Assembly Of Graphene Research Articles

ZIF‐67 Derived Co3O4/rGO Electrodes for Electrochemical Detection of H2O2 with High Sensitivity and Selectivity

AbstractIn this work, zeolitic imidazolate framework (ZIF) nanocrystal arrays were supported by graphene oxide (GO) nanosheets by a graphene assembly route. Then, ZIF‐67/GO was transformed into nanoporous Co3O4/rGO composites through calcination. Both ZIF‐67/GO and Co3O4/rGO were employed as active materials to modify glass carbon electrodes for hydrogen peroxide (H2O2) non‐enzymatic sensor. The measurement results indicate that ZIF‐67/GO presented excellent electro‐catalytic activity towards H2O2 with a linear range of 0.1‐22.9 mM and a low detection limit of 1.92 mM. More important, the Co3O4/rGO modified GC electrode showed higher detection sensitivity for H2O2 and the limit of detection can be as low as 7.87 nM. Furthermore, ZIF‐67/GO and Co3O4/rGO modified electrodes both exhibited excellent selectivity in phosphate buffer solution and NaOH.

Tunable three-dimensional graphene assembly architectures through controlled diffusion of aqueous solution from a micro-droplet

Spherical, twiddle and hollow hemispherical reduced graphene oxide (rGO) structures could be fabricated by tuning the GO assembly in the diffusion-controlled micro-droplets, and their size and thickness could be adjusted by controlling the concentration of GO and pH of the droplets. Besides, the porous rGO architecture was produced via wet etching of rGO-SiO2 composites, and their plasamon effect was characterized.

Ordered, Scalable Heterostructure Comprising Boron Nitride and Graphene for High-Performance Flexible Supercapacitors

Heterostructures based on combining two-dimensional (2D) crystals in one stack have unusual physical properties and allow the creation of novel devices. Although this method of mechanically transferring individual 2D crystals is required for precise control, it is not scalable. Large-scale fabrication of heterostructures remains a key challenge for practical applications. Here, we provide a simple solution-based method using electrostatic interaction assembly of boron nitride (h-BN) and graphene to produce hybrid films with van der Waals heterostructures. The hybrid films prepared by this fabrication method tend to be alternately stacked and provide compact structured films. For a potential application, the h-BN/graphene hybrid films are fabricated supercapacitor’s electrodes revealing high volumetric capacitance, superior rate capability, a permanent life cycle, and high flexibility due to their synergistic effects. We anticipate that the hybrid films are useful as scalable flexible electrodes in superca...

Facile synthesis of Pt nanoparticles supported on graphene/Vulcan XC-72 carbon and their application for methanol oxidation

A facile method was used for the preparation of Pt nanoparticles supported on graphene/Vulcan XC-72 carbon (denoted as Pt/Gr-C) by co-reduction of graphene oxide (GO) and H2PtCl6 with subsequent incorporation of Vulcan XC-72 carbon between graphene. The catalyst is extensively characterized by using scanning electron microscope (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy. SEM and TEM observations show that aggregation of graphene is weakened through carbon insertion, which is beneficial for increase of effective contact area between catalyst and electrolyte. The electrochemical active surface area (ECSA) of Pt/Gr-C is higher than both Pt/C and Pt/Gr catalysts. The forward peak current density of Pt/Gr-C for methanol oxidation is 0.3 A mg−1 Pt, which is 1.4 and 1.7 times larger than Pt/Gr and Pt/C, respectively, due to the high utilization of Pt and large three-phase interface for methanol oxidation.

Hierarchical and reversible assembly of graphene oxide/polyvinyl alcohol hybrid stabilized Pickering emulsions and their templating for macroporous composite hydrogels

Control over the reversible assembly of micro- and nano-scopic building blocks is highly important but very challenging in the fabrication of many hierarchical composite materials. Here we report the reversible assembly of emulsion micro-droplets stabilized by graphene oxide/polyvinyl alcohol (GO/PVA) hybrid via simply controlling the hydrogen bonding interaction between GO and PVA. The assembled emulsion droplets at acidic condition can be shaped into different macroscopic objects with a high degree of morphological control through injection molding. Attributed to the reversible hydrogen bonding interactions, the assembled emulsion monoliths/aggregates can be interestingly disassembled back into dispersed droplets when increasing the pH of aqueous phase. Utilizing this GO/PVA hybrid stabilized emulsion as a template, macroporous composite hydrogel was produced via facile polymerization of the aqueous phase, which can be further used for selective payload release, for example, anticancer drug Doxorubicin hydrochloride (DOX). It revealed that DOX release from the composite hydrogels was considerably accelerated when the pH of release medium decreased from 7.4 to 4.0, and the release DOX remained biologically active and had high capability to kill cancer cells, demonstrating the feasibility of using GO/PVA macroporous composite hydrogels as potential drug delivery platforms for cancer treatments.

Layer-By-Layer Assembly of Graphene Oxide/Polymer Coating Film to Improve Corrosion Resistance

Corrosion is a phenomenon that occur rust on the surface of metal. This phenomenon occurs in the overall part of the industry, causing a variety of problems to weakening mechanical properties of the material. Corrosion is prevented to coating treatment. This treatment can prevent corrosion by blocking water or oxygen molecules. Researchers have done many studies to prevent corrosion. In order to improve corrosion protection properties, pigments, such as zinc powder, clay etc, have been incorporated into coating materials. Coatings that imbedded pigments have a excellent corrosion protection properties. Recently, nano-sized pigments have better protection properties than conventional micro-size pigments. In this study, we fabricate graphene oxide(GO)/polymer composite coating thin film by using Layer-by-Layer(LBL) method. GO is role of a pigment that limits molecules to induce corrosion by the diffusion pathway. We survey anti-corrosion properties such as Tafel-Plot and Electrochemical Impedance Spectroscopy(EIS) by using electrochemical measurement system.

CVD Assembly of 3D Graphene and Their Contribution for Lithium-Sulfur Batteries with High Energy Density and Long Lifespan

Among various promising candidates with high energy densities, lithium-sulfur (Li-S) batteries with a high theoretical capacity and energy density are highly attractive;1-2 while the commercial application of Li-S batteries still faces some persistent obstacles, such as the low electrical conductivity of sulfur and lithium sulfide and the dissolution of polysulfides. The introduction of 3D graphene into the field of Li-S batteries sheds a light on the efficient utilization of sulfur by improving the conductivity of the composites and restraining the shuttle of polysulfides. In this presentation, the concept for the rational design of 3D graphene is explained. The advances in the use of 3D graphene in the cathode, separator, and anode is explained.3-12 New insights on the relationship between the 3D graphene structure and the electrochemical performance are presented. References Wang JG, Xie KY, Wei BQ. Nano Energy 2015, 15, 413. Manthiram A, Chung SH, Zu CX. Adv Mater 2015, 27, 1980. Zhao MQ, Zhang Q, Huang JQ, et al. Nature Commun 2014, 5, 3410. Cheng XB, Huang JQ, Zhang Q, et al. Nano Energy 2014, 4, 65. Huang JQ, Zhang Q, Peng HJ, et al. Energy Environ Sci 2014, 7, 347. Tang C, Zhang Q, Zhao MQ, et al. Adv Mater 2014. 26, 6100. Zhao MQ, Peng HJ, Tian GL, et al. Adv Mater 2014, 26, 7051 Yuan Z, Peng HJ, Huang JQ, et al. Adv Funct Mater 2014, 24, 6105. Zhao MQ, Liu XF, Zhang Q, et al. ACS Nano 2012, 6, 10759. Cheng XB, Peng HJ, Huang JQ, et al. ACS Nano 2015, 9, 6373. Huang JQ, Zhuang TZ, Zhang Q, et al. ACS Nano 2015, 9, 1506. Peng HJ, Zhang Q. Angew Chem Int Ed 2015, 54, 11018.

Challenges in Liquid-Phase Exfoliation, Processing, and Assembly of Pristine Graphene.

Recent developments in the exfoliation, dispersion, and processing of pristine graphene (i.e., non-oxidized graphene) are described. General metrics are outlined that can be used to assess the quality and processability of various "graphene" products, as well as metrics that determine the potential for industrial scale-up. The pristine graphene production process is categorized from a chemical engineering point of view with three key steps: i) pretreatment, ii) exfoliation, and iii) separation. How pristine graphene colloidal stability is distinct from the exfoliation step and is dependent upon graphene interactions with solvents and dispersants are extensively reviewed. Finally, the challenges and opportunities of using pristine graphene as nanofillers in polymer composites, as well as as building blocks for macrostructure assemblies are summarized in the context of large-scale production.

Synergistically Enhanced Electrocatalytic Activity of Sandwich-like N-Doped Graphene/Carbon Nanosheets Decorated by Fe and S for Oxygen Reduction Reaction.

Although N-doped graphene-based electrocatalysts have shown good performance for oxygen reduction reaction (ORR), they still suffer from the single-type active site in the as-prepared catalyst, limited accessible active surface area because of easy aggregation of graphene, and harsh condition for preparation process of graphene. Therefore, further developing a novel type of graphene-based electrocatalyst by a facile and environmentally benign method is highly anticipated. Herein, we first fabricate a sandwich-like graphene/carbon hybrid using graphene oxide (GO) and nontoxic starch. Then the graphene/carbon hybrid undergoes postprocessing with iron(III) chloride (FeCl3) and potassium sulfocyanide (KSCN) to acquire N-doped graphene/carbon nanosheets decorated by Fe and S. The resultant displays the features of interpenetrated three-dimensional hierarchical architecture composed of abundant sandwich-like graphene/carbon nanosheets and low graphene content in as-prepared sample. Remarkably, the obtained catalyst possesses favorable kinetic activity due to the unique structure and synergistic effect of N, S, and Fe on ORR, showing high onset potential, low Tafel slope, and nearly four-electron pathway. Meanwhile, the catalyst exhibits strong methanol tolerance and excellent long-term durability. In view of the multiple active sites, unique hierarchical structure, low graphene content, and outstanding electrochemical activity of the as-prepared sample, this work could broaden the thinking to develop more highly efficient graphene/carbon electrocatalysts for ORR in fuel cells.

Magnetic assembly of transparent and conducting graphene-based functional composites.

Innovative methods producing transparent and flexible electrodes are highly sought in modern optoelectronic applications to replace metal oxides, but available solutions suffer from drawbacks such as brittleness, unaffordability and inadequate processability. Here we propose a general, simple strategy to produce hierarchical composites of functionalized graphene in polymeric matrices, exhibiting transparency and electron conductivity. These are obtained through protein-assisted functionalization of graphene with magnetic nanoparticles, followed by magnetic-directed assembly of the graphene within polymeric matrices undergoing sol–gel transitions. By applying rotating magnetic fields or magnetic moulds, both graphene orientation and distribution can be controlled within the composite. Importantly, by using magnetic virtual moulds of predefined meshes, graphene assembly is directed into double-percolating networks, reducing the percolation threshold and enabling combined optical transparency and electrical conductivity not accessible in single-network materials. The resulting composites open new possibilities on the quest of transparent electrodes for photovoltaics, organic light-emitting diodes and stretchable optoelectronic devices.

Flexible capacitive behavior of hybrid carbon materials prepared from graphene sheets

High frequency ultrasonication was employed to reduce the aggregation of graphene by constructing hybrid carbon materials (HCMs), which are endowed with a large electrochemical reaction area and high energy density. HCMs exhibited a specific capacitance of 168.5 F · g−1 with ∼100% capacitance retention over 500 cycles. Flexible supercapacitors fabricated from HCMs also showed an excellent capacitive behavior even under tough conditions. These outstanding electrochemical properties were ascribed to the increased specific surface area and open structure of HCMs.

Three-dimensional porous aerogel constructed by Bi2WO6 nanosheets and graphene with excellent visible-light photocatalytic performance

A three-dimensional porous hybrid aerogel assembly of Bi2WO6 nanosheets and graphene has been prepared by a facile solvothermal route. The products are characterized by X-ray diffraction, Scanning electron microscope, Transmission electron microscopy, and so on. The results show the highly interconnected and porous network microstructure stacked by graphene and Bi2WO6 nanosheets in the hybrid aerogel. The specific surface area of hybrid aerogel (39.4m2g−1) is 1.6 times higher than that of Bi2WO6 nanosheets. The Rhodamine B removal ratio over the composite aerogel reaches up to 99.6% within 45min, which is higher than that of pure Bi2WO6 nansosheets (80%). The excellent photocatalytic performance is mainly owing to the porous structure of aerogel and high electrical conductivity of graphene. The study on the photocatalytic mechanism demonstrates that O2−• is the main reactive species for Rhodamine B degradation.

Flexible Circuits and Soft Actuators by Printing Assembly of Graphene.

An effective way to improve the electrical conductivity of printed graphene patterns was demonstrated by realizing the assembly of giant graphene oxide sheets during the printing process. The synergetic effect of printing-induced orientation and evaporation-induced interfacial assembly facilitated the formation of laminar-structured patterns. The resulting patterns after chemical reduction showed excellent electrical conductivity in printed graphene electronics. Because of their high conductivity, mechanical flexibility, and advantage in pattern design, printed graphene electrodes were applied in electrical-driven soft actuators, which can realize controllable deformation with low driving voltage. Such achievements will be of great significance for the development of graphene-based flexible and printed electronics.

Synthesis and photocatalytic CO2 reduction activity of a coal-based graphene assembly

Synthesis and photocatalytic CO2 reduction activity of a coal-based graphene assembly

Superelastic, Macroporous Polystyrene-Mediated Graphene Aerogels for Active Pressure Sensing.

Three-dimensional (3D) graphene-based polymer/graphene aerogels with excellent mechanical properties are crucial for broad applications. The creation of such polymer/graphene aerogels remains challenging because of the poor dispersion and compatibility of polymer within the graphene matrix. By using the freezing-directed assembly of graphene under the assistance of surfactant, 3D macroporous polystyrene/graphene aerogels (MPS-GAs) with lightweight, superelastivity (80 % strain), high strength (80 kPa), and good electrical properties have been achieved in this study. The as-prepared MPS-GAs shows excellent electromechanical performance with stable cyclic resilient properties and sensitive resistance responses, thus making the MPS-GAs promising candidates for applications in actuators, elastic conductors, strain/pressure sensors, and wearable devices.

Graphene/MnO2 composite prepared by a simple method for high performance supercapacitor

MnO2 nanoparticles are anchored on the graphene nanosheets and make a graphene nanosheets/MnO2 (GMn) composite by thermal decomposition for application in supercapacitor. The GMn composite exhibits specific capacitance of 450 F g− 1 at 1 A g− 1, which is more than three times higher than that of as-prepared graphene sheets. Meanwhile, the composite shows excellent cycle stability without decline over 5000 cycles. The high electrochemical performance of the GMn electrodes is attributed to the prevention of graphene aggregation by the MnO2 nanoparticles, and the synergistic effects between graphene and MnO2 nanoparticles.

A Phytic Acid Induced Super-Amphiphilic Multifunctional 3D Graphene-Based Foam.

Surfaces with super-amphiphilicity have attracted tremendous interest for fundamental and applied research owing to their special affinity to both oil and water. It is generally believed that 3D graphenes are monoliths with strongly hydrophobic surfaces. Herein, we demonstrate the preparation of a 3D super-amphiphilic (that is, highly hydrophilic and oleophilic) graphene-based assembly in a single-step using phytic acid acting as both a gelator and as a dopant. The product shows both hydrophilic and oleophilic intelligence, and this overcomes the drawbacks of presently known hydrophobic 3D graphene assemblies. It can absorb water and oils alike. The utility of the new material was demonstrated by designing a heterogeneous catalytic system through incorporation of a zeolite into its amphiphilic 3D scaffold. The resulting bulk network was shown to enable efficient epoxidation of alkenes without prior addition of a co-solvent or stirring. This catalyst also can be recovered and re-used, thereby providing a clean catalytic process with simplified work-up.

A Phytic Acid Induced Super‐Amphiphilic Multifunctional 3D Graphene‐Based Foam

AbstractSurfaces with super‐amphiphilicity have attracted tremendous interest for fundamental and applied research owing to their special affinity to both oil and water. It is generally believed that 3D graphenes are monoliths with strongly hydrophobic surfaces. Herein, we demonstrate the preparation of a 3D super‐amphiphilic (that is, highly hydrophilic and oleophilic) graphene‐based assembly in a single‐step using phytic acid acting as both a gelator and as a dopant. The product shows both hydrophilic and oleophilic intelligence, and this overcomes the drawbacks of presently known hydrophobic 3D graphene assemblies. It can absorb water and oils alike. The utility of the new material was demonstrated by designing a heterogeneous catalytic system through incorporation of a zeolite into its amphiphilic 3D scaffold. The resulting bulk network was shown to enable efficient epoxidation of alkenes without prior addition of a co‐solvent or stirring. This catalyst also can be recovered and re‐used, thereby providing a clean catalytic process with simplified work‐up.

Label-free electrochemical lead (II) aptasensor using thionine as the signaling molecule and graphene as signal-enhancing platform

A label-free and highly sensitive electrochemical aptasensor for Pb2+ was constructed using thionine (TH) as the signaling molecule and graphene (GR) as the signal-enhancing platform. The electrochemical sensing interface was fabricated by stepwise assembly of GR and TH on the lead (II) specific aptamer (LSA) modified electrode. Upon interaction with Pb2+, the aptamer probe on the sensor underwent conformational switch from a single-stranded DNA form to the G-quadruplex structure, causing the GR with assembled TH released from the electrode surface into solution. As a result, the electrochemical signal of TH on the aptasensor was substantially reduced. Under the optimal experimental conditions, the attenuation of peak currents presented a good linear relationship with the logarithm of Pb2+ concentrations over the range from 1.6×10−13 to 1.6×10−10M. The detection limit was estimated to be 3.2×10−14M. The aptasensor also exhibited good regenerability, excellent selectivity, and acceptable reproducibility, indicating promising application in environment monitoring of lead.

Stiff and Transparent Multilayer Thin Films Prepared Through Hydrogen‐Bonding Layer‐by‐Layer Assembly of Graphene and Polymer

Due to their exceptional orientation of 2D nanofillers, layer‐by‐layer (LbL) assembled polymer/graphene oxide thin films exhibit unmatched mechanical performance relative to any conventionally produced counterparts with similar composition. Unprecedented mechanical property improvement, by replacing graphene oxide with pristine graphene, is demonstrated in this work. Polyvinylpyrrolidone‐stabilized graphene platelets are alternately deposited with poly(acrylic acid) using hydrogen bonding assisted LbL assembly. Transmission electron microscopy imaging and the Halpin‐Tsai model are used to demonstrate, for the first time, that intact graphene can be processed from water to generate polymer nanocomposite thin films with simultaneous parallel‐alignment, high packing density, and exfoliation. A multilayer thin film with only 3.9 vol% of highly exfoliated, and structurally intact graphene, increases the elastic modulus (E) of a polymer multilayer thin film by 322% (from 1.41 to 4.81 GPa), while maintaining visible light transmittance of ≈90%. This is one of the greatest improvements in elastic modulus ever reported for a graphene‐filled polymer nanocomposite with a glassy (E > 1 GPa) matrix. The technique described here provides a powerful new tool to improve nanocomposite properties (mechanical, gas transport, etc.) that can be universally applied to a variety of polymer matrices and 2D nanoplatelets.