Graphene-based Material Research Articles

Functionalization of graphene with Prussian blue and its application for amperometric sensing of H2O2

As a two-dimensional carbon material with high surface area and conductivity, graphene shows great promise for designing composite nanomaterials to achieve high-performance electrochemical devices. In this work, we prepared graphene-based nanocomposite material by electrochemically depositing Prussian blue (PB) nanoparticles on the surface of graphene. Fourier transform infrared spectra, SEM, and cyclic voltammetry were used to characterize the successful immobilization of PB. Compared with PB films and graphene sheets, the PB–graphene composite films showed the largest current response to the reduction of H2O2, probably due to the synergistic effects between graphene sheets and PB nanoparticles. Therefore, a fast and highly sensitive amperometric sensor for H2O2 was obtained with a detection sensitivity of 1.6 μA μM−1 H2O2 per cm2 and a linear response range of 50∼5,000 μM. The detection limit of H2O2 was 20 nM at a signal-to-noise ratio of 3. These obtained results are much better than those reported for carbon nanotubes-based amperometric sensors.

Graphene Electromechanical Actuation; Origins, Optimization and Applications

ABSTRACTGraphene-based materials have emerged as exceptional candidates for the development of novel, high performance actuators. Developing such an actuation material requires an in depth knowledge of the physics of operation and, therefrom, how to best optimize its performance. We investigate the electromechanical actuation of pristine monolayer graphene to elucidate the origin of this material’s exceptional electromechanical actuation performance. It is shown that the electrostatic double-layer (EDL) effect is dominant compared to the quantum-mechanical (QM) effect upon charging and electrolyte immersion. Seeking to optimize the QM actuation performance, we preliminarily investigate graphene oxide (GO) as a potential graphene-based actuation material, and find that it exhibits both unique and high performance responses. Having demonstrated huge stresses (~100 GPa) and high strains (~0.4%), graphene-based materials are uniquely positioned to address future industrial actuation challenges.

A graphene-based composite material noncovalently functionalized with a chemiluminescence reagent: synthesis and intrinsic chemiluminescence activity

A bottom-up approach for preparing multifunctional graphene-based materials noncovalently functionalized with CL reagents with aromatic rings such as N-(aminobutyl)-N-(ethylisoluminol) (ABEI), luminol and isoluminol is reported. The as-prepared nanocomposites exhibit good CL activity, which may find future applications in analytical, electrochemical and biomedical fields.

Three-dimensional porous graphene-based composite materials: electrochemical synthesis and application

A general method for the fabrication of three-dimensional (3D) porous graphene-based composite materials is reported. This method involves two consecutive electrochemical steps. Firstly, 3D graphene (ERGO) porous material is prepared electrochemically by reducing a concentrated graphene oxide dispersion. Subsequently, the second component is electrochemically deposited onto this 3D ERGO matrix, yielding graphene-based 3D porous composite material. The prepared graphene-based composite materials have a conductive graphene network as the matrix, onto which the second component is homogeneously coated. Conducting polymers, noble metal nanoparticles and metal oxide were successfully incorporated into ERGO architectures, demonstrating the versatility of this method. Taking the ERGO–polyaniline composite as an example, the influence of deposition rate on the morphology of the composite was investigated. Finally, the application of the composite materials prepared with our method was discussed. The high surface area and low electrolyte transport resistance make these electrosynthesized composites suitable electrode materials for electrochemical devices. The ERGO–polyaniline composite electrode showed a high specific capacitance of 716 F g−1 at 0.47 A g−1, and this capacitance could be maintained at 502 F g−1 as the discharge current density was increased up to 4.2 A g−1.

Oxidative stress-mediated antibacterial activity of graphene oxide and reduced graphene oxide in Pseudomonas aeruginosa

BackgroundGraphene holds great promise for potential use in next-generation electronic and photonic devices due to its unique high carrier mobility, good optical transparency, large surface area, and biocompatibility. The aim of this study was to investigate the antibacterial effects of graphene oxide (GO) and reduced graphene oxide (rGO) in Pseudomonas aeruginosa. In this work, we used a novel reducing agent, betamercaptoethanol (BME), for synthesis of graphene to avoid the use of toxic materials. To uncover the impacts of GO and rGO on human health, the antibacterial activity of two types of graphene-based material toward a bacterial model P. aeruginosa was studied and compared.MethodsThe synthesized GO and rGO was characterized by ultraviolet-visible absorption spectroscopy, particle-size analyzer, X-ray diffraction, scanning electron microscopy and Raman spectroscopy. Further, to explain the antimicrobial activity of graphene oxide and reduced graphene oxide, we employed various assays, such as cell growth, cell viability, reactive oxygen species generation, and DNA fragmentation.ResultsUltraviolet-visible spectra of the samples confirmed the transition of GO into graphene. Dynamic light-scattering analyses showed the average size among the two types of graphene materials. X-ray diffraction data validated the structure of graphene sheets, and high-resolution scanning electron microscopy was employed to investigate the morphologies of prepared graphene. Raman spectroscopy data indicated the removal of oxygen-containing functional groups from the surface of GO and the formation of graphene. The exposure of cells to GO and rGO induced the production of superoxide radical anion and loss of cell viability. Results suggest that the antibacterial activities are contributed to by loss of cell viability, induced oxidative stress, and DNA fragmentation.ConclusionThe antibacterial activities of GO and rGO against P. aeruginosa were compared. The loss of P. aeruginosa viability increased in a dose- and time-dependent manner. Exposure to GO and rGO induced significant production of superoxide radical anion compared to control. GO and rGO showed dose-dependent antibacterial activity against P. aeruginosa cells through the generation of reactive oxygen species, leading to cell death, which was further confirmed through resulting nuclear fragmentation. The data presented here are novel in that they prove that GO and rGO are effective bactericidal agents against P. aeruginosa, which would be used as a future antibacterial agent.

Characterization and Electrochemical Behavior of Graphene-Based Anode for Li-Ion Batteries

In this study, we investigate the characteristics and electrochemical properties of graphene nanosheets derived from chemical-thermal exfoliation processes of SFG44 synthetic graphite (SFG44-GNS). The characterizations and electrochemical measurements were carried out by means of X-ray diffraction, scanning electron microscopy, transmission electron microscopy, cyclic voltammetry, BET, Raman, rate capability as well as cycling tests and AC impedance. The as-synthesized SFG44-GNS with larger d-spacing of 0.3407 nm exhibits reversible capacity of 626 mAh/g and good rate capability of ~ 300 mAh/g at 2C rate, which are superior to those of graphite anode. The enhanced electrochemical performance of GNS anode was resulted from larger d-spacing, lower impedance in the interface and enhanced pore volume. The results indicate that graphene-based material is a good candidate for HEV/EV application.

Optical Bifunctionality of Europium-Complexed Luminescent Graphene Nanosheets

Graphene is an intriguing two-dimensional material, which could be modified for achieving tunable properties with many applications. Photoluminescence of graphene due to plasmonic emission is well-known, however, attempts to develop strong luminescent graphene have been difficult. Synthesis of a graphene-based material with a dual optical functionality, namely quenching the fluorescence of organic dyes while maintaining its own self-luminescence, is an interesting and challenging proposition. Here, we demonstrate this optical bifunctionality in a lattice-modified luminescent graphene, where europium(III) cations are complexed with graphene through oxygen functionalities. After excitation at 314 nm, a hypersensitive red emission is observed at 614 and 618 nm showing the complexation of europium(III) with graphene. We demonstrate dual functionality of this graphene by the quenching of luminescence of Rhodamine-B while displaying its own hypersensitive red emission. The decay lifetime observed through the time-resolved spectroscopy confirms its potential for applications in biosensing as well as optoelectronics.

Graphene-Based Nanostructured Hybrid Materials for Conductive and Superhydrophobic Functional Coatings

A bi-functional, conductive and superhydrophobic, graphene-based nanostructured hybrid material was fabricated. In order to construct the bi-functional hybrid material, carbon nanotubes (CNT) and polyhedral oligomeric silsesquioxane (POSS) were introduced. The water contact angle (WCA) of the graphene/POSS/CNT coating reached about 155 degrees and its conductivity was about 1-10 S/cm. Such graphene-based nanostructured hybrid materials could have great potential as an antistatic and self-cleaning coating in various applications.

Surface functionalization-enhanced spillover effect on hydrogen storage of Ni–B nanoalloy-doped activated carbon

Surface functionalization-enhanced spillover effect on hydrogen storage behaviors of Ni–B nanoalloy-doped activated carbon is investigated in comparison to the 3D graphene-based material. It is discovered that the hydrogen storage capacity of the activated carbon increases from Ni–B nanoalloy-doping but much less than that of graphene. After surface functionalization, although the specific surface area and micropore volume of the doped activated carbon decrease significantly, a hydrogen storage capacity is still almost as same as that of the unfunctionalized larger surface one, while showing a large desorption hysteresis. We argue that the surface functionalization greatly enhances the spillover process on carbon based adsorbents, thus playing an essential role in hydrogen storage capacity improvement.

XRD characterization of bulk graphene-based material

XRD characterization of bulk graphene-based material

Graphene-Based Hybrid Electrode Material for High-Power Lithium-Ion Batteries

Graphene based hybrid electrode material is fabricated from an easy and simple chemical method and is demonstrated as a cathode material for Li rechargeable batteries with high capacity and excellent rate capability. The hybrid material delivers a specific capacity of 156 mAh g−1 at a current rate of 25 mA g−1 (0.125 C) after 100 cycles with coulombic efficiency of nearly 100%. At elevated current rates, the specific capacity of the hybrid material is over 100 mAh g−1 even at a current rate of 2500 mA g−1 (∼12.5 C). The excellent battery performance of the hybrid material is attributed to the easy Li ion and electron transport in the amorphous FePO4/graphene hybrid structure, in which electrochemically active amorphous FePO4 films are directly grown on graphene with superior electronic conductivity.

One-pot self-assembly of three-dimensional graphene macroassemblies with porous core and layered shell

The innate character of graphene, defined as the basic unit of sp2carbon materials, provides opportunities for the design and construction of carbon nanostructures with tuned properties. Here, we report a novel three-dimensional graphene macroassembly with a core–shell structure starting from reduced graphene oxides (RGO) by a one-pot self-assembly process under very mild conditions. In the presence of KMnO4, such an assembly process is initiated by low-temperature heating below 100 °C at atmospheric pressure and is totally free from a severe hydrothermal process. Such a core–shell structure is characterized by a porous core and layered membrane shell, and the macro-morphology and infrastructure of the macroassembly are well controllable and tunable. The macroassembly presented here and its self-assembly preparation directly from graphene nanosheets present the first example of the simultaneous formation of a coaxial hybrid infrastructure in a graphene-based nanostructured material, and such a core–shell structured macroassembly shows potential for use in energy storage and other applications.

Nitrogen-doped graphene nanosheet-supported non-precious iron nitride nanoparticles as an efficient electrocatalyst for oxygen reduction

Nitrogen-doped graphene-supported carbon-containing iron nitride (FeCN/NG) was synthesized by the chemical impregnation of iron and nitrogen-containing precursors in the presence of ammonia under thermal treatment. The resultant graphene-based material acted as an electrode with a much higher electrocatalytic activity in the catalysis via a 4-electron pathway in fuel cells. The results of X-ray diffraction, scanning electron microscopy, Fourier transform infrared and X-ray photoelectron spectroscopy indicated that graphite oxide was successfully reduced to nitrogen-doped graphene. X-Ray absorption spectroscopy further confirmed that carbon was incorporated into iron nitride, demonstrating that Fe–N–C catalytic active sites may be responsible for the oxygen reduction reaction. To the best of our knowledge, this is the first report of the combination of N-doped graphene with non-precious metal for oxygen reduction in fuel cells, and may open up a new possibility for preparing graphene-based nanoassemblies for intensive applications.

Exfoliation and Chemical Modification Using Microwave Irradiation Affording Highly Functionalized Graphene

Efficient exfoliation of graphite flakes by sonicating them in benzylamine was accomplished, affording stable suspensions of few-layers graphene. The latter were chemically modified following the Bingel reaction conditions, with the aid of microwave irradiation, producing highly functionalized graphene-based hybrid materials. The resulting hybrid materials, possessing cyclopropanated malonate units covalently grafted onto the graphene skeleton, formed stable suspensions for several days in a variety of organic solvents and were characterized by diverse and complementary spectroscopic, thermal, gravimetric, and high-resolution electron microscopy techniques. When a malonate derivative, bearing the electro-active extended tetrathiafulvalene (exTTF) moiety, was synthesized and used for the functionalization of graphene, energy dispersive X-ray (EDX) analysis verified the presence of sulfur in the corresponding graphene-based hybrid material. Moreover, the redox potentials of the exTTF-graphene hybrid material were determined by electrochemistry, while the formation of a radical ion pair that includes one-electron oxidation of exTTF and one-electron reduction of graphene was suggested with the energy gap of (graphene)(•-)-(exTTF)(•+) being calculated as 1.23 eV.

A Facile One‐step Method to Produce Graphene–CdS Quantum Dot Nanocomposites as Promising Optoelectronic Materials

A single-layer graphene–CdS quantum dot nanocomposite is synthesized by a one-step reaction from graphene oxide, and thus avoids the low-yield production and the aggregation of single-layer graphene sheets. This new graphene-based material shows promising optoelectronic properties. Picosecond ultrafast electron transfer from the CdS quantum dots to the graphene sheets has been observed by time-resolved fluorescence spectroscopy.

A hybrid material of graphene and poly (3,4-ethyldioxythiophene) with high conductivity, flexibility, and transparency

A novel hybrid material prepared from graphene and poly (3,4-ethyldioxythiophene) (PEDOT) shows excellent transparency, electrical conductivity, and good flexibility, together with high thermal stability and is easily processed in both water and organic solvents. Conductivities of the order of 0.2 S / cm and light transmittance of greater than 80% in the 400 1800 nm wavelength range were observed for fi lms with thickness of tens of nm. Practical applications in a variety of optoelectronic devices are thus expected for this transparent and fl exible conducting graphene-based hybrid material.