Electrochemically reduced graphene modified carbon ionic liquid electrode for the sensitive sensing of rutin

In this paper a graphene (GR) modified carbon ionic liquid electrode that was obtained by one-step potentiostatic electroreduction of a graphene oxide solution was described. The resulting electrode displayed excellent electrochemical performance due to the formation of highly conductive GR film on the electrode surface. Electrochemistry of rutin was carefully studied with a pair of well-defined redox peaks appeared in pH 2.5 buffer solution. Rutin exhibited a diffusion-controlled two-electron and two-proton transfer reaction on the modified electrode with the electrochemical parameters calculated. The reduction peak currents are linearly related to rutin concentration in the concentration range from 0.070 to 100.0 μmol/L with a detection limit as low as 24.0 nmol/L (3σ). The modified electrode displayed excellent selectivity with good stability, and was applied to the determination of rutin content in tablet, human serum and urine samples with satisfactory results.     

Coupling of short DNAs with reduced graphene oxide for electronic and sensing applications

Abstract

In this article, we described an approach for coupling of short DNAs with reduced graphene oxide and thus formation of transducer layer for biological sensors. We investigated the dependence of coupling ratio on the graphene oxide reduction level. We found optimal reduction parameters and showed successful conjugation of aptamers with reduced graphene oxide. We have revealed a trend to increase aptamer conjugation efficiency with a decrease of graphene oxide reduction rate. Finally, we made biosensor structures with Π-shaped reduction pattern and showed excellent sensitivity of the sensor during thrombin exposure. These results are important for the development of flexible low-cost biosensors of a new generation.     

Transparent, luminescent, antibacterial and patternable film forming composites of graphene oxide/reduced graphene oxide

Multifunctional graphene oxide/reduced graphene oxide (GO/RGO) composites were prepared through electrostatic interaction using biocompatible ingredients. Different functionalities were added to GO/RGO by anchoring materials such as native lactoferrin (NLf), NLf protected Au clusters (designated as Au@NLf), chitosan (Ch) and combinations thereof. Anchoring of Ch and NLf enhances the antibacterial property of RGO/GO. The addition of Ch to RGO/GO not only helped in forming stable dispersions but also helped in fabricating large (cm(2)) area films through a simple solvent evaporation technique. Functionalities such as photoluminescence were added to Ch-RGO/GO composites by anchoring Au@NLf on it. The composites thus formed showed stable luminescence in presence of various metal ions in the solid state. The composite showed reasonable stability against pH and temperature variations as well. The as-prepared films were transparent and the transparency could be modulated by controlling the concentration of RGO/GO in the composite. The antibacterial property and ability to form stable thin films may provide an opportunity to use such composites for medical and environmental remediation applications as well. Erasable patterns were fabricated on the film by stamping required patterns under compressive pressure. Luminescent patterns can be inscribed on the film and can be erased by simply wetting it. Such films with erasable information may be useful for security applications.     

Transparent conductive film of polyvinyl alcohol: reduced graphene oxide composite

Journal of Materials Science - The interest in the research for transparent conductive materials has intensified the last years due to the fascinating optical and electrical properties of graphene...     

Facile preparation of nitrogen-doped reduced graphene oxide as a metal-free catalyst for oxygen reduction reaction

The electronic and chemical properties of reduced graphene oxide (RGO) can be modulated by chemical doping foreign atoms and functional moieties. Nitrogen-doped reduced graphene oxide (N-RGO) is a promising candidate for oxygen reduction reaction (ORR) in fuel cells. However, there are still some challenges in further preparation and modification of N-RGO. In this work, a low-cost industrial material, urea, was chosen to modify RGO by a facile, catalyst-free thermal annealing approach in large scale. The obtained N-RGO, as a metal-free catalyst for oxygen reduction was characterized by XRD, XPS, Raman, SEM, TEM, and electrochemical measurements. It was found that the optimum synthesis conditions were a mass ratio of graphene oxide and urea equal to 1:10 and an annealing temperature of 800 °C. Detailed X-ray photoelectron spectrum analysis of the optimum product shows that the atomic percentage of N-RGO samples can be adjusted up to 2.6 %, and the resultant product can act as an efficient metal-free catalyst, exhibiting enhanced electrocatalytic properties for ORR in alkaline electrolytes. This simple, cost-effective, and scalable approach opens up the possibility for the synthesis of other nitrogen doping materials in gram-scale. It can be applied to various carbon materials for the development of other metal-free efficient ORR catalysts for fuel cell applications, and even new catalytic materials for applications beyond fuel cells.     

Appropriate conditions for preparing few-layered graphene oxide and reduced graphene oxide

Oxidation time and exfoliated conditions of graphite oxides (GOs) were investigated to prepare few–layer graphene oxide and reduced graphene oxide via a modified Hummers approach. Different oxidative degree of GOs was prepared by changing oxidation time, and the effects of oxidative degree of GOs in different oxidation time were studied by XRD, FT-IR. Afterwards, highly oxidized GOs were used as precursor to prepare graphene oxide and reduced graphene oxide by ultrasonic dispersion method and thermal expansion method. The exfoliated conditions (ultrasonic power and ultrasonic time, thermal exfoliated temperature) were investigated to prepare few-layered graphene oxide and reduced graphene oxide.     

Facile one-step hydrothermal synthesis of reduced graphene oxide/Co3O4 composites for supercapacitors

This paper reports a facile one-step hydrothermal treatment of graphene oxide (GO) and cobalt acetate (Co(Ac)₂) for preparing reduced GO (rGO)/Co₃O₄ composites which were used as electrode materials for supercapacitors containing electrolytes of 2 M KOH aqueous solution. The morphologies and structures of rGO/Co₃O₄ composites were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, Raman spectrum, and N₂ adsorption–desorption isotherms. The electrochemical performances of two-electrode supercapacitors were evaluated by cyclic voltammetry, galvanostatic charge–discharge, and electrochemical impedance spectroscopy techniques. During the hydrothermal reaction, GO was reduced and 10–30 nm-sized Co₃O₄ nanoparticles were in situ grown onto the rGO sheets simultaneously. The effects of mass ratios of GO and Co(Ac)₂ on the performances of supercapacitors were investigated. In comparison with pure Co₃O₄-based supercapacitor, supercapacitors based on rGO/Co₃O₄ composites show better performances because both the specific surface areas and the electrical conductivities of electrode materials were increased by the introduction of rGO. When the mass ratio of GO and Co(Ac)₂ is 1:2, rGO/Co₃O₄ composite electrode exhibits the highest capacitance of 263.0 F/g at a constant current density of 0.2 A/g in a two-electrode supercapacitor. In addition, the supercapacitor shows high rate capability and long cyclic durability.     

A platform for electrochemical sensing of biomolecules based on Europia/reduced graphene oxide nanocomposite

This study aimed at preparing and evaluating the europium oxide–reduced graphene oxide (rGO) composites. Inorganic nanoparticles anchored onto rGO sheets through a facile sonochemical method. The resultant products were characterized by FT-IR, XRD, SEM. Their activity in biomolecules’ analysis were examined by cyclic voltammetry. The rectified electrodes revealed an incredibly electroactive manner. The obtained progress provided excellent materials for scrutiny of biomolecules. The linear relationship was used in the region of 100–1500 µM ascorbic acid (AA), 50–600 µM dopamine (DA), and 10–700 µM uric acid (UA), between current intensities and concentrations. The detection restrictions (LOD) (S/N?=?3) decreased to 8 µM, 1.1 µM and 0.085 µM for AA, DA and UA respectively by differential pulse voltammetry (DPV).     

Ambient flash sintering of reduced graphene oxide/zirconia composites:Role of reduced graphene oxide

Fabrication of graphene/ceramic composites commonly requires a high-temperature sintering step with long times as well as a vacuum or inert atmosphere,which not only results in property degradation but also significant equipment complexity and manufacturing costs.In this work,the ambient flash sintering behavior of reduced graphene oxide/3 mol% yttria-stabilized ZrO₂(rGO/3 YSZ) composites utilizing rGO as both a composite component and a conductive additive is reported.When the sintering condition is carefully optimized,a dense and conductive composite can be achieved at room temperature and in the air within 20 s.The role of the rGO in the FS of the rGO/3 YSZ composites is elucidated,especially with the assistance of a separate investigation on the thermal runaway behavior of the rGO.The work suggests a promising fabrication route for rGO/ceramic composites where the vacuum and furnace are not needed,which is of interest in terms of simplifying the fabrication equipment for energy and cost savings.     

Thermally stable and highly conductive free-standing hybrid films based on reduced graphene oxide

Thermally stable and highly conductive films have been prepared based on thermally reduced graphene oxide and exfoliated α-zirconium phosphate nanoplatelet (ZrP) hybrids. Exfoliated ZrP and graphene oxide (GO) were first mixed in aqueous solution to form a stable dispersion and then cast into free-standing films through flow-directed assembly. Upon annealing at 750 °C in Argon atmosphere, significant amounts of oxidized species were removed from the GO and a noticeable recovery of sp² structure of the reduced GO sheets was observed. With the incorporation of the inorganic nanoplatelets, the thermal stability and structural integrity of the hybrid films were greatly improved, while the good electrical conductivity of the reduced GO was maintained. Potential applications for graphene-based hybrid films based on the current approach are discussed.     

Fibers of reduced graphene oxide nanoribbons

Reduced graphene oxide nanoribbon fibers were fabricated by using an electrophoretic self-assembly method without the use of any polymer or surfactant. We report electrical and field emission properties of the fibers as a function of reduction degree. In particular, the thermally annealed fiber showed superior field emission performance with a low potential for field emission (0.7?V?μm(-1)) and a giant field emission current density (400?A?cm(-2)). Moreover, the fiber maintains a high current level of 300?A?cm(-2) corresponding to 1?mA during long-term operation.     

Wafer-scale reduced graphene oxide films for nanomechanical devices

We report a process to form large-area, few-monolayer graphene oxide films and then recover the outstanding mechanical properties found in graphene to fabricate high Young's modulus ( =185 GPa), low-density nanomechanical resonators. Wafer-scale films as thin as 4 nm are sufficiently robust that they can be delaminated intact and resuspended on a bed of pillars or field of holes. From these films, we demonstrate radio frequency resonators with quality factors (up to 4000) and figures of merit ( f x Q>10(11)) well exceeding those of pure graphene resonators reported to date. These films' ability to withstand high in-plane tension (up to 5 N/m) as well as their high Q-values reveals that film integrity is enhanced by platelet-platelet bonding unavailable in pure graphite.     

Facile synthesis of reduced graphene oxide from Azadirachta indica for optical power limiting applications: an eco-friendly approach

Reduced graphene oxide (rGO) was synthesized successfully from dead leaves of neem trees using a novel synthesis method comprising combustion, washing, and drying. The synthesized carbonaceous material was subjected to systematic characterization analysis. The rGO material was subjected to X-ray powder diffraction analysis to determine the grain size and other structural parameters. The existence of defect and graphitic band was confirmed by FT-Raman analysis. The presence of a 2D band around 2700 cm^?1 indicated the formation of multi-layered graphene. SEM analysis was used to examine the structural morphology of the synthesized material. FTIR spectra revealed the information about the spectral properties of rGO. Compositional analysis revealed the presence of carbon and other contents in the specimen. The title material may be used in optical power limiters, according to z-scan and optical limiting analysis. The results indicate that the cost of synthesis would be significantly reduced when done on a large scale, using this procedure. Furthermore, rGO produced by this method is environmentally friendly, nontoxic and has a high yield.

     

Facile synthesis of reduced graphene oxide/trimethyl chlorosilane‐coated cellulose nanofibres aerogel for oil absorption

A hydrophobic and oleophilic trimethyl chlorosilane/reduced graphene oxide‐coated cellulose nanofibres (TMCS/rGO/CNFs) aerogel with a three‐dimensional structure was fabricated through a facile dip‐coating process. The prepared aerogel exhibited several advantageous properties for absorption and expulsion of oils from water surfaces, such as a high specific surface area, low density (6.78 mg/cm³) and good porosity (99.12％). In addition, the TMCS/rGO/CNFs aerogel demonstrated good absorption capacities up to 39 times its own weight over a short time (1.5 min) for a broad range of oils. This research suggests that practical application of TMCS/rGO/CNFs aerogel in the cleanup of an oil spill is feasible.Inspec keywords: graphene, nanofibres, aerogels, absorption, hydrophobicity, dip coating, oil pollution, nanofabricationOther keywords: facile synthesis, reduced graphene oxide‐trimethyl chlorosilane‐coated cellulose nanofibre aerogel, three‐dimensional structure, facile dip‐coating process, oil expulsion, water surfaces, TMCS‐rGO‐CNF aerogel, oil absorption capacities, oil spill cleanup, CO     

Nanoflakes of cobalt oxide for highly sensitive sensing of two orally iron chelating drugs deferasirox and deferiprone

The synthesis of nanoflakes of cobalt oxide via electrodeposition onto platinum electrode surface was reported. The morphology of the electrodeposited thin film was studied by means of scanning electron microscopy and atomic force microscopy techniques and the electrochemical characteristics were investigated using cyclic voltammetry. The applicability of the synthesised nanoflakes of cobalt oxide to electrocatalytic oxidation of two orally administered iron chelating drugs (deferasirox, ICL670 and deferiprone, CP20) was evaluated in an alkaline solution. The results indicate that the drugs were oxidised via oxyhydroxide species immobilised on the electrode surface through an electrocatalytic mechanism. The catalytic rate constants and the diffusion coefficients of the drugs were determined. A sensitive, simple and efficient amperometric procedure was developed for the analysis of deferasirox and deferiprone, with detection limits of 6.67 and 2.52?µM, respectively. The electrode was also used for the direct assay of deferasirox and deferiprone tablets and determination of their main metabolites in human serum and urine.     

A review of top-down and bottom-up synthesis methods for the production of graphene,graphene oxide and reduced graphene oxide

Journal of Materials Science - As nanotechnology floods application areas like medicine, electronics, water remediation, space and textiles, just to name a few, some nanomaterials remain in the...     

Reduction efficiencies of natural substances for reduced graphene oxide synthesis

Journal of Materials Science - Synthesis of graphene by reducing graphene oxide is the most propitious route for bulk graphene production. Reduction using eco-friendly techniques is more feasible...     

PdCo alloys@N-doped porous carbon supported on reduced graphene oxide as a highly efficient electrocatalyst for hydrogen evolution reaction

Journal of Materials Science - Water splitting is considered as one of the recommendable techniques to realize clear and renewable hydrogen production. However, it suffers from lacking efficient...