Utilizing Graphene Oxide Research Articles

Two-dimensional sandwich structured carbon nanosheets: facile fabrication and superior capacitive performance

A facile and cost-efficient strategy was developed to generate two-dimensional (2D) sandwich structured carbon nanosheets (SSCNs) by utilizing graphene oxide sheets (GO) as shape-directing agent and the in-situ formed resorcinol-formaldehyde polymer (RF) as the carbon source. The key point of this efficient synthesis is the self-catalytic effect of resorcinol, which is the cornerstone for the construction of SSCNs. The obtained 2D SSCNs possess a graphene-like morphology and a novel porous carbon/graphene/porous carbon sandwich structure, where porous carbon layer (∼16 nm thick) is coated on both sides of graphene sheets. Such a unique 2D structure endows the SSCNs with a high specific surface area of 1496 m2 g−1 and a hierarchical pore structure, which is expected to shorten paths for fast electrolyte ion diffusion and provide large exposed surface for capacitive energy storage. As designed, the SSCNs delivered specific capacitance as high as 313 F g−1 (at 0.2 A g−1) and retained 272 F g−1 at high current density of 20 A g−1. More importantly, the SSCNs showed no apparent capacity decay after 10 000 cycles at 1 A g−1. This work paves the way to develop 2D carbon nanosheets for high-performance energy storage devices.

A Mini Review Focused on the Recent Applications of Graphene Oxide in Stem Cell Growth and Differentiation.

Stem cells are undifferentiated cells that can give rise to any types of cells in our body. Hence, they have been utilized for various applications, such as drug testing and disease modeling. However, for the successful of those applications, the survival and differentiation of stem cells into specialized lineages should be well controlled. Growth factors and chemical agents are the most common signals to promote the proliferation and differentiation of stem cells. However, those approaches holds several drawbacks such as the negative side effects, degradation or denaturation, and expensive. To address such limitations, nanomaterials have been recently used as a better approach for controlling stem cells behaviors. Graphene oxide is the derivative of graphene, the first two-dimensional (2D) materials in the world. Recently, due to its extraordinary properties and great biological effects on stem cells, many scientists around the world have utilized graphene oxide to enhance the differentiation potential of stem cells. In this mini review, we highlight the key advances about the effects of graphene oxide on controlling stem cell growth and various types of stem cell differentiation. We also discuss the possible molecular mechanisms of graphene oxide in controlling stem cell growth and differentiation.

High-performance organic solar cells utilizing graphene oxide in the active and hole transport layers

We have successfully synthesized and employed graphene oxide (GO) to boost photons harvesting and charge transport process in thin film organic solar cells (TFOSCs). The graphene oxide was inlayed in both the P3HT:PCBM-based photoactive medium of the device, as well as, a dopant in PEDOT:PSS hole transport buffer layer (HTL). The parameters of the solar cells produced with the inclusion of GO in the HTL and the active layer results in high short-circuit current densities (Jsc), which translated into high power conversion efficiencies (PCEs). GO in the HTL facilitates charge transport, selective electron blocking and hole injection at the interface for enhanced device performance. On the other hand, the use of GO in the active layer remarkably improves the optical absorption leading to high charge carriers photogeneration requisite to efficient OSCs. Similarly, effective exciton dissociation is energetically favoured in the GO modified active layer devices which corroborated with improved conductivity of the medium that assisted charge carriers transport processes. Enhanced photocurrent has been recorded, as high as 18 mA cm−2, from the TFOSCs by the inlay of GO in the active layer. Consequently, increased PCE of up to 40% and 120% is achieved by the inclusion of GO in the HTL and photoactive layers, respectively.

Π-π Interaction Enabling Highly Stable Li-Organic Batteries with Graphene Oxide – Based Separators

CuTCNQ is a novel high capacity electrode material with three electrons transfer reaction. The main challenge of its practical application is the dissolution of the intermediate , which is similiar to the sulfur cathode in Li-S batteries. Here, we utilize graphene oxide (GO) coated separator to trap the dissolved aromatic active mateirals through charge transfer reaction by π-π interaction. Consequently, the CuTCNQ battery with GO separator is able to achieve a capacity of 252. mAh g-1 and show a high capacity retention of 81.3% over 100 cycles. Even at a higher current of 500 mA g-1, the cell still exhibits an outstanding cycle performance, delivering a capacity of 119.1 mAh g-1 with 75.8% capacity retention over 350 cycles. Not only for Li-organic battery, GO separator can also serve as a promising alternative separator in organic electrolyte based redox flow batteries. Figure 1

Label-free sensitive luminescence biosensor for immunoglobulin G based on Ag6Au6 ethisterone cluster-estrogen receptor α aggregation and graphene

A specific and label-free “on-off-on” luminescence biosensor based on a novel heterometallic cluster [Ag6Au6(ethisterone)12]-estrogen receptor α (Ag6Au6Eth-ERα) aggregation utilizing graphene oxide (GO) as a quencher to lead a small background signal was firstly constructed to detect immunoglobulin G (IgG) with a simple process and high selectivity. The efficient photoluminescent (PL) Ag6Au6Eth-ERα aggregation is strongly quenched by GO. In the presence of IgG, the PL of this system will be restored, and perceivable by human eyes under UV lamp excitation (365 nm). The quenching mechanism of GO on Ag6Au6Eth-ERα and enhancement mechanism of IgG on Ag6Au6Eth-ERα-GO were investigated in detail. Under the optimum conditions, the biosensor for high sensitive IgG detection expressed a wider linear range of 0.0078–10 ng/mL and a lower detection limit of 0.65 pg/mL with good stability and repeatability, which provided a new approach for label-free IgG detection.

Graphene Oxide and Microwave Synergism for Efficient Esterification of Fatty Acids

The synthesis of biodiesel or fatty acid methyl esters (FAMEs) from alternative feedstocks such as waste cooking oil through conventional transesterification process is challenged by the presence of significant amounts of free fatty acids (FFAs). Alternatively, these FFAs can also serve as raw material for the synthesis of FAMEs through acid-catalyzed esterification. In this study, we utilized graphene oxide (GO) as a carbon-based heterogeneous acid catalyst in synergy with microwave (MW) heating as a novel approach for an efficient synthesis of FAMEs by esterification reaction at a shorter reaction time. Under this process, 99.2% FAME was achieved at 3 min, methanol/oleic acid molar ratio of 12, MW power of 200 W, and 1 wt % catalyst. It shows excellent catalytic performance, which is more active than Amberlyst 15, sulfated zirconia, and graphite oxide. Among the process variables investigated, the ratio of methanol/oleic acid is the most important factor for higher FAME yield. Additionally, the MW absor...

Experimental investigation of graphene oxide nanofluid on heat transfer enhancement of pulsating heat pipe

Pulsating heat pipes (PHPs) are heat transfer devices which are widely utilized in electronic devices and energy systems. Improvement in thermal performance of PHPs will lead to higher heat transfer capacity and enhancement in the efficiency of systems which PHPs are applied. In this study, an experimental investigation was performed on the thermal performance of a pulsating heat pipe by applying graphene oxide nanofluid as working fluid. Four concentrations of graphene oxide (0.25, 0.5, 1, and 1.5g/lit) in water as base fluid were used in the PHP. Results indicate that adding graphene oxide sheets increased thermal conductivity and viscidity of the base fluid. Moreover, utilizing graphene oxide can decrease thermal resistance of PHP up to 42%. In addition, high concentration (1.5g/lit) of the nanofluid worsen thermal performance of the PHP in comparison with pure water which is attributed to increase in dynamic viscosity of nanofluid. Finally, a regression model is proposed in order to compare effects of heat input and concentration of nanofluid on thermal resistance mathematically.

Two-Dimensional Holey Nanoarchitectures Created by Confined Self-Assembly of Nanoparticles via Block Copolymers: From Synthesis to Energy Storage Property.

Advances in liquid-phase exfoliation and surfactant-directed anisotropic growth of two-dimensional (2D) nanosheets have enabled their rapid development. However, it remains challenging to develop assembly strategies that lead to the construction of 2D nanomaterials with well-defined geometry and functional nanoarchitectures that are tailored to specific applications. Here we report a facile self-assembly method leading to the controlled synthesis of 2D transition metal oxide (TMO) nanosheets containing a high density of holes. We utilize graphene oxide sheets as a sacrificial template and Pluronic copolymers as surfactants. By using ZnFe2O4 (ZFO) nanoparticles as a model material, we demonstrate that by tuning the molecular weight of the Pluronic copolymers we can incorporate the ZFO particles and tune the size of the holes in the sheets. The resulting 2D ZFO nanosheets offer synergistic characteristics including increased electrochemically active surface areas, shortened ion diffusion paths, and strong inherent mechanical properties, leading to enhanced lithium-ion storage properties. Postcycling characterization confirms that the samples maintain structural integrity after electrochemical cycling. Our findings demonstrate that this template-assisted self-assembly method is a useful bottom-up route for controlled synthesis of 2D nanoarchitectures, and these holey 2D nanoarchitectures are promising for improving the electrochemical performance of next-generation lithium-ion batteries.

Ultrahigh sensitive enhanced-electrochemiluminescence detection of cancer biomarkers using silica NPs/graphene oxide: A comparative study

The increasing progress in using nano-biomaterials for medical purposes has opened new horizons toward researchers around the globe. To investigate the presence of these nanomaterials and the impacts they might have, a comparative enhanced-electrochemiluminescence immunosensing study has been designed. The effects of utilizing graphene oxide, silica, and gold nanoparticles in cancer diagnosis were evaluated during the quantification of two major cancer biomarkers (CEA and AFP) in different approaches. In other words, first and second approaches were designed to employ nanomaterials while third and fourth approaches were developed in absence of those. Accordingly, resulted LODs experienced dramatic amplification when nano-biomaterials were included in the immunosensor modification (for AFP: 1st and 3rd approaches: 1.36fg/ml in comparison with 0.39ng/ml, and for CEA: 2nd and 4th approaches: 1.90fg/ml versus 0.46ng/ml, respectively). Correspondingly, capability of nano-biomaterials for developing highly sensitive and more efficient immunosensors was validated through selectivity, stability, reproducibility, and feasibility examinations.

Graphene Oxide as Mine of Knowledge: Using Graphene Oxide To Teach Undergraduate Students Core Chemistry and Nanotechnology Concepts

The aim of this laboratory experiment is to utilize graphene oxide (GO) material to introduce undergraduate students to many well-known concepts of general chemistry. GO is a new nanomaterial that has generated worldwide interest and can be easily produced in every well-equipped undergraduate chemical laboratory. An in-depth examination of GO synthesis, as well as a study of its structure and properties, allows students to familiarize themselves with the concepts of redox reactions, dispersity, and polarity, along with the basic concepts of spectroscopic methods. The inclusion of this carbonaceous nanomaterial within a basic chemistry curriculum can stimulate students’ interest and introduce them to the modern field of nanotechnology. Students are tasked to prepare GO using the well-known improved Hummers’ method. Then they study the dispersion behavior of GO and carry out Fourier transform infrared and UV–vis spectroscopic measurements to characterize the material. The experiments are designed to be acco...

Graphene: A Comprehensive Review

Graphene, a one-atom thick, two-dimensional sheets of sp2hybridized carbon atoms packed in a hexagonal lattice with a Caron-Carbon distance of about 0.142 nm. Its extended honeycomb network forms the basic building block of other important allotropes; it can be stacked to form 3-Dgraphite, rolled to form 1-D-nanotubes and wrapped to form 0-D-fullerenes. Long-range π conjugation in graphene results in its extraordinary thermal, mechanical and electrical properties, which have been the interest of many theoretical studies and recently became an exciting area for scientists. Graphene is impermeable to gas and liquids, has excellent thermal conductivity and higher current density in comparison to other most effective materials. All of its exceptional properties have opened up new avenues for the use of graphene in nano-devices and nano-systems, which initiated its prominent use as a material for drug targeting. In addition, several fabrication techniques are outlined, starting from the mechanical exfoliation of high-quality graphene to the direct growth on silicon carbide or metal substrates and from the chemical routes utilizing graphene oxide to the newly developed approach at the molecular level. By this article reviewers intend to emphasize on unique properties, fabrication techniques and updated applications of graphene. In addition, we discuss about the potential of graphene in drug targeting in fields of nanotechnology, biomedical engineering and technology and its use for innovations in various fields such as electronics and photonics.

Graphene/BiVO4/TiO2 nanocomposite: tuning band gap energies for superior photocatalytic activity under visible light

A facile, ultrasonic wave-assisted one pot hydrothermal method has been developed to fabricate reduced graphene oxide/bismuth vanadate/titanium oxide (RGO/BiVO4/TiO2) ternary nanocomposites. By utilizing graphene oxide (GO) as multifunctional structure, RGO/BiVO4/TiO2 (GBT) with diverse percentage composition possessing varying band gap energies is obtained. XRD and Raman spectroscopy evince formation of tetragonal and monoclinic phases of BiVO4. The band gap energies of the components of the composite were determined by applying modified Kubelka–Munk function on UV–Vis DRS data. Tuning of band gap energy of the BiVO4 and TiO2 were simultaneously achieved by modifying the concentrations of GO and TiO2 during synthesis. The GBT exhibited enhanced photocatalytic degradation of methylene blue (MB) under visible light irradiation. The relative photocatalytic activity rates of the composites in GBT series are in agreement with the photoluminescence data. The mechanism behind the activity suggests GO acting as an electron trapper and TiO2 behaving as an efficient mediating co-catalyst. The band gap energy tuning led to reduction in time needed for complete MB degradation from 40 min with RGO/BiVO4 to 10 min with the ternary composite GBT. It is expected that the work would encourage new vistas to engineer different combinations of graphene based ternary composites which might lead to potential applications guided by band gap tuning.

Highly Selective Sensing Platform Utilizing Graphene Oxide and Multiwalled Carbon Nanotubes for the Sensitive Determination of Tramadol in the Presence of Co‐Formulated Drugs

AbstractNovel insights into the strategy of highly precise, carbon‐based electrochemical sensors are presented by exploring the excellent properties of graphene oxide (GO) and multiwalled carbon nanotube composites (GO‐MWCNTs/CPE) for the sensitive determination of tramadol hydrochloride (TRH). Cyclic voltammetry, differential pulse voltammetry, chronoamperometry (CA), and electrochemical impedance spectroscopy (EIS) scanning electron microscopy, and X‐ray diffraction (XRD) techniques were used to characterize the properties of the sensor. The linear response obtained for TRH using the GO‐MWCNTs/CPE was found to be over the range of 2.0x10−9 to 1.1x10−3 M with a good linearity and high correlation (0.9996). The limits of detection and quantification were found to be 1.50x10−10 M and 4.99 x 10−10 M, respectively. The proposed sensor was applied for determination of TRH in the presence of presence of co‐formulated drugs ketorolac tromethamine (KTM) and paracetamol (PAR). The sensor was shown to successfully apply to the determination of TRH in plasma as real samples. Satisfactory recoveries of TRH from samples clearly revealed that the proposed sensor can be applied into clinical analysis, quality control and a routine determination of drugs in pharmaceutical formulations.

Non-Volatile ReRAM Devices Based on Self-Assembled Multilayers of Modified Graphene Oxide 2D Nanosheets.

2D nanomaterials have been actively utilized in non-volatile resistive switching random access memory (ReRAM) devices due to their high flexibility, 3D-stacking capability, simple structure, transparency, easy fabrication, and low cost. Herein, it demonstrates re-writable, bistable, transparent, and flexible solution-processed crossbar ReRAM devices utilizing graphene oxide (GO) based multilayers as active dielectric layers. The devices employ single- or multi-component-based multilayers composed of positively charged GO (N-GO(+) or NS-GO(+)) with/without negatively charged GO(-) using layer-by-layer assembly method, sandwiched between Al bottom and Au top electrodes. The device based on the multi-component active layer Au/[N-GO(+)/GO(-)]n /Al/PES shows higher ON/OFF ratio of ≈105 with switching voltage of -1.9 V and higher retention stability (≈104 s), whereas the device based on single component (Au/[N-GO(+)]n /Al/PES) shows ≈103 ON/OFF ratio at ±3.5 V switching voltage. The superior ReRAM properties of the multi-component-based device are attributed to a higher coating surface roughness. The Au/[N-GO(+)/GO(-)]n /Al/PES device prepared from lower GO concentration (0.01%) exhibits higher ON/OFF ratio (≈109 ) at switching voltage of ±2.0 V. However, better stability is achieved by increasing the concentration from 0.01% to 0.05% of all GO-based solutions. It is found that the devices containing MnO2 in the dielectric layer do not improve the ReRAM performance.

Graphene Oxide-Based Supercapacitor Immunosensor for D-Dimer Detection

The constantly-evolving field of biosensors has attracted the focus of attention of the biomedical field due to their outstanding capacities for performing real-time in-vivo non-invasive studies for biomarkers detection and quantification. Furthermore, the field of electrochemical biosensors has been of increase interest given its potential to easily convert biological phenomena into an electrical measurable signal. By using supercapacitors as a potential technique for developing biosensors, we have been able to target specific human serum proteins, in this case, D-Dimer. By utilizing graphene oxide as a base nanocomposite for antibody fixation, we have been able to immuno-functionalize an electrode with monoclonal antibodies and target this biomarker which has been identified as a target molecule for diagnosis of venous thromboembolism-related conditions. Nanocomposite characterization and electrode immuno-functionalization was studied with Fourier transform infrared (FTIR), Raman spectroscopy (RS), X-ray diffraction (XRD), and thermal gravimetric analysis (TGA). Finally, antibody-antigen interactions for D-Dimer detection were studied with cyclic voltammetry (CV) in a 3-electrode configuration.

A high sensitivity field effect transistor biosensor for methylene blue detection utilize graphene oxide nanoribbon

In this work, we developed a field effect transistor (FET) biosensor utilizing solution-processed graphene oxide nanoribbon (GONR) for methylene blue (MB) sensing. MB is a unique material; one of its crucial applications is as a marker in the detection of biomaterials. Therefore, a highly sensitive biosensor with a low detection limit that can be fabricated simply in a noncomplex detection scheme is desirable. GONR is made by unzipping multiwall carbon nanotubes, which can be mass-produced at low temperature. The GONR-FET biosensor demonstrated a sensitivity of 12.5μA/mM (determined according to the drain current difference caused by the MB concentration change). The Raman spectra indicate that the materials quality of the GONR and the domain size for the C=C sp2 bonding were both improved after MB detection. X-ray photoelectron spectroscopy revealed that the hydroxyl groups on the GONR were removed by the reductive MB. According to XPS and Raman, the positive charge is proposed to transfer from MB to GONR during sensing. This transfer causes charge in-neutrality in the GONR which is compensated by releasing •OH functional groups. With high sensitivity, a low detection limit, and a simple device structure, the GONR-FET sensor is suitable for sensing biomaterials.

Graphene Oxide Regulated Tin Oxide Nanostructures: Engineering Composition, Morphology, Band Structure, and Photocatalytic Properties.

A facile, one-step hydrothermal method has been developed to fabricate tin oxide-reduced graphene oxide (Sn-RGO) nanocomposites with tunable composition, morphology, and energy band structure by utilizing graphene oxide (GO) as a multifunctional two-dimensional scaffold. By adjusting the GO concentration during synthesis, a variety of tin oxide nanomaterials with diverse composition and morphology are obtained. Simultaneously, the varying of GO concentration can also narrow the bandgap and tune the band edge positions of the Sn-RGO nanocomposites. As a result, the Sn-RGO nanocomposites with controllable composition, morphology, and energy band structure are obtained, which exhibit efficient photoactivities toward methyl orange (MO) degradation under visible-light irradiation. It is expected that our work would point to the new possibility of using GO for directing synthesis of semiconductor nanomaterials with tailored structure and physicochemical properties.

A three-dimensional nitrogen-doped graphene structure: a highly efficient carrier of enzymes for biosensors.

In recent years, graphene-based enzyme biosensors have received considerable attention due to their excellent performance. Enormous efforts have been made to utilize graphene oxide and its derivatives as carriers of enzymes for biosensing. However, the performance of these sensors is limited by the drawbacks of graphene oxide such as slow electron transfer rate, low catalytic area and poor conductivity. Here, we report a new graphene-based enzyme carrier, i.e. a highly conductive 3D nitrogen-doped graphene structure (3D-NG) grown by chemical vapour deposition, for highly effective enzyme-based biosensors. Owing to the high conductivity, large porosity and tunable nitrogen-doping ratio, this kind of graphene framework shows outstanding electrical properties and a large surface area for enzyme loading and biocatalytic reactions. Using glucose oxidase (GOx) as a model enzyme and chitosan (CS) as an efficient molecular binder of the enzyme, our 3D-NG based biosensors show extremely high sensitivity for the sensing of glucose (226.24 μA mM(-1) m(-2)), which is almost an order of magnitude higher than those reported in most of the previous studies. The stable adsorption and outstanding direct electrochemical behaviour of the enzyme on the nanocomposite indicate the promising application of this 3D enzyme carrier in high-performance electrochemical biosensors or biofuel cells.

An enzyme-aided amplification strategy for sensitive detection of DNA utilizing graphene oxide (GO) as a fluorescence quencher

A facile, sensitive and rapid method has been developed for detection of disease-related DNA based on lambda exonuclease-aided signal amplification by utilizing graphene oxide (GO) as a fluorescence quencher. The fluorescence of the carboxyfluorescein-labeled DNA probe (F-DNA) was sharply quenched due to the electron or energy transfer between the fluorescence dye and GO. While in the presence of target DNA, the formation of a DNA hybrid released F-DNA from the surface of GO, leading to a fluorescence recovery. Then, the fluorescence enhancement was further amplified by using lambda exonuclease (λexo) to liberate target DNA for cyclic hybridization. Fluorescence polarization and gel electrophoresis further verified the reliability of the principle. Disease-related DNA can be sensitively detected based on the enzyme-aided amplification strategy. More importantly, single-base mismatched DNA can be effectively discriminated from complementary target DNA and random DNA. Therefore, it offered a universal, simple, sensitive and specific method for detection of disease-related genes.

Thrombin aptasensing with inherently electroactive graphene oxide nanoplatelets as labels

Graphene and its associated materials are commonly used as the transducing platform in biosensing. We propose a different approach for the application of graphene in biosensing. Here, we utilized graphene oxide nanoplatelets as the inherently electroactive labels for the aptasensing of thrombin. The basis of detection lies in the ability of graphene oxide to be electrochemically reduced, thereby providing a well-defined reduction wave; one graphene oxide nanoplatelet of dimension 50 × 50 nm can provide a reduction signal by accepting ~22,000 electrons. We demonstrate that by using graphene oxide nanoplatelets as an inherently electroactive label, we can detect thrombin in the concentration range of 3 pM-0.3 μM, with good selectivity of the aptamer towards interferences by bovine serum albumin, immunoglobulin G and avidin. Therefore, the inherently electroactive graphene oxide nanoplatelets are a material which can serve as an electroactive label, in a manner similar to metallic nanoparticles.