Electrochemical bisphenol A sensor based on N-doped graphene sheets

Bisphenol A (BPA), which could disrupt endocrine system and cause cancer, has been considered as an endocrine disruptor. Therefore, it is very important and necessary to develop a sensitive and selective method for detection of BPA. Herein, nitrogen-doped graphene sheets (N-GS) and chitosan (CS) were used to prepare electrochemical BPA sensor. Compared with graphene, N-GS has favorable electron transfer ability and electrocatalytic property, which could enhance the response signal towards BPA. CS also exhibits excellent film forming ability and improves the electrochemical behavior of N-GS modified electrode. The sensor exhibits a sensitive response to BPA in the range of 1.0 × 10⁻⁸–1.3 × 10⁻⁶ mol L⁻¹ with a low detection limit of 5.0 × 10⁻⁹ mol L⁻¹ under the optimal conditions. Finally, this proposed sensor was successfully employed to determine BPA in water samples with satisfactory results.     

Electrochemical gene sensor based on a glassy carbon electrode modified with hemin-functionalized reduced graphene oxide and gold nanoparticle-immobilized probe DNA

Microchimica Acta - The authors describe an electrochemical DNA biosensor based on a glassy carbon electrode modified with gold nanoparticles (AuNPs) and reduced graphene oxide that was...     

An electrochemical ascorbic acid sensor based on palladium nanoparticles supported on graphene oxide

In this study, an electrochemical ascorbic acid (AA) sensor was constructed based on a glassy carbon electrode modified with palladium nanoparticles supported on graphene oxide (PdNPs-GO). PdNPs with a mean diameter of 2.6 nm were homogeneously deposited on GO sheets by the redox reaction between PdCl₄²⁻ and GO. Cyclic voltammetry and amperometric methods were used to evaluate the electrocatalytic activity towards the oxidation of AA in neutral media. Compared to a bare GC or a Pd electrode, the anodic peak potential of AA (0.006 V) at PdNPs-GO modified electrode was shifted negatively, and the large anodic peak potential separation (0.172 V) of AA and dopamine (DA), which could contribute to the synergistic effect of GO and PdNPs, was investigated. A further amperometric experiment proved that the proposed sensor was capable of sensitive and selective sensing of AA even in the presence of DA and uric acid. The modified electrode exhibited a rapid response to AA within 5 s and the amperometric signal showed a good linear correlation to AA concentration in a broad range from 20 μM to 2.28 mM with a correlation coefficient of R = 0.9991. Moreover, the proposed sensor was applied to the determination of AA in vitamin C tablet samples. The satisfactory results obtained indicated that the proposed sensor was promising for the development of novel electrochemical sensing for AA determination.     

Electrochemical sensors based on graphene materials

Single?Clayered graphene, emerging as a true two?Cdimensional nanomaterial, has tremendous potential for electrochemical catalysis and biosensing as a novel electrode material. Considering the excellent properties of graphene, such as large surface?Cto?Cvolume ratio, high conductivity and electron mobility at room temperature, low energy dynamics of electrons with atomic thickness, robust mechanical and flexibility, we give a general view of recent advances in electrochemical sensors based on graphene. We are highlighting here important applications of graphene and graphene nanocomposites, and the assay strategies in electrochemical sensors for DNA, proteins, neurotransmitters, phytohormones, pollutants, metal ions, gases, hydrogen peroxide, and in medical, enzymatic and immunosensors.

Synthesis of graphene oxide nanosheet: A novel glucose sensor based on nickel-graphene oxide composite film

The graphene oxide (GO) nanosheets were produced by chemical conversion of graphite, and were characterized by transmission electron microscope (TEM), Fourier transform infrared spectroscopy (FT-IR). An electrochemical sensor based on Ni/graphene (GR) composite film was developed by incorporating Ni²⁺ into the graphene oxide film modified glassy carbon electrode (Ni/GO/GCE) through the electrostatic interactions with negatively charged graphene oxide. The Ni²⁺/graphene modified glassy carbon electrode (Ni/GR/GCE) was prepared by cyclic voltammetric scanning of Ni/GO/GCE in the potential range from ?1.5 to 0.2 V at 50 mV s^?1 for 5 cycles. The electrochemical activity of Ni/GR/GCE was illustrated in 0.10 M NaOH using cyclic voltammetry. The Ni/GR/GCE exhibits the characteristic of improved reversibility and enhanced current responses of the Ni(III)/Ni(II) couple. The introduction of conductive graphene not only greatly facilitates the electron transfer of Ni²⁺, but also dramatically improves the long-term stability of the sensor by providing the electrostatic interactions. Ni/GR/GCE also shows good electrocatalytic activity toward the oxidation of glucose. The Ni/GR/GCE gives a good linear range over 10 to 2700 μM with a detection limit of 5 μM towards the determination of glucose by amperometry. This sensor keeps over 85% activity towards 0.1 mM glucose after being stored in air for a month, respectively. Furthermore, the modified sensor was successfully applied to the sensitive determination of glucose in blood samples.     

Electrochemical tyrosine sensor based on a glassy carbon electrode modified with a nanohybrid made from graphene oxide and multiwalled carbon nanotubes

We report on a glassy carbon electrode that was modified with a composite made from graphene oxide (GO) and multiwalled carbon nanotubes (MWCNT) that enables highly sensitive determination of L-tyrosine. The sensor was characterized by transmission electron microscopy and electrochemical impedance spectroscopy, and its electrochemical properties by cyclic voltammetry, chronocoulometry and differential pulse voltammetry. The GO/MWCNT hybrid exhibits strong catalytic activity toward the oxidation of L-tyrosine, with a well defined oxidation peak at 761 mV. The respective current serves as the analytical information and is proportional to the L-tyrosine concentration in two ranges of different slope (0.05 to 1.0 μM and 1.0 to 650.0 μM), with limits of detection and quantification as low as 4.4 nM and 14.7 nM, respectively. The method was successfully applied to the analysis of L-tyrosine in human body fluids. The excellent reproducibility, stability, sensitivity and selectivity are believed to be due to the combination of the electrocatalytic properties of both GO and MWCNT. They are making this hybrid electrode a potentially useful electrochemical sensing platform for bioanalysis.

Voltammetric sensor for caffeine based on a glassy carbon electrode modified with Nafion and graphene oxide

A facile, one-step and template-free method has been developed for the electrodeposition of well-dispersed platinum nanoparticles (Pt-NPs) on a glassy carbon electrode. The effects of various inorganic anions and overpotential on the morphologies and dimensions of the final products were investigated. The resulting Pt-NPs show high electrocatalytic activity towards methanol oxidation and are less easily poisoned by carbon monoxide.

Electrochemical sensor for ultrasensitive determination of ceftazidime using hollow platinum nanoparticles/reduced graphene oxide/pencil graphite electrode

In this paper, an electrochemical sensor was prepared based on the modification of pencil graphite electrode (PGE) by hollow platinum nanoparticles/reduced graphene oxide (HPtNPs/rGO/PGE) for determination of ceftazidime (CFZ). Initially, rGO was electrodeposited on the electrode surface, and then, hollow platinum nanoparticles were placed on the electrode surface via galvanic displacement reaction of Pt(IV) ions with cobalt nanoparticles (CoNPs) that had electrodeposited on the electrode surface. Several significant parameters controlling the performance of the HPtNPs/rGO/PGE were examined and optimized using central composite design as one optimization methodology. The surface morphology and elemental characterization of the bare PGE, rGO/PGE, CoNPs/rGO/PGE, and HPtNPs/rGO/PGE-modified electrodes was analyzed by field-emission scanning electron microscopy, transmission electron microscopy, energy-dispersive X-ray spectroscopy, and electrochemical impedance spectroscopy. The electrochemical activity of CFZ on resulting modified electrode was investigated by cyclic voltammetry (CV) and adsorptive differential pulse voltammetry (AdDPV). Adsorptive differential pulse voltammetry indicates that peak current increases linearly with respect to increment in CFZ concentration. CFZ was determined in the linear dynamic range of 5.0 × 10^?13 to 1.0 × 10^?9 M, and the detection limit was determined as 2.2 × 10^?13 M using AdDPV under optimized conditions. The results showed that modified electrode has high selectivity and very high sensitivity. The method was used to determine of CFZ in drug injection and plasma samples.     

An electrochemical sensor based on molecularly imprinted polydopamine coated on reduced graphene oxide for selective detection of ornidazole

The electrochemical sensing of ornidazole (OR) was achieved with a highly selective sensor fabricated by a combination of an electrochemically reduced graphene oxide (ERGO) and molecularly imprinted polydopamine (PDA). The sensor (OR-imp@PDA/ERGO/GCE) was synthesized by electrochemical polymerization of dopamine (DA) on ERGO modified glassy carbon electrode (GCE). The analytical response of the sensor changed linearly with OR concentration varying from 1.5 × 10⁻⁹ M to 1.0 × 10⁻⁸ M and 1.0 × 10⁻⁸ M to 2.0 × 10⁻⁷ M, and the detection limit was defined as 1.1 × 10⁻⁹ M. The proposed sensor ensured the highly sensitive detection of OR concentration because of the advantages of ERGO and molecularly imprinted PDA.     

基于羟基化酞菁锌-石墨烯纳米材料的和厚朴酚电化学传感器的构建及其应用

通过非共价作用制备了可溶性四羟基酞菁锌-石墨烯纳米复合材料,并将其应用于构建新型高灵敏度和厚朴酚电化学传感器.由于水溶性四羟基酞菁锌和石墨烯的协同作用,显著提高了纳米复合材料的比表面积和导电性,增强了和厚朴酚的电化学响应.在最优实验条件下测定,和厚朴酚在0.01～1.0μmol/L和1.0～100 μmol/L范围内呈...     

Electrochemical quercetin sensor based on a nanocomposite consisting of magnetized reduced graphene oxide,silver nanoparticles and a molecularly imprinted polymer on a screen-printed electrode

An electrochemical quercetin (QR) sensor is described that is based on the use of magnetic reduced graphene oxide (MrGO) incorporated into a molecularly imprinted polymer (MIP) on the surface of a screen-printed electrode (SPE). The MrGO consists of reduced graphene oxide (rGO), magnetite (Fe₃O₄) and silver nanoparticles (Ag). The analyte (QR) is electrostatically adsorbed on the surface of the MrGO. Finally, the MIP was deposited via in-situ polymerization. The composite was characterized by X-ray diffraction, Fourier transform infrared spectroscopy and Vibrating sample magnetometry. The morphologies and electrochemical properties of different electrodes were characterized by Field emission scanning electron microscopy, Electrochemical impedance spectroscopy and differential pulse voltammetry. Under optimal conditions, the modified electrode has a linear response in the 20 nM to 250 μM QR concentration range. The limit of detection is 13 nM (at an S/N ratio of 3). The electrode is selective, stable, regenerable and reliable. It was applied to the determination of QR in spiked pharmaceutical samples and gave satisfactory results.

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Graphical abstract Schematic presentation of a method for sensing quercetin. It is based on the use of screen printed electrode modified with magnetized reduced graphene oxide and a molecularly imprinted polymer.

     

Polyaniline-iron oxide nanohybrid film as multi-functional label-free electrochemical and biomagnetic sensor for catechol

Polyaniline-iron oxide magnetic nanohybrid was synthesized and characterized using various spectroscopic, microstructural and electrochemical techniques. The smart integration of Fe₃O₄ nanoparticles within the polyaniline (PANI) matrix yielded a mesoporous nanohybrid (Fe₃O₄@PANI) with high surface area (94 m² g⁻¹) and average pore width of 12.8 nm. Catechol is quasi-reversibly oxidized to o-quinone and reduced at the Fe₃O₄@PANI modified electrodes. The amperometric current response toward catechol was evaluated using the nanohybrid and the sensitivity and detection limit were found to be 312 μA μL⁻¹ and 0.2 nM, respectively. The results from electrochemical impedance spectroscopy (EIS) indicated that the increased solution resistance (R_s) was due to elevated adsorption of catechol on the modified electrodes. Photoluminescence spectra showed ligand-to-metal charge transfer (LMCT) between p-π orbitals of the phenolate oxygen in catechol and the d-σ* metal orbital of Fe₃O₄@PANI nanohybrid. Potential dependent spectroelectrochemical behavior of Fe₃O₄@PANI nanohybrid toward catechol was studied using UV/vis/NIR spectroscopy. The binding activity of the biomagnetic particles to catechol through Brownian relaxation was evident from AC susceptibility measurements. The proposed sensor was used for successful recovery of catechol in tap water samples.     

Eggplant-based bioamperometric sensor for the detection of catechol

Polyphenol oxidases from eggplant have a high catalytic activity for the aerobic oxidation of catechol to o-quinone with selectivity over other phenolic substrates. An amperometric biosensor can therefore be constructed by incorporating selected portions of eggplant tissue in a carbon paste electrode. The proposed biosensor provides a selective response for catechol in the micromolar range, with a very fast response time and a useful lifetime of at least 3 weeks.     

Electrochemical reduction and electric conductivity of graphene oxide films

The types of cells and methods of electrochemical reduction of graphene oxide films were described. The possibility of creating ultrathin membrane–electrode assemblies of supercapacitor cells was demonstrated. The peculiarities of the electrochemical behavior of films of different thicknesses that contact with carbon and metal current collectors were shown. The limiting charge (1500–2000 C/g) for complete electrochemical reduction of graphene oxide was determined. Possible mechanisms of proton conductivity along the basal faces of graphene oxide flakes were proposed. The nature of the current collector was shown to affect the electron–hole conductivity of graphene oxide films and the observed contact potential difference.     

Electrochemical sensor for detection of p-nitrophenol based on nanoporous gold

Nanoporous gold (NPG) with uniform pore sizes and ligaments was prepared by a simple dealloying method. The as-prepared NPG samples were used as the working electrodes to investigate the redox behavior of p-nitrophenol (p-NP) by cyclic voltammetry (CV). Quite different from the voltammetric behavior of polycrystalline gold electrode, the CV profiles of NPG display a pair of nearly symmetric redox waves which are ascribed to the reaction of 4-(hydroxyamino)phenol/4-nitrosophenol couple. It is interesting that this pair of redox waves are hardly affected by the isomers of p-NP; and moreover, their peak areas are linear with the concentration of p-NP in the range from 0.25 to 10 mg dm^?3. Because of high sensitivity and good selectivity, NPG is expected to act as a promising electrochemical sensor material for detecting trace p-NP in wastewaters.     

Oximation reaction induced reduced graphene oxide gas sensor for formaldehyde detection

High-performance gas sensors can offer great potentials for monitoring and detection of volatile organic compounds (VOCs) in both domestic and industrial environment. In the present work, a new HCHO gas sensor was constructed with reduced graphene oxide (RGO) induced by the oximation reaction. The gas-sensing performance test results suggested that the RGO hydroxylamine hydrochloride (RGO/HA-HCl) sensor presented a high response of 75% at 16 ppm HCHO at room temperature, and a high selectivity for HCHO suffering little interference with high concentrations of volatile organic compounds, including methanol, ethanol, and methylbenzene, dichloromethane and water. Additionally, the RGO/HA-HCl sensor also showed a good long-term stability with RSD of 5.83% for a 15-day continuous sensing test, and the detection limit (DL) could reach 0.023 ppm under ambient conditions. Moreover, the mechanism for the high sensitivity and selectivity of formaldehyde was further established by in-situ gas chromatography mass spectrometry (GC–MS). This work would provide a reliable new HCHO gas sensor which could be used for monitoring and forewarning the emission of HCHO for a better protection and improvement of our environment.