Surface Of Glassy Carbon Electrode Research Articles

Simultaneous Electrochemical Determination of Hydroquinone and Catechol by Lignocellulose Biopolymers Derived Porous Carbon

AbstractHemicellulose and lignin, which are main components of wood biomass with different structures, were carbonized and activated by KOH to prepare wood biomass‐derived porous carbons (WBM‐PCs). The resulting WBM‐PCs were characterized by SEM, XRD, Raman, FI‐IR, and N2‐adsorption/desorption isotherms, and successfully utilized as an effective modifier on the glassy carbon electrode surface (GCE) for simultaneous electrochemical determination of dihydroxybenzene isomers, i. e. hydroquinone (HQ) and catechol (CC), which are highly toxic and non‐degradable. The resulting WBM‐PCs‐modified GCEs allowed simultaneous determination of HQ and CC with cyclic voltammetry and constant‐potential amperometry. The linear range for determination of HQ by hemicellulose‐derived carbon (HC) was from 1.0 to 3000 μmol/L with the limit of detection (LOD) of 1.05 μmol/L, and that for CC was from 1.0 to 5000 μmol/L with LOD of 0.4 μmol/L. For lignin‐derived carbon (LC), the linear range for HQ was from 0.5 to 1000 μmol/L with LOD of 0.095 μmol/L, and that for CC was from 0.5 to 3000 μmol/L with LOD of 0.15 μmol/L. These results imply that wood biomass (hemicellulose and lignin), which is sustainable, renewable and environment‐friendly material, have potential as an effective precursor of electrochemically active porous carbon materials applicable to various electrochemical sensors.

Single-walled carbon nanotube coated with Ponceau4R-doped over-oxidized polypyrrole as a sensitive sensor for voltammetric monitoring of salbutamol

A sensitive voltammetric sensor is fabricated by the electrochemical oxidation of polypyrrole (PPy) on a glassy carbon electrode surface covered with a thin film of single-walled carbon nanotubes (SWCNT/GCE). Ponceau4R (P4R) used as an anionic dopant controlled the structure, stability, conductivity, and electrochemical properties of the PPy. The porosity and oxygen-containing active sites on the P4R-PPy/SWCNT/GCE were increased by over-oxidation of the PPy layer to achieve P4R-oPPY/SWCNT/GCE. Morphology features of the P4R-oPPY/SWCNT layer are thoroughly characterized using microscopy instruments. The salbutamol (SAL) voltammetric behavior is evaluated by P4R-oPPY/SWCNT/GCE and a mechanism for its electrochemical oxidation is proposed. Optimizing the important parameters in the electrode modification procedure, including the amount of SWCNT and electrochemically deposited P4R-oPPY, and SAL sensing steps such as the solution pH, potential and accumulation time of SAL are optimized precisely. At the best condition, a ~ 20 times enhancement of the SAL oxidation current was observed by P4R-oPPY/SWCNT modifier. Using P4R-oPPY/SWCNT/GCE, a wide two-part linear range of 0.02–10 μM with a detection limit of 6 nM is resulted in the electrochemical measurement of SAL. The P4R-oPPY/SWCNT/GCE with good reproducibility and stability succeeded in correctly measuring SAL in pharmaceutical and clinical samples.

An Electrochemical Sensor Based on Three-Dimensional Porous Reduced Graphene and Ion Imprinted Polymer for Trace Cadmium Determination in Water

Three-dimensional (3D) porous graphene-based materials have displayed attractive electrochemical catalysis and sensing performances, benefiting from their high porosity, large surface area, and excellent electrical conductivity. In this work, a novel electrochemical sensor based on 3D porous reduced graphene (3DPrGO) and ion-imprinted polymer (IIP) was developed for trace cadmium ion (Cd(II)) detection in water. The 3DPrGO was synthesized in situ at a glassy carbon electrode (GCE) surface using a polystyrene (PS) colloidal crystal template and the electrodeposition method. Then, IIP film was further modified on the 3DPrGO by electropolymerization to make it suitable for detecting Cd(II). Attributable to the abundant nanopores and good electron transport of the 3DPrGO, as well as the specific recognition for Cd(II) of IIP, a sensitive determination of trace Cd(II) at PoPD-IIP/3DPrGO/GCE was achieved. The proposed sensor exhibited comprehensive linear Cd(II) responses ranging from 1 to 100 μg/L (R2 = 99.7%). The limit of detection (LOD) was 0.11 μg/L, about 30 times lower than the drinking water standard set by the World Health Organization (WHO). Moreover, PoPD-IIP/3DPrGO/GCE was applied for the detection of Cd(II) in actual water samples. The satisfying recoveries (97–99.6%) and relative standard deviations (RSD, 3.5–5.7%) make the proposed sensor a promising candidate for rapid and on-site water monitoring.

Electrochemical Detection of Metol through the Cobalt Nickel Oxide Nanosheets Incorporated with MCM-41 Nanospheres Composites Modified Glassy Carbon Electrode

In this study, contaminations of metol (or Elon) in environmental water and industrial wastewater are the major causes of toxicity, which is very harmful to human health and other living things. Hence the determination of metol in high demand is more important. Further, the Mobil Composition of Matter (MCM-41) mesoporous silica nanoparticles incorporated with cobalt nickel oxide (CoNiO2) complex to form MCM-41/CoNiO2 composite modifying the glassy carbon electrode (GCE) used for metol detection. The MCM-41/CoNiO2 composite coated on the GCE surface exhibited fast electron transfer kinetics, improved conductivity, a large surface area, active stability, and improved catalytic efficiency. The structural morphology of the MCM-41/CoNiO2 composite was investigated using several spectroscopic and microscopic techniques. Here, the MCM-41/CoNiO2 composite was verified using different characterization studies such as Field Emission Scanning Electron Microscopy, Transmission Electron Microscopy, Energy Dispersive X-ray Analysis, X-ray Diffraction Analysis, and X-ray Photoelectron Spectroscopy. Additionally, the electrochemical investigations have included Electrochemical Impedance Spectroscopy, Cyclic Voltammetry, and Differential Pulse Voltammetry studies. The GCE/MCM-41/CoNiO2 electrode shows a low detection limit of 10 nM and the LOQ value is 0.1 μM with a broad linear response range of 0.1–750 μM, and greater sensitivity of 0.411 μA μM−1 cm−2 under optimal voltammetry.

Preparation of graphene-supported S-doped cobalt molybdate composite towards efficient electrochemical oxygen evolution reaction

In this paper, graphene-supported S-doped cobalt molybdate composite (S-CoMoO4/GR) was prepared by a simple in situ hydrothermal method. X-ray diffractometer (XRD) was employed to determine the component, which verified that S was doped in the CoMoO4. X-ray photoelectron spectroscopy (XPS), N2 adsorption-desorption analysis and scanning electron microscopy (SEM) was used to observe the surface valence state, microstructure and the morphology of the composite, which demonstrated that S-CoMoO4 was dispersed on the carrier of GR with small plate morphology. Then, the composite was applied on the surface of glassy carbon electrode with oxygen evolution reaction (OER) performance investigated by different electrochemical technologies including linear sweep voltammetry, cyclic voltammetry, electrochemical impedance spectroscopy and i-t tests. The results demonstrate that the prepared catalyst needs an overpotential of 354 mV to achieve the current density of 10 mA cm−2 (η10) and presents good long-term stability with a negligible current decrease in 30 h i-t test, verifying its good OER performance.

Electrochemical deposition of Pd on MoS2 supported graphene nanoflakes over functionalised MWCNTs as an immunosensor for detection of lung cancer biomarker

An electrochemical immunosensor was designed to quantify carcinoembryonic antigen (CEA), which is regarded asa tumour marker and prognostic indicator. The glassy carbon electrode (GCE) surface was modified using MoS2, graphene nanoflakes (GNs), fMWCNTs, and electrodeposited PdNPs for the first time to prepare a Pd-MoS2-GNs@fMWCNTs/GCE. The platform was activated with monoclonal anti-CEA. The prepared nanocomposite material helps in improving the surface area and conductivity of the GCE. Moreover, PdNPs act as a linker between nanocomposite materials and anti-CEA, which enhances electron transport. The procedure used to analyse CEA involve sequential addition of CEA into the solution of 5 mM [Fe(CN)6]3-/4- prepared in 0.1 M PBS (pH 7.4) in the presence of fabricated electrode and DPV and EIS methods were used as detection technique. The change in signal response for the [Fe(CN)6]3-/4- redox reaction before and after CEA interaction is considered as the immunosensor response which is directly correlated with CEA concentration. Further, in DPV, the signal inhibition approach was used to measure CEA by monitoring the decrease in oxidation peak current of [Fe(CN)6]3-/4- due to the formation of CEA/anti-CEA immunocomplex. The electrochemical immunosensor demonstrated low LOD of 2 pg/mL and a correlation coefficient of 0.98 within a broad linear range of CEA concentration from 0.002 to 500 ng/mL. The fabricated immunosensor displayed excellent selectivity, repeatability, and stability. Further, the proposed immunosensor effectively measured CEA levels in human blood serum, making it an effective tool for testing CEA in clinical samples.

Electrochemical sensor for simultaneous determination of antiviral favipiravir drug, paracetamol and vitamin C based on host–guest inclusion complex of β-CD/CNTs nanocomposite

Favipiravir (FVI) is extensively used as an effective medication against several diverse infectious RNA viruses. It is widely administered as an anti-influenza drug. Combination therapy formed from FVI, paracetamol (PAR) and vitamin C (VC) is needed for treating patients diseased by RNA viruses. Thus, an efficient electrochemical sensor is developed for detecting FVI in human serum samples. The sensor is fabricated by casting a thin layer of carbon nanotubes (CNTs) over a glassy carbon (GC) electrode surface followed by electrodeposition of another layer of β-cyclodextrin (β-CD). Under optimized conditions, the sensor shows excellent catalytic effect for FVI, PAR and VC oxidation in the concentration ranges (0.08 µM → 80 µM), (0.08 µM → 50 µM) and (0.8 µM → 80 µM) with low detection limits of 0.011 μM, 0.042 μM and 0.21 μM, respectively. The combined effect of host–guest interaction ability of β-CD for the drugs, and a large conductive surface area of CNTs improves the sensing performance of the electrode. The sensor exhibits stable response over 4 weeks, good reproducibility, and insignificant interference from common species present in serum samples. The reliability of using the sensor in serum samples shows good recovery of FVI, PAR and VC.

Cobalt di-selenide embedded polymerised melamine paraformaldehyde resin: A robust and efficient electrocatalyst for OER with operando investigations

In past research metal selenides have reported versatile results in the field of water splitting. Cobalt di-selenide has received much attention in the oxygen evolution reaction (OER) due to its excellent results towards OER. To excel the reaction capability, herein we have reported CoSe2, pMF-R and CoSe2@pMF-R nanostructures in which the freshly prepared CoSe2 nanostructures were decorated on the surface of pMF-R (polymerised melamine paraformaldehyde resin). The study showed that the bonds between cobalt and nitrogen were well formed, which is maintaining the improved charge transfer channels to annihilate the barriers between the GC (glassy carbon) electrode surface and active sites of CoSe2. Because of the coaction of CoSe2 and pMF-R, the OER calibration of the CoSe2@pMF-R catalyst has shown a low onset potential 1.56 V and its electrochemical activity towards OER was found to be much higher as 10 mAcm−2 at 1.608 V Vs. RHE. Operando spectroelectrochemical investigations revealed that active sites of selenium, Co2+, Co3+ and pMF-R available for generation of intermediate oxygen species and responsible for exponential increase in rate of OER. The order of reaction is found to one. The compositional and structural characteristics of CoSe2@pMF-R composite over other electrocatalysts is responsible for outstanding electrochemical performance.

Synthesis of metal–organic nanofiber/rGO nanocomposite as the sensing element for electrochemical determination of hypoxanthine

Abstract In this study, metal–organic nanofibers (MONFs) and reduced graphite oxide (rGO) nanocomposite were used to modify the surface of glassy carbon electrode, and the electrochemical sensor was applied to the differential pulse voltammetry determination of hypoxanthine, the oxidation intermediate of human purine degradation metabolism. The preparation of MONFs/rGO nanocomposite is simple, efficient, and environmentally friendly. The morphology and structure of MONFs/rGO nanocomposite were characterized by field emission scanning electron microscopy and X-ray diffraction. The results show that the improved sensor has a significant increase in current density, with linear ranges of 0.1–10 and 20–100 μM. Detection limit 0.01 μM (S/N = 3). Under the optimized conditions, the improved sensor shows very good stability, selectivity, and improved accuracy.

Electro‐elucidation and quantification of olopatadine hydrochloride in bulk form and eye drops using modification free glassy carbon electrode with its development by different electrolytes and surfactants

AbstractThe electro‐oxidation pathway of olopatadine hydrochloride which is used in eye drops as antihistaminic agent was proposed and discussed in detail as the first time using different voltammetry methods at the modification free glassy carbon electrode surface. The oxidation process of olopatadine hydrochloride based on the presence of electro‐active tertiary amine group was irreversible. The dissociation constants were attained by the dependence of peak current and potential on the pH values. Some kinetic parameters were also estimated. Depending on the oxidation of olopatadine hydrochloride in citrate buffer (pH 5.5; 0.1 M) and sodium dodecyl sulfate (3×10−5 M) as supporting electrolyte and a modifier, respectively, sensitive, simple, accurate and inexpensive a novel square wave voltammetry method was achieved. The method was validated for linearity, precision, accuracy, ruggedness, specificity and stability. Limit of detection of 9×10−7 M in bulk form was attained. The characterized method was successfully used for routine analysis of olopatadine hydrochloride in pharmaceutical eye drops (Olohistine® and olopalite). No electroactive interferences from the inactive ingredients present in eye drops were noticed. So the proposed method does not necessitate any extraction step preceding the drug analysis. Also, the obtained data of the calibration curve and standard addition methods were compared statistically with a reported spectrophotometrically method showing no differences between them with respect to accuracy and precision, what proved the reproducibility, suitability and reliability of the described voltammetric method for assay of olopatadine hydrochloride in its formulation.

Simple and Intelligent Electrochemical Detection of Ammonia over Cuprous Oxide Thin Film Electrode

To realize simple and intelligent electrochemical ammonia (NH3) detection in water, highly dense colloidal copper nanoparticles (CuNPs) were prepared and subsequently deposited onto a glassy carbon electrode (GCE). The CuNPs/GCE was then placed in an oven at 60 °C to intelligently transform CuNPs into cuprous oxide (Cu2O) thin film. The colloidal CuNPs were characterized by ultraviolet-visible (UV-Vis) spectroscopy, whereas the fabricated Cu2O/GCE was subjected to Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and electrochemical impedance spectroscopy (EIS). The XRD of Cu2O/GCE showed the crystalline nature of the thermally converted Cu2O thin film, whereas XPS demonstrated that the thin film formed on the surface of GCE was primarily composed of Cu2O. The SEM images of Cu2O/GCE revealed Cu2O crystals with hexapod morphology. The EIS study exhibited substantially higher charger transfer activity of Cu2O/GCE compared to bare GCE. The drop coating of ammonia (NH3) solution onto Cu2O/GCE enabled the fabricated electrode to be utilized as an electrochemical sensor for NH3 detection in water. The cyclic voltammetric (CV) behavior of NH3/Cu2O/GCE was investigated in 0.1 M pH 7 phosphate buffer, which led to the formation of a copper-ammonia complex and revealed the nobility of the fabricated electrode. The square wave voltammetric (SWV) response was linear over the 10 µM and 1000 µM ranges with a detection limit of 6.23 µM and good reproducibility. The NH3/Cu2O/GCE displayed high selectivity for the detection of NH3 in the presence of various coexisting cations and anions in 0.1 M pH 7 phosphate buffer. The recovery of NH3 in the drinking water sample varied from 98.2% to 99.1%.

A sensitive biosensor for cyanide detection using modified glassy carbon electrode with reduced graphene oxide and immobilization of horseradish peroxidase

AbstractCyanide is a highly poisonous and hazardous substance which may release into the environment from natural sources or industrial effluent; therefore, cyanide detection is a fundamental step to prevent environmental pollution and secure health and safety. In this study, we prepared a sensitive amperometric inhibition biosensor for cyanide detection by immobilization of horseradish peroxidase (HRP) enzyme and reduced graphene oxide (rGO) on the surface of glassy carbon electrode (GCE). To do so, we performed the amperometric measurement by modified GCE to test its efficiency in detecting cyanide. The optimum conditions of pH equal to 7.5, −100 mV applied potential, 0.7 μM mediator concentration, and 0.5 mM substrate concentration were found. Then, experiments were performed at different boundary conditions in a range of 0.1 to 10 μM cyanide concentration at optimal conditions and a low detection limit of 0.01 μM was obtained. Also, the possible mechanism of inhibition was analyzed based on the Michalis–Menten equation and non‐competitive inhibition was observed. Due to high sensitivity, low detection limit, and low cost, this biosensor is proposed as a useful method for cyanide determination in real samples.

Efficient Electro-Oxidation of 2-Propanol at Platinum- and Gold-Modified Palladium Nanocatalysts

This study aims at investigating the catalytic performance of Pd, Pd/Pt, and Pd/Au nanocatalysts toward the 2-propanol electro-oxidation reaction (2POR) in an alkaline medium. The catalyst components (Pd, Pt, and Au) were sequentially electrodeposited onto the glassy carbon (GC) electrode surface and further characterized using electrochemical (cyclic voltammetry (CV)) and materials (field-emission scanning electron microscopy (FE-SEM) coupled with energy-dispersive X-ray (EDX)) characterization methods. The Pd/Au/GC catalyst showed the highest catalytic activity in terms of the highest oxidation current (0.386 mA) and the highest stability in terms of the highest obtained current after 1800 s of continuous electrolysis. This behaviour was attributed to the enhancement in the charge transfer kinetics where the Pd/Au/GC catalysts acquired the lowest charge transfer resistance (Rct, 1.85 kΩ) during the 2POR.

Investigations on the electrochemical behavior of sunitinib and metabolites N-desethyl-sunitinib and sunitinib-N-oxide and its selective determination using molecularly imprinted polymer-based sensor

Sunitinib (SUN) is an orally administered tyrosine kinase inhibitor and is mainly metabolized via N-deethylation to form the primary active metabolite N-desethyl-sunitinib (M1) and via oxidation to sunitinib-N-oxide (M2). In this study, we first investigated the electrochemical behavior of sunitinib and its N-desethyl and N-oxide metabolites on a bare glassy carbon electrode (GCE) by cyclic voltammetry (CV) technique. Based on the results, a plausible electrooxidation mechanism is proposed, yielding the oxo-desfluoro-sunitinib (quinoneimine metabolite) via oxidative defluorination of sunitinib. After this phase of the study, due to the low sensitivity and selectivity results obtained from the bare GCE, we aimed to develop the first molecularly imprinted polymer (MIP)-based electrochemical sensor for the sensitive and selective determination of SUN. The MA@SDS/MIP-GCE sensor was prepared by thermal polymerization of methacrylic acid (MA) as a functional monomer in the presence of SUN on a GCE surface under the optimized parameters such as template/monomer ratio, drop amount, polymerization temperature and time, removal solution and time, and rebinding time, which affect the structure and response of the sensor. The surface characterization of the developed sensor was performed by scanning electron microscopy (SEM), and the electrochemical characterization was performed by CV and electrochemical impedance spectroscopy (EIS). The electroanalytical performance of the MA@SDS/MIP-GCE sensor was tested by differential pulse voltammetry (DPV) under the optimized conditions in comparison with the NIP-based sensor. The linearity of the developed sensor for the determination of SUN was investigated in the concentration range of 0.5 – 5.0 nM for standard and serum solutions with low LOD and LOQ values. The application of the MIP sensor for the determination of SUN in pharmaceutical dosage form (capsule) and serum samples was demonstrated with excellent recoveries. The results showed that the MA@SDS/MIP-GCE sensor is a sensitive, specific, selective, rapid, and economical option for the quantitative determination of SUN.

Electrochemical sensing of cysteine using a novel carbon black and cobalt phthalocyanine composite

In this work, a novel composite material using carbon black and cobalt phthalocyanine (CoPc/CB) was produced. Characterizations by spectroscopic techniques (Raman and infrared), scanning electron microscopy, and X-ray diffraction confirmed the formation of the composite material. The proposed material was cast on the glassy carbon electrode surface, and its electrochemical sensing properties were checked using cysteine (CYS), an important amino acid widely used in medicine, food additives, and cosmetics, as a model molecule. Studies by cyclic voltammetry revealed that the modified electrode caused considerable electrocatalytic effects (detection at a potential close to 0.1 V) and enhanced in peak current compared to the unmodified electrode. A wide linear range (1—150 µmol/L) and adequate detectability (LOD = 0.75 µmol/L) were achieved by Batch Injection Analysis (BIA) with amperometric detection. Repeatability tests (n = 20) at two concentration levels (20 and 40 µmol/L) confirmed the precision of the method (RSD < 11 %). Interestingly, even under high flow conditions, good stability of the electrode modification was noticed. The proposed method was applied to determine CYS concentration in pharmaceutical samples, where adequate recovery values (89 and 110 %) and results statistically similar to those achieved by capillary electrophoresis indicated the accuracy and reliability of the electrochemical analyses.

CoCr2O4/Graphene modified glass carbon electrode for highly dual-sensing detection of hydrogen peroxide and glucose

The development of a non-enzymatic electrochemical sensor possessing well dual-sensing to H2O2 and glucose remains challenging due to less report. Herein, spinel CoCr2O4 nanoparticles with small size were synthesized by sol–gel reaction, which were then simply mixed with commercial graphene under ultrasonic to obtain uniformly dispersed CoCr2O4/Graphene composite. They were deposited onto the surface of bare glassy carbon electrode (GCE) through a common drop-coating method. The CoCr2O4/Graphene/GCE sensor firstly achieves highly dual-sensing to H2O2 and glucose in 0.1 M NaOH solution. At 0.4 and 0.55 V, its sensitivities to H2O2 and glucose can separately reach up to 1168.6 and 1722.5 μA mM−1 cm−2, and the corresponding detection limits are as low as 18 nM and 12 nM. These key indexes are the best among reported dual-functional spinel oxide-based electrodes. This excellent electrochemical sensing ability stems from its large electrode active area, good conductivity, and the synergism between graphene and CoCr2O4 nanoparticles with mixed redox couplings, which provides an efficient platform for dual-sensing detection. In addition, the modified electrode can accurately determine glucose in human tears, rat serum and orange juice, as well as H2O2 in milk whey, mouthwash and disinfectant, thus predicting its good application prospects.

Zeolitic imidazolate framework-8/polyaniline nanocomposite-based electrochemical sensor for sensitive detection of imidaclothiz

Imidaclothiz (IMZ) is a class of neonicotinoid insecticide which can pose potential threat to human health and be frequently detected in water and foods. Herein, a zeolitic imidazolate framework-8/polyaniline (ZIF-8/PANI) nanocomposite has been modified on the surface of glassy carbon electrode (GCE) for the electrochemical determination of IMZ, and the electrochemical detection performance of the modified electrode was investigated by cyclic voltammetry (CV) and square wave voltammetry (SWV). With the large surface area of ZIF-8 and great electric conductivity of PANI, the ZIF-8/PANI-modified electrode showed a high catalytic performance towards IMZ reduction in PBS. Under the optimized conditions, the linear range was from 1.0 × 10−7 to 1.0 × 10−5 mol/L and the limit of detection was as low as 2.5 × 10−8 mol/L (S/N = 3). In addition, the developed sensor displayed high reproducibility, excellent stability, and applicability in real vegetable sample analysis, indicating that the proposed method offered an alternative approach for IMZ residues analysis.Graphical abstract

Electrocatalytic response of nitrogen-doped hollow carbon spheres modified glassy carbon electrode for sulphite detection in water

In this work, the glassy carbon electrode (GCE) surface was modified with nitrogen-doped hollow carbon spheres (N-HCSs) to achieve a new electrochemical sulphite sensor (N-HCSs/GCE) in water samples. The N-HCSs were explored for electrocatalytic behavior through voltammetric approaches using a routine three-electrode system. The findings revealed an admirable efficiency for modified electrodes towards sulphite oxidation, highlighting the effectiveness of our as-produced sulphite sensor. The differential pulse voltammetry was utilized under obtained optimal circumstances to study the as-developed sensor, the results of which underlined linear electrochemical current in relation to sulphite concentration, with dynamic range as wide as 1.0-100.0 μM and limit of detection as narrow as 0.35 μM. Moreover, N-HCSs/GCE had commendable practical applicability for sensing sulphite present in real specimens with voltammetric techniques.

(111) Facet-enhancing performance of pure octahedral Cu2O nanocrystal for the electrochemical detection of malachite green

ABSTRACT Malachite Green (MG) is a widely used triphenyl alkyl dye, which can cause serious water pollution. Therefore, it is necessary to monitor the MG residue in the environment. In this paper, octahedral cuprous oxide (o-Cu2O) nanoparticle has been synthesised for the modification of glassy carbon electrode (GCE), aiming to determine trace MG by square wave anodic stripping voltammetry (SWASV). Since the exposed (111) crystal facet of o-Cu2O contains abundant unsaturated active ‘copper’ atoms, it can not only enrich MG to the surface of GCE through strong coordination, but also amplify MG response signal due to its excellent electrocatalytic activity. Finally, the electrochemical detection of trace MG can be realized by only using the synthesised o-Cu2O as the electrode modification material. Mechanism studies reveal that the adsorption of MG onto o-Cu2O/GCE surface is controlled by an irreversible ‘two-electron/single-proton’ transfer process. Under optimal conditions, the peak current of MG shows a good linear relationship with its concentration in the range of 0.04 μmol/L − 10 μmol/L and 10 μmol/L − 100 μmol/L, and the limit of detection is 4.57 nmol/L (S/N = 3). This novel electrochemical sensor can be applied for the determination of MG residues in real aquatic products and water resources. In conclusion, this work has successfully developed a simple, economical and environmentally friendly MG analysis method, which can be realized by modifying the electrode with only one single highly active material, providing new possibilities for the efficient detection of similar poisons by electrochemical methods in a more convenient way.

BiW9-based electrochemical sensor for the simultaneous determination of cadmium(II) and lead(II) in water

Heavy metal pollution has been considered as an important concern for the environment, and effective detection methods are crucial for the sensitive and selective determination of toxic heavy metal ions such as lead and cadmium. Among various detection methods, electrochemical stripping analysis has been regarded as an efficient approach for the determination of heavy metal ions, especially on bismuth-based materials. Polyoxometalates have been received lots of attention and widely applied in many fields. However, the bismuth-containing polyoxometalate has never been reported for the determination of heavy metals. In this study, Na9[BiW9O33]·16H2O (BiW9) was utilized to construct an electrochemical sensor towards the simultaneous detection of Cd(II) and Pb(II). The prepared bismuth-containing polyoxometalate BiW9 was characterized by X-ray diffraction and Fourier transform infrared spectroscopy, which was then casted onto the surface of glassy carbon electrode (GCE) to test the electrochemical behavior by square wave anodic stripping voltammetry. The results showed that BiW9/GCE possesses a good electroanalytical performance for the simultaneous determination of Cd(II) and Pb(II) with wide linear ranges and low detection limits. Moreover, the sensor shows good selectivity, repeatability, reproducibility and stability, and owns broad application prospects in the detection of practical water samples. The proposed bismuth-based polyoxometalate fabricated electrochemical sensor exhibits good performance towards the heavy metal ions detection, which may benefit the further application in practical fields.