Surface Of Glassy Carbon Electrode Research Articles

Molecularly imprinted nanoparticles doped graphene oxide based electrochemical platform for highly sensitive and selective detection of L-tyrosine

A highly sensitive and selective electrochemical sensor was developed using a surface modified glassy carbon electrode (GCE) through molecularly imprinted polymerization on the surface of vinyltrimethoxysilane (VTMS) coated magnetic nanoparticle (Fe3O4) decorated silver nanoparticles incorporated graphene oxide, GO (VTMS-Fe3O4/AgGO) for L- Tyrosine (Tyr) detection. A molecular imprinting technique based on free radical polymerization was applied to synthesize molecularly imprinted Methacrylic acid (MAA) and Acrylamide (AA) grafted VTMS-Fe3O4/AgGO polymer (MAA/AA-g- VTMS-Fe3O4/AgGO) designated as MIP and non-imprinted polymer (NIP). The structure and morphology of the prepared polymers were FTIR, XRD, FE-SEM and VSM. MIP and NIP were chosen for modifying the GCE surface by drop casting process to construct the sensors and their electrochemical properties were characterized via EIS and CV. Compared with NIP/GCE sensor, MIP /GCE sensor exhibits excellent sensing response towards Tyr with a wide linear range of 0.25 × 10−13 M to 0.10 × 10−3 M and the limit of detection and limit of quantification as 0.15 × 10−13 M and 0.50 × 10−13 M, respectively with R2 value of 0.9934 by DPV technique. Moreover, MIP/GCE sensor exhibits long-time storage, excellent selectivity and good stability in multiple cycle usage. The practical applicability of MIP/GCE sensor was tested in human blood serum sample. The recovery percentage was obtained between 98.8% and 106.0% with a relative standard deviation (RSD) between 1.01% and 1.59%. Results of the investigations revealed the clinical applicability of the MIP/GCE sensor.

Electrochemical Sensor Based on N–Doped Carbon Nanodots Derived from the Agro-Waste Cotton Boll Peel Extracts for Nano Molar Determination of an Anti-Cancer Drug, Pemetrexed

A green and facile one-step synthetic route was proposed for the synthesis of nitrogen-doped carbon nanodots (N-CDs) from agro-waste cotton boll peel extract as a natural carbon source and glycine as a nitrogen source. The prepared N-CDs were utilized further in the fabrication of an electrochemical sensor for the nanomolar determination of an anti-cancer drug, pemetrexed (PMT). The electrode material was characterized by XRD, FTIR, TEM, Raman, EDX, UV–vis, fluorescence, cyclic voltammetric and electrochemical impedance spectroscopic studies. The N-CDs drop-casted on the surface of glassy carbon electrode (GCE) served as a good sensing material and exhibited electrocatalytic activity as evident from ∼20-fold enhancement in the oxidation peak current of PMT at N-CDs/GCE with 130 mV lesser positive oxidation peak potential than that at bare GCE. This was attributed to excellent conductivity, higher electroactive surface area, graphitic cores of N-CDs besides the interactions between PMT and N-CDs via hydrogen bonding and π–π stacking. The sensing performance of the demonstrated electrode was optimized by varying the peak current dependant parameters and also by investigating the influence of interfering substances in the determination of PMT. The electrochemical behaviour of PMT at different pH revealed the adsorption controlled electrode process with the involvement of protons. Under optimized conditions, differential pulse voltammetric (DPV), square wave voltammetric (SWV) and adsorptive differential pulse voltammetric (AdSDPV) methods were developed for sensitive determination of PMT at nano molar level. Further, these developed analytical methods were applied successfully for the determination of PMT in analyte fortified human urine samples and pharmaceutical formulations.

A-082 Measuring Peroxynitrite as an Early Biomarker for Cystic Fibrosis Using Organoselenide-Modified Glassy Carbon Electrode

Abstract Background Cystic fibrosis (CF) is a genetic disease that affects the respiratory, digestive, and reproductive systems. One of the issues associated with CF is oxidative stress, which is an imbalance between the production of reactive oxygen species (ROS) and the ability of the body to neutralize them. Peroxynitrite, a member of ROS, is a very noxious molecule formed from the reaction of nitric oxide (NO) and superoxide and can damage cellular components such as proteins, lipids, and DNA. Studies have shown that peroxynitrite levels are elevated in people with CF and that this increased oxidative stress can contribute to the development of lung damage, airway obstruction, and other symptoms associated with the disease. Therefore, understanding the role of peroxynitrite in the pathogenesis of CF is important for developing new therapeutic strategies to reduce oxidative stress and improve the quality of life for people with this disease. Methods In this study, we have quantified peroxynitrite levels, which could serve as an early biomarker for CF. A modified glassy carbon electrode (GCE) with a series of organoselenide compounds was adopted using the electro-grafting method to measure peroxynitrite levels in situ. Scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX) were used to examine the structure and surface chemistry of organoselenide. Quartz Crystal Microbalance (QCM) analysis was used to determine the thickness of the electrodeposited selenium on the GCE surface. Results Our organoslenide GCE allowed for the application of low positive potential, which enhances the separation of peroxynitrite from other analytes sensitive to higher potentials. Cyclic voltammetry and amperometry showed sensitivity at 110 nA/mol, and the detection limit was recorded at 10 micromolar. This electrochemical technique of our modified electrodes can be miniaturized to detect peroxynitrite at the cell line. The sensitive probe, which was constructed, can be utilized to target the ratiometric changes in several lung slices, from healthy to lung inflammation and cystic fibrosis, via peroxynitrite fluctuation. In addition, ratiometric alterations and the prevalence of cystic fibrosis have a strong linear association, resulting in good potential in predicting the progression of cystic fibrosis in the early stage and improving effective treatment. Conclusion The study aimed to quantify peroxynitrite levels in cystic fibrosis (CF) patients as a potential early biomarker for the disease. We have used a modified glassy carbon electrode with organoselenide compounds and adopted an electro-grafting method to measure peroxynitrite levels. The modified electrodes showed sensitivity and a limit of detection of 10 micromolar, which can be miniaturized to detect peroxynitrite in the cell line. The results suggest that peroxynitrite’s sensors could serve as an early biomarker for CF by understanding its role in the pathogenesis, which can improve the quality of life for people with this disease.

Application of Pt@ZIF-8 nanocomposite-based electrochemical biosensor for sensitive diagnosis of tau protein in Alzheimer’s disease patients

Alzheimer’s disease (AD) is a progressive brain disorder characterized by the ongoing decline of brain functions. Studies have revealed the detrimental effects of hyperphosphorylated tau (p-tau) protein fibrils in AD pathogenesis, highlighting the importance of this factor in the early-stage detection of AD conditions. We designed an electrochemical immunosensor for quantitative detection of the cis conformation of the p-tau protein (cis-p-tau) employing platinum nanoparticles (Pt NPs) supported on zeolitic imidazolate frameworks (ZIF) for modifying the glassy carbon electrode (GCE) surface. Under optimum conditions, the immunosensor selectively and sensitively detected cis-p-tau within the broad linear range of 1 fg mL−1 to 10 ng mL−1 and the low limit of detection (LOD) of 1 fg mL−1 with desired reproducibility and stability. Furthermore, the fabricated immunosensor's performance was examined for the cis-p-tau analysis in the serum of AD patients, indicating its accuracy and feasibility for real-sample analysis. Notably, this is the first application of Pt@ZIF-8 nanocomposite in fabricating a valid immunosensor for selective cis-p-tau detection, even in the presence of trans-p-tau. It is worth mentioning that the enzyme-linked immunosorbent assay (ELISA) reference technique is not able to evaluate pico- or femtomolar concentrations of cis-p-tau, making the fabricated immunosensor superior for early-stage measurement and screening of AD.

Preparation of voltammetric sensors for taurine detection from Cu(II)-loaded carbon materials

ABSTRACT. In this study, for the detection of taurine in philological fluids, modified electrodes were prepared from glassy carbon electrodes with MWCNT (multi-wall carbon nanotube) + Cu(NO3)2 + carbon-based material. A carbon-based material was obtained by carbonization of Pinus sylvestris branch needles (CPS). Cu(NO3)2 and MWCNT structure (Cu(NO3)2/MWCNT) were added to the carbon-based material and the obtained mixture was used in the modification of the glassy carbon electrode surface. The surface morphology and structure of the prepared electrodes were characterized by electron microscopy scanning (SEM) and atomic force microscopy (AFM). Taurine detection with a modified electrode was made by cyclic voltammetry (CV) in 0.1 M KCl (vs. Ag/AgCl). The calibration curve of the modified electrode for taurine in the 10-150 µM range showed a linear response, and R2 value was 0.976. Limit of detection (LOD) and limit of quantification (LOQ) of the modified electrode were found 19 µM and 9.75 µM, respectively. The application of the electrode as a chemical sensor was carried out with commercially available energy drink samples. Satisfactory results have been obtained from the samples. The sensor can be used for routine taurine analysis. This electrode can quickly determine the amount of taurine in real samples with 90% accuracy in two minutes.
 KEY WORDS: Taurine detection, Modified electrode, MWCNT, Sensor, Cyclic voltammetry
 Bull. Chem. Soc. Ethiop. 2023, 37(6), 1565-1576. DOI: https://dx.doi.org/10.4314/bcse.v37i6.20

An Electrochemical Sensor Based on Cu-MOF-199@MWCNTs Laden with CuNPs for the Sensitive Detection of Creatinine.

In this study, the synthesis of Cu-MOF-199@multiwalled carbon nanotubes (Cu-MOF-199@MWCNTs) composites was achieved and utilized to create an advanced electrochemical sensor for creatinine (Cre) detection. The composites were modified on a glassy carbon electrode surface through direct drip coating, followed by the deposition of copper nanoparticles (CuNPs) via constant potential deposition. Characterized by various techniques and electrochemical analyses, the Cu-MOF-199@MWCNTs composite increased the CuNPs load, improving the detection sensitivity for Cre. Under optimal conditions, the modified electrode exhibited good linearity across a broad range of Cre concentrations (0.05-40.0 μM) with a low detection limit of 11.3 nM. The developed sensor demonstrated remarkable stability, reproducibility, and selectivity, showing promise in sensitive and accurate Cre detection in serum samples.

Non-enzymatic CuCr2O4/GCE amperometric sensor for high sensing and rapid detection of nM level H2O2

Herein, spinel CuCr2O4 nanocrystals with multiple mixed valence states have been synthesized through a sol–gel technique and simply modified on the surface of bare glassy carbon electrode (GCE), which achieved high response of non-enzymatic CuCr2O4/GCE to nM-level H2O2 for the first time. In 0.1 M sodium hydroxide solution, the fabricated CuCr2O4/GCE amperometric sensor exhibited a large sensitivity of 886 μA mM−1 cm−2 to H2O2 during linear detection range of 0.3 μM ∼ 8.1 mM. Meanwhile, its detection limit is as low as 160 nM. This superior electrochemical sensing ability is mainly attributed to the synergism of its relatively large electrode active area, high electric conductivity and valence-mixed Cu/Cr redox couplings. In addition, the modified electrode can also accurately detect traces of H2O2 in milk whey, mouthwash and disinfectant solutions, which in turn has potential applications in the above related fields.

Green synthesis of gallic acid–capped gold nanoparticles as novel electro-catalyst for electro-oxidation of ethylene glycol in alkaline media

This study reports the synthesis of gallic acid–capped gold nanoparticles (GA-AuNPs) through a simple, inexpensive, and environmentally friendly chemical method and their applications in fuel cells. In the proposed method, gallic acid acts as the reducing agent and stabilizer. The studies showed that the size and distribution of AuNPs could be controlled by controlling the molar ratio of gallic acid to gold ions. The prepared GA-AuNPs were used as an electro-catalyst to oxidize ethylene glycol (EG) molecules on the glassy carbon electrode (GCE) surface in alkaline media. The results showed that the modified electrode using GA-AuNPs with a 1:1 M ratio has a higher electrochemical active surface area (ECSA); therefore, it has improved electro-catalytic activity, increased stability, and durability for EG oxidation compared to other ratios of GA/Au and even to the bare Au electrode.

A Comparative Study of Molecular Imprinting Techniques Used for Fabrication of Electrochemical Sensor of Olaparib

This study reported the molecular imprinting process investigated by two techniques: photopolymerization (PP) and thermal polymerization (TP). These techniques were integrated with an electrochemical sensor to determine the new generation anticancer drug Olaparib (OLP), which is a poly(ADP-ribose) polymerase (PARP) inhibitor with high sensitivity and selectivity. The PP-MIP film was formed by PP, while TP-MIP film was formed by TP on a glassy carbon electrode (GCE). In the PP-MIP(OLP)/GCE sensor, which was developed using PP, 4-aminobenzoic acid (4-AB) as a functional monomer was designed, and obtained in the presence of basic monomer (HEMA, 2-hydroxyethyl methacrylate), crosslinker (EGDMA, ethylene glycol dimethacrylate), and initiator (2-hydroxy-2-methyl propiophenone) by keeping it under a UV lamp at 365 nm. For TP-MIP(OLP)/GCE was obtained by using a mixture of 4-AB as a functional monomer, NH3 solution, surfactant sodium dodecyl sulfate (SDS), and tetraethyl orthosilicate (TEOS): ethanol (1:1, v/v) and keeping it in an oven at 50 °C for 40 min. After each process, the GCE surfaces were characterized via scanning electron microscope and electrochemical techniques (cyclic voltammetry and electrochemical impedance spectroscopy). The required optimization studies were performed for both techniques. After obtaining the optimum MIP-integrated electrochemical sensors, the analytical performances of PP-MIP(OLP)/GCE and TP-MIP(OLP)/GCE were evaluated, and the validation parameters were compared. The linear ranges of PP-MIP(OLP)/GCE and TP-MIP(OLP)/GCE are 0.1–1 nM. The PP-MIP(OLP)/GCE and TP-MIP(OLP)/GCE were applied to commercial serum samples and pharmaceutical dosage forms. The selectivity of proposed sensors was also proven using similar structures of OLP through imprinting factor. The results show that the proposed PP-MIP(OLP)/GCE and TP-MIP(OLP)/GCE sensors have good selectivity, high sensitivity, accuracy, and precision. The determination of OLP was achieved with these electrochemical sensors for the first time.

Electrochemical Determination of 17-β-Estradiol Using a Glassy Carbon Electrode Modified with α-Fe2O3 Nanoparticles Supported on Carbon Nanotubes.

In this study, a novel electrochemical assay for determining 17-β-estradiol (E2) was proposed. The approach involves modifying a glassy carbon electrode (GCE) with a nanocomposite consisting of α-Fe2O3 nanoparticles supported on carbon nanotubes (CNTs)-denoted as α-Fe2O3-CNT/GCE. The synthesis of the α-Fe2O3-CNT nanocomposite was achieved through a simple and cost-effective hydrothermal process. Morphological and chemical characterization were conducted using scanning electron microscopy (SEM), Raman spectroscopy, and energy-dispersive X-ray spectroscopy (EDX). The presence of the α-Fe2O3-CNT film on the GCE surface resulted in an enhanced electrochemical response to E2, preventing electrode surface fouling and mitigating the decrease in peak current intensity during E2 oxidation. These outcomes substantiate the rationale behind the GCE modification. After the optimization of experimental conditions, E2 was determined by the square wave voltammetry technique using 0.1 mol L-1 KCl solution (pH = 7.0) with 20% ethanol as a supporting electrolyte. A linear concentration range of 5.0-100.0 nmol L-1 and a low limit of detection of 4.4 nmol L-1 were obtained. The electroanalytical method using α-Fe2O3-CNT/GCE was applied for E2 determination in pharmaceutical, lake water, and synthetic urine samples. The obtained results were attested by recovery tests and by high-performance liquid chromatography as a comparative technique at a 95% confidence level. Thus, the developed electrochemical sensor is simple and fast to obtain, presents high accuracy, and is viable for determining E2 in routine analysis.

Easy cleaning plus stable activation of glassy carbon electrode surface by oxygen plasma

Glassy carbon (GC) electrodes are widely used in electroanalytical applications especially in bioelectrochemistry. Their use starts with an efficient surface cleaning and activation protocol, mostly based on surface polishing steps. We studied the use of an oxygen plasma exposure of GC electrodes to replace common polishing procedures. The cyclic voltammetry (CV) responses of ferrocyanide and ferrocene-dimethanol were used to compare brand new, surface-polished and plasma-treated GC electrodes. Plasma treatment induces CV responses with improved features, close to theoretical values, as compared to other methods. The plasma effects were quasi-stable over a week when electrodes were stored in water, this being explained by increased surface energy and hydrophilicity. Furthermore, when electroreduction of diazonium was performed on GC electrodes, the surface blockade could be removed by the plasma. Thus, a short oxygen plasma treatment is prone to replace polishing protocols, that display person-dependent efficiency, in most of the experiments with GC electrodes.

Nanoarchitectonics of on–off ratiometric signal amplified electrochemical sensor for chlorpromazine with molecularly imprinted polymer based on Ni-MOF/Fe-MOF-5 hybrid Au nanoparticles

A novel and stable on–off ratiometric electrochemical sensing platform for chlorpromazine (CPZ) detection by combing the selective recognition of molecularly imprinted polymer (MIP) technology and ratiometric quantification strategy. Gold nanoparticles (AuNPs) were first electrodeposited on a bare glassy carbon electrode surface and then modified with a mixture of Ni-MOF/Fe-MOF-5 by drop-coating, and subsequently electropolymerization polythionine (pTHi) as an internal reference to achieve a ratiometric on–off response. The reference signal of pTHi was obtained by the boiling water-bath-assisted in-situ electropolymerization method for the first time. Ni-MOF/Fe-MOF-5 hybrid AuNPs (Ni-MOF/Fe-MOF-5/AuNPs) not only benefited the output signal amplification, but also provided the enlarged surface for immobilization of pThi and MIPs, and served as catalytic active centers to oxidation CPZ. Then, the MIPs membrane was fabricated through in-situ electropolymerization by using CPZ as the template molecule, nicotinamide as a functional monomer. Ratiometric identifying and quantitative sensing model has been proposed based on the combination of MIP membrane as molecular recognition receptor and pTHi used as an internal reference probe, which improves the sensitivity and selectivity of the sensor. Under the optimal conditions, the ratiometric signals of peak current (ICPZ/IpTHi) were linear to CPZ concentration in the range of 0.001–40 μM and 40–900 μM, with the ultralow detection limit of 0.025 μM (S/N = 3). Furthermore, this sensor exhibited high anti-interference ability, reproducibility, satisfactory stability, and outstanding measurement performance in biological samples with favorable recoveries in the range of 98.11–100.81%. Together, the constructed on–off ratiometric MIP sensing platform is a promising tool for the rapid and accurate determination of antipsychotic drugs with high selectivity and stability.

Highly sensitive and selective response of agnuside using a chemical sensor based on molecularly imprinted polymer/Pd/MWCNT nanocomposite at the surface of glassy carbon electrode

Highly sensitive and selective response of agnuside using a chemical sensor based on molecularly imprinted polymer/Pd/MWCNT nanocomposite at the surface of glassy carbon electrode

Fabrication of Electrochemical Sensor for the Detection of Mg(II) Ions Using CeO2 Microcuboids as an Efficient Electrocatalyst

In human blood serum, the concentration of magnesium ions typically ranges from 0.7 mM to 1.05 mM. However, exceeding the upper limit of 1.05 mM can lead to the condition known as hypermagnesemia. In this regard, a highly sensitive and selective electrochemical sensor for Mg(II) ion detection was successfully fabricated by immobilizing cerium oxide (CeO2) microcuboids, synthesized via microwave radiation method, onto the surface of glassy carbon electrode (GCE). Cyclic voltammetry studies revealed the exceptional electrocatalytic effect of CeO2 microcuboid-modified GC electrode, particularly in relation to the irreversible reduction signal of Mg(II). The microcuboid-like structure of CeO2 microparticles facilitated enhanced adsorption of Mg(II) ion (Γ=2.17×10−7mol cm−2) and electron transfer (ks=8.94 s−1) between the adsorbed Mg(II) ions and GCE. A comprehensive analysis comparing the performance characteristics of amperometry, differential pulse voltammetry, cyclic voltammetry, and square wave voltammetry was conducted. The square wave voltammetry-based Mg(II) sensor exhibited remarkable sensitivity of 2.856 μA mM−1, encompassing a broad linear detection range of 0–3 mM. The detection and quantification limits were impressively low, with values of 19.84 and 66.06 μM, respectively. Remarkably, the developed electrode showed a rapid response time of less than 140 s. Multiple linear regression and partial least squares regression models were employed to establish a mathematical relationship between magnesium ion levels and electrochemical parameters. Notably, the proposed sensor exhibited excellent anti-interferent ability, repeatability, stability, and reproducibility, enabling the fabricated electrode to be used effectively for Mg(II) ion sensing in real-world samples.

Electrochemical Sensors Based on Manganese and Cobalt Oxide Nanostructures for the Detection of Flutamide and its Derivatives in Real Water Samples

AbstractFlutamide (FLU), bicalutamide (BIC), and hydroxyflutamide (OHF), having a low biodegradability, may cause severe health effects on humans as antiandrogens. In this work, we have developed two electrochemical sensors using manganese oxide (MnO) and Cobalt oxide (CoO) nanostructures (NSs) as electrocatalysts. The GCE modified with MnO is referred to as MnO/GCE and the GCE modified by CoO is referred to as CoO/GCE. The electrochemical behaviours of CoO/GCE and MnO/GCE were examined in ferricyanide solution. It was observed through the employment of cyclic voltammetry that MnO/GCE exhibit better electron transfer than CoO/GCE. The calculated surface coverage values, 1.46 x10−9 mol cm−2 and 5.02 x10−9 mol cm−2 of MnO/GCE and CoO/GCE suggest a multilayer of a metal oxide molecule film at the surfaces of glassy carbon electrodes (GCE). FLU, BIC and OHF were detected at a linear range from 32.01 to 50.00 µM. The limits of detection of FLU, BIC and OHF were 18.5, 13.0 and 78.8 µM at MnO/GCE respectively and 18.8, 18.7 and 18.5 µM at CoO/GCE respectively. Both MnO/GCE and CoO/GCE showed good catalytic stability towards detecting FLU and its derivatives. FLU, BIC and OHF were also detected in the presence of interferents for both electrochemical sensors in phosphate buffer solution. Both MnO/GCE and CoO/GCE confirmed good selectivity without cross interference. Some of the health effects associated with FLU, BIC and OHF are liver damage, prostate inflammation, and methamoglobenia. Although FLU, BIC and OHF are detected in low concentration levels in water bodies, their continuous ingestion is a great concern. As far as we know, MnO and CoO NSs have not been used to electrochemically detect FLU, BIC and OHF. Furthermore, OHF has not been detected electrochemically before and there are only a few studies on the electrochemical detection of BIC. Hence, MnO and CoO NSs are used in this study for the first time for an electrochemical sensor fabrication towards the detection of FLU, BIC and OHF.

Folic acid electrocatalytic oxidation on the carbon electrode surface modified with ferrocenyl grafted polymethylhydrosiloxane

In this research, we synthesized ferrocenyl‐grafted polymethylhydrosiloxane (PMHS) through a hydrosilylation reaction between 3‐butenylferrocene and PMHS. The incorporation of the ferrocenyl derivative into the polymer backbone imparted electrochemical properties to the modified polymer. The modification of the polymer was confirmed by various techniques, including FT‐IR, 1H NMR, and UV–Vis spectroscopy. To prepare the new ferrocenyl polymer, we utilized cross‐linking agents, namely terephthaldehyde (TPA) and fresh egg white (FEW). The resulting polymer was drop‐coated onto a glassy carbon electrode (GCE) surface (5 μL). Electrochemical impedance spectroscopy (EIS) analysis confirmed the successful immobilization of the polymer on the GCE surface. Under physiological pH conditions (pH = 7), the Fc/Fc + couple facilitated the oxidation of folic acid (FA) at a potential of 0.40 V vs. the Ag/AgCl reference electrode. The GC/PMHS‐Fc/(TPA + FEW) electrode exhibited excellent stability, retaining 89% and 90% of its electrocatalytic activity after 500 cycles and 30 days of storage in a refrigerator, respectively. Thus, it shows promising potential for the determination of FA in biological fluids. The ferrocene‐modified electroactive polymer demonstrated satisfactory linear ranges for FA determination (5–150 μM) and a low limit of detection (LOD = 36 nM). These results highlight the effectiveness of the new polymer in detecting FA in biological samples.

Scheming the best metal tungstate laden on boron nitride: Budding en route for electrochemical sensing of ornidazole

Due to the shape, high active surface area, and defective sites among other factors, the fabrication of shape-influenced nanoparticles across the surface of glassy carbon electrodes (GCE) promotes electrocatalytic activity. To achieve this, cobalt tungstate (CoWO4), lead tungstate (PbWO4), copper tungstate (CuWO4), barium tungstate (BaWO4), calcium tungstate (CaWO4), and cobalt tungstate (CoWO4) on chemically exfoliated boron nitride (CE-BN) on GCE are prepared and used for micromolar level detection of pharmaceutical compound namely ornidazole (OZ). We compared the tungstates for electrochemical OZ sensing to examine the effect of shape. Various microscopic and spectroscopic methods were used to characterize the physicochemical characteristics of synthetic materials. These investigations resulted in CoWO4/CE-BN being created solely and with the best reaction without any intervention. Furthermore, when exposed to room temperature at an ideal working buffer pH of 7.0, CoWO4/CE-BN/GCE exhibits greater reduction behavior in comparison to other tungstate electrodes. It is interesting to note that the electrode was able to generate a larger linear response (0.04 to 122.18 µM) with greater sensitivity (1.0225 µA µM−1 cm−2) and a lower micromolar detection limit (0.002 µM). The proposed sensor possesses outstanding selectivity, repeatability, reproducibility, reversibility, and storage stability according to the practicability study using digital pulse voltammetry (DPV). Additionally, the examination of a lake water sample was completed with higher recovery outcomes.

Enzyme-indole Pyrazole-capped SeNPs based Electrochemical Biosensor for Sensitive Detection of Adenosine Triphosphate

Abstract: In this study, an electrochemical biosensor for the indirect detection of Adenosine triphosphate (ATP) was developed, which was based on the immobilization of the multiwalled carbon nanotubes (MWCNTs) decorated with pyrazole-capped selenium nanoparticles (TRPIDC-CH3 SeNPs) and dual enzyme reaction (hexokinase and glucose oxidase) onto the surface of a bare glassy carbon electrode (GCE) as a working electrode. As confirmed byUltraviolet–visible spectroscopy (UV-Vis), Fourier transform infrared (FTIR) and High-resolution electron microscope (HRTEM), the TRPIDC-CH3 SeNPs successfully green synthesised using Allium sativum cloves and indole pyrazole ligand. The electrochemical study of ATP was performed using cyclic voltammetry (CV) and square wave voltammetry (SWV) techniques on a modified electrode for indirect detection of ATP where the required strong electroactive was [Fe(CN)6]3-/4-. The phosphate buffer solution (PBS; 0.1 M) was used as a supporting electrolyte at pH 7 containing 1 mM K4[Fe(CN)6]/K3[Fe(CN)6] as the redox probe operated at an average potential of 0.23 V. The electrochemical enzymic biosensor showed outstanding sensitivity, good stability, and satisfactory reproducibility with an average RSD of 2.30%. The ATP was quantifiable in spiked tablets with a limit of detection (LOD) of 0.015 mM and a limit of quantification (LOQ) of 0,050 mM.

Signal-on electrogenerated chemiluminescence detection of gonyautoxin 1/4 based on proximity ligation-induced an electrode-bound pseudoknot DNA

A “signal on” electrogenerated chemiluminescence (electrochemiluminescence, ECL) aptasensor based on proximity ligation-induced an electrode-bound pseudoknot DNA for sensitive detection of gonyautoxin 1/4 (GTX1/4) was developed on basis of the competitive type reaction mode. Aptamer was adopted as recognition element. Ru(bpy)32+ as ECL signal, was attached on the glassy carbon electrode (GCE) surface modified with nafion and gold nanoparticles (AuNPs) by electrostatic attraction to obtain the ECL platform. The pseudoknot DNA as capture probe, was immobilized onto the ECL platform via Au–S bond to obtain the ECL aptasensor. In the absence of GTX1/4, Y-shape proximate cooperative complex among aptamer, pseudoknot DNA and DNA1 was formed, drawing the ferrocene groups Fc, as ECL quencher) of both pseudoknot DNA and DNA1 near the electrode surface and resulting in low ECL signal. In the presence of GTX1/4, GTX1/4 competed with pseudoknot DNA and DNA1 for aptamer in homogeneous solution, preventing the formation of proximate cooperative complex and keeping the capture DNA in the pseudoknot conformation with Fc groups far away from the electrode surface, generating a high ECL signal. The recovery of ECL intensity increased with the GTX1/4 concentration and allowed the detection of GTX1/4 in the range of 0.01 ng/mL to 10 ng/mL with a detection of limit as low as 6.56 pg/mL. Additionally, the accuracy of this method was validated for analysis of spiked sea water samples with good recoveries, which indicates great potential in commercial application.

Fabrication of Poly (Trans-3-(3-Pyridyl)Acrylic Acid)/Multi-Walled Carbon Nanotubes Membrane for Electrochemically Simultaneously Detecting Catechol and Hydroquinone.

Herein, conductive polymer membrane with excellent performance was successfully fabricated by integrating carboxylated multi-walled carbon nanotubes (MWCNTs) and poly (trans-3-(3-pyridyl) acrylic acid) (PPAA) film. The drop-casting method was employed to coated MWCNTs on the glassy carbon electrode (GCE) surface, and PPAA was then electropolymerized onto the surface of the MWCNTs/GCE in order to form PPAA-MWCNTs membrane. This enables the verification of the excellent performances of proposed membrane by electrochemically determining catechol (CC) and hydroquinone (HQ) as the model. Cyclic voltammetry experiments showed that the proposed membrane exhibited an obvious electrocatalytic effect on CC and HQ, owing to the synergistic effect of PPAA and MWCNTs. Differential pulse voltammetry was adopted for simultaneous detection purposes, and an increased electrochemical responded to CC and HQ. A concentration increase was found in the range of 1.0 × 10-6 mol/L~1.0 × 10-4 mol/L, and it exhibited a good linear relationship with satisfactory detection limits of 3.17 × 10-7 mol/L for CC and 2.03 × 10-7 mol/L for HQ (S/N = 3). Additionally, this constructed membrane showed good reproducibility and stability. The final electrode was successfully applied to analyze CC and HQ in actual water samples, and it obtained robust recovery for CC with 95.2% and 98.5%, and for HQ with 97.0% and 97.3%. Overall, the constructed membrane can potentially be a good candidate for constructing electrochemical sensors in environmental analysis.