Gold Nanoparticle-modified Glassy Carbon 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.

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.

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.

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.

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.

Electrochemical Determination of Dopamine by a Reduced Graphene Oxide–Gold Nanoparticle-Modified Glassy Carbon Electrode

ABSTRACTA novel electrochemical aptasensor is reported for the label-free determination of dopamine by electrochemically reduced graphene oxide and a gold nanocomposite with a ribonucleic acid (RNA) aptamer. The nanocomposite was fabricated by layer-to-layer electrochemical deposition. The aptamer was immobilized on the surface of the gold nanoparticles through the formation of thiol–gold bonds. Dopamine was determined through specific interaction with the immobilized aptamer. The redox activity of the analyte enabled direct electrochemical analysis. The conductivity and structure of the nanocomposite were characterized by cyclic voltammetry and scanning electron microscopy. In contrast to bare or reduced graphene oxide-modified electrodes, the nanocomposite-modified electrode significantly enhanced the current response. The electrochemical aptasensor provided a detection limit of 0.13 µM with a linear dynamic range from 0.5 to 20 µM. In addition, the sensor was shown to provide high selectivity and satisfactory stability for the determination of dopamine in the presence of analogs and in human serum.

Electromembrane extraction and anodic stripping voltammetric determination of mercury(II) using a glassy carbon electrode modified with gold nanoparticles

This study presents a method for the selective determination of Hg(II) using electromembrane extraction (EME), followed by square wave anodic stripping voltammetry (SWASV), using a gold nanoparticle-modified glassy carbon electrode, (AuNP/GCE). By applying an electrical potential of typically 60 V for 12 min through a thin supported liquid membrane (1-octanol), Hg(II) ions are extracted from a donor phase (i.e., the sample solution) to an acidic acceptor solution (15 μL) placed in the lumen of a hollow fiber. The influences of experimental parameters during EME were optimized using face-centered central composite design. The calibration plot, established at a working voltage of 0.55 V (vs. Ag/AgCl), extends from 0.2 to 10 μg.L−1 of Hg(II). The limit of detection, at a signal to noise ratio of 3, is 0.01 μg.L−1 and the relative standard deviations (for 5 replicate determinations at 3 concentration levels) are between 7.5 and 8.7 %. The method was successfully applied to the determination of Hg(II) in spiked real water samples to give recoveries ranging from 89 to 97 %. The results were validated by cold vapor atomic absorption spectroscopy.

Electromembrane extraction coupled to square wave anodic stripping voltammetry for selective preconcentration and determination of trace levels of As(III) in water samples

In this Study for the first time, a combination of electromembrane extraction (EME) and anodic stripping voltammetry (ASV) using a gold nanoparticle-modified glassy carbon electrode (AuNPs/GCE) is introduced, for selective and sensitive determination of trace As(III) in water samples. The process was based on the electrokinetic migration of As(III) ions from a donor phase (sample solution) toward an electrode with opposite charge and into an alkaline aqueous acceptor solution placed inside the lumen of a hollow fiber. The acceptor solution was then analyzed using anodic stripping voltammetry. A linear relationship was observed between the ASV peak currents and the concentration of As(III) ions over two intervals in the range of 0.5–10μg/L and 10–600μg/L. The detection limit of the proposed method was found to be 0.18μg/L using three sigma criteria and the relative standard deviations for 5 replicate measurements of three different concentration levels of As(III) were found to be within the range of 6.7–8.5%. The proposed method was finally applied to determination of As(III) in water samples with satisfactory results.

Electrochemical Investigation of Gold Nanoparticle-Modified Glassy Carbon Electrode and its Application in Ketoconazole Determination

Ketoconazole (KCZ) is an extensively used antifungal compound and is an active ingredient of anti-scaling shampoos, pomades, and skin ointments. In this work, the cyclic voltammetric behaviour of KCZ was studied with a gold nanoparticle (AuNP)-modified glassy carbon (GC) electrode. The conditions for KCZ determination with GC/AuNP were optimised to achieve the best possible response. A pre-adsorption voltage of –1.6 V, a deposition time of 120 s, pH 4.0, and stirring of the KCZ solution during deposition were chosen as the optimum conditions for KCZ determination. The anodic peak at 0.697 V was used for KCZ determination. A linear concentration range of 20–100 μM (R2 = 0.9986) and a detection limit of 2.3 μM (3σ) was achieved for KCZ using the GC/AuNP electrode.

Mercury(II) trace detection by a gold nanoparticle-modified glassy carbon electrode using square-wave anodic stripping voltammetry including a chloride desorption step

Gold nanoparticles (AuNPs) were deposited on a glassy carbon (GC) substrate by constant potential electrolysis and characterized by cyclic voltammetry in H2SO4 and field emission gun scanning electron microscopy (FEG-SEM). The modified AuNPs–GC electrode was used for low Hg(II) concentration detection using a Square Wave Anodic Stripping Voltammetry (SWASV) procedure which included a chloride desorption step. The comparison of the obtained results with our previous work in which no desorption step was used showed that this latter step significantly improved the analytical performances, providing a three time higher sensitivity and a limit of detection of 80pM for 300s preconcentration, as well as a lower average standard deviation. The influence of chloride concentration on the AuNPs–GC electrode response to Hg(II) trace amounts was also studied and its optimal value confirmed to be in the 10−2M range. Finally, the AuNPs–GC electrode was used for the determination of Hg(II) in a natural groundwater sample from south of France. By using a preconcentration time of 3000s, a Hg(II) concentration of 19±3pM was found, which compared well with the result obtained by cold vapor atomic fluorescence spectroscopy (22±2pM).

Electrochemical sensor for nitroaromatic type energetic materials using gold nanoparticles/poly(o-phenylenediamine–aniline) film modified glassy carbon electrode

In this work, a novel electrochemical sensor was developed for the detection of nitroaromatic explosive materials, based on a gold nanoparticle-modified glassy carbon (GC) electrode coated with poly(o-phenylenediamine–aniline film) (GC/P(o-PDA-co-ANI)-Aunano electrode). Nitroaromatic compounds were detected through their π-acceptor/donor interactions with o-phenylenediamine–aniline functionalities on the modified electrode surface. The enhanced sensitivities were achieved through π–π and charge-transfer (CT) interactions between the electron-deficient nitroaromatic compounds and σ-/π-donor amine/aniline groups linked to gold nanoparticles (Au-NPs), providing increased binding and preconcentration onto the modified GC-electrodes. Selective determination of nitroaromatic type explosives in the presence of nitramines was enabled by o-PDA and reusability of the electrode achieved by Au-NPs. Calibration curves of current intensity versus concentration were linear in the range of 2.5–40mgL−1 for 2,4,6-trinitrotoluene (TNT) with a detection limit (LOD) of 2.1mgL−1, 2–40mgL−1 for 2,4-dinitrotoluene (DNT) (LOD=1.28mgL−1), 5–100mgL−1 for tetryl (LOD=3.8mgL−1) with the use of the GC/P(o-PDA-co-ANI)-Aunano electrode. For sensor measurements, coefficients of variation of intra- and inter-assay measurements were 0.6% and 1.2%, respectively (N=5), confirming the high reproducibility of the proposed assay. Deconvolution of current contributions of synthetic (TNT+DNT) mixtures at peak potentials of constituents was performed by multiple linear regression analysis to provide high sensitivity for the determination of each constituent. Determination options for all possible mixture combinations of nitroaromatic explosives are presented in this work. The proposed methods were successfully applied to the analysis of nitroaromatics in military explosives, namely comp B, octol, and tetrytol. Method validation was performed against GC–MS on real post-blast residual samples containing both explosives.

Oxygen electroreduction on polycrystalline gold electrodes and on gold nanoparticle-modified glassy carbon electrodes

The oxygen reduction reaction (ORR) in acid media can be catalyzed on gold electrodes when the surface is activated by mechanical or electrochemical pretreatments. The activation is caused by increased surface roughness and defects, or asperities. After activation, a slow recrystallization of the surface as a function of relaxation time leads to deactivation of the surface for the ORR. After removal of active centers, the surface is not affected over time, which reveals that the surface recrystallization is associated with the deactivation. Experiments using various amounts of Au nanoparticles (AuNPs) immobilized on glassy carbon (GC) show a positive shift of peak potential of oxygen reduction and peroxide oxidation with increasing particle coverage.

Sensitive electrochemical immunoassay of a biomarker based on biotin-avidin conjugated DNAzyme concatamer with signal tagging

This work reports a new electrochemical immunoassay protocol with signal amplification for the sensitive detection of a biomarker (carcinoembryonic antigen, CEA, used in this case) by coupling hemin/G-quadruplex-constructed DNAzyme concatamer with the biotin-avidin amplification system. Initially, polyclonal rabbit anti-human CEA antibody (pAb1) was immobilized onto a gold nanoparticle-modified glassy carbon electrode, which was used for the capture of target CEA, and biotin-labeled mouse anti-human monoclonal CEA antibody (bio-mAb2) was then used as a secondary antibody for the formation of the sandwiched immunocomplex in the presence of target CEA on the pAb1-modified electrode. The carried biotin could react with streptavidin and a biotin-labeled initiator strand (S0) in sequence. Two auxiliary DNA strands (S1 and S2) were designed for the concatamer reaction with the S0. The DNA initiator stand (S0) could propagate a chain reaction of hybridization events between alternating S1 and S2 to form a nicked double-helix. Upon addition of hemin, the hemin-binding aptamers can be bound to form the hemin/G-quadruplex-based DNAzymes on the S1 probe. Meanwhile, the formed double-helix DNA polymers could also cause the numerous intercalation of electroactive methylene blue. During the electrochemical measurements, the DNAzymes could catalyze the reduction of H2O2 in a detection solution with the aid of the intercalated methylene blue. Under the optimal conditions, the electrochemical immunosensor exhibited a dynamic working range of 1.0 pg mL−1–50 ng mL−1 toward CEA standards with a detection limit of 0.5 pg mL−1. The reproducibility and selectivity of the developed immunoassay were acceptable (CV <10%). In addition, 6 spiked CEA samples with various concentrations were assayed by using the developed immunoassay, and the recovery was 92–120%.

A kinetic study of oxygen reduction reaction and characterization on electrodeposited gold nanoparticles of diameter between 17 nm and 40 nm in 0.5 M sulfuric acid

Kinetic and mechanistic studies of the oxygen reduction reaction (ORR) in oxygen saturated 0.5 M sulfuric acid at 298 K at a gold macroelectrode and at an electrodeposited gold nanoparticle-modified glassy carbon electrode are reported. The conditions of electrodeposition are optimized to obtain small nanoparticles of diameter from 17 nm to 40 nm. The mechanism and kinetics of ORR on the gold macroelectrode are investigated and compared with those obtained for nanoparticle-modified electrodes. The mechanism for this system includes two electron and two proton transfers and hydrogen peroxide as the final product. The first electron transfer step corresponding to the reduction of O2 to O2(-)˙ is defined as the rate determining step. No significant changes are found for the nanoparticles here employed: electron transfer rate constant (k0) is k0,bulk = 0.30 cm s(-1) on the bulk material and k0,nano = 0.21 cm s(-1) on nanoparticles; transfer coefficient (α) changes from αbulk = 0.45 on macro-scale to αnano = 0.37 at the nano-scale.

Highly Sensitive Determination of Hg(II) Using Self-Assembled Monolayer of 4-Pyridineethanthiol on Gold Nanoparticles Modified-Glassy Carbon Electrode Pretreated by Exclusively Cathodic Polarization

Highly Sensitive Determination of Hg(II) Using Self-Assembled Monolayer of 4-Pyridineethanthiol on Gold Nanoparticles Modified-Glassy Carbon Electrode Pretreated by Exclusively Cathodic Polarization

Gold Nanoparticles Modified Glassy Carbon Electrodes as Electrochemical Biosensors

Gold Nanoparticles Modified Glassy Carbon Electrodes as Electrochemical Biosensors

Selective detection of neurotransmitter serotonin by a gold nanoparticle-modified glassy carbon electrode

Gold nanoparticles (GNPs) were allowed to self-assemble onto a glassy carbon electrode (GCE) that was prior modified by L-cysteine. The modified electrode was then used as a voltammetric sensor in detecting the neurotransmitter serotonin. The electrode exhibited a linear voltammetric response for serotonin within a concentration range of 6.0 x 10(-8) M to 6 x 10(-6) M, with a detection limit of 2 x 10(-8) M. The detection of serotonin was found to be unaffected by the presence of epinephrine, dopamine, ascorbic acid and folic acid. The electrode was applied to detect serotonin added to human blood serum, with an average recovery value of 104.67%.

Gold nanoparticle-modified glassy carbon electrode for electrochemical investigation of aliphatic di-carboxylic acids in aqueous media

The electrochemical reduction of di-carboxylic acids; oxalic, succinic, malic, and tartaric have been studied on the gold nanoparticles modified electrode in aqueous media solution of 0.1 M KCl. Gold nanoparticle (AuNPs)-modified electrodes were prepared by the electrodeposition with cyclic voltammetric method onto glassy carbon electrode in acidic media. The surface morphology of the electrodeposited gold nanoparticles was examined by SEM. Also, the electrochemical properties of the prepared electrodes were investigated with different electrochemical techniques; cyclic voltammetry, chronoamperometry, and electrochemical impedance spectroscopy. Cyclic voltammetric, chronoamperometric, and electrochemical impedance spectroscopic techniques were used for investigating the electrochemical behavior of the particulate acids. The modification of the electrode with Au nanoparticles (AuNPs) enables the appearance of cyclic voltammogram peaks completely clear and sharp for the acids under investigation in comparison with the poor behavior of them in absence of the modification. All acids undergo totally irreversible redox reaction in neutral and acid media. The cyclic voltammetric response of the investigated acids is sensitive to pH, as well as of the scan rate. Each acid has a different reduction peak position from the other acids depending on the structure of the acid undergo the electroreduction process. Further, the lowest unoccupied molecular orbital energies of the investigated acids have been theoretically evaluated and are compared with their electroreduction potential peaks.

Electrochemical Behavior and Sensitive Determination of l-Tyrosine with a Gold Nanoparticles Modified Glassy Carbon Electrode

The electrocatalytic oxidation of L-tyrosine was investigated on a gold nanoparticles self-assembled glassy carbon electrode (gold nanoparticles/cysteamine/glassy carbon) using cyclic voltammetry and differential pulse voltammetry. Cyclic voltammetry was carried out to study the electrochemical oxidation mechanism of L-tyrosine, which showed an irreversible oxidation process at a potential of 0.681 V at a modified electrode and 0.807 V at a bare glassy carbon electrode. The anodic peak current linearly increased with the square root of the scan rate, suggesting that the oxidation of L-tyrosine at this kind of modified electrode is a diffusion-controlled process. A good linear relationship between the oxidation peak current and the L-tyrosine concentration in the range of 1.0 x 10(-7) to 3.0 x 10(-4) mol L(-1) was obtained in a phosphate buffer solution at pH 7.0. Good sensitivity, selectivity and stability of the modified electrode make it very suitable for L-tyrosine determination in a commercial amino acid oral solution.

Electrochemical Investigation of Calcium Dobesilate and Interactions with Bovine Serum Albumin on Gold Nanoparticle–Modified Glassy Carbon Electrode

The electrochemical behavior of calcium dobesilate (CD) and its interaction with bovine serum albumin (BSA) have been investigated, and the stoichiometric coefficient and association constant between CD and BSA were obtained. It was found that gold nanoparticles have a strong electrocatalytic effect on CD. With the addition of BSA in CD solution, both the oxidation and reduction currents decreased, but the peak potentials stayed almost unchanged. Non-electrochemical-active supramolecular complex BSA-CDm was formed via the reaction of CD with BSA. This makes it feasible for CD to be used as an electrochemical probe for determining the concentration of BSA.