Graphene Hybrid Nanosheets Research Articles

Catalyst-free synthesis of a three-dimensional nanoworm-like gallium oxide–graphene nanosheet hybrid structure with enhanced optical properties

Here, we report synthesis and growth of catalyst-free three-dimensional β-gallium oxide nanoworm-like nanostructures on graphene nanosheets using a solid mixture of graphite oxide and gallium acetylacetonate by the microwave (MW)-assisted method.

MoS2-graphene hybrid nanosheets constructed 3D architectures with improved electrochemical performance for lithium-ion batteries and hydrogen evolution

ABSTRACT Advanced materials for energy conversion and storage are central to clean and reliable energy research. Herein, three-dimensional (3D) architectures composed of MoS 2 -graphene hybrid nanosheets are synthesized via a simple solvothermal method for this purpose. The architectures are self-assembled with hybrid nanosheets, which are fabricated through the in situ growth of few-layer MoS 2 nanosheets on the surface of graphene substrates. Rooted in the intriguing advantages of sheet-on-sheet structures and 3D features, the composite materials exhibit improved electrochemical lithium storage performances when used as anode materials, in terms of high reversible capacity, superior cycling stability (904 mAh g −1 after 200 cycles at 200 mA g −1 ), and high rate capability. It is also employed as integrated electrode for electrochemical water splitting and delivers remarkably enhanced catalytic performance for hydrogen evolution, such as low onset overpotential (110 mV), small Tafel slope (47 mV decade −1 ), and stable cycling performance.

Controllable Formation of Niobium Nitride/Nitrogen-Doped Graphene Nanocomposites as Anode Materials for Lithium-Ion Capacitors

Niobium nitride/nitrogen-doped graphene nanosheet hybrid materials are prepared by a simple hydrothermal method combined with ammonia annealing and their electrochemical performance is reported. It is found by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) that the as-obtained niobium nitride nanoparticles are about 10-15 nm in size and homogeneously anchored on graphene. A non-aqueous lithium-ion capacitor is fabricated with an optimized mass loading of activated carbon cathode and the niobium nitride/nitrogen-doped graphene nanosheet anode, which delivers high energy densities of 122.7-98.4 W h kg(-1) at power densities of 100-2000 W kg(-1), respectively. The capacity retention is 81.7% after 1000 cycles at a current density of 500 mA g(-1). The high energy and power of this hybrid capacitor bridges the gap between conventional high specific energy lithium-ion batteries and high specific power electrochemical capacitors, which holds great potential applications in energy storage for hybrid electric vehicles.

Polydimethyl siloxane–graphene nanosheets hybrid membranes with enhanced pervaporative desulfurization performance

A series of polydimethyl siloxane-graphene nanosheets (PDMS-GNS) hybrid membranes were fabricated via physically blending method. In these hybrid membranes, GNS exhibit different orientation and dispersity with the variation of GNS content. An appropriate interfacial structure favoring permeate molecules transport is constructed, which mainly arises from the non-covalent interactions between PDMS and GNS. The mechanical stability, thermal stability and anti-swelling property of the hybrid membranes are simultaneously enhanced. Pervaporative desulfurization performance of PDMS-GNS/PVDE hybrid membranes was investigated utilizing n-octane/thiophene mixture as a model gasoline system. The prepared hybrid membranes show an enhanced permeation flux while maintaining a constant enrichment factor, which should be attributed to the optimized free volume characteristics of the membranes and pi-pi interactions between GNS and thiophene. Especially, when GNS/PDMS mass ratio reaches 0.2 wt%, the membrane shows an optimum desulfurization performance with a permeation flux of 622 kg/(m(2) h) (65.9% higher than that of pure PDMS membrane) and an enrichment factor of 3.58 (similar to that of pure PDMS membrane). Additionally, the effects of GNS content, operation temperature, thiophene content, feed Row rate and operation time on membrane separation performance were investigated systematically. The prepared hybrid membranes may find potential applications in the separation of aromatics-containing mixtures. (C) 2015 Elsevier B.V. All rights reserved.

Spectrophotometric analysis of phenols, which involves a hemin–graphene hybrid nanoparticles with peroxidase-like activity

Phenols are well known noxious compounds, which are often found in various water sources. A novel analytical method has been researched and developed based on the properties of hemin–graphene hybrid nanosheets (H–GNs). These nanosheets were synthesized using a wet-chemical method, and they have peroxidase-like activity. Also, in the presence of H2O2, the nanosheets are efficient catalysts for the oxidation of the substrate, 4-aminoantipine (4-AP), and the phenols. The products of such an oxidation reaction are the colored quinone-imines (benzodiazepines). Importantly, these products enabled the differentiation of the three common phenols – pyrocatechol, resorcin and hydroquinone, with the use of a novel, spectroscopic method, which was developed for the simultaneous determination of the above three analytes. This spectroscopic method produced linear calibrations for the pyrocatechol (0.4–4.0mgL−1), resorcin (0.2–2.0mgL−1) and hydroquinone (0.8–8.0mgL−1) analytes. In addition, kinetic and spectral data, obtained from the formation of the colored benzodiazepines, were used to establish multi-variate calibrations for the prediction of the three phenol analytes found in various kinds of water; partial least squares (PLS), principal component regression (PCR) and artificial neural network (ANN) models were used and the PLS model performed best.

Carbon buffered-transition metal oxidenanoparticle–graphene hybrid nanosheets as high-performance anode materials for lithium ion batteries

In this article, we report a simple and general method for the synthesis of carbon buffered-metal oxidenanoparticle (NP)–graphene hybrid 2D nanosheets, which include C-SnO2–rGO and C-Fe2O3–rGO nanosheets. For the preparation of these anodes, tannic acid (TA), a kind of polyphenol extracted from plants, was used as a dispersing agent to introduce a metal precursor on the surface of rGO, and the metal precursor was subsequently converted to the corresponding metal oxide NPs by thermal annealing in a vacuum. During the thermal annealing process, TA was decomposed to form carbon materials, which acted as a buffering matrix to effectively suppress the aggregation and pulverization of the active NPs during the electrochemical performances. It is found that the as-prepared C-SnO2–rGO and C-Fe2O3–rGO nanosheets both exhibited high reversible capacity and rate capability. After 100 discharge/charge cycles, the C-SnO2–rGO nanosheet delivered the reversible capacity of 633.2 mA h g−1 at a current density of 200 mA g−1 with extremely low capacity fading (0.32 mA h g−1 per cycle), and it can deliver discharge capacities of 641.3, 526.5, 452.7, 408.1 and 379.5 mA h g−1 in the 10th cycle at current densities of 200, 400, 800, 1200 and 1600 mA g−1, respectively. Upon return to a cycling rate of 200 mA g−1, the C-SnO2–rGO can maintain a specific capacity of 607.0 mA h g−1 even after 35 cycles. As for the C-Fe2O3–rGO nanosheet, it can deliver 504.1 mA h g−1 at a current density of 500 mA g−1 after 100 cycles, and the corresponding discharge capacities in the 10th cycle at current densities of 1000, 1500 and 2000 mA g−1 are 365.9, 319.0 and 288.6 mA h g−1, respectively.

Using self-assembly to prepare a graphene-silver nanowire hybrid film that is transparent and electrically conductive

Silver nanowires (AgNWs), modified by cysteamine, with a high electrical conductivity can be combined with high surface area graphene nanosheets (GNs) to form AgNW–GN hybrid nanomaterials. These materials with –NH3+ functional groups in an alkaline environment can be deposited on waterborne polyurethane surfaces with the attraction of sulfonate functional groups to prepare transparent conductive films with high transmittance and low surface electrical resistance. This self-assembly method provides highly controllable transmittance and surface electrical resistance. The AgNWs can inhibit GNs from restacking and aggregation after reduction from graphene oxide, increasing the electrical conductivity between the GN interlayers. The AgNW–GN hybrid nanomaterial films show a sheet resistance of 86Ω/sq with 80% light transmittance, and the value of DC conductivity to optical conductivity ratio reaches 19.81.

Synthesis of MoS2 nanosheet–graphene nanosheet hybrid materials for stable lithium storage

A facile method to synthesize a MoS(2) nanosheet-graphene nanosheet hybrid has been developed via the combination of a lithiation-assisted exfoliation process and a hydrazine monohydrate vapour reduction technique. The as-obtained nanosheet-nanosheet hybrid is more robust and exhibits much improved cycle life (>700), which make it an efficient morphological solution to the stable lithium storage problem of nanomaterials.

An In Situ Simultaneous Reduction‐Hydrolysis Technique for Fabrication of TiO2‐Graphene 2D Sandwich‐Like Hybrid Nanosheets: Graphene‐Promoted Selectivity of Photocatalytic‐Driven Hydrogenation and Coupling of CO2 into Methane and Ethane

AbstractA novel, in situ simultaneous reduction‐hydrolysis technique (SRH) is developed for fabrication of TiO2‐‐graphene hybrid nanosheets in a binary ethylenediamine (En)/H2O solvent. The SRH technique is based on the mechanism of the simultaneous reduction of graphene oxide (GO) into graphene by En and the formation of TiO2 nanoparticles through hydrolysis of titanium (IV) (ammonium lactato) dihydroxybis, subsequently in situ loading onto graphene through chemical bonds (Ti–O–C bond) to form 2D sandwich‐like nanostructure. The dispersion of TiO2 hinders the collapse and restacking of exfoliated sheets of graphene during reduction process. In contrast with prevenient G‐TiO2 nanocomposites, abundant Ti3+ is detected on the surface of TiO2 of the present hybrid, caused by reducing agent En. The Ti3+ sites on the surface can serve as sites for trapping photogenerated electrons to prevent recombination of electron–hole pairs. The high photocatalytic activity of G‐TiO2 hybrid is confirmed by photocatalytic conversion of CO2 to valuable hydrocarbons (CH4 and C2H6) in the presence of water vapor. The synergistic effect of the surface‐Ti3+ sites and graphene favors the generation of C2H6, and the yield of the C2H6 increases with the content of incorporated graphene. The work may open a new doorway for new significant application of graphene for selectively catalytic C–C coupling reaction

A Versatile Multicomponent Assembly via β‐cyclodextrin Host–Guest Chemistry on Graphene for Biomedical Applications

A multi-component nanosystem based on graphene and comprising individual cyclodextrins at its surface is assembled, creating hybrid structures enabling new and important functionalities: optical imaging, drug storage, and cell targeting for medical diagnosis and treatment. These nanohybrids are part of a universal system of interchangeable units, capable of mutilple functionalities. The surface components, made of individual β-cyclodextrin molecules, are the "hosts" for functional units, which may be used as imaging agents, for anti-cancer drug delivery, and as tumor-specific ligands. Specifically, individual β-cyclodextrin (β-CD), with a known capability to host various molecules, is considered a module unit that is assembled onto graphene nanosheet (GNS). The cyclodextrin-functionalized graphene nanosheet (GNS/β-CD) enables "host-guest" chemistry between the nanohybrid and functional "payloads". The structure, composition, and morphology of the graphene nanosheet hybrid have been investigated. The nanohybrid, GNS/β-CD, is highly dispersive in various physiological solutions, reflecting the high biostability of cyclodextrin. Regarding the host capability, the nanohybrid is fully capable of selectively accommodating various biological and functional agents in a controlled fashion, including the antivirus drug amantadine, fluorescent dye [5(6)-carboxyfluorescein], and Arg-Gly-Asp (RGD) peptide-targeting ligands assisted by an adamantine linker. The loading ratio of 5(6)-carboxyfluorescein is as high as 110% with a drug concentration of 0.45 mg mL(-1). The cyclic RGD-functionalized nanohybrid exhibits remarkable targeting for HeLa cells.

One-step fabrication of layered double hydroxides/graphene hybrid as solid-phase extraction for stripping voltammetric detection of methyl parathion

We developed a green and facile electrochemical approach to synthesize novel Ni/Al layered double hydroxides decorated graphene nanosheets hybrid (labeled as LDHs-GNs) on a cathodic substrate. The as-prepared LDHs-GNs composite is highly efficient to capture organophosphate pesticides (OPs), combining the advantages of LDHs (high enrichment capability for OPs by a selective intercalation) together with GNs (large surface area and high conductivity). It dramatically facilitates the enrichment of OPs onto their surface and realizes the sensitive stripping voltammetric detection of methyl parathion (MP) as a model of OPs. The detection limit for MP in aqueous solutions was determined to be of 0.6ngmL−1 (S/N=3). This work provides a green and facile route for the preparation of GN-based hybrid, and also offers a new promising protocol for OP analysis.

Facile synthesis of zirconia nanoparticles-decorated graphene hybrid nanosheets for an enzymeless methyl parathion sensor

This paper proposed a facile electrochemical approach to the synthesis of high quality zirconia nanoparticles decorated graphene nanosheets (labeled as ZrO2NPs-GNs) onto a cathodic substrate. This facile one-step co-electrodeposition approach for the construction of GNs based hybrid is environmentally friendly, without involving the chemical reduction of GO, and therefore will not result in further contamination. The electrochemically synthesized ZrO2NPs-GNs composite has been carefully characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM) and various electrochemical techniques. Such a nanostructured composite, combining the advantages of ZrO2NPs (high recognition and enrichment capability for phosphoric moieties) together with GNs (large surface area and high conductivity), is highly efficient to capture organophosphate pesticides (OPs). Combined with the square-wave voltammetry, a highly sensitive enzymeless OPs sensor was fabricated using the prepared ZrO2NPs-GNs composite as solid phase extraction (SPE). The detection limit for methyl parathion (MP) in aqueous solutions was determined to be of 0.6ngmL−1 (S/N=3). This work provides a green and facile route for the preparation of GNs-based hybrid, and also offers a new promising protocol for OPs analysis.

Porphyrin functionalized graphene nanosheets-based electrochemical aptasensor for label-free ATP detection

A facile strategy for the preparation of meso-terakis(4-methoxyl-3-sulfonatophenyl) porphyrin (T(4-Mop)PS4)-graphene hybrid nanosheets (TGHNs) was demonstrated for the first time, which combines the features of both graphene (high conductivity and large specific surface area) and porphyrins (photochemical electron-transfer ability and excellent electrochemical activity). The as-obtained TGHNs were characterized by UV-vis spectroscopy, X-ray photoelectron spectroscopy, Raman spectroscopy, atomic force microscopy, transmission electron microscopy and cyclic voltammetry, which confirmed that the porphyrin had been effectively functionalized on the surface of graphene. Combined with the high affinity and specificity of an aptamer, a simple, rapid, sensitive and label-free electrochemical aptasensor was successfully fabricated for adenosine triphosphate (ATP) detection. The proposed TGHN-based aptasensor achieved the direct electron transfer of porphyrin and showed good affinity and specificity towards ATP, which avoided interference such as the introduction of labeled-substances and the [Fe(CN)6]3−/4− probe. The preferable linear range for ATP was from 2.2 nM to 1.3 μM (R = 0.9982) with a detection limit of 0.7 nM.

α-MnO2 nanorods grown in situ on graphene as catalysts for Li–O2 batteries with excellent electrochemical performance

Through in situ nucleation and growth of α-MnO2 nanorods on graphene nanosheets (GNs), a α-MnO2 nanorod/GN hybrid was synthesized and employed as the catalyst for non-aqueous lithium oxygen (Li–O2) batteries. The α-MnO2/GN hybrid showed excellent catalytic property. It was demonstrated that the catalytic performance of α-MnO2 for ORR and OER was not only associated with the morphology and size of the particles but also with their combination with graphene. The developed in situ synthetic strategy can also be applied to prepare analogous MOx/GN hybrids used in Li–O2 batteries and other energy storage systems.

A high performance electrochemical sensor for acetaminophen based on single-walled carbon nanotube–graphene nanosheet hybrid films

A high performance electrochemical sensor for the detection of acetaminophen (APAP) at the single-walled carbon nanotube (SWCNT)–graphene nanosheet (GNS) hybrid film modified electrode is reported. The morphology and pore structure of the SWCNT–GNS hybrid were characterized by field emission scanning electron microscopy (SEM) and nitrogen isothermal adsorption–desorption technique, respectively. The electrochemical behavior of APAP at the SWCNT–GNS modified glassy carbon (GC) electrode was investigated by cyclic voltammetry. The results showed significantly enhanced electrochemical reactivity and voltammetric response of APAP. The electrochemical sensor based on the hybrid modified electrode exhibited excellent analytical performance for APAP detection in neutral solution with a low detection limit of 38 nM and a wide linear range of 0.05–64.5 μM. Moreover, the SWCNT–GNS/GC electrode also showed good selectivity and stability. The high performances of the novel APAP sensor are mainly attributed to high surface area and multi-modal pore structure of the SWCNT–GNS hybrid, which provide an increased sensing area and effective mass transportation pathway.

Improved storage capacity and rate capability of Fe 3O 4–graphene anodes for lithium-ion batteries

By employing an ultrasonic deposition followed by heat treatment, magnetite (Fe 3O 4)–graphene nanosheet (GN) hybrid anode was synthesized to examine its electrochemical performance in Li-ion battery. The Fe 3O 4 nanocrystals with an average size of 10 nm can be homogeneously incorporated into the GNs to form Fe 3O 4–GN composites. In comparison with fresh GN anode, the composite anode exhibits high reversible capacity of 753 mAh/g at 0.1 C, high rate capability (533 mAh/g at 5 C), and enhanced cyclic performance with high coulombic efficiency. This improvement can be attributed to the fact that since Fe 3O 4 acts not only as a redox site but also as a spacer, the Fe 3O 4–GN hybrid creates a three-dimensional architecture that effectively facilitates ionic diffusion, Li-storage, and electronic transport. This result opens an efficient route for synthesis and application of GN hybrid as anode material for Li-ion batteries with superior performance.

Ionic liquid–graphene hybrid nanosheets as an enhanced material for electrochemical determination of trinitrotoluene

Trinitrotoluene, usually known as TNT, is a kind of chemical explosive with hazardous and toxic effects on the environment and human health. Ever-increasing needs for a secure society and green environment essentially require the detection of TNT with rapidity, high sensitivity and low cost. In this article, ionic liquid–graphene hybrid nanosheets (IL–GNs) have been used as an enhanced material for rapidly electrochemical detection of trinitrotoluene (TNT). IL–GNs were characterized by atomic force microscopy (AFM), transmission electron microscopy (TEM), X-ray photo-electron spectroscopy, electrochemical impedance spectroscopy, Fourier transform infrared (FT-IR) spectroscopy and Raman spectroscopy, which confirmed that IL has been effectively functionalized on the surface of GNs. Significantly, IL–GNs modified glassy carbon electrode (GCE) showed 6.2 and 51.4-folds higher current signals for TNT reduction than IL–CNTs/GCE and bare GCE, respectively. Adsorptive stripping voltammetry (ASV) for the detection of TNT on IL–GNs exhibited a good linear range from 0.03 to 1.5 ppm with a detection limit of 4 ppb on the basis of the signal-to-noise characteristics (S/N = 3). Moreover, IL–GNs/GCE exhibited good stability and reproducibility for the detection of TNT. And, IL–GNs based electrochemical detection platform was also successfully demonstrated for the detection of TNT in ground water, tap water, and lake water with satisfactory results.

Hemin−Graphene Hybrid Nanosheets with Intrinsic Peroxidase-like Activity for Label-free Colorimetric Detection of Single-Nucleotide Polymorphism

This paper demonstrated for the first time a simple wet-chemical strategy for synthesizing hemin-graphene hybrid nanosheets (H-GNs) through the π-π interactions. Significantly, this new material possesses the advantages of both hemin and graphene and exhibits three interesting properties. First, H-GNs have intrinsic peroxidase-like activity, which can catalyze the reaction of peroxidase substrate, due to the existence of hemin on the graphene surface. Second, their dispersion follow the 2D Schulze-Hardy rule, that is to say, the coagulation of H-GNs in electrolyte solution results from the interplay between van der Waals attraction and electric double-layer repulsion. Third, H-GNs exhibit the ability to differentiate ss- and ds-DNA in optimum electrolyte concentration, owing to the different affinities of ss- and ds-DNA to the H-GNs. On the basis of these unique properties of the as-prepared H-GNs, we have developed a label-free colorimetric detection system for single-nucleotide polymorphisms (SNPs) in disease-associated DNA. To our knowledge, this is the first report concerning on SNPs detection using functionalized graphene nanosheets. Owing to its easy operation and high specificity, it was expected that the proposed procedure might hold great promise in the pathogenic diagnosis and genetic diseases.

Self assembly of acetylcholinesterase on a gold nanoparticles–graphene nanosheet hybrid for organophosphate pesticide detection using polyelectrolyte as a linker

A nanohybrid of gold nanoparticles (Au NPs) and chemically reduced graphene oxide nanosheets (cr-Gs) was synthesized by in situgrowth of Au NPs on the surface of graphene nanosheets in the presence of poly(diallyldimethylammonium chloride) (PDDA), which not only improved the dispersion of Au NPs but also stabilized cholinesterase with high activity and loading efficiency. The obtained nanohybrid was characterized by TEM, XRD, XPS, and electrochemistry. Then an enzyme nanoassembly (AChE/Au NPs/cr-Gs) was prepared by self-assembling acetylcholinesterase (AChE) on Au NP/cr-Gs nanohybrid. An electrochemical sensor based on AChE/Au NPs/cr-Gs was further developed for ultrasensitive detection of organophosphate pesticide. The results demonstrate that the developed approach provides a promising strategy to improve the sensitivity and enzyme activity of electrochemical biosensors.

Cyclodextrin–graphene hybrid nanosheets as enhanced sensing platform for ultrasensitive determination of carbendazim

In this paper, cyclodextrin–graphene hybrid nanosheets (CD–GNs) for the first time have been used as an enhanced material for ultrasensitive detection of carbendazim by electrochemistry method. The peak currents of carbendazim on the GNs modified glassy carbon electrode (GNs/GCE) and the CD–GNs/GCE are increased by 11.7 and 82.0 folds compared to the bare GCE, respectively. This indicates the nanocomposite film not only shows the excellent electrical properties of GNs but also exhibits high supramolecular recognition capability of CDs. At the CD–GNs/GCE, the peak currents increase linearly with the concentration of carbendazim in the range of 5 nM–0.45 μM. The detection limit of carbendazim reached to 2 nM on the basis of the signal-to-noise characteristics (S/N = 3) and the recoveries were between 98.9% and 104.5%. The developed electrochemical sensor exhibited good stability and reproducibility for the detection of carbendazim. And the CD–GNs based electrochemical sensor was also successfully demonstrated for the detection of carbendazim in water sample with satisfactory results. Furthermore, this simple sensing platform can in principle be extended to the detection of other benzimidazole fungicide which can form host–guest complexes with cyclodextrin.