytic activity over BPGE which was assessed by linear sweep voltammetry (LSV), cyclic voltammetry (CV) and differential pulse voltammetry (DPV) in phosphate buffer solution (PBS). Under optimized conditions, the anodic peak current of the analyte was directly proportional to the concentration of the analyte (1.0–26.0 μM) with the limit of detection (LOD) 0.10 μM. Various parameters like heterogeneous rate constant (k0 = 1.13 × 10−9 cm s−1), number of electrons transferred, and surface concentration (Γ = 4.85 × 10-11 mol cm−2) were calculated. The analytical applicability and selectivity of the modified sensor were deliberated by real sample analysis of VNL in presence of dopamine (DA) and uric acid (UA). Thus, a developed electrochemical sensor could be successfully employed for the analysis of VNL present in real samples.

Highly sensitive molecularly imprinted polymer-based electrochemical sensor for voltammetric determination of Adenine and Guanine in real samples using gold screen-printed electrode

Novel screen-printed gold electrodes (AuSPE) modified with molecularly imprinted (MIP) polyphenol were fabricated to detection of guanine (GU) and Adenine (AD) in the presence of each other species. The electrochemical polymerization method in the presence of specific analyte (GU or AD) as template molecules was used for synthesize of MIP thin layer on AuSPE surface. To investigate the effect of the presence of a molecular template in the surface layer via the produce of binding sites, MIP electrodes were compared with non-imprinted (NIP) electrodes. The fabricated MIP sensors (GU-MIP-AuSPE and AD-MIP-AuSPE) were used in the detection of GU and AD by differential pulse voltammetry (DPV) in 0.1 M phosphate buffer solution at pH 7.0 as optimized pH. Anodic peak currents for AD and GU show two linearity intervals in the range of 5 to 50 nM and 50 to 500 nM for GU and 5 to 50 nM and 50 to 700 nM for AD. Also, the values of limit of detection (LOD = 3Sb/m) and the limit of quantification (LOQ = 10Sb/m) were calculated as 0.37 × 10−9 M and 1.25 × 10−9 M for GU and 0.24 × 10−9 M and 0.80 × 10−9 M for AD, respectively. On the other hand, he fabricated MIP sensors exhibited high sensitivity, good repeatability and long-term stability. The MIP sensors were successfully utilized for the measurement of GU and AD in real human serum samples.

Electrochemical detection of methyl parathion using calix[6]arene/bismuth ferrite/multiwall carbon nanotube-modified fluorine-doped tin oxide electrode.

A highly sensitive electrochemical sensor using a calix[6]arene/bismuth ferrite/multiwall carbon nanotube-modified fluorine-doped tin oxide electrode (CA6/BFO/MWCNTs/FTO) was fabricated for the detection of methyl parathion. The MWCNTs, BFO, and CA6 were consecutively cast onto the FTO electrode surface to enhance the surface area, electron transfer, and selectivity of sensors. The electrochemical behavior of CA6/BFO/MWCNTs/FTO was studied via cyclic voltammetry and electrochemical impedance spectroscopy. MP was detected via cyclic voltammetry in a phosphate buffer solution at pH 7.0. The working principle of the sensor involves a linear decrease in the anodic peak current of BFO with increasing MP concentration. The linear working ranges are 0.005-0.05nM and 0.07-1.5nM. The CA6/BFO/MWCNTs/FTO sensor provides a low detection limit (S/N = 3) of 5pM and a high electrochemical sensitivity of 1.23 A μM-1cm-2. The fabricated sensor was successfully applied to assess the presence and amount of MP in vegetables and fruits (recoveries of 82.0-106.8%), with results comparable to high-performance liquid chromatography.