Surface Of Carbon Electrode Research Articles

Scenedesmus sp. MN738556 as a whole cell biosensor for sub-part per billion detections of Cd2+ cations in freshwater sources

Recent increases in human activity and contamination of the marine environment have led to the advent of biosensors as sensitive, easy-to-operate, and rapid devices for water pollution screening. In the present study, a whole-cell electrochemical biosensor based on the native green microalgae Scenedesmus sp. MN738556 was developed, for the first time, to assess the biotoxicity of Cd2+ ions in freshwater. This electrochemical biosensor was constructed by immobilization of microalgae-BSA film on a glassy carbon electrode surface. The biosensor responses were based on chronoamperometric currents generated by alkaline phosphatase (ALP) activity. Since Cd2+ ions have an inhibition effect on ALP, the reduction in the general current can be used to determine the toxicity degree of these ions. The feasibility was evaluated and the application of the biosensor was optimized for parameters such as pH and cell density. The sensitivity of the biosensor was verified through the IC50 value of 0.26 ppb for Cd2+cation with the LOD of 0.1 ppb at pH 8.5 and 107 cells/mL. These values are practical for natural water environment monitoring based on the World Health Organization limit (3 ppb for Cd2+ ions in drinking water). The selectivity of the fabricated biosensor was investigated in binary mixtures of other divalent cations such as Zn2+, Ni2+, Cu2±, and Hg2+ at 1:1 and 1:10 ratios. The results indicated that the fabricated Scenedesmus biosensor is highly sensitive with a good selectivity at a 1:1 ratio for measuring the concentration of Cd2+ cations except in the presence of Hg2+. Moreover, this biosensor could respond with only one drop of an analyte (50 μL of 1000 ppb Cd2+ ions), resulting in suitability for simple and on-site water toxicity testing. Finally, two real freshwater samples were selected to prove the reliability, reproducibility, and performance of the Scenedesmus biosensor for the detection of Cd2+ cations discharges in the aquatic environment.

Electrodeposition of CoFeS nanoflakes on Cu2O nanospheres as an ultrasensitive sensing platform for measurement of the hydrazine and hydrogen peroxide in seawater sample

Nanoarchitectured design of the metal sulfides with highly available surface and abundant electroactive centers and using them as electrocatalyst for fabricate the electrochemical sensors for the detection of hydrazine (N2H4) and hydrogen peroxide (H2O2) is challenging and desirable. Herein, Cu2O nanospheres powder is firstly prepared using chemical reduction of copper chloride and then drop-casted on the glassy carbon electrode (GCE) surface. In the next step, CoFeS nanoflakes are electrodeposited on Cu2O nanospheres by cyclic voltammetry method to form CoFeS/Cu2O nanocomposite as a detection platform for measuring N2H4 and H2O2. Accordingly, Cu2O nanospheres are not only used as substrate, but also guided the CoFeS nanoflakes to adhere to the electrode surface without need to any binder or conductive additive, which enhances the electrical conductivity of the sensing active materials. As the hydrazine sensor, the CoFeS/Cu2O/GCE displayed wide linear ranges (0.0001–0.021 mM and 0.021–1.771 mM), low detection limit (0.12 μM), very high sensitivities (103.33 and 21.23 mA mM−1 cm−2), and excellent selectivity. The as-made nanocomposite also exhibited low detection limit of 1.26 μM for H2O2 sensing with very high sensitivities (12.31 and 3.96 mA mM−1 cm−2) for linear ranges of 0.001–0.03 mM and 0.03–2.03 mM, respectively, and negligible response against interfering substances. The superior analytical performance of the CoFeS/Cu2O for N2H4 electro-oxidation and H2O2 electro-reduction can be attributed to structure stability, high electroactive surface area, and good availability to analyte species and electrolyte diffusion. Moreover, to examine the potency of the prepared nanocomposite in real applications, the seawater sample was analyzed and results display that the CoFeS/Cu2O/GCE can be utilized as a reliable and applicable platform for measuring N2H4 and H2O2.

Rational design and synthesis of triazene-amonafide derivatives as novel potential antitumor agents causing oxidative damage towards DNA through intercalation mode

In this work, we rationally designed and synthesized two novel triazene-amonafide derivatives 2-(2-(diisopropylamino)ethyl)-5-(3,3-dimethyltriaz-1-en-1-yl)-1H-benzo[de]isoquinoline-1,3(2H)-dione (D-11) and 5-(3,3-diethyltriaz-1-en-1-yl)-2-(2-(diisopropylamino)ethyl)-1H-benzo[de]isoquinoline-1,3(2H)-dione (D-12) as potential antitumor agents. The DNA damage induced by the intercalation mode of D-11 (D-12) towards DNA was electrochemically detected through the construction of efficient biosensors. The consecutive processes of reversible redox of naphthylimide ring and irreversible oxidation of triazene moiety were elucidated on the surface of glassy carbon electrode (GCE) by CV, SWV, and DPV methods. Electrochemical biosensors were obtained through the immobilization of ctDNA, G-quadruplexes, poly(dG), and poly(dA), respectively, on the clean surface of GCE. After the incubation of biosensors with D-11 or D-12, the peaks of dGuo and dAdo decreased prominently, and the peak of 8-oxoGua appeared at +0.50 V, suggesting that the interaction between D-11 (D-12) and DNA could result in the oxidative damage of guanine. Unexpected, the as-prepared DNA biosensor possessed satisfactory anti-interference property and good practicability in real samples. UV–vis and fluorescence spectra, and gel electrophoresis assays were employed to further confirm the intercalation mode of D-11 (D-12) towards DNA base pairs. Moreover, D-11 was proved to exhibit stronger anti-proliferation activity than mitionafide and amonafide against both A549 and HeLa cell lines.

A facile electrochemical cortisol sensing based on zinc oxide nanostructures for monitoring stress and recovery in high-performance athletes

This work created a simple electrochemical cortisol sensing method based on ZnO nanostructures to track high-performance athletes' stress levels and recuperation times. ZnO nanorods (ZnO NRs) were deposited on the surface of a glassy carbon electrode (ZnO/GCE) using an electrodeposition technique. Subsequently, 3-aminopropyltriethoxysilane (APTES) was applied to the electrode surface in order to improve cortisol antibody (C-M ab) immobilization and stability (C-M ab/APTES/ZnO/GCE). Successful immobilization of C-M ab on APTES/ZnO/GCE and electrodeposition of ZnO NRs on GCE were confirmed by structural investigations conducted using XRD, FT-IR, and FE-SEM. Cortisol was detected using an electrochemical immunosensor (C-M ab/APTES/ZnO/GCE) by monitoring the change in DPV and CV currents following cortisol binding to C-M ab. According to electrochemical experiments, the immunosensor exhibited a steady, selective, and sensitive response when it detected cortisol at concentrations between 10−6 nM and 106 nM, with a detection limit of 2 × 10−4 nM. It was assessed if the C-M ab/APTES/ZnO/GCE combination could identify cortisol in human serum. The samples' relative standard deviation (RSD) values range from 3.63% to 4.30%, and their recovery rates range from 90.00% to 98.50%, according to the analytical study. These findings imply that the C-M ab/APTES/ZnO/GCE offers accurate evaluations for cortisol detection in human serum samples.

Electrochemical Aptasensor for Selective and Sensitive Detection of Staphylococcus aureus Using Graphene oxide/poly Deep Eutectic Solvent/Nickel Oxide Nanocomposite Modified Electrode

AbstractSince that pathogenic bacteria are major threats to human health; this research describes the fabrication of an effective and sensitive platform based on graphene oxide/poly deep eutectic solvent/nickel oxide nano particles (GO/PDES/NiO NPs) nanocomposite at the surface of glassy carbon electrode for selective detection of Staphylococcus aureus (S. aureus). The DNA aptamers were immobilized on the modified electrode through the EDC/NHS chemistry. Each aptasensor modification step was checked by with cyclic voltammetry (CV) and electrochemical impedance spectra (EIS) techniques. The linear dynamic range of the proposed electrochemical aptasensor covered a large variation of S. aureus concentrations from 101 – 108 CFU.mL−1 and a detection limit of 10 CFU.mL−1 under optimum conditions was obtained. Analysis of spiked tap water, lake water and human serum samples revealed high potential of this aptasensor as a sensitive, effective, and label‐free promising tool for S. aureus detection. This is the first time that poly deep eutectic solvents used in live bacteria detection.

Electrochemical sensing of aniline based on bio-inspired cauliflower shaped tin-oxide nanoparticle using Solanum trilobatum leaf extract

The quantitative detection and determination of aniline (AN) in water samples are of significant importance due to its potential to induce adverse effects in humans and other livestock when consumed in excess. Therefore, it is the need of the hour to develop a highly sensitive conductive matrix for the electrochemical detection and quantification of AN in-water samples. In this regard, tin oxide nanoparticles (SnO2 NPs) were synthesized using Solanum trilobatum leaf extract for the first time. Upon conducting structural analysis of the synthesized SnO2 NPs, aggregates of spherical nanoparticles were observed, resulting in the formation of a cauliflower-like structural morphology. Subsequently, the cauliflower-shaped SnO2 nanoparticles were drop-casted onto the surface of a screen-printed carbon electrode using nafion as a binder, thereby developing an electrochemical sensing platform for the detection of AN. Later, differential pulse voltammetry technique was employed to detect AN over a concentration range of 2.0–14.0 nM, with a limit of detection of 0.897 nM based on the signal-to-noise ratio (S/N = 3). Importantly, the sensing of AN remained unaffected by tested interfering species from various pollutants, as confirmed by recovery values (99.2–101.0%) in water samples. These results collectively demonstrate that the newly designed sensor exhibits good selectivity, sensitivity, and reproducibility for the detection of AN.

An AuNPs-based electrochemical aptasensor for the detection of 25-hydroxy vitamin D3.

Vitamin D3 (VD3) is the main form of vitamin D and an essential nutrient for maintaining human life. Currently, traditional methods for detecting 25-hydroxyvitamin D3(25(OH)D3) are complex and expensive. In this study, we constructed an accurate, sensitive, simple, and cost-effective label-free biosensor based on an aptamer for the detection of 25(OH)D3. The aptamer-modified sulfhydryl adopted self-assembly as a way to stably immobilize at the glassy carbon electrode (GCE) surface modified by gold nanoparticles (AuNPs). Upon 25(OH)D3 binding to the aptamer, the complexes inhibit electron transfer at the electrode surface, leading to reduced [Fe(CN)6]3-/4- redox peak current. Consequently, the quantity of 25(OH)D3 that interacts with the electrode-bound aptamer correlates with the observed electric current response values. The Aptamer/AuNPs/GCE aptasensor achieved direct and highly sensitive detection of 25(OH)D3 over a wide concentration range (1.0-1000nM), with a limit of detection of 1.0nM. At the same time, other molecules with a similar structure, such as 25(OH)D2, Vitamin D3, and Vitamin D2, had lower response interference than 25(OH)D3. Therefore, this biosensor has great potential to become a portable diagnostic device for 25(OH)D3.

Hydrothermal synthesis of MnO2 nanorods for efficient electrochemical detection of environmental anthropogenic pollutants and nitrobenzene

Glassy carbon (GC) electrodes are fabricated with nanoscale manganese dioxide (MnO2) rods for efficient detection of the toxic anthropogenic pollutant and nitrobenzene (NB) in real water. The MnO2 nanorods were prepared using a hydrothermal method. Its structure and morphology were characterized by X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), and Transmission Electron Microscopy (TEM). In this study, MnO2 nanorods were used to modify a glassy carbon (MnO2/GCE) electrode surface. The electrode was optimized and developed as an electrochemical detector under different experimental conditions to obtain good sensitivity and selectivity. It has shown excellent electrocatalytic activity for the reduction of NB to phenylhydroxylamine as a product. The calibration plots from the observed data of the differential pulse voltametric technique between the linear range of 0.03 µM–2 µM with a detection limit of 0.025 μM displayed the high stability and reproducibility as well as the detection of NB in the real water sample.

Nanoflower MoS2/rGO composite rich in edge defects for enhanced electrochemical sensing of nM-level dopamine

The development of electrochemical dopamine (DA) sensor with anti-interfering ascorbic acid and uric acid is challenging due to the presence of their overlapping electrical signals. Herein, MoS2 nanoflower assembled from ultrathin nanosheets were uniformly loaded on rGO substrate through one-step hydrothermal reaction. Then, the composite (MoS2/rGO) was modified on the surface of glassy carbon electrode (GCE) by a drop coating method, successfully assembling non-enzymatic electrochemical sensor for ultra-selective DA detection. The test results show that the MoS2/rGO/GCE probe exhibits good sensitivity (15.73 μA μM−1 cm−2), small limit of detection (13 nM) and wide range of detection (0.1 ∼ 110.0 μM) for DA in 0.1 M PBS medium (pH = 7.4), as well as good interference resistance, reproducibility and stability. This excellent sensing ability mainly stems from the synergistic effect of the prepared electrode material with abundant edge defects, small charge transfer resistance, large electrochemically active area, and more negative Zeta potential (–23.4 mV). Furthermore, the satisfactory and accurate detection of DA content in animal serums predicts its potential for practical applications in related biological aspects.

Electroless Deposition of Gold on a Glassy Carbon Electrode (GCE) Surface for Selective Detection of Hydrogen Peroxide

AbstractElectroless deposition technique was employed to coat the surface of a glassy carbon electrode (GCE) with nanoparticles of gold (AuNPs). Afterward, sulfur (S) components were immobilized onto this AuNPs/GC electrode via an in‐situ chemisorption approach that considerably enhanced the catalytic activity, conductivity, and persistent durability of the electrode. Scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and X‐ray photoelectron spectroscopy (XPS) were used to characterize the modified electrode surface. The experimental results indicated that the S−AuNPs/GC electrode exhibits outstanding catalytic activity for the selective detection of H2O2 (HP). SWV measurements showed that the electrochemical sensor has a wide linear range of 10 to 2500 μM and a heightened sensitivity of 50.08 μA mM−1 cm−2. The proposed HP sensor demonstrated adequate repeatability and durability, as well as interference‐free quantitative analysis capability.

Highly sensitive electrochemical biosensor for MUC1 detection based on DNA-functionalized CdTe quantum dots as signal enhancers.

In this paper, an electrochemical biosensor based on a cadmium telluride/polypyrrole (CdTe/PPy) nanocomposite was developed for the detection of MUC1 with high selectivity and sensitivity. Results indicate that the CdTe/PPy nanocomposite is modified on the surface of the glassy carbon electrode (GCE), which affords a large surface area for immobilizing cap-DNA, ensuring its high selectivity and sensitivity. Next, CdTe-linked sig-DNA (MUC1 aptamer) was introduced, allowing the MUC1 aptamer to hybridize with cap-DNA. CdTe is a signal amplification element used to generate a differential pulse voltammetry (DPV) signal. Conceivably, target MUC1 detection was based on current signal change due to concentration change in the signal amplification element CdTe. In the presence of MUC1, the MUC1 aptamer specifically binds to MUC1, resulting in the release of CdTe-sig-DNA from the electrode surface and a decrease in peak current. Under optimized experimental conditions, the electrochemical biosensor is highly selective, sensitive, stable, and reproducible for MUC1 ranging from 0.1 nM to 100 nM with a detection limit of 0.05 nM (S/N = 3). Therefore, the electrochemical biosensor has potential applications in medical disease diagnosis.

Electrochemical sensors based on the composite of reduced graphene oxide and a multiwalled carbon nanotube-modified glassy carbon electrode for simultaneous detection of hydroquinone, dopamine, and uric acid.

Using a simple drop-casting technique, we successfully fabricated a sensitive electrochemical sensor based on the composite of reduced graphene oxide (RGO) and multiwalled carbon nanotubes (MWCNT) deposited on the surface of a glassy carbon electrode (GCE) for individual and simultaneous measurements of hydroquinone (HQ), dopamine (DA), and uric acid (UA). The nanocomposite of RGO/MWCNT was further characterized in terms of its structural properties, surface morphology, and topography using Raman, FT-IR spectroscopy, SEM, HRTEM, and AFM. Then, the proposed sensor for simultaneous measurement of HQ, DA, and UA based on RGO/MWCNT-modified GCE was investigated for its electrochemical behavior and electroanalytical performances using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS), and differential pulse voltammetry (DPV). In addition, the composition ratio between RGO and MWCT was 1 : 1 showing the highest electrochemical response for simultaneous detection of HQ, DA, and UA. Owing to the synergistic effect between RGO and MWCNT leading to excellent conductivity properties, the proposed sensor exhibited improved electrochemical response at pH 7 toward the oxidation processes of HQ, DA, and UA on the surface of modified electrode. The proposed sensor demonstrated three well-defined anodic peaks of these analytes with their linear concentrations ranges of 3.0-150.0 μM for HQ, 4.0-100.0 μM for DA, and 2.0-70.0 μM for UA. The limit of detection values for the simultaneous detection of HQ, DA, and UA were found as follows 0.400 ± 0.014, 0.500 ± 0.006, and 0.300 ± 0.016 μM, respectively. The additional features of this proposed sensor are high reproducibility and stability for the simultaneous detection of HQ, DA, and UA with negligible interference effect from interferents such as Mg2+, K+, Cl-, ascorbic acid, and glucose. An acceptable percentage of recovery was also shown by this sensor for simultaneous measurements of HQ, DA, and UA using 6 samples of human urine. In summary, the RGO/MWCNT nanocomposite has been shown to be a promising platform for rapid, simple, and reliable determination of simultaneous measurements of HQ, DA, and UA in practical applications.

An electrochemical aptasensor based on silver-thiolated graphene for highly sensitive detection of Pb2.

The presence of lead ions (Pb2+) in the environment not only leads to environmental contamination but also poses a significant risk to public health through their migration into food and drinking water. Therefore, the development of rapid and effective techniques for detection of trace amounts of Pb2+ is crucial for safeguarding both the environment and biosafety. In this study, an aptamer-based electrochemical sensor was developed for specific detection of Pb2+ by modifying a polylysine (PLL) coated silver-thiolated graphene (Ag-SH-G) nanocomposite (PLL/Ag-SH-G) on the surface of a glassy carbon electrode, which was further modified with gold nanoparticles (AuNPs) for attachment of aptamers (Apt) that specifically recognized Pb2+. The Ag-SH-G particles were synthesized using a one-step in situ method, resulting in significantly enhanced electrochemical properties upon incorporating Ag nanoparticles into the PLL/Ag-SH-G composite. Coating of the covalently or no-covalently bonded Ag-SH-G particles with PLL provides an excellent supporting matrix, facilitating the assembly of AuNPs and a thiol-modified aptamer for Pb2+. Under optimized conditions, Apt/AuNPs/PLL/Ag-SH-G/GCE exhibited excellent sensing performance for Pb2+ with a wide linear response range (10-1000 nM), a low detection limit (0.047 nM) and extraordinary selectivity. The sensor was employed and satisfactory results were obtained in river water, soil and vegetable samples for the detection of Pb2+.

Degradation and detection of organophosphorus pesticides based on peptides and MXene-peptide composite materials.

Safety problems caused by organophosphorus pesticide (OP) residues are constantly occurring, so the development of new methods for the degradation and detection of OPs is of great scientific significance. In the present study, β-sheet peptides and β-hairpin peptides for catalyzing the hydrolysis of OPs were designed and synthesized. The peptide sequences with the highest hydrolytic activity (EHSGGVTVDPPLTVEHSAG) were screened by investigating the effect of the location of the active sites of the peptide and the peptide's structure on the degradation of OPs. In addition, the relationship between the peptides' conformation and hydrolytic activity was further analyzed based on density functional theory calculations. The noncovalent interactions of the peptides with the OPs and the electrostatic potential on the molecular surface and molecular docking properties were also investigated. It was found that peptides with approximate active amino acids consisting of the catalytic triad and with the hairpin structure had enhanced hydrolytic activity toward the hydrolysis of OPs. To develop an electrochemical sensor technique to detect OPs, the conductive MXene (Ti3C2) material was first immobilized with a caffeic acid monolayer via enediol-metal complex chemistry and then bound with the β-hairpin peptide (EHSGGVTVDPPLTVEHSAG) via carboxy-amine condensation chemistry between the -COOH of caffeic acid and the -NH2 of the peptide to prepare a MXene-peptide composite. Then, the prepared composite was modified on the surface of a glassy carbon electrode to construct an electrochemical sensor for the detection of OPs. The developed technique could be used to monitor OPs within 15 min with a two orders of linear working range and with a detection limit of 0.15 μM. Meanwhile, the sensor showed good reliability for the detection of OPs in real vegetables.

A NiO-nanostructure-based electrochemical sensor functionalized with supramolecular structures for the ultra-sensitive detection of the endocrine disruptor bisphenol S in an aquatic environment.

Herein, NiO nanoparticles (NPs) functionalized with a para-hexanitrocalix[6]arene derivative (p-HNC6/NiO) were synthesized by using a facile method and applied as a selective electrochemical sensor for the determination of bisphenol S (BPS) in real samples. Moreover, the functional interactions, phase purities, surface morphologies and elemental compositions of the synthesized p-HNC6/NiO NPs were investigated via advanced analytical tools, such as Fourier-transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and energy dispersive X-ray spectroscopy (EDX). Additionally, the synthesized p-HNC6/NiO NPs were cast on the surface of a bare glassy carbon electrode (GCE) via a drop casting method, which resulted in uniform deposition of p-HNC6/NiO/GCE over the surface of the GCE. Additionally, the developed p-HNC6/NiO/GCE sensor demonstrated an outstanding electrochemical response to BPS under optimized conditions, including a supporting electrolyte, a Briton-Robinson buffer electrolyte at pH 4, a scan rate of 110 mV s-1 and a potential window of between -0.2 and 1.0 V. The wide linear dynamic range was optimized to 0.8-70 μM to obtain a brilliant linear calibration curve for BPS. The limit of detection (LOD) and limit of quantification (LOQ) of the developed sensor were estimated to be 0.0059 and 0.019 μM, respectively, which are lower than those of reported sensors for BPS. The feasibility of the developed method was successfully assessed by analyzing the content of BPS in waste water samples, and good recoveries were achieved.

Development of an efficient electrochemical sensing platform based on ter-poly(luminol-o-anisidine-o-toluidine)/ZnO/GNPs nanocomposites for the detection of antimony (Sb3+) ions.

A poly(luminol-o-anisidine-o-toluidine) terpolymer was synthesized, characterized, and modified with GNPs and ZnO NPs. The nanocomposites were then examined for their electroactivity and potential use as cationic electrochemical sensors for detecting Sb3+ ions in phosphate buffer on the surface of a glassy carbon electrode (GCE). Among the different compositions and the terpolymer, the GCE adapted with the PLAT/ZnO/GNPs-5% nanocomposite displayed the highest current response. The fabricated nanocomposite sensor exhibited high sensitivity, with a value of 21.4177 μA μM-1 cm-2, and a low detection limit of 95.42 pM. The analytical performance of the sensor was evaluated over the linear dynamic range (LDR) of 0.1 nM to 0.01 mM. The proposed sensor is effective in detecting and measuring carcinogenic Sb3+ ions in real environmental samples using an electrochemical approach, making it a promising tool for environmental monitoring.

Chemometrically assisted differential pulse voltammetry for simultaneous and interference-free quantification of gallic and caffeic acids.

This article explores the application of chemometric tools including multivariate curve resolution with alternating least squares for the simultaneous determination of gallic and caffeic acids on the surface of a glassy carbon electrode without additional modification. Gallic and caffeic acids are primary polyphenols, the most abundant in red wines produced in Argentina, and are often used as quality markers for them. These polyphenols significantly contribute to the organoleptic properties of wines from this origin, but their electrochemical signals overlap significantly, making simultaneous quantification challenging without additional experiments such as electrode modification or alternative analytical techniques beyond differential pulse voltammetry. This study successfully quantified these compounds in complex mixtures by generating second-order data from differential pulse voltammetry experiments conducted at various potential steps and subsequently applying multivariate curve resolution with alternating least squares. The use of constraints during optimization prevented rotational ambiguities common in this modeling, leading to unique results in validation samples. The limits of detection (LOD) found for gallic and caffeic acids were 1.6 and 7.6 mg L-1, which are in excellent agreement with the expected concentrations of these compounds in red wines. The concentration ranges analyzed showed a linear dependency (between the LOD and 300 mg L-1) with the signals estimated by the model for both analytes. Advantages such as simplicity, low cost, and high speed, as well as not requiring electrode modification, combined with excellent results obtained for real samples, make it a promising alternative for polyphenol analysis in the wine industry.

Determination of tetracycline in honey by flow-injection amperometry on an electrode modified with gold and palladium particles, and reduced graphene oxide

A method of immobilizing Au–Pd binary system on a glassy carbon (GC) electrode surface covered by reduced graphene oxide (GOred) was developed. Using GOred as a matrix for inclusion of Au–Pd binary system resulted in significant increase of its catalytic activity in tetracycline (TC) electro-oxidation process due to increased dispersion of the deposit and formation of nano-sized metal particles (average diameter of particles was around 50 nm). Optimal conditions of immobilizing Au–Pd binary system for achieving maximum electrocatalytic effect were determined. A possibility of amperometric detection of TC on GC modified with Au–Pd and GOred composite (Au–Pd–GOred–GC) by flow injection analysis (FIA) was demonstrated. The method demonstrated high sensitivity (the lowest detection limit of 5 nM), rapidity and efficiency (about 60 samples per hour). The flow injection amperometric method for TC determination hereby developed was tested in analyzing flower honey samples from different Volga Region districts.

Nanosheet like Ni-MOFs/MWCNTs Composite Synthesis: Application to Trace Level Dopamine Measurement

Nanosheet like nickel metal organic frameworks (Ni-MOFs) have been synthesized using solvothermal route at room temperature. Functionalized multiwalled carbon nanotubes (MWCNTs) have been embedded into these MOFs through equilibration to prepare the composite. The composite (Ni-MOFs/MWCNTs) has been used as a modifier in sensor fabrication on glassy carbon electrode surface and successfully applied in dopamine measurement through cyclic voltammetry and square wave voltammetry techniques. The composite has exhibited enhanced electrochemical performance with a very low detection limit of 0.017 μM. The protocol showed wide linearity in the concentration range 2–200 μM with a sensitivity of 17.14 μAμM−1cm−2. The proposed electrochemical platform exhibited high sensitivity and selectivity in dopamine sensing which has been successfully applied to real sample matrices like human blood serum and injection.

Development of a facile electrochemical sensor based on GCE modified with one-step prepared PNMA-CeO2-fMWCNTs composite for simultaneous detection of UA and 5-FU.

In this study, a poly(N-methyl aniline)-cerium oxide-functionalized MWCNTs (PNMA-CeO2-fMWCNTs) composite was synthesized in a one-step preparation technique. As a highly efficient modifier, the composite was used to modify the glassy carbon electrode surface for simultaneous detection of uric acid (UA) and 5-fluorouracil (5-FU). Morphological characterization of the GCE/PNMA-CeO2-fMWCNTs was studied using scanning electron microscopy. Structural characterization of the composite was performed using X-ray diffraction and Fourier-transformed infrared spectroscopy. Electron transfer properties of the prepared electrodes were carried out with electrochemical impedance spectroscopy and cyclic voltammetry. The linear working range for UA and 5-FU was found to be 0.25-50 μM and 0.5-750 μM, respectively. The limit of detection values for UA and 5-FU were 0.04 μM and 0.19 μM, respectively. The effects of various interfering substances on the electrochemical response of UA and 5-FU were investigated. The GCE/PNMA-CeO2-fMWCNTs sensor has excellent stability, reproducibility, anti-interference ability, and reproducibility. To demonstrate the practical application of the sensing platform, fetal bovine serum was selected and tested in the spiked samples, and satisfactory results were obtained. The prepared composite proved to be a promising platform for simple, rapid, and simultaneous analysis of UA and 5-FU.