Glassy Carbon Research Articles

A novel electrochemical sensor based on ꞵ-cyclodextrin/bismuth oxybromide/multi-walled carbon nanotubes modified electrode with in situ addition of tetrabutylammonium bromide for the simultaneous detection and degradation of tebuconazole.

A novel electrochemical sensor-based glassy carbon electrode (GCE) was fabricated and appliedtosimultaneous detection and degradation of tebuconazole (TBZ) for the first time.TheGCE was consecutively modified by multi-walled carbon nanotubes (MWCNTs), bismuth oxybromide (BiOBr), ꞵ-cyclodextrin (ꞵ-CD), and in situ addition of tetrabutylammonium bromide (TBABr). The detection was based on the decreasing of Bi signal at its anodic potential (Epa) of 0.05V. Under the optimum conditions, the modified electrode exhibited a linear response to TBZ in the concentration range 1-100μg L-1 with a detection limit of 0.9μg L-1. TBZ was firstly adsorbed on the surface of the modified electrode through host-guest molecule interactions of the ꞵ-CD. The adsorption was further enhanced by the large surface area of BiOBr and MWCNTs. The adsorbed TBZ on the electrode surface hindered the electron transfer of Bi, thus decreasing the oxidation of Bi. In addition, the in situ addition of tetrabutylammonium bromide (TBABr) enriched TBZ via electrostatic interactions, increasing its detection sensitivity. The fabricated electrochemical sensor was applied to determine TBZ in water and soil samples from rice fields with recoveries of 80.5-100.5% and 87.6-112%, respectively. Furthermore, the degradation of TBZ on the modified electrode was studied under a solar light simulator. The degradation percentage (100%) of TBZ (50µg L-1) was achieved in5min owing to the excellent photocatalytic properties of BiOBr.

Electrocatalytic Applications in Hydrogen Evolution of Two Nitrogen Heterocyclic Cu(I) Coordination Polymer Modified Electrodes

ABSTRACTThe development of low‐cost, high‐efficiency, stable, and structurally adjustable electrocatalysts for hydrogen evolution reaction (HER) is of great significance for energy conversion. In this study, two new Cu(I) coordination polymers (CPs), formulated as {[Cu(L1)](PF6)·CH2Cl2}n (1) and {[Cu2(L2)1.5(PPh3)](PF6)2}n (2) (L1 = 1,3‐bis[1‐(pyridin‐3‐ylmethyl) ‐1H‐benzimidazol‐2‐yl]propane, L2 = 1,4‐bis[1‐(3‐pyridylmethyl)‐1H‐benzimidazol‐2‐yl]butane), were synthesized by interfacial diffusion method and characterized by single‐crystal x‐ray diffraction and IR and UV–Vis spectra. Structural analysis shows that the CP‐1 is a one‐dimensional chain structure, whereas the CP‐2 is a two‐dimensional layered structure, which is due to the different coordination modes of ligands L1 (bridging chelation) and L2 (bridging). The electrocatalytic activity for HER of Cu(I) CPs was studied by preparing modified glassy carbon electrodes (CP‐1/GCE and CP‐2/GCE). Electrochemical HER studies manifest that in 0.5 M H2SO4, the overpotential (η10298K) and Tafel slope (b 298K) are −769 mV and 173 mV dec−1 for CP‐1/GCE, −933 mV and 301 mV dec−1 for CP‐2/GCE, and −930 mV and 298 mV dec−1 for bare/GCE, respectively. The η10298K and b298K of CP‐1/GCE were significantly positive shifted and decreased compared with the bare/GCE, indicating that CP‐1/GCE has significant electrocatalytic activity and electrocatalytic HER activity order is CP‐1/GCE > CP‐2/GCE ≈ bare/GCE. This work provides an important reference for the application of non‐noble metal CPs in the field of electrocatalysis.

Sensitive Detection of Theophylline Using a Modified Glassy Carbon Electrode with g-C3N4

Sensitive Detection of Theophylline Using a Modified Glassy Carbon Electrode with g-C3N4

Stationary and pulsed electrodeposition of silicon in LiCl–KCl–CsCl–K2SiF6 melt

Silicon and its materials are widely used in metallurgy, micro- and nano-electronics, solar energy, and are also promising materials for anodes of lithium-ion power sources with increased specific capacity. The expansion of application areas of silicon with controlled morphology necessitates the development of new energy–efficient methods of its production. In the present work, the influence of the mode as well as parameters of electrolysis of the LiCl–KCl–CsCl–K2SiF6 melt with a temperature of 545 оC on the morphology of electrolytic precipitation of silicon on glassy carbon has been studied. The galvanostatic mode of electrodeposition, widely used in industry, as well as the pulsed mode, which is actively investigated at present, were used for the electrolysis. Silicon electrodeposition was carried out by varying such parameters as cathodic current density (from 3 to 50 mA/cm2) and electrolysis duration (from 30 to 180 min) in the galvanostatic mode, as well as by varying the density and duration of the cathodic current pulse, the duration of current pauses and the total duration of electrolysis in the pulsed mode. It is shown that electrodeposition of silicon on glassy carbon is accompanied by the formation of a continuous sediments of hemispherical nuclei with a diameter of about 1 micron on the electrode surface. An increase in the cathodic current density and an increase in the cathodic current pulse pause frequency contribute to the disruption of the sediment continuity and the growth of dendrites of ordered or arbitrary shape. At the same time, the pulsed mode allows to increase the cathode current density at silicon electrodeposition (from 25–30 to 250–500 mA/cm2) and stabilize the value of the cathode potential during electrolysis.

Investigation of Some Crown Ether Compounds for Electrochemical Determination of Dopamine

In this study, the use of three different crown ether-modified electrodes prepared by electropolymerization of different crown ether compounds (CE1, CE2 and CE3) on multi-walled carbon nanotube (MWCNT) modified glassy carbon electrode (GCE) surfaces was investigated for electrochemical dopamine determination. The number of cycles during the electropolymerization of crown ethers and the pH of the buffer solution were optimized. Under optimum conditions, the sensitivities of MWCNT-modified GCE and crown ether-MWCNT-modified electrodes were determined in the range of 4.0×10-6 – 5.7×10-4 M dopamine. The sensitivity of MWCNT/GCE was found to be 6.71 µA mM-1, while the sensitivities of CE1/MWCNT/GCE, CE2/MWCNT/GCE and CE3/MWCNT/GCE were 19.53, 16.32 and 20.80 µA mM-1, respectively. The performance characteristics of the crown ether-MWCNT-modified electrodes such as detection limit, quantification limit, reusability and reproducibility were also investigated. The study showed that crown ether compounds significantly enhanced the electrochemical response in dopamine determination.

CuO@3D graphene modified glassy carbon electrode towards the detection of Orange II and Rhodamine B

Synthetic dyes are illegally used in foodstuffs and cause serious health issues in humans due to their carcinogenic nature. To avoid serious health issues, it is compulsory to detect and remove even the minute quantities of these harmful dyes in foodstuffs. Electrochemical sensors are accredited as an efficient and promising platform for the robust and sensitive determination of food toxins in various foodstuffs. Therefore, an efficient, facile, and competent sensor is devised for the simultaneous detection of Orange II (OR II) and Rhodamine B (RhB) supported by rGO and CuO nanoparticles. The synergism between rGO’s immense surface area and the adsorption properties of CuO enhances selectivity and response time for the detection of OR II and RhB. This work elaborated the synthesis, characterization, and electrochemical behavior of CuO@3DGr electrode towards simultaneous sensing of OR II and RhB. Physicochemical techniques were utilized to validate the fabrication of targeted material. On the other hand, the electrochemical features of the developed sensor were characterized by cyclic voltammetry (CV) and electron impedance spectroscopy (EIS). Differential pulse voltammetry technique was employed to detect simultaneously Orange II and Rhodamine B on the surface of bare (GCE), GO/GCE, CuO/GCE, and CuO@3DGr/GCE. Multi-analyte detection is possible with DPV, a sensitive electrochemical method. Based on each toxin’s specific electrochemical signature, the sensor may generate separate peaks by delivering a sequence of potential pulses and detecting the ensuing current. The parameters which influence the performance of the modified sensor were carefully evaluated. Under ambient conditions, the developed sensor exhibited excellent electrocatalytic activity in oxidation at 0.67 V of OR II and 0.96 V RhB with a low limit of detection 08 nM for OR II and 4.5 nM for RhB in Britton- Robinson buffer (BRB pH:7). The described methodology allowed a robust and fast analysis of food toxins in different foodstuff establishing this sensor as a novel tool for detecting food toxins. Tap water was used to analyze the practical applicability of developed electrode material and suitable results were achieved. These results showed that the as-synthesized novel electrochemical sensor has the potential for ultrasensitive determination and detection of toxins in different foodstuffs.

Sensitive determination of hydroquinone and catechol using an electrochemical sensor based on nitrogen-doped malic acid carbon quantum dots

This study introduces an advanced electrochemical sensor fabricated by immobilizing nitrogen-doped malic acid carbon quantum dots (N-MCQDs) onto a glassy carbon electrode (GCE) via microwave-assisted synthesis and electrodeposition. The N-MCQDs were comprehensively characterized using high-resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, and atomic force microscopy (AFM), confirming their successful synthesis and uniform distribution on the GCE surface. The N-MCQDs-modified GCE electrode (N-MCQDs/GCE) sensor displayed a remarkable linear detection range of 1–500 μM for hydroquinone (HQ) and 1–200 μM for catechol (CC), with ultra-low detection limits of 0.18 μM for HQ and 0.13 μM for CC. It also exhibits commendable stability, interference resistance, and the capability to accurately measure in complex real sample. These superior characteristics were attributed to the enhanced electrical conductivity and increased active sites due to nitrogen doping. This study not only broadens the application spectrum of carbon quantum dots but also offers a novel perspective for the design of high-performance electrochemical sensors for environmental analysis.

Construction of a ratiometric electrochemical sensor for Bisphenol A detection by coupling nonionic surfactant-decorated conductive carbon black with ferricyanide probe

In this work, a novel ratiometric electrochemical sensor for bisphenol A (BPA) detection was facilely constructed by coupling conductive carbon black (VXC-72R) with ferricyanide probe. The VXC-72R was decorated with nonionic surfactant Tween to enhance the sensitivity and coated on glassy carbon electrode (GCE), whereas K3[Fe(CN)6] was introduced into electrolyte solution as an internal reference probe to realize dual-signal outputs. The present ratiometric electrochemical sensor achieved a highly sensitive and selective detection of BPA in PBS solution (pH = 7.0), with a linear range of 0.08–40.0 μM and detection limit of 0.05 μM. Moreover, it has been successfully applied to the determination of BPA in real lake water and milk samples with the satisfactory recoveries rates of 94.8–102.3 %.

Biosensor Based on the Immobilization of Laccase on β-Cyclodextrin Membrane for the Evaluation of Antioxidant Capacity in Real Samples.

The optimization of a new amperometric biosensor for evaluating antioxidant capacity in real samples is reported. The biosensor is based on the immobilization of Laccase from Trametes versicolor on an electropolymerized β-cyclodextrin polymeric membrane on a glassy carbon electrode. The process of electropolymerization, which was successful even in the presence of the enzyme, was a key step in biosensor synthesis. Variables such as pH, temperature, and enzyme concentration were optimized using a factorial design with two levels for each factor. Different electrodes were constructed and tested using caffeic acid as a standard. The best biosensor is synthesized at pH 3.0 with 6 mg/mL of enzyme and 30 °C. The biosensor presented a response time of ≤30 seconds and good stability in its amperometric response. The biosensor was used to evaluate the antioxidant capacity of real samples. Infusions of green, black, red, and white tea were assessed. The biosensor showed excellent stability and good performance regarding response time, stability, and easy fabrication. The proposed biosensor is a good option for evaluating antioxidant capacity in real samples without sample pretreatment. It combines a simple fabrication methodology and a minimal extraction process for rapid and reliable phenolic content determination in real samples.

Copper-Based Electrochemical Sensor Derived from Thiosemicarbazide for Selective Detection of Neurotransmitter Dopamine.

This paper presents the synthesis of the ligand 1-picolinoyl-4-cyclohexyl-3-thiosemicarbazide (H2pctc) and new metal complexes [Ni(Hpctc)2] (1), [Cu(Hpctc)Cl] (2), and [Cd(Hpctc)2] (3). The synthesized metal complexes were precisely characterized using single crystal X-ray diffraction (SC-XRD). In addition, complexes 1-3 were also characterized by UV-vis, fluorescence, and infrared spectroscopy. SC-XRD data confirmed the distorted octahedral geometry around the Ni(II) and Cd(II) centers and the distorted square planar geometry around the Cu(II) center. Data derived from the emission spectra depict that higher fluorescence intensity was exhibited by complexes 1, 2, and 3 in comparison to that of the free ligand H2pctc, and complex 3 showed the maximum intensity. Further, these metal complex-modified GCEs (glassy carbon electrodes) were utilized for electrochemical sensing of dopamine (DPM). The electrochemical studies of these complexes were performed using modified glassy carbon electrodes supported by electrical impedance spectroscopy (EIS) and cyclic voltammetry (CV) methods. In contrast to complexes 1 and 3, complex 2 is a superior electrode material with a high effective surface area for the electrochemical oxidation of DPM, according to the electrochemical response results. The derived sensor had a wide linear detection range of 1 to 1400 μM, an acceptable sensitivity of 0.01531 μA cm-2 μM-1, and a low LOD of 0.38 μM. The proposed approach was free of the interfering effects of ascorbic acid, uric acid, aminophenol, and other substances. During the successive scans, no fouling of the electrode surface was observed. The proposed electrochemical sensor had excellent stability, sensitivity, and a low detection limit making it suitable for the analysis of a variety of real samples. Additionally, it was proven to be useful for analyzing biological fluids.

The Effect of Electrochemical Ageing of Glassy Carbon Electrodes on VII-VIII and VIV-VV Kinetics

Abstract Electrode activity towards the negative and positive half-cell reactions of a vanadium flow battery were investigated. Cyclic voltammetry and electrochemical impedance spectroscopy were employed to monitor electrode activity of glassy carbon electrodes towards VII-VIII and VIV-VV redox reactions during electrochemical ageing through repeated anodic and cathodic treatments.
Electrode activity is found to increase with number of treatment steps, showing little difference initially between anodised and cathodised electrodes. However, after several treatments, a potential-differentiated behaviour emerges, with distinct enhanced and inhibited states. For VII-VIII, anodised electrodes showed enhanced activity, while cathodised electrodes were inhibited. Conversely, for VIV-VV, cathodised electrodes had enhanced activity. In almost all cases, the activity is greater than that of an untreated electrode.
Eventually, electrode activities stabilise in a steady-state region where activity depends on the final treatment potential rather than the number of steps. In this region, activity can be toggled reproducibly between enhanced and inhibited states. Therefore, it can be concluded that functional groups, rather than surface roughening or defect formation, are responsible for this toggling capability. Furthermore, for VIV-VV, number of treatment steps required to reach and the activity levels in this region are found to be dependent on the upper and lower treatment potentials.

Anthraquinone/Activated Carbon Electrochemical Sensor and its Application in Ofloxacin Analysis

AbstractOfloxacin (OFL) has antibacterial and anti‐inflammatory effects on respiratory tract infection, skin soft tissue infection and urogenital tract infection caused by sensitive bacteria. In this study, an electrochemical sensor on account of glassy carbon electrode (GCE) and anthraquinone (AQ)/Vulcan XC‐72 (C) composite was prosperity prepared for the determination of ofloxacin (OFL) drug. The morphology and structure of C/20%AQ composites were characterized by SEM. The electrochemical behavior of OFL on the C/20%AQ/GCE sensor was tested using differential pulse voltammetry (DPV) and cyclic voltammetry (CV). The consequences indicate that the linear response of the sensor to OFL at pH 6.5 in 0.2 M phosphate buffer solution (PBS) was in the scope of 0.1–550.0 μM (R2=0.998) with the limit of detection of 0.01 μM. The prepared C/20%AQ/GCE sensor exhibited good anti‐interference ability and repeatability against OFL. The sensor presents a sensitive, simple and low cost OFL detection method, and has been successfully applied to real samples.

Tailoring glassy carbon electrode surface with FeBiO3 for electrochemical detection of dinitrophenol isomers

ABSTRACT This study presents a simultaneous, rapid, and highly sensitive electrochemical detection of 2,4- and 2,5-dinitrophenol isomers using an iron bismuth oxide (FeBiO3)-modified glassy carbon electrode (GCE). The FeBiO3-modified GCE exhibited superior electrochemical performance over bare GCE, Bi2O3-modified GCE, and Fe2O3-modified GCE, as demonstrated by electrochemical impedance spectroscopy (EIS) with the potassium ferricyanide (Fe(CN6)3-/4-) standard. The synthesised electrocatalyst FeBiO3 exhibited strong absorption both in the visible and UV regions of the spectrum, attributed to band gap transitions and charge transfer transitions linked to its Bi2O3 and Fe2O3 components. The morphology and the structure of the FeBiO3 were characterised using scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD), while Fourier transform infrared spectroscopy (FTIR) was employed to analyse the functional groups attached to the surface of FeBiO3. Cyclic voltammetry (CV) clearly demonstrated an increased current and improved peak resolution for the reduction of 2,4- and 2,5-dinitrophenols at the FeBiO3/GCE, compared to the bare GCE. The mechanism shows that the reduction of 2,4- and 2,5-dinitrophenols occurs through interactions with the surface oxygen functional groups of FeBiO3, resulting in the stepwise reduction of their NO2 groups to hydroxyamino compounds and then to nitrosophenols. Using square wave voltammetry (SWV), the reduction peak currents were significantly improved, enhancing detection sensitivity beyond that reported in previous works. A linear range from 1 µM to 1 mm for the dinitrophenol isomers was established, with detection limits of 0.07 µM for 2,4-dinitrophenol and 0.09 µM for 2,5-dinitrophenol. The FeBiO3/GCE electrode showed interferences with mono-nitrophenols and mono-/di-chlorophenols in solution but maintained excellent long-term stability and reproducibility, allowing it to effectively detect dinitrophenol isomers in drinking water, tap water, and wastewater samples.

Glassy Carbon Electrodes Modified with Ru nanoparticles Loaded in B-Doped Imidazolium Porous Organic Polymers for Hydrogen Evolution Reaction.

Porous organic polymers (POPs) are a type of porous material composed of organic structural units connected by covalent bonds and POPs have been used as efficient electrocatalysts for hydrogen evolution reaction (HER). Herein, glassy carbon electrode (GCE) is chemically modified by B-doped imidazolium-based porous organic polymers loaded with Ru nanoparticles on the GCE surface. The incorporation of B in the POPs regulates the electronic structure of electrocatalysts to enhance their inherent electrocatalytic activity for HER. The optimized modified electrode GCE-Ru/PIM-Br2 exhibits a low overpotential of 271 mV at a current density of 10 mA cm-2 with a small Tafel slope (80 mV dec-1) in acidic solutions, and shows long-term stability for up to 22 h. This work presents a strategy to develop B-doped porous electrodes with loaded metal nanoparticles to strengthen the catalytic performance of electrocatalysts.

Phosphorous doped graphitic carbon nitride (P‐g‐C3N4) as an electrochemical platform for the simultaneous detection of xanthine and caffeine

A one step strategy was employed for the preparation of phosphorous doped g‐C3N4 (P‐g‐C3N4) using melamine phosphate. Herein, the precursor upon thermal condensation at 550º C resulted in the formation of P‐g‐C3N4 nanosheets. The as‐synthesised P‐g‐C3N4 nanosheets were characterized by UV‐vis, FT‐IR and Raman spectroscopy. Later, surface morphological analysis were carried out using FESEM and HRTEM. Moreover, the crystalline nature and elemental composition analysis were conducted using XRD and XPS. Following this, P‐g‐C3N4 nanosheets modified glassy carbon (GC) electrode was employed for the simultaneous detection of xanthene and caffeine. The modified electrode was found to be linear in the range of 0.1 to 100 μM (for xanthine) and 0.05 to 100 μM (for caffeine). The limit of detection was found to be 10 nM and 14 nM for xanthine and caffeine respectively. Further, the electrode exhibited a highly selective detection towards each of these analyte when they co‐exists.

Ce-MOF@Au-Based Electrochemical Immunosensor for Apolipoprotein A1 Detection Using Nanobody Technology.

Apolipoprotein A1 (Apo-A1) is a well-recognized biomarker in tissues, closely associated with cardiovascular diseases such as atherosclerosis, coronary artery disease, and heart failure. However, existing methods for Apo-A1 determination are limited by costly equipment and intricate operational procedures. Given the distinct advantages of electrochemical immunosensors, including affordability and high sensitivity, along with the unique attributes of nanobodies (Nbs), such as enhanced specificity and better tissue permeability, we developed an electrochemical immunosensor for Apo-A1 detection utilizing Nb technology. In our study, Ce-MOF@AuNPs nanocomposites were synthesized by using ultrasonic methods and applied to modify a glassy carbon electrode. The Nb6, screened from an Apo-A1 immunized phage library, was immobilized onto the nanocomposite material, establishing a robust binding interaction with Apo-A1. The recorded peak current values demonstrated a logarithmic increase corresponding to Apo-A1 concentrations ranging from 1 to 100,000 pg/mL, with a detection limit of 36 fg/mL. Additionally, the developed immunosensors demonstrated high selectivity, good stability, and reproducibility. Our methodology was also effectively utilized for serum sample analysis, showing good performance in clinical assessments. This electrochemical immunosensor represents a promising tool for Apo-A1 detection, with significant potential for advancing cardiovascular disease diagnostics.

Non-enzymatic electrochemical detection of sarcosine in serum of prostate cancer patients by CoNiWBO/rGO nanocomposite

Selective and sensitive sarcosine detection is crucial due to its recent endorsement as a prostate cancer (PCa) biomarker in clinical diagnosis. The reduced graphene oxide-cobalt nickel tungsten boron oxides (CoNiWBO/rGO) nanocomposite is developed as a non-enzymatic electrochemical sensor for sarcosine detection in PCa patients’ serum. CoNiWBO/rGO is synthesized by the chemical reduction method via a one-pot reduction method followed by calcination at 500 °C under a nitrogen environment for 2 h and characterized by UV-Vis, XRD, TGA, and SEM. CoNiWBO/rGO is then deposited on a glassy carbon electrode, and sarcosine sensing parameters are optimized, including concentration and pH. This non-enzymatic sensor is employed to directly determine sarcosine in serum samples. Differential pulse voltammetry (DPV) and linear sweep voltammetry (LSV) are employed to monitor the electrochemical behavior where sarcosine binding leads to oxidation. Chronoamperometric studies show the stability of the developed sensor. The results demonstrate a wide linear range from 0.1 to 50 µM and low limits of detection, i.e., 0.04 µM and 0.07 µM using DPV and LSV respectivel. Moreover, the calculated recovery of sarcosine in human serum of prostate cancer patients is 78–96%. The developed electrochemical sensor for sarcosine detection can have potential applications in clinical diagnosis.

Innovative Use of Carbon Nanofibers/Praseodymium Cobaltite for Targeted Detection of Hematologic Sulfamethazine.

Antibiotics are essential for treating illnesses, but abuse has resulted in serious consequences. Rapid and precise detection of antibiotic residues, such as sulfamethazine (SFZ), in water and biological samples is critical for public health and environmental safety. To address this challenge, we have introduced a pioneering electrochemical sensor incorporating a nanocomposite of perovskite-structured praseodymium cobaltite (PrCoO3) integrated with carbon nanofibers (CNFs) on a glassy carbon electrode (GCE|CNF/PrCoO3). We synthesized the CNF/PrCoO3 nanocomposite using ultrasonic fabrication and confirmed its formation with advanced techniques. GCE|CNF/PrCoO3 offer superior SFZ detection with a 2.889 nM/L limit and high selectivity, due to PrCoO3's electrocatalytic properties and CNF's enhanced conductivity. We validated the sensor's effectiveness in detecting SFZ in various real-water samples, demonstrating its repeatability, reproducibility, and stability. This confirms its reliability for environmental monitoring. The study highlights the potential of perovskite-carbon composites and paves the way for developing cost-effective sensors for pharmaceutical contaminants.

Simultaneous Electrochemical Determination of Sildenafil Citrate and Tadalafil using a Multi Walled Carbon Nanotubes Modified Glassy Carbon Electrode by Adsorptive Stripping Linear Sweep Voltammetry

An adsorptive stripping linear sweep voltammetric method was developed for the simultaneous determination of sildenafil citrate and tadalafil. The voltammetric working electrode was a glassy carbon electrode modified with carboxylic multi‐walled carbon nanotubes. The sensitivity of the developed voltammetric method was significantly increased by this modification. Both analytes spontaneously adsorbed on the modified electrode surface due to their adsorption affinities. The irreversible oxidation signals of both analytes were used as the analytical signals. The electrochemical behaviour of sildenafil citrate and tadalafil was assessed0.99

Cobalt vanadate intertwined in carboxylated multiple-walled carbon nanotubes for simultaneous electrochemical detection of ascorbic acid, dopamine and uric acid

Low-cost transition metal vanadate-based electrochemical sensors have attracted a lot of attention recently. A cobalt vanadate and carboxylated multi-walled carbon nanotube composite (CoV/MWCNTs-COOH) was prepared by an ultrasonic-assisted assembly method. The uniform and dense MWCNTs-COOH attached to the surface of CoV not only combines the large surface area and superior conductivity of MWCNTs-COOH with the excellent electrochemical activity of CoV, but also enhances the redox reaction between CoV/MWCNTs-COOH composite and the analyte through synergistic effect of hydrogen bonding and electrostatic interaction. The electrochemical behaviors of CoV/MWCNTs-COOH composite modified glassy carbon electrode (CoV/MWCNTs-COOH/GCE) were investigated by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and differential pulse voltammetry (DPV). The simultaneous electrochemical sensing of ascorbic acid (AA), dopamine (DA) and uric acid (UA) on CoV/MWCNTs-COOH/GCE possesses good peak current signals with well-defined peak potentials. The linear ranges of AA, DA, and UA at CoV/MWCNTs-COOH/GCE are 1.0–100.0 μM, and the limits of detection (LODs; S/N = 3) are 0.4 μM, 0.03 μM, and 0.1 μM, respectively. The practicality of the designed sensor was further confirmed by the good recoveries obtained in the simultaneous measurement of actual samples including fetal bovine serum, human serum, urine, and Vitamin C tablets. Overall, the developed electrochemical sensor shows potential therapeutic applications for simultaneous determination of AA, DA and UA in biological fluids.