Electrografting of amino-TEMPO on graphene oxide and electrochemically reduced graphene oxide for electrocatalytic applications

4-Amino-2,2,6,6-tetramethyl-1-piperridine N-oxyl (4-amino-TEMPO), an electroactive nitroxide radical, was attached to the surface of graphene oxide (GO) and electrochemically reduced graphene oxide (ERGO) modified glassy carbon electrode by a simple, rapid and green electrografting method. The electroactive interfaces were analyzed by X-ray photoelectron spectroscopy (XPS) and cyclic voltammetry (CV). The calculated surface coverage for 4-amino-TEMPO is up to 1.55 × 10^− 9 mol·cm^− 2. The modified electroactive interface exhibited excellent electrocatalytic activity towards the electro-oxidation of reduced glutathione (GSH) and hydrogen peroxide (H₂O₂).     

Enzymatic glucose biosensor based on bismuth nanoribbons electrochemically deposited on reduced graphene oxide

We describe the electrochemical preparation of bismuth nanoribbons (Bi-NRs) with an average length of 100 ± 50 nm and a width of 10 ± 5 μm by a potentiostatic method. The process occurs on the surface of a glassy carbon electrode (GCE) in the presence of disodium ethylene diamine tetraacetate that acts as a scaffold for the growth of the Bi-NRs and also renders them more stable. The method was applied to the preparation of Bi-NRs incorporated into reduced graphene oxide. This nanocomposite was loaded with the enzyme glucose oxidase onto a glassy carbon electrode. The resulting biosensor displays an enhanced redox peak for the enzyme with a peak-to-peak separation of about 28 mV, revealing a fast electron transfer at the modified electrode. The loading of the GCE with electroactive GOx was calculated to be 8.54 × 10⁻¹⁰ mol∙cm⁻², and the electron transfer rate constant is 4.40 s⁻¹. Glucose can be determined (in the presence of oxygen) at a relatively working potential of −0.46 V (vs. Ag|AgCl) in the 0.5 to 6 mM concentration range, with a 104 μM lower detection limit. The sensor also displays appreciable repeatability, reproducibility and remarkable stability. It was successfully applied to the determination of glucose in human serum samples.

A potentiostatic method was used to prepare reduced graphene oxide and bismuth nanoribbons nanocomposite on a glassy carbon electrode. This nanocomposite was loaded with enzyme glucose oxidase to fabricate a glucose biosensor.

     

Indicator-free impedimetric detection of BCR/ABL fusion gene based on ordered FePt nanoparticle-decorated electrochemically reduced graphene oxide

A novel indicator-free DNA hybridization biosensor with a graphene-based nanocomposite as the enhanced sensing platform was developed for the detection of the BCR/ABL fusion gene in chronic myelogenous leukemia. The platform was constructed by homogenously distributing ordered FePt nanoparticles (NPs) onto the electrochemically reduced graphene oxide (ERGNO). The surface structure and electrochemical performance of the FePt/ERGNO nanocomposite were systematically investigated. Owing to the synergistic effects of FePt NPs and ERGNO with a large surface area and excellent electron transfer ability, the obtained nanocomposite greatly facilitated the sensing behavior for DNA detection, resulting in excellent sensitivity and selectivity. A remarkable change has been observed in the impedance spectra before and after hybridization of the probe single-stranded DNA (ssDNA) with the target DNA. Under the optimized conditions, the complementary target genes could be quantified in a wide range of 1.0?×?10^?14 to 1.0?×?10^?9 mol/L with a detection limit of 2.6?×?10^?15 mol/L. The approach does not need an oligonucleotide probe or target to be labeled previously, which makes it advantageous in terms of simplicity and noninvasiveness.     

氧化石墨烯浓度对还原氧化石墨烯/ZnS电化学性能的影响

以氧化石墨烯(GO)、乙酸锌(Zn(CH₃COO)₂)和硫脲为原料,采用水热法成功制备了还原氧化石墨烯/ZnS(rGO/ZnS)复合材料,并将该材料用作锂离子电池负极。高导电性的 rGO可以为锂离子和电子的传输提供有效的路径,ZnS可以提供较高的理论比容量。rGO/ZnS复合材料在rGO与纳米级高度分散的类球形ZnS颗粒协同作用下展现了较好的嵌锂容量和循环性能。当GO质量浓度为2 mg·mL^-1时制备的rGO/ZnS复合材料的倍率性能最好,循环稳定性最佳。     

氧化石墨烯浓度对还原氧化石墨烯/ZnS电化学性能的影响

以氧化石墨烯(GO)、乙酸锌(Zn(CH₃COO)₂)和硫脲为原料,采用水热法成功制备了还原氧化石墨烯/ZnS(rGO/ZnS)复合材料,并将该材料用作锂离子电池负极。高导电性的 rGO可以为锂离子和电子的传输提供有效的路径,ZnS可以提供较高的理论比容量。rGO/ZnS复合材料在rGO与纳米级高度分散的类球形ZnS颗粒协同作用下展现了较好的嵌锂容量和循环性能。当GO质量浓度为2 mg·mL^-1时制备的rGO/ZnS复合材料的倍率性能最好,循环稳定性最佳。     

Synthesis of adenine-modified reduced graphene oxide nanosheets

We report here a facile strategy to synthesize the nanocomposite of adenine-modified reduced graphene oxide (AMG) via reaction between adenine and GOCl which is generated from SOCl(2) reacted with graphite oxide (GO). The as-synthesized AMG was characterized by transmission electron microscopy (TEM), atomic force microscopy (AFM), UV-vis absorption spectroscopy, Fourier transform infrared (FT-IR) spectroscopy, Raman spectroscopy, thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS), cyclic voltammetry (CV), and galvanostatic discharge analysis. The AMG owns about one adenine group per 53 carbon atoms on a graphene sheet, which improves electronic conductivity compared with reduced graphene oxide (RGO). The AMG displays enhanced supercapacitor performance compared with RGO accompanying good stability and good cycling behavior in the supercapacitor.     

A bioelectrocatalysis method for the kinetic measurement of thermal inactivation of a redox enzyme, bilirubin oxidase.

The thermal stability of a redox enzyme, bilirubin oxidase (BOD), has been quantitatively evaluated by measuring the inactivation kinetics of BOD at several temperatures. The enzyme activity is directly related to the mediated bioelectrocatalytic current for the BOD-catalyzed reduction of O(2). Thus, the inactivation process is measured by the time-dependent decrease in the bioelectrocatalytic current. The results reveal that the inactivation obeys first-order kinetics, whose rate constants (k) are determined at pH 7.0 and at 50 - 70 degrees C. The half life of BOD activity, calculated from the k value at 50 degrees C is 114 min, which is in harmony with the thermal-stability data given in a catalog by Amano Enzyme Inc. The bioelectrocatalysis method allows in situ measurements of the inactivation kinetics in the period of a few minutes at relatively high temperatures. The rate constants show a large temperature dependence, leading to a large Arrhenius activation energy (E(A)) of 221 kJ mol(-1). The activation Gibbs energy (DeltaG(not equal)), activation enthalpy (DeltaH(not equal)), and activation entropy (DeltaS(not equal)) are also determined.     

Ultrasensitive aptamer-based on-off assay for lysozyme using a glassy carbon electrode modified with gold nanoparticles and electrochemically reduced graphene oxide

The authors describe an electrochemical aptamer based assay for the determination of the serine protease lysozyme in very low (pM) concentrations. The method is based on the formation of a complex between anti-lysozyme aptamer fragments and lysozyme, and on electrochemical detection by differential pulse voltammetry (DPV) and electrochemical impedance spectroscopy (EIS). The surface of a glassy carbon electrode was modified with a nanocomposite consisting of gold nanoparticles and electrochemically reduced graphene oxide nanosheets (AuNPs/erGO), and the thiolated aptamer was then linked to the AuNPs by self-assembly through Au-S bonds. The interaction of immobilized aptamers with lysozyme leads to the decreased peak current in DPV and increased charge transfer resistance (R_ct) in EIS when using hexacyanoferrate or Methylene Blue as a redox probe. The calibration plot, when applying EIS and working at a typical voltage of ?0.22 V (vs. SCE), is linear over 1.0 to 104.3 pM concentration range, with a detection limit of 0.06 pM (at a signal-to-noise ratio of 3). The respective data for DPV are a 9.6–205.5 pM linear range with a detection limit of 0.24 pM. Depending on the redox marker applied, the method works in the “signal-off” or “signal-on” mode in DPV and EIS protocols, respectively. The sensing interface is high specific for lysozyme and not affected by other proteins. The method was applied to the determination of lysozyme in spiked diluted human serum, and the results agreed well with data obtained with a standard ELISA.

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Graphical abstract The surface of a glassy carbon electrode was modified with a nanocomposite consisting of gold nanoparticles and electrochemically reduced graphene oxide nanosheets (AuNPs/erGO). Then, the thiolated aptamer was linked to the AuNPs by self-assembly through Au-S bonds. The modified electrode was applied to the determination of lysozyme with “signal off” and “signal on” strategies.

     

Evaluation of a biosensor based on reduced graphene oxide and glucose oxidase enzyme on the monitoring of second-generation ethanol production

Journal of Solid State Electrochemistry - An easily prepared biosensor based on reduced graphene oxide (rGO) and glucose oxidase (GOx) enzyme was developed to monitor the enzymatic hydrolysis...     

Ultrasonic route synthesis,characterization and electrochemical study of graphene oxide and reduced graphene oxide

Research on Chemical Intermediates - In this study, an efficient route for graphene oxide (GO) and reduced GO (RGO) synthesis was developed by using an ultrasonic probe and bath alternatively. RGO...     

Lactate biosensor based on a bionanocomposite composed of titanium oxide nanoparticles, photocatalytically reduced graphene, and lactate oxidase

We have developed a lactate biosensor based on a bionanocomposite (BNC) composed of titanium dioxide nanoparticles (TiO₂-NPs), photocatalytically reduced graphene, and lactate oxidase. Graphene oxide was photochemically reduced (without using any chemical reagents) in the presence of TiO₂-NPs to give graphene nanosheets that were characterized by atomic force microscopy, Raman and X-ray photoelectron spectroscopy. The results show the nanosheets to possess few oxygen functionalities only and to be decorated with TiO₂-NPs. These nanosheets typically are at least 1 μm long and have a thickness of 4.2 nm. A BNC was obtained by mixing lactate oxidase with the nanosheets and immobilized on the surface of a glassy carbon electrode. The resulting biosensor was applied to the determination of lactate. Compared to a sensor without TiO₂-NPs, the sensor exhibits higher sensitivity (6.0 μA mM^?1), a better detection limit (0.6 μM), a wider linear response (2.0 μM to 0.40 mM), and better reproducibility (3.2 %).

Synthesis,characterization, and preparation of nickel nanoparticles decorated electrochemically reduced graphene oxide modified electrode for electrochemical sensing of diclofenac

Journal of Solid State Electrochemistry - In this work, nickel nanoparticles (NiNPs) and graphene oxide (GO) were synthesized and characterized independently using spectroscopic and microscopic...     

Preparation of electrochemically reduced graphene oxide-modified electrode and its application for determination of p-aminophenol

A simple and eco-friendly electrochemical method to reduce graphene oxide precursor was employed for fabrication of graphene sheets modified glassy carbon electrode, and then, the resulting electrode [electrochemically reduced graphene oxide (ERGO)/glassy carbon electrode (GCE)] was used to determine p-aminophenol. The experimental results demonstrated that the modified electrode exhibited excellent electrocatalytic activity toward the redox of p-aminophenol as evidenced by the significant enhancement of redox peak currents and the decreased peak-to-peak separation in comparison with a bare GCE. A highly sensitive and selective voltammetry determination of p-aminophenol is developed using the ERGO/GCE. This method has been applied for the direct determination of p-aminophenol in artificial wastewater.     

Visible-light-induced dye degradation over copper-modified reduced graphene oxide

Previously, it was found that reduced graphene oxide (RGO) can degrade rhodamine B (RhB) under visible-light irradiation, but with an extraordinarily slow rate. It was also found that modification of RGO with gold nanoparticles can dramatically accelerate the photoreaction rate. Herein, we describe the preparation and photocatalytic properties of copper-ion-modified RGO composite materials, which display a faster photocatalytic reaction rate and better mineralization under visible-light irradiation than gold-modified RGO. The copper-ion-modified RGO composites were prepared by an immersion method. The characterization results of X-ray diffraction, transmission electron microscopy, field-emission scanning electron microscopy, and X-ray photoelectron spectroscopy show the presence of crystalline copper species Cu(2)(OH)(3)NO(3) and Cu(2)(OH)(3)Cl on the surface of RGO. Modification of RGO with the copper species greatly enhances the degradation of RhB--after 3 hours of reaction under visible-light irradiation, the total organic carbon is decreased by about 31%. The copper species act as an electron relay, passing the excited electrons from the RGO sheets to adsorbed oxygen, thus leading to continuous generation of reactive oxygen species for the degradation of RhB.     

Double laminated reduced graphene/Cu_2S/reduced graphene/graphene oxide nanofilms and their photoelectrochemical properties

In this work,an efficient photocatalytic material was prepared directly on Indium tin oxide(ITO)glass substrates by fabricating Cu_2 S and graphene oxide onto graphene for photoelectrochemical(PEC) water splitting.The double laminated reduced graphene/Cu_2S/reduced graphene/graphene oxide(RG/Cu_2S/RG/GO) nanofilms were characterized,and an enhanced photoelectrochemical response in the visible region was discovered.The photocurrent density of the nanofilms for PEC water splitting was measured to be up to 1.98 m A/cm~2,which could be ascribed to the followings:(i) a higher efficiency of light-harvesting because of GO coupling with Cu_2 S that could broaden the absorbing solar spectrum and enhance the light utilization efficiency;(ii) a stepwise structure of band-edge levels in the Cu_2S/GO electrode was constructed;(iii) double laminated electron accelerator(RG) was used in the Cu_2S/GO materials to get better electron-injecting efficiency.     

Synthesis of reduced graphene oxide and its electrocatalytic properties

The method of the chemical synthesis of reduced graphene oxide was developed. Sodium hypophosphite and sulfi te were used as reducing agents. The formation of reduced graphene oxide was confi rmed by several methods. Volt-ampere characteristics of electrodes based on reduced graphene oxide were investigated in an experimental model of an oxygen fuel cell with an alkaline electrolyte. Characteristics of oxygen electrodes based on reduced graphene oxide were stable over semiannual tests. The resulting reduced graphene oxide is a promising material for oxygen electrodes of chemical current sources.     

Local current mapping and patterning of reduced graphene oxide

Conductive atomic force microscopy (C-AFM) has been used to correlate the detailed structural and electrical characteristics of graphene derived from graphene oxide. Uniform large currents were measured over areas exceeding tens of micrometers in few-layer films, supporting the use of graphene as a transparent electrode material. Moreover, defects such as electrical discontinuities were easily detected. Multilayer films were found to have a higher conductivity per layer than single layers. It is also shown that a local AFM-tip-induced electrochemical reduction process can be used to pattern conductive pathways on otherwise-insulating graphene oxide. Transistors with micrometer-scale tip-reduced graphene channels that featured ambipolar transport and an 8 order of magnitude increase in current density upon reduction were successfully fabricated.     

Computational studies for reduced graphene oxide in hydrogen-rich environment

We employ molecular dynamic simulations to study the reduction process of graphene oxide (GO) in a chemically active environment enriched with hydrogen. We examine the concentration and pressure of hydrogen gas as a function of temperature in which abstraction of oxygen is possible with minimum damage to C-sp(2) bonds, hence preserving the integrity of the graphene sheet. Through these studies we find chemical pathways that demonstrate beneficiary mechanisms for the quality of graphene including formation of water as well as suppression of carbonyl pair holes in favor of hydroxyl and epoxide formation facilitated by hydrogen gas in the environment.     

High-rate lithium-sulfur batteries promoted by reduced graphene oxide coating

Lithium-sulfur batteries have a poor rate performance and low cycle stability due to the shuttling loss of intermediate lithium polysulfides. To address this issue, a carbon-sulfur nanocomposite coated with reduced graphene oxide was designed to confine the polysulfides.