Nanoparticle-modified Glassy Carbon Electrode Research Articles

The Ultrasensitive Detection of Aflatoxin M1 Using Gold Nanoparticles Modified Electrode with Fe3+ as a Probe.

The increasing incidence of diseases caused by highly carcinogenic aflatoxin M1 (AFM1) in food demands a simple, fast, and cost-effective detection technique capable of sensitively monitoring AFM1. Recent works predominantly focus on the electrochemical aptamer-based biosensor, which still faces challenges and high costs in experimentally identifying an efficient candidate aptamer. However, the direct electrochemical detection of AFM1 has been scarcely reported thus far. In this study, we observed a significant influence on the electrochemical signals of ferric ions at a gold nanoparticle-modified glassy carbon electrode (AuNPs/GCE) by adding varying amounts of AFM1. Utilizing ferricyanide as a sensitive indicator of AFM1, we have introduced a novel approach for detecting AFM1, achieving an unprecedentedly low detection limit of 1.6 × 10-21 g/L. Through monitoring the fluorescence quenching of AFM1 with Fe3+ addition, the interaction between them has been identified at a ratio of 1:936. Transient fluorescence analysis reveals that the fluorescence quenching process is predominantly static. It is interesting that the application of iron chelator diethylenetriaminepentaacetic acid (DTPA) cannot prevent the interaction between AFM1 and Fe3+. With a particle size distribution analysis, it is suggested that a combination of AFM1 and Fe3+ occurs and forms a polymer-like aggregate. Nonetheless, the mutual reaction mechanism between AFM1 and Fe3+ remains unexplained and urgently necessitates unveiling. Finally, the developed sensor is successfully applied for the AFM1 test in real samples, fully meeting the detection requirements for milk.

Electroanalytical Determination of Ziram by Differential Pulse Voltammetry with Reduced Graphene Oxide/Gold Nanoparticles Modified Glassy Carbon Electrode

The preparation of gold nanoparticles-reduced graphene oxide-based sensor materials for the determination of zinc(II)dimethyldithiocarbamate (ziram) is described in this paper. The graphene oxide (GO) was synthesized using a modified Hummer's method. A composite sensor consisting of gold nanoparticles (AuNPs) and reduced graphene oxide (RGO) was electrochemically fabricated on a glassy carbon electrode. The nanocomposite was evaluated utilizing scanning electron microscopy (SEM). Cyclic voltammetry was used to illuminate the modified sensor's electrochemical properties at each stage of the modification. The suggested sensor was demonstrated good analytical performance to determine ziram pesticide in water and peach juice, including a very low detection limit, a large linear range, and a low RSD.

Arsenic (III) detection with underpotential deposition on gold

We report a new, sensitive stripping voltammetric method for the detection of As(III) in aqueous solution using either a gold macroelectrode or a gold nanoparticle-modified glassy carbon electrode (GCE) based on the underpotential deposition (UPD) of As ad-atoms. The pre-concentration step deposits and accumulates As ad-atoms onto gold and is followed by a potential sweep to strip the ad-atoms with no interference from Cu(II) or Cl- at either electrode. Linear responses were found for the range 0.01 μM to 0.1 μM or 0.005 μM to 0.1 μM at gold macroelectrodes and gold nanoparticle-modified electrodes, respectively. The visually clearly discernable signals recorded at 0.005 μM (0.4 ppb) on gold nanoparticle-modified electrodes suggests that this method has practical value given the WHO limit of 0.13 μM (10 ppb) for drinking water.

Enhanced Electrocatalytic Oxidation of Glucose on Nickel Oxides/Graphene Nanoparticles Modified Glassy Carbon Electrode

Enhanced Electrocatalytic Oxidation of Glucose on Nickel Oxides/Graphene Nanoparticles Modified Glassy Carbon Electrode

Electrochemical Analysis of Free Glycerol in Biodiesel Using Reduced Graphene Oxide and Gold/Palladium Core-Shell Nanoparticles Modified Glassy Carbon Electrode

Glycerol is a major byproduct obtained in the production of biodiesel, an important renewable fuel. The presence of free glycerol in fuel can have structural and performance consequences with respect to the engine, making fuel quality control important. The standard method to analyze glycerol in biodiesel is gas chromatography, a time-consuming and expensive technique. In this context, an electrode based on glassy carbon electrodes (GCEs) modified with reduced graphene oxide and core-shell gold@palladium nanoparticles was developed for the determination of glycerol in biodiesel. The free glycerol analysis was performed in the aqueous phase obtained by liquid–liquid extraction from a biodiesel sample. Cyclic voltammetry was chosen as the method for glycerol electrochemical analysis to regenerate active sites and promote greater sensor stability. The modified Au@Pd/rGO/GCE electrode showed an excellent performance, obtaining a linear range of 18.2 to 109 µmol L−1 with a correlation coefficient of 0.9895, limits of detection and quantification of 5.33 and 17.6 µmol L−1, respectively, high stability during 1000 cycles, and recovery values of 86% and 87% in the quantification of glycerol in biodiesel samples. The proposed method proved to be a great alternative for the analysis of glycerol in biodiesel, being a fast, sensitive, and low-cost technique due to its high stability and the use of small quantities of reagents.

End-labeling-based electrochemical strategy for detection of adenine methylation in nucleic acid by differential pulse voltammetry.

Apromising electrochemical strategy for assay of N6-methyladenosine (m6A)/N6-methyladenine (6mA) in RNA/DNA is proposed. The key of this strategy is the end-labeling of nucleic acid, which makes it possible to detect methylation level in unknown sequence. Firstly, the end of m6A-RNA or 6mA-DNA was labeled with sulfhydryl group through T4 polynucleotide kinase (T4 PNK) and then directly assembled on agold nanoparticle-modified glassy carbon electrode (AuNPs/GCE). Secondly, methylation sites in RNA/DNA were specifically recognized by anti-m6A-antibody, and then, horseradish peroxidase-labeled goat anti-rabbit IgG (HRP-IgG) was further conjugated on the antibody. Thirdly, HRP-IgG catalyzed the hydroquinone oxidation reaction to generate amplified current signal which correlates with the amount of m6A/6mA in nucleic acid. This method showed a wide linear range from 0.0001 to 10 nM for m6A-RNA, 0.001 to 100 nM for 6mA-dsDNA, and 0.0001 to 10 nM for 6mA-ssDNA. The method was successfully applied to detection of m6A/6mA in RNA/DNA from HeLa cells and E. coli cells and validation of the decrease of m6A-RNA in HeLa cells after treatment with FTO protein.

Ultra-selective determination of carbofuran by electrochemical sensor based on nickel oxide nanoparticles stabilized by ionic liquid

In this work, an electrochemical sensor based on glassy carbon electrode modified with nickel oxide nanoparticles assisted by ionic liquid was developed for selective determination of carbofuran in green vegetables. Controlled synthesis of NiO nanoparticles was carried out by aqueous chemical growth procedure. Synthesized NiO nanoparticles were found to be ostensible candidate for selective determination of carbofuran, which is a highly toxic and hazardous pesticide. The crystallinity and morphology of as-synthesized NiO was confirmed by XRD, EDXS, and SEM. The average size of IL-assisted NiO nanoparticles was calculated to be 22.7 nm. Cyclic voltammetry was employed to compare the electrochemical behavior of NiO nanoparticles-modified glassy carbon electrode using IL with bare glassy carbon electrode by discriminating oxidation peak current response. For the determination of carbofuran, the linear dynamic range for IL-assisted NiO nanoparticles was achieved as 5.0–305 µM with limit of detection 0.5 µM. The developed sensor was successfully applied for selective determination of carbofuran in real samples of green vegetables with the percent recoveries observed from 93.3 to 103.5.

Nickel oxide nanoparticles-modified glassy carbon electrodes for non-enzymatic determination of total sugars in commercial beverages

Nickel oxide nanoparticles of about 6 nm were obtained in two simple steps. Nanoparticles were characterized by using FTIR spectroscopy, TEM images, thermal analysis, X-ray diffraction and electrochemical techniques. GCEs were modified with nanoparticles by the casting method and their sensing properties were optimized. Electrochemical tests confirmed their excellent electrocatalytic properties, which are able to detect glucose, fructose, lactose and sucrose. Under optimized conditions NiO NPs-modified sensors showed a good sensitivity of about 3.06 A M−1 cm−2 (R2:0.999), linear range up to 0.6 mM, a fast time response (ca. 3 s) with a limit of detection of 0.39 μM. Their selectivity was tested for common interferences with promising results. The application of the sensor in real samples was evaluated by determining the total sugar content in different commercial beverages with recoveries of about 100%.

Differential Electroanalysis of Dopamine in the Presence of a Large Excess of Ascorbic Acid at a Nickel Oxide Nanoparticle-Modified Glassy Carbon Electrode

Electrochemical determination of dopamine (DA) in the presence of a large excess of ascorbic acid (AA) in their coexistence at a nickel oxide nanoparticle-modified preoxidized glassy carbon electrode (GCox/nano-NiOx) is achieved. The GCox/nano-NiOx electrode is prepared by electrodeposition of nickel nanoparticles (nano-Ni) onto an electrochemically activated glassy carbon (GC) electrode, and the thus prepared nano-Ni were subjected to electrochemical oxidation in alkaline medium for the formation of nickel oxide (NiOx). Modified electrodes were electrochemically and morphologically characterized. The effect of loading level of nickel was investigated by changing the number of potential cycles for the deposition of nano-Ni, i.e., 1, 2, 5, and 10 potential cycles, in the potential range from 0 to -1.0 V vs. SCE. Also, the experimental and instrumental parameters were optimized. Experimental results showed that the modified electrode differentiates well the oxidation peaks of DA and AA enabling the electrochemical determination of DA in the presence of a large excess of AA. Remarkably, it is found that the oxidation current of DA is 2 times larger than that of AA even the concentration of AA is about 5 times larger than that of DA. The LOD and LOQ of DA were calculated and were found to equal 0.69 and 2.3 mM, respectively. This offers the advantage of simple and selective detection of DA free of the interference of AA in real samples.

Magneto-Biosensor for the Detection of Uric Acid Using Citric Acid-Capped Iron Oxide Nanoparticles.

In this work, a magneto-biosensor based on iron (II, III) oxide (magnetite, Fe₃O₄) nanoparticles for the detection of uric acid is developed and demonstrated. These Fe₃O₄ nanoparticles are successfully synthesized by a co-precipitation method comprising Fe2+ and Fe3+ with ammonium hydroxide, NH4OH, and using citric acid as a surfactant. Comparative studies of Fe₃O₄ nanoparticles with and without surfactant are also carried out to examine their characteristics. Both types of synthesized iron oxide nanoparticles are characterized by X-ray diffraction, X-ray photoelectron spectroscopy, field emission-scanning electron microscopy, transmission electron microscopy, and vibrating sample magnetometry. The images obtained by field emission-scanning electron microscopy show an average diameter of 30 nm for citric acid-Fe₃O₄ nanoparticles. The Fourier transform infrared spectra indicate that the carboxylate groups of citric acid are bound onto the surface of magnetite nanoparticles by chemical bonds. For sensing experiments, the synthesized nanoparticles are used to modify the glassy carbon electrode, and the resultant citric acid-Fe₃O₄ modified glassy carbon electrode is used for the detection of uric acid through cyclic voltammetry. In the case of the citric acid-Fe₃O₄ nanoparticles-modified glassy carbon electrode, uric acid is oxidized at a less positive potential compared to oxidation using the naked Fe₃O₄ nanoparticles and a bare glassy carbon electrode. The citric acid-Fe₃O₄ nanoparticles-modified glassy carbon electrode exhibit a good linear response range for the detection of uric acid of 7.5 μM-0.18 mM, with a lower detection limit of 7.5 μM uric acid. This excellent performance of the fabricated biosensor is attributed to the larger surface area availability of citric acid-Fe₃O₄ nanoparticles, which promotes constant electron transfer between the modified glassy carbon electrode and the biomolecules (uric acid). The improved electrocatalytic activity of this modified electrode clearly proves that the proposed method is promising for the development of other electrochemical biosensors.

Cephradine-Capped Gold Nanoparticle Modified Glassy Carbon Electrode for Trace Level Sensing of Triphenyltin Hydroxide

Synthesis of highly stable gold nanoparticles (AuNps) was accomplished using cephradine (Cep) drug as the capping molecule and sodium borohydride as the reducing agent. Characterization studies such as ultraviolet-visible (UV–vis) spectroscopy confirmed the formation of AuNps while fourier transform infra-red (FT-IR) spectroscopy showed the interaction of AuNps with Cep. The size and shape of Cep-AuNps were investigated using atomic force microscopy (AFM) while their crystallinity was determined through X-ray diffractometry (XRD). The synthesized Cep-AuNps, after getting deposited on a glassy carbon electrode (GCE), proved as a highly responsive sensor for low-level detection of triphenyltin hydroxide (TPTH) using cyclic voltammetry (CV) as the determining mode in stirred solution. The developed sensor linearly responded to TPTH in the range of 1–80 nM with a lower detection limit (LDL) of 0.12 nM and R2 value of 0.9948 under optimized conditions. Importantly, the sensor was highly stable and reproducible, showing a relative standard deviation (RSD) value of 1.1% based on 15 replicative runs and proved to be extremely selective for TPTH with negligible interference in the presence of expected interfering species. The developed sensor was effectively utilized for monitoring TPTH in natural water samples.

Non-enzymatic monitoring of hydrogen peroxide using novel nanosensor based on CoFe2O4@CdSeQD magnetic nanocomposite and rifampicin mediator.

In this work, a novel strategy was introduced to develop a non-enzymatic hydrogen peroxide (H2O2) sensor based on rifampicin (RIF) electrodeposited on a polyvinylpyrrolidone (PVP)-capped CdSe quantum dot (CdSeQD), CoFe2O4 magnetic nanoparticle-modified glassy carbon electrode (CoFe2O4@CdSeQDs/RIF/GCE). CoFe2O4@CdSeQD magnetic nanocomposite (CoFe2O4@CdSeQD MNCs) was synthesized by a chemical co-precipitation method and characterized by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), Fourier-transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD). To prepare the non-enzymatic H2O2 sensor, firstly, the glassy carbon electrode surface was modified by dropping 10μL of 5mgmL-1 CoFe2O4@CdSeQD MNCs. Then, rifampicin was electrodeposited on the activated CoFe2O4@CdSeQDs/GCE by applying a potential of - 0.7V for 400s in pH2.0 phosphate buffer containing 190μM of rifampicin. Cyclic voltammetry and electrochemical impedance spectroscopy was used to investigate the electrochemical behavior of this sensor and was used for the reduction of H2O2. Construction of the calibration plot for H2O2 was performed using an amperometric method (- 0.2V vs. Ag/AgCl) at the modified electrode. Two linearity ranges were obtained from 7 to 145μM and 145μM to 1.43mM with sensitivities of 143.01μAmM-1 and 28.67μAmM-1 for the first and second linearity ranges, respectively. The detection limit was obtained as 0.38μM (S/N = 3). Finally, the reliability of the nanosensor was confirmed with real sample analysis in different beverages such as juice and milk with satisfactory recovery results.

A facile synthesis of nanostructured CoFe2O4 for the electrochemical sensing of bisphenol A

This work reports a novel, highly sensitive and cost-effective electrochemical sensor for the detection of bisphenol A in environmental water samples. Attractive non-noble transition metal oxide CoFe2O4 nanoparticles were successfully synthesized using a sol–gel combustion method and further characterized by X-ray diffraction, scanning electron microscopy and X-ray photoelectron spectroscopy. Under optimal conditions, the CoFe2O4 nanoparticle modified glassy carbon electrode exhibits high electrochemical activity and good catalytic performance for the detection of bisphenol A. The linear calibration curves are obtained within a wide concentration range from 0.05 μmol L−1 to 10 μmol L−1, and the limit of detection is 3.6 nmol L−1 for bisphenol A. Moreover, this sensor also demonstrates excellent reproducibility, stability, and good anti-interference ability. The sensor was successfully applied to determine bisphenol A in practical samples, and the satisfactory recovery rate was between 95.5% and 102.0%. Based on the great electrochemical properties and practical application results, this electrochemical sensor has broad application prospects in the sensing of bisphenol A.

A Portable Setup for the Voltammetric Determination of Total Mercury in Fish with Solid and Nanostructured Gold Electrodes.

A simple procedure for field fish sample pretreatment was developed. This treatment in combination with square wave anodic stripping voltammetry (SW-ASV) with solid gold electrodes (SGE) and gold nanoparticle-modified glassy carbon electrodes (AuNPs-GCE) was applied for the determination of total mercury content. A certified reference material (CRM, Tuna Fish BCR 463), ten freeze-dried samples of canned tuna and two fresh fish samples were analysed both with a bench-top voltammetric analyser after microwave digestion and with a portable potentiostat after mild eating using a small commercial food warmer. The results obtained by the two SW-ASV approaches and by a Direct Mercury Analyser (DMA), the official method for mercury determination, were in very good agreement. In particular, (i) the results obtained with in field procedure are consistent with those obtained with the conventional microwave digestion; (ii) the presence of gold nanoparticles on the active electrode surface permits an improvement of the analytical performance in comparison to the SGE: the Limit of Quantification (LOQ) for mercury in fish-matrix was 0.1 μg L−1 (Hg cell concentration), corresponding to 0.06 mg kg−1 wet fish, which is a performance comparable to that of DMA. The pretreatment proposed in this study is very easy and applicable to fresh fish; in combination with a portable potentiostat, it proved to be an interesting procedure for on-site mercury determination.

Enzyme-free electrochemical detection of nanomolar levels of the organophosphorus pesticide paraoxon-ethyl by using a poly(N-isopropyl acrylamide)-chitosan microgel decorated with palladium nanoparticles.

A rapid voltammetric method is described for the determination of the organophosphorus pesticide paraoxon-ethyl (PEL). A glassy carbon electrode (GCE) was modified with a composite consisting of a poly(N-isopropylacrylamide)-chitosan microgel with incorporated palladium nanoparticles. The microgel was characterized by FE-SEM, EDX, XPS, FTIR, XRD, and EIS. The modified GCE is shown to enable direct electro-reductive determination of PEL by using differential pulse voltammetry. The method works in pH7 solution and in the 0.01μM to 1.3mM PEL concentration range. At a typical working potential of -0.66V (vs. Ag/AgCl) (at50mV/s), the detection limit is as low as 0.7 nM, and the electrochemical sensitivity is 1.60μAμM-1cm-2. Intriguingly, the modified GCE displays good recovery when applied to bok choy and water samples. Graphical abstract Schematic of an electrochemical method for determination of paraoxon ethyl (PEL) in bok choy extract and water by using poly(N-isopropyl acrylamide)-chitosan microgel decorated with palladium nanoparticle-modified glassy carbonelectrodes (PdNPs/PNIPAM-CT microgel/GCE).

Ultrasensitive Reduced Graphene Oxide-Poly(Procion)/Gold Nanoparticles Modified Glassy Carbon Electrode for Selective and Simultaneous Determination of Ascorbic Acid, Dopamine, and Uric Acid

A highly ultrasensitive electrochemical sensor based on electrochemically reduced graphene oxide (ERGO), Procion Red MX-5B (PR) and gold nanoparticles (AuNPs) modified glassy carbon electrode (GCE) was developed. Cyclic voltammetry (CV) was employed to electropolymerize GO-PR mixture on GCE followed by deposition of AuNPs to obtain ERGO-poly(PR)/AuNPs/GCE. The physical properties of the nanocomposite were explored through field emission scanning electron microscopy (FESEM) and Fourier transform infrared spectroscopy (FT-IR). The electrochemical performance of the ERGO-poly(PR)/AuNPs/GCE showed remarkable enhancement in the peak current toward oxidation of AA, DA, and UA with peak potentials separation of 0.21 V for AA-DA, and 0.15 V for DA-UA. Differential pulse voltammetry (DPV) was applied to perform individual and simultaneous analysis of the aforementioned analytes at optimized pH. DPV responses of AA, DA, and UA concentration were obtained over the range of 0.4–110, 0.4–170 and 0.4–150 μM with sensitivities of 0.48, 0.40, and 0.63 μA/μM (S/N = 3), respectively. Limit of detections for AA, DA, and UA were 54, 5.6 and 5.8 nM, respectively. Good repeatability, reproducibility as well as long-term stability were obtained. The developed modified electrode was used successfully to monitor AA, DA, and UA in vitamin C tablets, and human urine samples with favorable recoveries.

A sensitive enzyme-free lactic acid sensor based on NiO nanoparticles for practical applications

A facile and efficient electrochemical sensing platform has been successfully exploited for the first time for the determination of lactic acid using a nickel oxide (NiO) nanoparticle-modified glassy carbon electrode (GCE).

Impedance sensing platform for 4,4′-dibromobiphenyl based on a molecularly imprinted polymerized ionic liquid film/gold nanoparticle-modified glassy carbon electrode

1-Vinyl-3-butyl-imidazolium hexafluorophosphate (VBimPF6) was used as a functional monomer to fabricate an imprinted film onto a glassy carbon electrode modified with gold nanoparticle under the conditions applying 4,4′-dibromobiphenyl (DiBB) as a template, ethylene glycol dimethacrylate (EGDMA) as a cross-linker, and ammonium persulfate and N,N,N′,N′-tetramethylethylenediamine as initiators at room temperature. After the fabrication process, the embedded DiBB template was removed to obtain a new electrochemical sensor with high specific recognition sites toward DiBB. The morphology of the electrode surface was characterized with scanning electron microscope and atomic force microscope. Electrochemical impedance spectroscopy was used to test the sensing performances of this newly developed electrode. The imprinted film exhibited high selectivity and sensitivity in the determination of DiBB. Under optimized conditions, the charge transfer resistance attributed to the interaction of DiBB with the electrode was found linearly related to the logarithm of DiBB concentration in the range from 0.005 to 10.0 μM. The estimated detection limit is 0.001 μM (S/N = 3). Therefore, this electrode shows great application potential for the determination of trace DiBB contents in soil samples.

A novel electrochemical biosensor for antioxidant evaluation of phloretin based on cell-alginate/ʟ-cysteine/gold nanoparticle-modified glassy carbon electrode

Antioxidant evaluation of bioactive compounds is limited, since many methods lack a real physiological environment that can be used conveniently and intuitively. In this study, a simple, label-free and effective electrochemical biosensor method has been developed to evaluate the antioxidant effect of phloretin (Ph) by 3D cell modification on a glassy carbon electrode (GCE). In response to this, A549 cells were immobilized onto a self-assembled ʟ-cysteine/gold nanoparticle (AuNPs/ʟ-Cys)-modified GCE surface by a simple drop casting after encapsulated in alginate. The electrochemical impedance spectroscopy (EIS) results showed that the impedance value (Ret) increased with the concentration of H2O2 in the range of 0–60 μmol/L with the correlation of 0.990 which acted as an oxidative stress model inducer. However, the EIS value decreased with the co-incubation of Ph ranging from 10 to 100 μmol/L, showing a dose-dependent manner and time effect, indicating that the variation of Ret was responded to the antioxidant effect. The response impedance of the biosensor is linear to Ph concentrations from 20 μmol/L to 100 μmol/L with the detection limit (LOD) as 1.96 μmol/L. A significant correlation was observed between reactive oxygen species (ROS) values and Ret values following the concentrations of Ph, thus demonstrating the good biological relevance of cell-based electrochemical method. The strategy has been used to evaluate Ph antioxidant capacity in real cells with satisfactory results, indicating the feasibility of biosensor analysis for antioxidant evaluation.

Fabrication of a Biocompatible Nanocomposite-Based Voltammetric Sensor for Sensitive Determination of Mercazole

Application of fungicides and pesticides is highly demanded and effective for improvement of agricultural production. In this study, the electrochemical behavior of mercazole (CDZ) at the chitosan-carbon nanoparticles-modified glassy carbon electrode (CS-CNPs/GCE) was discussed in detail through cyclic voltammetry. The results of the investigation of the electrochemical response of CDZ revealed a considerable improvement in the oxidation and reduction peak currents of CDZ on the CS-CNPs/GCE compared to the bare GCE. CDZ underwent totally reversible oxidation at this system and well-defined peaks were observed. Furthermore, density functional theory studies were carried out to investigate the nature of the adsorption process of CDZ molecules on the outer surface of CS-CNPs/GCE. Square wave voltammetry was used as a powerful tool for detection of CDZ in different concentrations. The oxidation mechanism of CDZ was a reversible, pH-dependent and adsorption-controlled process. Under the optimal conditions, the highly sensitive response with a wide linear range from 0.04 μM to 1.0 μM with a sufficiently low detection limit of 17.7 nM was obtained which demonstrates promising results for the future usage in agricultural applications.