Electrochemical determination of picric acid based on platinum nanoparticles–reduced graphene oxide composite

Platinum nanoparticles–reduced graphene oxide composite-modified glassy carbon electrode (PtNPs–rGO/GCE) was developed as a simple, selective and sensitive electrochemical sensor for determination of picric acid (PA). Cyclic voltammogram (CV) of PA showed three well-defined irreversible reduction peaks at the potentials of ?0.43, ?0.57 and ?0.66 V versus Ag/AgCl. In this work, the interference effect of other nitrophenol compounds (NPhCs) was significantly reduced by appropriate adjusting of pH. Square wave voltammetry was used for quantification of PA in the range of 5–500 µM (1.15–115 mg L^?1) with practical detection limit of 1 µM (0.23 mg L^?1). The proposed sensor was successfully applied for the determination of PA in two natural water samples.     

Highly-sensitive label-free electrochemical carcinoembryonic antigen immunosensor based on a novel Au nanoparticles–graphene–chitosan nanocomposite cryogel electrode

For the first time, a simple and highly sensitive label-free electrochemical carcinoembryonic antigen (CEA) immunosensor based on a cryogel electrode has been developed and tested. The as-prepared nanocomposite combined the advantages of the graphene, AuNPs and chitosan (AuNPs–GP–CS) together with the ease of preparing a cryogel coupled to a silver deposition, to act as a redox mediator, on a Au electrode. Under the optimal conditions, the decrease of the cyclic voltammetry (CV) silver peak current was proportional to the CEA concentration over a range of from 1.0 × 10⁻⁶ to 1.0 ng mL⁻¹ with a detection limit of 2.0 × 10⁻⁷ ng mL⁻¹. This AuNPs–GP–CS cryogel electrode gave a 1.7 times higher sensitivity and 25 times lower detection limit than the non-cryogel electrode. Moreover, the proposed electrochemical immunosensor exhibited good selectivity, reproducibility and stability. When applied to analyse clinical serum samples, the data determined by the developed immunosensor were in agreement with those obtained by the current hospital analysis system (enzyme linked fluorescent assay) (P > 0.05), to indicate that the immunosensor would be potentially useful for clinical diagnostics.     

Electrochemical biosensor for amplified detection of Pb2+ based on perfect match of reduced graphene oxide–gold nanoparticles and single-stranded DNAzyme

Analytical and Bioanalytical Chemistry - In this study, a sensitive amplification strategy for Pb2+ detection using reduced graphene oxide (RGO) and gold nanoparticles (AuNPs) was proposed....     

Electrochemical immunosensor for the breast cancer marker CA 15–3 based on the catalytic activity of a CuS/reduced graphene oxide nanocomposite towards the electrooxidation of catechol

The authors report on an electrochemical immunosensor for the tumor marker carbohydrate antigen 15–3 (CA15–3). It is based on the use of a composite consisting of reduced graphene oxide (RGO) and copper sulfide (CuS) that was placed on a screen-printed graphite electrode. The electrode shows excellent activity towards the oxidation of catechol acting as an electrochemical probe, best at a working potential of 0.16 V. The electrode was modified with antibody against CA15–3. Once the analyte (CA15–3) binds to the surface of the electrode, the response to catechol is reduced. The assay has a linear response in the 1.0–150 U mL^?1 CA15–3 concentration range, with a 0.3 U mL^?1 lower detection limit and a sensitivity of 1.88 μA μM^?1 cm^?2. The immunosensor also shows good reproducibility (2.7%), stability (95% of the initial values after storing for four weeks). The method was successfully applied to the determination of CA15–3 in serum samples, and results were found to compare well to those obtained by an ELISA. Conceivably, this nanocomposite based detection scheme has a wider scope and may be applied to numerous other immunoassays.

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Graphical abstract A label-free electrochemical immunosensor based on copper sulfides/graphene nanocomposites was developed for enzyme-free determination of CA15–3 biomarker. This immunosensor can be utilized as a tool to detect of CA15–3 in real samples.

     

Determination of carcinoembryonic antigen using a novel amperometric enzyme-electrode based on layer-by-layer assembly of gold nanoparticles and thionine

Electrochemical sensing of carcinoembryonic antigen(CEA)on a gold electrode modified by the se- quential incorporation of the mediator,thionine(Thi),and gold nanoparticles(nano-Au),through co- valent linkage and electrostatic interactions onto a self-assembled monolayer configuration is de- scribed in this paper.The enzyme,horseradish peroxidase(HRP),was employed to block the possible remaining active sites of the nano-Au monolayer,avoid the non-specific adsorption,instead of bovine serum albumin(BSA),and amplify the response of the antigen-antibody reaction.Electrochemical ex- periments indicated highly efficient electron transfer by the imbedded Thi mediator and adsorbed nano-Au.The HRP kept its activity after immobilization,and the studied electrode showed sensitive response to CEA and high stability during a long period of storage.The working range for the system was 2.5 to 80.0 ng/mL with a detection limit of 0.90 ng/mL.The model membrane system in this work is a potential biosensor for mimicking the other immunosensor and enzyme sensor.     

The detection of bergenin based on the gold nanoparticles/chitosan/reduced graphene oxide modified electrodeEI北大核心CSCD

Gold nanoparticles (AuNPs)/chitosan (CS)/reduced graphene oxide (RGO) modified electrode was prepared. The electrochemical behaviors of bergenin on this modified electrode was investigated by cyclic voltammetry. The results showed that the proposed electrode exhibited an obvious electrocatalytic ability to the oxidation of bergenin. The differential pulse voltammetry was employed to detect bergenin in 0.1 mol/L phosphate buffer solution (pH 6.0). A good linear relationship between the oxidation peak current and the concentration of bergenin was found in the range of 2.0×10-7-1.2×10-6 mol/L with the detection limit of 6.0×10-8 mol/L (S/N=3).The prepared electrode had good anti-interference ability and potential application in the actual detection of bergenin. © 2023, Youke Publishing Co.,Ltd. All rights reserved.     

Prussian blue–gold nanoparticles-ionic liquid functionalized reduced graphene oxide nanocomposite as label for ultrasensitive electrochemical immunoassay of alpha-fetoprotein

In this work, poly(diallyldimethylammonium chloride) (PDDA) protected Prussian blue/gold nanoparticles/ionic liquid functionalized reduced graphene oxide (IL-rGO-Au-PDDA-PB) nanocomposite was fabricated. The resulting nanocomposite exhibited high biocompatibility, conductivity and catalytic activity. To assess the performance of the nanocomposite, a sensitive sandwich-type immunosensor was constructed for detecting alpha-fetoprotein (AFP). Greatly enhanced sensitivity for this immunosensor was based on triple signal amplification strategies. Firstly, IL-rGO modified electrode was used as biosensor platform to capture a large amount of antibody due to its increased surface area, thus amplifying the detection response. Secondly, a large number of Au-PDDA-PB was conjugated on the surface of IL-rGO, which meant the enrichment of the signal and the more immobilization of label antibody. Finally, the catalytic reaction between H₂O₂ and the IL-rGO-Au-PDDA-PB nanocomposite further enhanced the signal response. The signals increased linearly with AFP concentrations in the range of 0.01–100 ng mL⁻¹. The detection limit for AFP was 4.6 pg mL⁻¹. The immunosensor showed high sensitivity, excellent selectivity and good stability. Moreover, the immunosensor was applied to the analysis of AFP in serum sample with satisfactory result.     

Novel potentiometric immunosensor for determination of diphtheria antigen based on compound nanoparticles and bilayer two-dimensional sol–gel as matrices

A novel method for fabrication of a diphtheria potentiometric immunosensor has been developed by means of self-assembling compound nanoparticles to a thiol-containing sol–gel network. A cleaned gold electrode was first immersed in a 3-mercaptopropyltrimethoxysilane (MPS) sol–gel solution to assemble a silica sol–gel monolayer. The silane entities were then polymerized into a two-dimensional sol–gel network (2D network) by dipping into aqueous NaOH. The second silane layer was formed by re-immersion in the MPS sol–gel solution overnight. The compound nanoparticles (nanocompounds) containing gold nanoparticles and silver nanoparticles were then chemisorbed on to the thiol groups of the second silane layer. Finally, diphtheria antibody (anti-Diph) was adsorbed on to the surface of the compound nanoparticles. The modified process was characterized by cyclic voltammetry (CV). Detection is based on the change in the potentiometric response before and after the antigen–antibody reaction. A direct potentiometric response to diphtheria antigen (Diph) was obtained from the immobilized diphtheria antibody. The potentiometric response of the resulting immunosensor was rapid and the linear range was from 22 to 800 ng mL^–1 with the linear regression equation E=–79.5+69.4 log [Diph] and a detection limit of 3.7 ng mL^–1 (at 3). Up to 19 successive assay cycles with retention of sensitivity were achieved for probes regenerated with 0.2 mol L^–1 glycine–hydrochloric acid (Gly–HCl) buffer solution. Moreover, analytical results from several serum samples obtained using the developed technique were in satisfactory agreement with those given by the ELISA method, implying a promising alternative approach for detecting diphtheria antigen in clinical diagnosis.     

Immunosensor for α-fetoprotein based on a glassy carbon electrode modified with electrochemically deposited N-doped graphene,gold nanoparticles and chitosan

The authors describe a voltammetric immunosensor with antibody immobilized on a glassy carbon electrode (GCE) modified with N-doped graphene (N-GS), electrodeposited gold nanoparticles (AuNPs) and chitosan (Chit). The preparation is simple and the thickness of the electrodeposited films can be well controlled. Due to the specific advantages of N-GS, AuNPs and Chit, the electrode has a large specific surface, improved conductivity, high stability. A new label-free immunosensor for the model antigen (alpha fetoprotein, AFP) detection was then designed by employing N-GS-AuNP-Chit as the antibody immobilization and signal amplification platform. Differential pulse voltammetry and electrochemical impedance spectroscopy were used for the characterization of the stepwise assembly process. Under the optimized conditions, at a typical working potential of +0.20 V (vs. SCE), and by using hexacyanoferrate as an electrochemical probe, the immunosensor has a detection limit as low as 1.6 pg mL^?1 and a linear analytical range that extends from 5 pg mL^?1 to 50 ng mL^?1. AFP was quantified in spiked human serum samples with acceptable precision.

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Graphical Abstract Schematic of sensitive and effective label-free electrochemical immunosensor for the detection of AFP based on N-GS-AuNP-Chit as signal amplification matrix.

     

Voltammetric determination of the anti-cancer drug nilutamide using a screen-printed carbon electrode modified with a composite prepared from β-cyclodextrin,gold nanoparticles and graphene oxide

The authors describe an electrochemical method for the determination of the anti-cancer drug nilutamide. The method is based on the use of a composite prepared from β-cyclodextrin, gold nanoparticles and graphene oxide (β-CD-AuNP/GO). An alkaline solution of glucose was used as a reducing agent to reduce the gold ions, rather than citric acid and a harmful reducing agent such as hydrazine and sodium borohydride. The structure and surface morphology of the β-CD-AuNP/GO composite was characterized by Raman spectroscopy, transmission electron microscopy and energy-dispersive X-ray spectroscopy. A screen printed carbon electrode was modified with the nanocomposite, and the resulting electrode used as a disposable sensor for the determination of nilutamide by differential pulse voltammetry. Best operated at a working voltage of 0.43 V (vs Ag/AgCl), it exhibits excellent electrocatalytic activity and a detection limit as low as 0.4 nM. The sensor was applied to the determination of nilutamide in (spiked) human serum, as well as in a tablet, where it displays good recovery and accuracy. The sensor is repeatable, reproducible, stable and selective even in the presence of other aromatic nitro compounds.

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Graphical abstract An electrochemical method for the determination of the anti-cancer drug nilutamide is described. A screen printed carbon electrode is modified with the nanocomposite prepared from β-cyclodextrin, gold nanoparticles and graphene oxide (β-CD-AuNP/GO). Best operated at a working voltage of 0.43 V (vs Ag/AgCl), it exhibits excellent electrocatalytic activity and a detection limit as low as 0.4 nM. The sensor was applied to the determination of nilutamide in (spiked) human serum and a tablet where it displays good recovery and accuracy.

     

Electrochemical synthesis of copper nanoparticles on nafion–graphene nanoribbons and its application for the synthesis of diaryl ethers

Electrochemical synthesis of copper nanoparticles on nafion–graphene nanoribbons support for the synthesis of diaryl ethers via Ullmann type coupling is reported. The catalyst showed excellent performance for C–O cross coupling reactions under ligand free condition. The catalyst was characterized by various techniques such as SEM, TEM, XRD, EDX, BET, TGA, and UV spectrophotometry. It was recycled several times without significant loss in its catalytic activity.     

CuO–Fe2O3 nanoparticles embedded onto reduced graphene oxide nanosheets: a high-performance nanocomposite anode for Li-ion battery

Journal of Solid State Electrochemistry - The development of safe, fast charging, and long-lasting Li-ion batteries has been taking major steps forward through novel combinations of nanomaterials....     

Highly sensitive electrochemiluminescence “turn-on” aptamer sensor for lead(II) ion based on the formation of a G-quadruplex on a graphene and gold nanoparticles modified electrode

We have developed a “turn on” model of an electrochemiluminescence (ECL) based assay for lead ions. It is based on the formation of a G-quadruplex from an aptamer labeled with quantum dots (QDs) and placed on an electrode modified with of graphene and gold nanoparticles (AuNPs). A hairpin capture probe was labeled with a thiol group at the 5′-end and with an amino group at the 3′-end. It was then self-assembled on the electrode modified with graphene and AuNPs. In the absence of Pb(II), the amino tag on one end of the hairpin probe is close to the surface of the electrode and therefore unable to interact with the QDs because of steric hindrance. The ECL signal is quite weak in this case. If, however, Pb(II) is added, the stem-loop of the aptamer unfolds to form a G-quadruplex. The amino group at the 3′-end will become exposed and can covalently link to a carboxy group on the surface of the CdTe QDs. This leads to strong ECL. Its intensity increases (“turns on”) with the concentration of Pb(II). Such a “turn-on” method does not suffer from the drawbacks of “turn-off” methods. ECL intensity is linearly related to the concentration of Pb(II) in the 10 p mol·L^?1 to 1 n mol·L^?1 range, with a 3.8 p mol·L^?1 detection limit. The sensor exhibits very low detection limits, good selectivity, satisfying stability, and good repeatability.

Pd nanoparticles supported on reduced graphene oxide as an effective and reusable heterogeneous catalyst for the Mizoroki–Heck coupling reaction

A general method for the synthesis of palladium nanoparticles loaded on reduced graphene oxide functionalized with diethylenetriamine (PdNPs/rGO-NH₂) using a sonochemical procedure is described. The heterogeneous nanocomposite was characterized by Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy, energy dispersive X-ray, thermogravimetric analysis, high-angle annular dark field scanning transmission electron microscopy, X-ray photoelectron spectroscopy, UV–visible absorption, and inductively coupled plasma optical emission spectrometry. The PdNPs/rGO-NH₂ was very effective for the Mizoroki–Heck coupling reaction of several aryl iodide compounds with different alkenes in the presence of triethylamine. The reaction provides the coupling products in good to excellent yields (59–100%). Additionally, the PdNPs/rGO-NH₂ catalyst can be reutilized for six successive runs without any apparent diminution of its catalytic reactivity.     

One-step co-electrodeposition of graphene oxide doped poly(hydroxymethylated-3,4-ethylenedioxythiophene) film and its electrochemical studies of indole-3-acetic acid

A novel graphene oxide(GO) doped poly(hydroxymethylated-3,4-ethylenedioxythiophene)(PEDOTM)film has been achieved via one-step co-electrodeposition and utilized for electrochemical studies of indole-3-acetic acid(IAA).The incorporation of GO into PEDOTM film facilitated the electrocatalytic activity and exhibited a favorable interaction between the PEDOTM/GO film and the phytohormone during the oxidation of IAA.Under optimized conditions,differential pulse voltammetry and square wave voltammetry were used for the quantitative analysis of IAA,respectively,each exhibiting a wide linearity range from 0.6 μmol L~(-1) to 10 μmol L~(-1) and 0.05 μmol L~(-1) to 40 μmol L~(-1),good sensitivity with a low detection limit of 0.087 μmol L~(-1) and 0.033 μmol L~(-1) respectively,as well as good stability.With the notable advantages of a green,sensitive method,expeditious response and facile operation,the as-prepared PEDOTM/GO organic-inorganic composite film provides a promising platform for electrochemical studies of IAA.     

Voltammetric cadmium(II) sensor based on a fluorine doped tin oxide electrode modified with polyamide 6/chitosan electrospun nanofibers and gold nanoparticles

The authors have developed an electrochemical sensor for cadmium(II) that is based on the use of a conventional fluorine doped tin oxide (FTO) electrode modified with polymeric electrospun nanofibers consisting of polyamide 6 (PA6) and chitosan which were further modified with gold nanoparticles (AuNPs). The materials were characterized by infrared spectroscopy, thermal analysis (DSC and TGA), and scanning electron microscopy. The modified electrode was applied to the detection of Cd(II) by square wave voltammetry. Response is linear in the 25 to 75 μg ? L^?1 Cd(II) concentration range, with a detection limit of 0.88 μg ? L^?1. The relative standard deviations are 4.6% and 8.2% for intra- and inter-electrode measurements, respectively. Mercury(II), lead(II), and copper(II) did not significantly interfere.

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Graphical abstract The sensing platform developed can detect cadmium(II) with a detection limit of 0.88 μg L^?1, with no significant interference by mercury(II) and lead(II).