Hydrogen Peroxide Sensor Based on Carbon Nanotubes/β‐Ni(OH)2 Nanocomposites

Ni(OH)₂ nanoflowers were synthesized by a simple and energy‐efficient wet chemistry method. The product was characterized by scanning electron microscopy (SEM) and X‐ray powder diffraction (XRD). Then Ni(OH)₂ nanoflowers attached multi‐walled carbon nanotubes (MWCNTs) modified glassy carbon electrodes (GCE) were proposed (MWCNTs/Ni(OH)₂/GCE) to use as electrochemical sensor to detect hydrogen peroxide. The results showed that the synergistic effect was obtained on the MWCNTs/Ni(OH)₂/GCE whose sensitivity was better than that of Ni(OH)₂/GCE. The linear range is from 0.2 to 22 mmol/L, the detection limit is 0.066 mmol/L, and the response time is <5 s. Satisfyingly, the MWCNTs/Ni(OH)₂/GCE was not only successfully employed to eliminate the interferences from uric acid (UA), acid ascorbic (AA), dopamine (DA), glucose (GO) but also NO₂^? during the detection. The MWCNTs/Ni(OH)₂/GCE allows highly sensitive, excellently selective and fast amperometric sensing of hydrogen peroxide and thus is promising for the future development of hydrogen peroxide sensors.     

Sensitive Nucleic Acid Detection at NH2‐MWCNTs Modified Glassy Carbon Electrode and its Application for Monitoring of Gemcitabine‐DNA Interaction

An electrochemical dsDNA nanobiosensor was fabricated using amino‐functionalized multi walled carbon nanotubes modified glassy carbon electrode (NH₂fMWCNTs/GCE) for the sensitive detection of DNA bases and electrochemical monitoring of drug‐DNA interaction. The influence of functional groups on MWCNT was studied by MWCNT functionalized with NH₂ (NH₂fMWCNTs) and COOH (COOHfMWCNT) groups based on the signal of DNA bases. The modified electrodes were characterized by scanning electron microscopy. One layer of calf thymus double stranded deoxyribonucleic acid (ct‐dsDNA) was immobilized onto the NH₂fMWCNTs/GCE (dsDNA/NH₂fMWCNTs/GCE). The dsDNA/NH₂fMWCNTs/GCE were used to investigate the interaction between the dsDNA and the anticancer drug gemcitabine by differential pulse voltammetry in acetate buffer of pH 4.70. For the confirmation of interaction, the lowering in intensity of the current signals of guanine and adenine was considered as an indicator. Electrochemical impedance spectroscopy studies were performed for the comparison of the modified surfaces. In order to define and visualize the interaction mechanism between gemcitabine and dsDNA/NH₂fMWCNTs/GCE at the molecular level, in silico methods including docking and molecular dynamics simulations were employed.     

A Comparison of a Nanostructured Enzymeless Au/Fe2O3/MWCNTs/GCE Electrode and a GOx Modified One in Electrocatalytic Detection of Glucose

Acid functionalized multi‐walled carbon nanotubes (f‐MWCNTs) were decorated with Au and Fe₂O₃ nanoparticles (FeONPs) and deposited on glassy carbon electrode (GCE). The resulting hybrid Au/Fe₂O₃/f‐MWCNTs/GCE electrode and the one further modified by glucose oxidase were compared for detection of glucose. FeONPs and Au were deposited on the f‐MWCNTs by sonication‐assisted precipitation and deposition‐precipitation methods, respectively. The morphology and structure of the samples were characterized by transmission electron microscopy, scanning electron microscopy, X‐ray diffraction and Raman spectroscopy. A uniform distribution of FeONPs with an average size of 5 nm increased the surface area of functionalized nanotubes from 39 to 50 m²/g. The electrocatalytic glucose detection on the modified electrodes was evaluated using cyclic voltammetry and chronoamperometry in 0.1 M phosphate buffer solution at pH 7.0. The non‐enzymatic and enzymatic electrodes show sensitivity of 512.4 and 921.4 mA/mM.cm² and detection limit of 1.7 and 0.9 mM, respectively. The enzymatic and enzymeless electrodes retained more than 70 % and 80 % of their cathodic faradic current after 70 days, respectively. The sensing mechanism of the non‐enzymatic biosensor is described through the reaction of glucose with iron (III) ions, while in the case of enzymatic electrode, glucose is oxidized by glucose oxidase.     

Highly Sensitive Amperometric Sensor for Eugenol Quantification Based on CeO2 Nanoparticles and Surfactants

Amperometric sensor for eugenol based on glassy carbon electrode (GCE) modified with CeO₂ nanoparticles dispersed in surfactant was fabricated. The effect of surfactant nature (sodium dodecylsulfate, cetylpyridinium bromide (CPB) and Brij® 35) on eugenol voltammetric behaviour was tested. In comparison to CeO₂‐H₂O/GCE, CeO₂‐CPB/GCE showed 2.8‐fold increased current and 70 mV cathodic shift of potential in the diffusion‐controlled irreversible electrooxidation. The electrodes were characterized with SEM and EIS. CeO₂‐CPB/GCE showed significantly lower charge transfer resistance (2.6±0.3 kΩ vs. 20±1 kΩ for CeO₂‐H₂O/GCE and 173±9 kΩ for GCE). Under conditions of DPV, the sensor linear dynamic range is 0.075‐75.0 μM of eugenol with the limits of detection (LOD) and quantification (LOQ) of 19.1 and 63.8 nM, respectively. The sensor exhibited high sensitivity, selectivity, good reproducibility and fast response and was applied for the real samples analysis (essential oils and clove spices). The results obtained correspond well to the data of spectrophotometric method.     

Fabrication of Cu−CeO2 Coated Multiwall Carbon Nanotube Composite Electrode for Simultaneous Determination of Guanine and Adenine

A copper nano particles and cerium (IV) oxide modified carbon nanotube based composite on glassy carbon electrode (Cu−CeO₂/MWCNT/GCE) was fabricated for simultaneous determination of guanine and adenine. The surface morphology, chemistry and conductance of the prepared electrodes were characterized by scanning electron microscopy (SEM), energy dispersion X‐ray (EDX), X‐Ray photoelectron spectroscopy (XPS) and electrochemical impedance spectroscopy (EIS). The Cu−CeO₂/MWCNT/GCE improved electrochemical behaviour of guanine and adenine compared to other electrodes. The modified electrode was also used for individual and simultaneous determination of guanine and adenine. Under optimized conditions, the calibration curves were obtained linearly in the range of 0.20 to 6.00 μM for the guanine and 0.10 to 8.0 μM for the adenine by differential pulse voltammetry. The limits of detection of guanine and adenine were calculated as 0.128 and 0.062 μM, respectively. Interferences studies were also performed in the presence of inorganic and organic compounds. Moreover, the determination of guanine and adenine contents were carried out in a calf thymus DNA sample by the developed method with satisfactory results.     

Adsorptive Stripping Differential Pulse Voltammetric Determination of Risperidone with a Multi‐Walled Carbon Nanotube‐Ionic Liquid Paste Modified Glassy Carbon Electrode

A new composite electrode has been fabricated based on coating multi‐walled carbon nanotubes (MWCNTs) and n‐octylpyridinum hexafluorophosphate (OPPF₆) ionic liquid composite on a glassy carbon (GC) electrode (OPPF₆‐MWCNTs/GCE). This electrode shows very attractive electrochemical performances for electrooxidation of risperidone (RIS) compared to conventional electrodes using carbon and mineral oil, notably improved sensitivity and stability. The oxidation peak potentials in cyclic voltammogram of RIS on the OPPF₆‐MWCNTs/GCE was occurred around 230 mV vs. SCE at Britton–Robinson (B–R) buffer (pH 4.0) at scan rate of 100 mV s^?1. The electrochemical parameters such as diffusion coefficient (D), charge transfer coefficient (α) and the electron transfer rate constant (k/_s) were determined using cyclic voltammetry. Under the optimized conditions, the peak current was linear to risperidone concentration over the concentration range of 10–200 nM with sensitivity of 0.016 μA/nM^?1 using differential pulse voltammetry. The detection limit was 6.54 nM (S/N = 3). The electrode also displayed good selectivity and repeatability. In the presence of clozapine (CLZ) the response of RIS kept almost unchanged. Thus this electrode could find application in the determination of RIS in some real samples. The analytical performance of the OPPF₆‐MWCNTs/GCE was demonstrated for the determination of RIS in human serum and pharmaceutical samples.     

Electrochemical Determination of Phenylethanolamine A Based on Nafion/MWCNTs/AuNPs Modified Carbon Electrode

Phenylethanolamine A (PEA), a β‐agonist, was found to be illegally used as a growth promoter in pigs last year, causing Chinese government's great attention. Here, a sensitive electrochemical method was developed for detecting PEA by immobilization of gold nanoparticles (AuNPs), multiwalled carbon nanotubes (MWCNTs) and Nafion on the surface of a glassy carbon electrode (GCE). The Nafion/MWCNTs/AuNPs film was characterized by scanning electronic micrographs (SEM) and electrochemical impedance spectroscopy (EIS). The electrochemical behaviors of PEA at the modified GCE were investigated in detail. The synergetic effects of AuNPs, MWCNTs and Nafion amplify the electrochemical reduction signal of PEA, and result in high sensitivity for PEA determination. Under the optimal conditions, the electrochemical sensor shows a wide linear range of 0.01 to 10 (mol/L with a detection limit of 0.005 µmol/L. Moreover, the fabricated sensor presents high selectivity and long‐term stability, which paves a new way for simple, rapid, sensitive detection of PEA.     

MWCNTs/Ionic Liquid/Graphene Quantum Dots Nanocomposite Coated with Nickel‐Cobalt Bimetallic Catalyst as a Highly Selective Non‐enzymatic Sensor for Determination of Glucose

In this work, a glassy carbon electrode (GCE) was modified with multiwall carbon nanotubes/ionic liquid/graphene quantum dots (MWCNTs/IL/GQDs) nanocomposite. Then, the nanocomposite was decorated with nickel‐cobalt nanoparticles (Ni?Co NPs), and it was used as a non‐enzymatic glucose sensor. Field emission scanning electron microscopy, X‐ray diffraction spectroscopy, and energy dispersive spectroscopy were employed to prove the electrodeposition of the Ni?Co NPs on the surface of MWCNTs/IL/GQDs/GCE. Also, cyclic voltammetric and amperometric methods were utilized for the investigation of the electrochemical behaviour of the Ni?Co NPs/MWCNTs/IL/GQDs/GCE for glucose oxidation. The novel amperometric sensor displayed two linear ranges from 1.0 to 190.0 μmol L^?1 and 190.0 to 4910 μmol L^?1 with a low detection limit of 0.3 μmol L^?1 as well as fast response time (2 s) and high stability. Also, the sensor showed good selectivity for glucose determination in the presence of ascorbic acid, citric acid, dopamine, uric acid, fructose, and sucrose, as potential interference species. Finally, the performance of the proposed sensor was investigated for the glucose determination in real samples. Ni?Co NPs/MWCNTs/IL/GQDs/GCE showed good sensitivity and excellent selectivity.     

CuO Crystalline Modified Glassy Carbon Electrodes for Anodic Amperometric Determination of Hydrogen Peroxide

As an alternative selection of electrocatalytic surface modifier, the electrochemically generated copper oxides is re‐ investigated by using cyclic voltammetry (CV), scanning electron microscopy (SEM) and X‐ray photoelectron spectroscopy (XPS). Interesting phenomena have been found, which indicate that the electrodeposition from the Cu²⁺ solution under cyclic voltammetric conditions can generate a transparent Cu(OH)₂ crystalline on the surface of glassy carbon electrodes, and this crystalline can be further transferred to a novel cubic opaque CuO crystalline of about 300 nm in size by second step of cyclic voltammetry in pH 12 NaOH solution. The final electrode (denoted as nano‐CuO/GCE) can catalyze the oxidation (as well as the reduction) of H₂O₂ in basic solutions. It shows pH dependent three‐part catalytic mechanism in the range from pH 7 to pH 14. In 0.10 mol/L NaOH solution, the amperometric response at 0.15 V (vs. SCE) can give a current sensitivity as high as 139 mA/(mol·L^?1) in the rage of 5.0×10^?7?6.0×10^?4 mol/L with a lower detection limit (s/n=3) of 2.5×10^?8 mol/L, and a current sensitivity of 78.4 mA/(mol·L^?1) in the rage of 6.0×10^?4–2.0×10^?3 mol/L. This electrode also has excellent reproducibility and stability. The mechanisms for the two steps of preparation and the catalytic reactions are proposed. The nano‐CuO crystalline modified electrode may have more applications in the field of electrochemical sensing.     

Electroanalytical method for determination of shikonin based on the enhancement effect of cyclodextrin functionalized carbon nanotubes

A simple and sensitive electroanalytical method for determination of shikonin,a widely used antitumoral agent,using β-cyclodextrin-functionalized multiwalled carbon nanotubes composite modified glassy carbon electrodes(MWCNTs/β-CD/GCE) was presented.CDs are water-soluble and environmentally friendly and can improve the dispersibility of MWCNTs/β-CD functional materials,which was confirmed by SEM.The electrochemical behaviors of shikonin on different electrodes were investigated by cyclic voltammetry(CV) and differential pulse voltammograms(DPVs).The results demonstrated that the redox peak currents of shikonin obtained at MWCNTs/β-CD/GCE were much higher than those at theβ-CD/GCE and MWCNTs/GCE,which can be attributed to the combination of the excellent electrocatalytic properties of MWCNTs and the molecular recognition ability of β-CD.At MWCNTs/β-CD/GCE,the response current exhibits a linear range from 5.0 nmol/L to 10.0 μmol/L with a detection limit of 1.0 nmol/L(S/N = 3).As a practical application,the proposed method was applied to quantitatively determine shikoninin urine samples with satisfying results.     

Direct Electrochemistry and Electrocatalysis of Hemoglobin/ZnO‐Chitosan/nano‐Au Modified Glassy Carbon Electrode

The highly efficient H₂O₂ biosensor was fabricated on the basis of the complex films of hemoglobin (Hb), nano ZnO, chitosan (CHIT) dispersed solution and nano Au immobilized on glassy carbon electrode (GCE). Biocompatible ZnO‐CHIT composition provided a suitable microenvironment to keep Hb bioactivity (Michaelis‐Menten constant of 0.075 mmol L^?1). The presence of nano Au in matrix could effectively enhance electron transfer between Hb and electrode. The electrochemical behaviors and effects of solution pH values were carefully examined in this paper. The (ZnO‐CHIT)‐Au‐Hb/GCE demonstrated excellently electrocatalytical ability for H₂O₂. This biosensor had a fast response to H₂O₂ less than 4 s and excellent linear relationships were obtained in the concentration range from1.94×10^?7 to 1.73×10^?3 mol L^?1 with the detection limit of 9.7×10^?8 mol L^?1 (S/N=3) under the optimum conditions. Moreover, the stability and reproducibility of this biosensor were evaluated with satisfactory results.     

Characterization and Electrocatalytic Activity of Nanocomposites Consisting of Nanosized Cobalt Tetraaminophenoxy Phthalocyanine,Multi‐walled Carbon Nanotubes and Gold Nanoparticles

Glassy carbon electrodes were modified with composites containing cobalt tetraaminophenoxy phthalocyanine nanoparticles (CoTAPhPc NP ), multi‐walled carbon nanotubes (MWCNT) and gold nanorods (AuNRs). The modified electrodes were studied for their electrocatalytic behavior towards the reduction of hydrogen peroxide. Phthalocyanine nanoparticles significantly improved electron transfer kinetics as compared to phthalocyanines which are not in the nanoparticle form when alone or in the presence of multiwalled carbon nanotubes (MWCNTs). CoTAPhPc NP ‐MWCNT‐GCE proved to be suitable for hydrogen peroxide detection with a catalytic rate constant of 3.45×10³ M^?1 s^?1 and a detection limit of 1.61×10^?7 M. Adsorption Gibbs free energy ΔG^o was found to be ?19.22 kJ mol^?1 for CoTAPhPc NP ‐MWCNT‐GCE.     

A Highly Sensitive Electrochemical Impedance Spectroscopy Immunosensor for Determination of 1‐Pyrenebutyric Acid Based on the Bifunctionality of Nafion/Gold Nanoparticles Composite Electrode

A simple, highly sensitive and label‐free electrochemical impedance spectroscopy (EIS) immunosensor was developed using Nafion and gold nanoparticles (nano‐Au/Nafion) composites for the determination of 1‐pyrenebutyric acid (PBA). Under the optimal conditions, the amount of immobilized antibody was significantly improved on the nano‐Au/Nafion electrode due to the synergistic effect and biocompatibility of Nafion film and gold nanoparticles composites. The results showed that the sensitivity and stability of nano‐Au/Nafion composite electrode for PBA detection were much better than those of nano‐Au modified glassy carbon electrode (nano‐Au/GCE). The plot of increased electron transfer resistances (R_ets) against the logarithm of PBA concentration is linear over the range from 0.1 to 150 ng·mL^?1 with the detection limit of 0.03 ng·mL^?1. The selectivity and accuracy of the proposed EIS immunosensor were evaluated with satisfactory results.     

Glassy Carbon Electrode Modified via Molybdenum Disulfide Decorated Multiwalled Carbon Nanotubes for Sensitive Voltammetric Detection of Aristolochic Acids

In this study, a molybdenum disulfide/multiwalled carbon nanotubes (MoS₂@MWCNTs) nanocomposite was synthesized by employing a simple hydrothermal method. The flower‐like structure of the MoS₂@MWCNTs was characterized via scanning electron microscopy (SEM) and transmission electron microscopy (TEM), and the load of crystalline MoS₂ was verified via X‐ray diffraction (XRD) and energy‐dispersive spectroscopy (EDS). The as‐prepared MoS₂@MWCNTs nanocomposite was used to modify glassy carbon electrode (GCE) as an electrochemical sensor for detecting aristolochic acids (AAs). With the optimized parameters, the proposed electrochemical sensor exhibited good sensitivity and a broad linear concentration range for detecting AAs from 0.2 to 10 μ mol/L and 10 to 100 μ mol/L, with the sensitivity of ?3.10 μ A/(μ mol/L) and ?0.91 μ A/(μ mol/L), respectively. The detection limit was also calculated as 0.06 μ mol/L (S/N=3) based on the low background signal. Furthermore, the modified electrochemical sensor exhibited good selectivity, repeatability, reproducibility, and stability, thus showing potential application for detecting AA in chinese herbs with good mean recovery and accuracy. In other words, the MoS₂@MWCNTs/GCE can be used as an excellent platform to detect AAs.     

Electroanalysis of Bisphenol A at a Multiwalled Carbon Nanotubes‐gold Nanoparticles Modified Glassy Carbon Electrode

A sensitive electrochemical method was developed for the determination of bisphenol A (BPA) at a glassy carbon electrode (GCE) modified with a multiwalled carbon nanotubes (MWCNTs)‐gold nanoparticles (GNPs) hybrid film, which was prepared based on the electrostatic interaction between positively charged cetyltrimethylammonium bromide (CTAB) and negatively charged MWCNTs and GNPs. The MWCNT‐GNPs/GCE exhibited an enhanced electroactivity for BPA oxidation versus unmodified GCE and MWCNTs/GCE. The experimental parameters, including the amounts of modified MWCNTs and GNPs, the pH of the supporting electrolyte, scan rate and accumulation time, were examined and optimized. Under the optimal conditions, the differential pulse voltammetric anodic peak current of BPA was linear with the BPA concentration from 2.0×10^?8 to 2×10^?5 mol L^?1, with a limit of detection of 7.5 nmol L^?1. The proposed procedure was applied to determine BPA leached from real plastic samples with satisfactory results.     

Simultaneous Determination of Dopamine and Ascorbic Acid Using the Nano‐Gold Self‐Assembled Glassy Carbon Electrode

Electrochemical behavior of dopamine (DA) was investigated at the gold nanoparticles self‐assembled glassy carbon electrode (GNP/LC/GCE), which was fabricated by self‐assembling gold nanoparticles on the surface of L ‐cysteine (LC) modified glassy carbon electrode (GCE) via successive cyclic voltammetry (CV). A pair of well‐defined redox peaks of DA on the GNP/LC/GCE was obtained at E_pa=0.197 V and E_pc=0.146 V, respectively. And the peak separation between DA and AA is about 0.2 V, which is enough for simultaneous determination of DA and AA. The peak currents of DA and AA were proportional with their concentrations in the range of 6.0×10^?8–8.5×10^?5 mol L^?1 and 1.0×10^?6–2.5×10^?3 mol L^?1, with the detection limit of 2.0×10^?8 mol L^?1 and 3.0×10^?7 mol L^?1 (S/N=3), respectively. The modified electrode exhibits an excellent reproducibility, sensibility and stability for simultaneous determination of DA and AA in human serum with satisfactory result.     

Sensitive Determination of Terbutaline Using a Platform Based on Nanoparticles of Europium Oxide and Carbon Nanotubes

This study presents a sensitive voltammetric determination of terbutaline (TER) on a platform based on carbon nanotubes (CNTs) and europium oxide nanoparticles (Eu₂O₃NPs) coated glassy carbon electrodes (GCEs). An ultrasonic bath was performed for the preparation of composite material. The material was characterized by energy dispersive X‐ray spectroscopy (EDX), X‐ray diffraction method (XRD) and scanning electron microscopy (SEM). The Eu₂O₃NPs/CNTs/GCE system was assessed for the oxidation of terbutaline (TER). A broad oxidation peak was appeared at 0.71 V using a bare GCE. However, the voltammetry of TER has been improved at a GCE coated with CNTs and a well‐defined anodic peak exhibited at 0.61 V. Furthermore, the nanoparticles of Eu₂O₃ and CNTs coated GCE has greatly improved the electrochemical behaviour of TER and a sharp peak was appeared at 0.59 V. Cyclic voltammetry at Eu₂O₃NPs/CNTs/GCE also reveals a high catalytic effect for the oxidation of TER with an oxidation peak that is distinctly enhanced compared to GCE and CNTs/GCE. Eu₂O₃ nanoparticles were utilized to enhance the surface area of GCE and then improve the sensitivity of the procedure. The response of TER was linear over a concentration range of 2.0×10^?8 M ?9.5×10^?6 M with an LOD of 3.7×10^?9 M. Square wave voltammetric analysis of tablets by Eu₂O₃NPs/CNTs/GCE yielded a recovery of 99.2 % with an RSD% of 3.2. The modified electrode (EuO₂NPs/CNTs/GCE) provides accuracy and precision to the analysis of samples.     

A Solid‐State Electrochemiluminescence Immunosensor Based on MWCNTs‐Nafion and Ru(bpy)32+/Nano‐Pt Nanocomposites for Detection of α‐Fetoprotein

A approach was successfully employed for constructing a solid‐state electrochemiluminescence (ECL) immunosensor by layer‐by‐layer self‐assembly of multiwall carbon nanotubes (MWCNTs)‐Nafion composite film, Ru(bpy)₃²⁺/nano‐Pt aggregates (Ru‐PtNPs) and Pt nanoparticles (PtNPs). The influence of Pt nanoparticles on the ECL intensity was quantitatively evaluated by calculating the electroactive surface area of different electrodes with or without PtNPs to immobilize Ru(bpy)₃²⁺. The principle of ECL detection for target α‐fetoprotein antigen (AFP) was based on the increment of resistance after immunoreaction, which led to a decrease in ECL intensity. The linear response range was 0.01–10 ng mL^?1 with the detection limit of 3.3 pg mL^?1. The immunosensor exhibited advantages of simple preparation and operation, high sensitivity and good selectivity.     

Highly Sensitive Hydrazine Sensor Based on Co(OH)2 Nanoflakes Electrochemically Deposited on MWCNTs

We delineate the electrochemical preparation of cobalt hydroxide nanoflakes Co(OH)₂ NFs on multi‐walled carbon nanotubes (MWCNTs) by potentiostatic methods. The preparation was done on the surface of glassy carbon electrode (GCE). The prepared nanocomposite was characterized by field emission scanning electron microscopy (FESEM), X‐ray diffraction spectroscopy (XRD) and X‐ray photo electron spectroscopy (XPS). The resulting f‐ MWCNTs/Co(OH)₂ NFs modified GCE exhibits a good electrocatalytic activity for the oxidation of hydrazine in terms of decreasing over potential and increasing peak current. The modified electrode holds good in the linear range from 0.5 to 15.5 μM with limit of detection as 87.5 nM. The sensitivity of our modified electrode is calculated to be 5733 μA/mM cm‐2. Remarkably, the obtained LOD value of our sensor is very lower compared to the recommended concentration of hydrazine in water by World health organization (WHO) and Environmental protective agency (EPA). The modified electrode detects hydrazine selectively even in the presence of common interferants. Various water samples were chosen to study the practical feasibility of our sensor. The sensor also exhibited an appreciable stability, repeatability and reproducibility.     

Electrochemical Analysis of Sulfisoxazole Using Glassy Carbon Electrode (GCE) and MWCNTs/Rare Earth Oxide (CeO2 and Yb2O3) Modified-GCE Sensors

In this work, new electrochemical sensors based on the modification of glassy carbon electrode (GCE) with multiwalled carbon nanotubes (MWCNTs)—rare metal oxides (REMO) nanocomposites were fabricated by drop-to-drop method of MWCNTs-REMO dispersion in ethanol. REMO nanoparticles were synthesized by precipitation followed by hydrothermal treatment at 180 °C in absence and presence of Triton^TM X-100 surfactant. Cyclic voltammetry (CV) analysis using MWCNTs-CeO₂@GCE and MWCNTs-Yb₂O₃@GCE sensors were used for the analysis of sulfisoxazole (SFX) drug in water samples. The results of CV analysis showed that MWCNTs-REMO@GCE sensors have up to 40-fold higher sensitivity with CeO₂ compared to the bare GCE sensor. The estimated values of the limit of detection (LoD) of this electrochemical sensing using MWCNTs-CeO₂@GCE and MWCNTs-Yb₂O₃@GCE electrodes reached 0.4 and 0.7 μM SFX in phosphate buffer pH = 7, respectively. These findings indicate that MWCNTs-REMO@GCE electrodes are potential sensors for analysis of sulfonamide drugs in water and biological samples.