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.     

A turn-on fluorescence-sensing technique for glucose determination based on graphene oxide–DNA interaction

Graphene is a two-dimensional carbon nanomaterial one atom thick. Interactions between graphene oxide (GO) and ssDNA containing different numbers of bases have been proved to be remarkably different. In this paper we propose a novel approach for turn-on fluorescence sensing determination of glucose. Hydrogen peroxide (H₂O₂) is produced by glucose oxidase-catalysed oxidation of glucose. In the presence of ferrous iron (Fe²⁺) the hydroxyl radical (?OH) is generated from H₂O₂ by the Fenton reaction. This attacks FAM-labelled long ssDNA causing irreversible cleavage, as a result of the oxidative effect of ?OH, producing an FAM-linked DNA fragment. Because of the weak interaction between GO and short FAM-linked DNA fragments, restoration of DNA fluorescence can be achieved by addition of glucose. Due to the excellent fluorescence quenching efficiency of GO and the specific catalysis of glucose oxidase, the sensitivity and selectivity of this method for GO-DNA sensing are extremely high. The linear range is from 0.5 to 10 μmol L^?1 and the detection limit for glucose is 0.1 μmol L^?1. The method has been successfully used for analysis of glucose in human serum. Figure

?     

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....     

Highly sensitive electrochemical sensing based on 2-hydroxypropyl-β-cyclodextrin-functionalized graphene nanoribbons

In this communication, 2-hydroxypropyl-β-cyclodextrin (HP-β-CD) funtionalized graphene nanoribbons (HP-β-CD/GNRs) were prepared for the first time by using a simple wet chemical strategy, and then, the HP-β-CD/GNRs were applied for constructing electrochemical sensors for three representative analytes (p-aminophenol, p-AP; l-tyrosine, Tyr; rhodamine B, RhB). Owing to the synergetic effects of GNRs (excellent electrochemical properties and large surface area) and HP-β-CD (high host–guest recognition and enrichment capability), the highly sensitive electrochemical sensing platforms of three analytes were established by using HP-β-CD/GNRs modified electrode, and the detection limits were 0.0008, 0.003, and 0.001 μM for p-AP, Tyr, and RhB, respectively.     

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.

Open image in new window

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.

     

A novel nanocomposite matrix based on graphene oxide and ferrocene-branched organically modified sol–gel/chitosan for biosensor application

A novel platform for the fabrication of a glucose biosensor was successfully constructed by entrapping glucose oxidase (GOD) in a ferrocene (Fc)-branched organically modified silica material (ormosil)/chitosan (CS)/graphene oxide (GO) nanocomposite. The morphology, structure, and electrochemistry of the nanocomposite were characterized by transmission electron microscopy, X-ray powder diffraction, UV–vis spectroscopy, Fourier transform infrared spectroscopy, and electrochemical techniques. Results demonstrated that the proposed electrochemical platform not only provided an excellent microenvironment to maintain the bioactivity of the immobilized enzyme, but also effectively prevented the leakage of both the enzyme and mediator from the matrix and retained the electrochemical activity of Fc. Furthermore, dispersing GO within the Fc-branched ormosil/CS matrix could significantly improve the stability of GO and make it exhibit a positive charge, which was more favorable for the further immobilization of biomolecules, such as GOD, with higher loading. Moreover, it could also improve the conductivity of the matrix film and facilitate the electron shuttle between the mediator and electrode. Under optimal conditions, the designed biosensor to glucose exhibited a wide and useful linear range of 0.02 to 5.39 mM with a low detection limit of 6.5 μM. The value of K _M ^app was 4.21 mM, indicating that the biosensor possesses higher biological affinity to glucose. The present approach could be used efficiently for the linkage of other redox mediators and immobilize other biomolecules in the process of fabricating novel biosensors.     

Sensitive electrochemical sensing for polycyclic aromatic amines based on a novel core–shell multiwalled carbon nanotubes@ graphene oxide nanoribbons heterostructure

Being awfully harmful to the environment and human health, the qualitative and quantitative determinations of polycyclic aromatic amines (PAAs) are of great significance. In this paper, a novel core–shell heterostructure of multiwalled carbon nanotubes (MWCNTs) as the core and graphene oxide nanoribbons (GONRs) as the shell (MWCNTs@GONRs) was produced from longitudinal partially unzipping of MWCNTs side walls using a simple wet chemical strategy and applied for electrochemical determination of three kinds of PAAs (1-aminopyrene (1-AP), 1-aminonaphthalene and 3,3′-diaminobiphenyl). Scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, Raman spectroscopy, thermogravimetric analysis and electrochemical methods were used to characterize the as-prepared MWCNTs@GONRs. Due to the synergistic effects from MWCNTs and GONRs, the oxidation currents of PAAs at the MWCNTs@GONRs modified glassy carbon (GC) electrode are much higher than that at the MWCNTs/GC, graphene/GC and bare GC electrodes. 1-AP was used as the representative analyte to demonstrate the sensing performance of the MWCNTs@GONRs/GC electrode, and the proposed modified electrode has a linear response range of 8.0–500.0 nM with a detection limit of 1.5 nM towards 1-AP.     

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.     

Electrochemical immunosensor for the carcinoembryonic antigen based on a nanocomposite consisting of reduced graphene oxide,gold nanoparticles and poly(indole-6-carboxylic acid)

We describe a label-free electrochemical immunosensor for the carcinoembryonic antigen (CEA). It is based on a nanocomposite consisting of electrochemically reduced graphene oxide, gold nanoparticles (AuNPs), and poly(indole-6-carboxylic acid). Coupled to nanoparticle-amplification techniques and modified with ionic liquid (IL), this immunoassay shows high sensitivity and good selectivity for CEA. At the best working voltage of 0.95 V (vs. Ag/AgCl), the lower detection limit is 0.02 ng·mL^?1, and the response to CEA is linear in the range from 0.02 to 90 ng·mL^?1. The method was applied to the determination of CEA in spiked serum samples and gave recoveries in the range from 98.5 % to 102 %.

Open image in new window

Graphical abstract A label-free electrochemical immunosensor was fabricated for the carcinoembryonic antigen (CEA) with a detection limit of 0.02 ng·mL^?1. It is based on a nanocomposite consisting of electrochemically reduced graphene oxide (erGO), gold nanoparticles (Au NP), and poly(indole-6-carboxylic acid) (PICA).

     

An ultrasensitive lysozyme chemiluminescence biosensor based on surface molecular imprinting using ionic liquid modified magnetic graphene oxide/β-cyclodextrin as supporting material

In this work, ionic liquid modified Fe₃O₄@dopamine/graphene oxide/β-cyclodextrin (ILs-Fe₃O₄@DA/GO/β-CD) was used as supporting material to synthesize surface molecularly imprinted polymer (SMIP) which then was introduced into chemiluminescence (CL) to achieve an ultrasensitive and selective biosensor for determination of lysozyme (Lys). ILs and β-CD was applied to provide multiple binding sites to prepare Lys SMIP and Fe₃O₄@DA was designed to make the product separate easily and prevent the aggregation of GO which could improve absorption capacity for its large specific surface area. The ILs-Fe₃O₄@DA/GO/β-CD-SMIP showed high adsorption capacity (Q = 101 mg/g) to Lys in the adsorption isotherm assays. The adsorption equilibrium was reached within 10 min for all the concentrations, attributing to the binding sites situated exclusively at the surface, and the adsorption model followed Langmuir isotherm. Under the suitable CL conditions, the proposed biosensor could response Lys linearly in the range of 1.0 × 10⁻⁹–8.0 × 10⁻⁸ mg/mL with a detection limit of 3.0 × 10⁻¹⁰ mg/mL. When used in practical samples in determination of Lys, the efficient biosensor exhibited excellent result with the recoveries ranging from 94% to 112%.     

A novel electrochemical DNA biosensor construction based on layered CuS–graphene composite and Au nanoparticles

A novel CuS–graphene (CuS-Gr) composite was synthesized to achieve excellent electrochemical properties for application as a DNA electrochemical biosensor. CuS-Gr composite was prepared by a hydrothermal method, in which two-dimensional graphene served as a two-dimensional conductive skeleton to support CuS nanoparticles. A sensitive electrochemical DNA biosensor was fabricated by immobilizing single-stranded DNA (ss-DNA) labeled at the 5′ end using 6-mercapto-1-hexane (HS-ssDNA) on the surface of Au nanoparticles (AuNPs) to form ssDNA-S–AuNPs/CuS-Gr, and hybridization sensing was done in phosphate buffer. Cyclic voltammetry and electrochemical impedance spectroscopy were performed for the characterization of the modified electrodes. Differential pulse voltammetry was applied to monitor the DNA hybridization using an [Fe(CN)₆]^3?/4? solution as a probe. Under optimum conditions, the biosensor developed exhibited a good linear relationship between the current and the logarithm of the target DNA concentration ranging from 0.001 to 1 nM, with a low detection limit of 0.1 pM (3σ/S). The biosensor exhibited high selectivity to differentiate one-base-mismatched DNA and three-base-mismatched DNA. The results indicated that the sensing platform based on CuS-Gr provides a stable and conductive interface for electrochemical detection of DNA hybridization, and could easily be extended to the detection of other nucleic acids. Graphical abstracts

?     

[3 + 2] Cycloaddition promoted by zinc oxide nanoparticles anchored on reduced graphene oxide using green solvent

ZnO anchored on RGO-catalyzed [3?+?2] cycloaddition of nitriles and sodium azide in the synthesis of 5-substituted 1H-tetrazoles in water is an efficient and simple protocol with low catalyst loading under reflux condition. It is applied to a wide range of substrates with an excellent yield, simple workup procedure, recovery, and reusability of catalyst with consistent activity and high turnover number. It is proposed that the functional groups present in RGO surface are effective for preventing the aggregation of catalytically active ZnO species during the reaction. Moreover, the excellent performance of ZnO–RGO nanocomposite is ascribed to the excellent dispersity of catalyst in water, hydrophilic nature of the RGO for the accumulation of organic substrates in water, and the “Breslow effect.”     

Electrochemical biosensor for simultaneous determination of guanine and adenine based on dopamine-melanin colloidal nanospheres–graphene composites

Dopamine-melanin colloidal nanospheres (Dpa-melanin CNDs)–graphene composites-modified glassy carbon electrode (GCE) was prepared by a simple procedure and then successfully used to simultaneously determine guanine and adenine. Scanning electron microscopy (SEM) images and transmission electron microscopy (TEM) were used to characterize the morphology of the Dpa-melanin CNSs–graphene composite. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were used to characterize the electrode modifying process. Differential pulse voltammetry (DPV) was used to study the electrocatalytic activity toward the electrochemical oxidation of guanine and adenine. The modified electrode exhibited enhanced electrocatalytic behavior and good stability for the simultaneous determination of guanine and adenine compared with bare GCE. The electrochemical biosensor exhibited wide linear range of 0.5 to 150 μM with detection limit of 0.05 and 0.03 μM for guanine and adenine detection (S/N?=?3), respectively. Furthermore, the biosensor showed high sensitivity, good selectivity, good reproducibility, and long-term stability to guanine and adenine detection. At the same time, the fabricated electrode was successfully applied for the determination of guanine and adenine in denatured DNA samples with satisfying results. These results demonstrated that Dpa-melanin CNSs–graphene composite was a promising substrate for the development of high-performance electrochemical biosensor.     

A novel ε-HNIW-based insensitive high explosive incorporated with reduced graphene oxide

A novel ε-HNIW-based explosive formula with low sensitive and high energy was developed by systematically researching the processes of recrystallization, granularity gradation, and coating of ε-HNIW and option of energetic deterrents. The grain size and morphology of HNIW crystals were modified by solvent/antisolvent recrystallization. The ε-HNIW particles were graded and coated by emulsion polymerization method with 551 glue. The binder reduced the mechanical sensitivity of ε-HNIW significantly and showed good compatibility with ε-HNIW, but also weakened the decomposition enthalpy. With the purpose of developing new energetic deterrents in insensitive high explosive formulations, novel carbon materials graphene oxide (GO) and reduced graphene oxide (rGO) were prepared and incorporated in plastic-bonded explosive (PBX) formulations. For comparison, the effects of conventional deterrent flake graphite were also involved. It turned out that the mechanical sensitivities of ε-HNIW/551 glue have all reduced to some extent with the incorporation of graphite, GO, and rGO. Flake graphite induced the PBX decompose earlier slightly and weaken the heat output. The addition of GO resulted in noticeable antedating decomposition of ε-HNIW/551 glue although remarkably increased the decomposition heat. The formula of ε-HNIW/551 glue/rGO provided a moderate growth in decomposition heat and best thermal stability. In slow cook-off tests, the formulas of ε-HNIW/551 glue and ε-HNIW/551 glue/rGO showed good thermal stability and might be qualified to apply safely under 200 °C. Comprehensively considering the mechanical sensitivity, thermals stability, energy performance, and practical application, ε-HNIW/551 glue/rGO is supposed to be an eligible insensitive high-energy PBX formula.     

Electrochemiluminescence DNA biosensor based on the use of gold nanoparticle modified graphite-like carbon nitride

The authors describe an electrochemiluminescent (ECL) DNA biosensor that is based on the use of gold nanoparticles (AuNPs) modified with graphite-like carbon nitride nanosheets (g-C₃N₄ NSs) and carrying a DNA probe. In parallel, nanoparticles prepared from gold-platinum (Au/Pt) alloy and carbon nanotubes (CNTs) were placed on a glassy carbon electrode (GCE). Once the g-C₃N₄ NHs hybridize with DNA-modified AuNPs, they exhibit strong and stable cathodic ECL activity. The Au/Pt-CNTs were prepared by electrochemical deposition of Au/Pt on the surface of the CNTs in order to warrant good electrical conductivity. On hybridization of immobilized capture probe (S₁), target DNA (S₂) and labeled signal probe (S₃), a sandwich-type DNA complex is formed that produces a stable ECL emission at a typical applied voltage of ?1.18 V and in the presence of peroxodisulfate. Under optimized conditions, the method has a response to target DNA that is linearly related to the logarithm of its concentration in the range between 0.04 f. and 50 pM, with a 0.018 f. detection limit.

Open image in new window

Graphical abstract Schematic presentation of an electrochemiluminescent DNA biosensor based on two-dimensional graphite-like carbon nitride nanosheets (g-C₃N₄ NSs) hybridized with gold nanoparticles. Abbreviations: MCH: 6-mercapto-1-hexanol; S1: Capture probe; S2: target DNA. 

     

A highly sensitive nonenzymatic glucose sensor based on nickel oxide–carbon nanotube hybrid nanobelts

In this study, we demonstrated a highly sensitive electrochemical sensor for the determination of glucose in alkaline aqueous solution by using nickel oxide single-walled carbon nanotube hybrid nanobelts (NiO–SWCNTs) modified glassy carbon electrode (GCE). The hybrid nanobelts were prepared by the deposition of SWCNTs onto the Ni(SO₄)_0.3(OH)_1.4 nanobelt surface, followed by heat treatment at different temperatures ranging from 400 °C to 600 °C. The NiO–SWCNTs hybrid nanobelts modified electrode prepared at 500 °C displays enhanced electrocatalytic activity towards glucose oxidation, revealing a synergistic effect between the NiO and the deposited SWCNTs. The as-fabricated nonenzymatic glucose sensor exhibits excellent glucose sensitivity (2,980 μA cm^?2 mM^?1), lower detection limit (0.056 μM, signal/noise [S/N] ratio?=?3), and wider linear range (0.5–1,300 μM). Moreover, the sensor has been successfully used for the assay of glucose in serum samples with good recovery, ranging from 96.4 % to 102.4 %.     

UV-assisted synthesis of reduced graphene oxide–ZnO nanorod composites immobilized on Zn foil with enhanced photocatalytic performance

Research on Chemical Intermediates - ZnO nanorods were hydrothermally grown on Zn foil in an alkaline solution and the immobilized nanorods were subsequently hybridized with reduced graphene oxide...