Mixing Graphene Oxide Research Articles

The influence of gamma radiation on the structure and morphology of AgNWs/GO nanocomposites

In this study, AgNWs/GO nanocomposites were prepared by mechanically mixing graphene oxide (GO) synthesized using a modified Hummers' method and silver nanowires (AgNWs) synthesized using a modified polyol method. These nanocomposites were subjected to gamma radiation at three different doses (8, 25, and 50 kGy). Modification of materials by gamma radiation is a very important issue in materials science. The effects of gamma radiation on the structure of the nanocomposites were investigated through X-Ray diffraction (XRD) analyses. Changes in morphology depending on the radiation dose were examined using transmission electron microscope (TEM) images. Elemental analysis was performed before and after irradiation. For GO irradiated at a dose of 25 kGy, the strain and dislocation density values reached their highest levels (ε = 0.065 and σ = 3.33 × 1012 cm−2). Following gamma radiation exposure, the strain and dislocation density of AgNWs showed a non-linear decrease compared to the initial sample. The highest values for both strain and dislocation density were recorded at the 0 kGy dose (ε = 0.0064 and σ = 0.0036 × 1012cm−2). Elemental analysis (EDS) indicated that reduction processes occurred depending on the radiation dose, with the highest reduction observed in the sample irradiated at 25 kGy. Studies indicate that gamma radiation can modify the structural and physical properties of the AgNWs/GO nanocomposite.

Synthesis of Plasma-Reduced Graphene Oxide/Lithium Titanate Oxide Composite and Its Application as Lithium-Ion Capacitor Anode Material

A plasma-reduced graphene oxide/lithium titanate oxide (PrGO/LTO) composite is prepared as an anode material to enhance the performance of lithium-ion capacitors (LICs). The PrGO/LTO composite is synthesized by mixing graphene oxide (GO) and LTO, followed by a series of freeze-drying and plasma-treatment processes. PrGO forms a porous three-dimensional (3D) structure with a large surface area, effectively preventing the restacking of PrGO while covering LTO. The GO/LTO mixing ratio is controlled to optimize the final structure for LIC applications. In lithium-ion half-cell assembly, the PrGO/LTO-based anode with an 80% mixing ratio exhibits the highest specific capacity of 73.0 mAh g−1 at 20 C. This is attributed to the optimized ratio for achieving high energy density from LTO and high power density from PrGO. In a LIC full-cell comprising PrGO/LTO as the anode and activated carbon as the cathode, the energy and power densities at 1 A g−1 are 40.3 Wh kg−1 and 2000 W kg−1, respectively, with a specific capacitance of 36.3 F g−1 and capacitance retention of 94.1% after 2000 cycles. Its outstanding performance, obtained from incorporating 3D-structured PrGO with LTO at an optimized ratio, lowers the cell resistance and provides efficient lithium-ion diffusion pathways.

Correlation study of thermal charging, discharging, and efficiency of graphene oxide-reinforced paraffin wax for thermal energy storage system

Nanocomposites, produced through mechanical blending, serve to enhance thermal performance of heat exchangers, solar collectors, and photovoltaic-thermal systems. This work employs an experimental methodology to assess the thermal charging (TC) and thermal discharging (TDC) of a composite generated by mixing graphene oxide (GO) and paraffin wax. TC and TDC of the GO-reinforced paraffin wax-based phase change material (PCM) have been examined across different flow rates (0.375, 0.75, and 1.5 L/min) and concentrations of GO (ranging from 0.25 to 1.00 vol%). The results exhibit a direct correlation between TC, TDC and efficiency, and reaction parameters (flow rate and volume concentration of GO). The experimental and predicted values of TCs, TDCs, and efficiencies fell ±15% (for TC and TDC), and ±9% for thermal efficiency, demonstrating a satisfactory level of agreement. This holds a practical application and valuable predictive tool for estimating TC, TDC, and thermal efficiency on known flow rates and concentrations of GO in wax-based PCMs.

Synergistic enhancement in permittivity and energy storage capacity of epoxy dielectrics via constructing continuous 3D BaTiO3 network collaborated with graphene oxide

Three-dimensional (3D) ceramic network has advantages over conventional ceramic nanoparticles in achieving high-performance flexible polymer dielectrics. However, the energy storage capacity cannot be substantially improved due to the relatively large dielectric loss and low breakdown strength. In this study, hierarchical 3DBT/EP-GO (GEBT) dielectric hybrid composites with greatly improved permittivity and energy storage density were obtained by reversely introducing a mixed graphene oxide (GO)/epoxy (EP) solution into three-dimensional BaTiO3 (3DBT) network, which was facilely constructed by sol-gel method using cleanroom wiper as the template. A relatively high dielectric constant (ε′ = 15.6) and breakdown strength (E0 = 239.8 kV mm−1) were simultaneously achieved for the GEBT-4 system with ∼15.4 wt% 3DBT and 0.75 wt% GO (to the epoxy). This system was much superior to the GEBT-1 with only 15 wt% 3DBT (ε′ = 9.2, E0 = 128.8 kV mm−1) and epoxy nanocomposite with 25 wt% BT nanoparticles (ε′ = 6.3, E0 = 121.0 kV mm−1). The continuous 3DBT ceramic network provided an effective polarization pathway within epoxy matrix, in which GO prevented electrical breakdown of the composites, thereby resulting in the significantly enhanced energy storage performance.

Bubble Up Induced Graphene Microspheres for Engineering Capacitive Energy Storage

AbstractTranslating the material merits of graphene to practical supercapacitor devices is critical for promoting capacitive energy storage, but is challenging due to the limited scalability in fabricating high‐performance graphene electrode films. Here, we demonstrate a method for fabricating graphene microsphere films, formed by the bubble‐induced destruction and agglomeration of the self‐assembled toplayer of mixed graphene oxide and exfoliated graphene over an adequately heated solution. The microspheres have compact, randomly distributed graphene flakes, endowing the films with a high bulk density (0.92 g cm−3) and ion conductivity to allow ultrahigh charge/discharge current densities of up to 1,000 A g−1 in an ionic liquid. The stack cell with an areal mass loading of 10 mg cm−2 exhibits an excellent energy density of 83.4 Wh L−1, superior to the state‐of‐the‐art carbon‐based supercapacitors, and approaching that of lead‐acid batteries. More importantly, a meter‐scale film is fabricated within half a minute by a developed roll‐to‐roll process, demonstrating the enormous potential of these films in the industrial manufacturing of supercapacitors. Furthermore, the film electrode is infilled with an ionogel electrolyte and assembled into an all‐solid‐state, flexible device with durable flexibility and multiple optional outputs, demonstrating the potential of these supercapacitors for powering flexible electronic devices.

Improved Electrical and Thermal Conductivities of Graphene–Carbon Nanotube Composite Film as an Advanced Thermal Interface Material

Thermal management has become a crucial issue for the rapid development of electronic devices, and thermal interface materials (TIMs) play an important role in improving heat dissipation. Recently, carbon−based TIMs, including graphene, reduced graphene oxide, and carbon nanotubes (CNTs) with high thermal conductivity, have attracted great attention. In this work, we provide graphene−carbon nanotube composite films with improved electrical and thermal conductivities. The composite films were prepared from mixed graphene oxide (GO) and CNT solutions and then were thermally reduced at a temperature greater than 2000 K to form a reduced graphene oxide (rGO)/CNT composite film. The added CNTs connect adjacent graphene layers, increase the interlayer interaction, and block the interlayer slipping of graphene layers, thereby improving the electrical conductivity, through−plane thermal conductivity, and mechanical properties of the rGO/CNT composite film at an appropriate CNT concentration. The rGO/CNT(4:1) composite film has the most desired properties with an electrical conductivity of ~2827 S/cm and an in−plane thermal conductivity of ~627 W/(m·K). The produced rGO/CNT composite film as a TIM will significantly improve the heat dissipation capability and has potential applications in thermal management of electronics.

Mechanically Robust and Elastic Graphene/Aramid Nanofiber/Polyaniline Nanotube Aerogels for Pressure Sensors.

The preparation of graphene-based aerogels with excellent mechanical strength, elasticity, and compressibility is still a challenge. Herein, we demonstrate a robust, elastic, and lightweight graphene/aramid nanofiber/polyaniline nanotube (rGO/ANF/PANIT) aerogel that is prepared by mixing graphene oxide (GO), ANF, and PANIT dispersions, followed by thermal treatment at 90 °C, freeze-drying, and a low-temperature annealing process. The PANIT bonds the graphene sheets tightly, benefitting the formation of composite gels. The ANF tightly interconnects the graphene sheets and further reinforces the composite network framework significantly, hence endowing rGO/ANF/PANIT composite aerogels with robust mechanical property. The prepared aerogels present a low density of ∼12 mg cm-3, high conductivity, good resilience, and high compressibility. The rGO/ANF/PANIT aerogels as pressure sensors exhibit a high sensitivity of 1.73 kPa-1, low detection limit (40 Pa), wide detection range, and excellent compressive cycle stability, highlighting the promising applications in pressure-sensitive electrical devices, including medical health detection, wearable electronics, and intelligent packaging fields.

Dual-functional superwettable nano-structured membrane: From ultra-effective separation of oil-water emulsion to seawater desalination

Freshwater contamination and scarcity have progressively exacerbated the worldwide water crisis. Developing a feasible method to remediate polluted water as well as converting the abundant seawater to freshwater has become a matter of urgency. Here we demonstrate a nanofibrous poly(vinyl alcohol) based membrane (NPM) with dual functions: oil/water separation and solar water desalination. Interconnected polypyrrole (PPY) nanoparticles were decorated on the NPM as solar light absorber as well as enabling the membrane with superwettability. The underwater superoleophobic property endows the NPM with excellent anti-fouling performance and capacity to treat surfactant-stabilized industrial wastewater containing oil or various non-polar organic solvents with a separation efficiency of more than 99%. Mechanical robustness of the membrane is enhanced by mixing graphene oxide (GO) into NPM. Meanwhile, the efficient solar thermal conversion enables NPM to further desalinize the seawater under one sun solar radiation with excellent efficiency and durability with an evaporation rate of 2.87 kg m−2h−1. In the on-site desalination test, the solar vapor system demonstrated a daily solar water purification yield of 14.3 L m−2 under natural sunlight irradiation, suggesting a promising “green” application as mass manufacture seawater purification system without extra energy source. The outstanding performances of NPM for oil-in-water emulsion separation and the high-rate seawater desalination suggest its great potential for industrial applications in the future.

A highly sensitive nonenzymatic H2O2 sensor based on 3D N-doped porous graphene aerogel decorated with AuPd alloy nanoparticles

3D N-doped porous graphene aerogel (3D NPGA) was facilely prepared through a one-step hydrothermal reduction by mixing graphene oxide (GO) and p-phenylenediamine with ammonia solution, followed by a freeze-drying process. Then, the AuPd alloy nanoparticles were deposited on the 3D NPGA to synthesize AuPd/NPGA by reduction of HAuCl4 and PdCl2 using NaBH4 as a reducing agent. NPGA composite shows a microporous with 3D structure, a large specific surface area and reveals edge plane like-sites/defects and can act as support sites for nanoparticles. The obtained AuPd/NPGA exhibits better catalytic activity towards H2O2 reduction compared with Pd/NPGA, Au/NPGA, and 3D NPGA composites. The improved performance of AuPd/NPGA attributed to the 3D porous structure of NPGA and the synergistic effect between Au and Pd NPs in the AuPd alloy as well as between 3D NPGA and AuPd NPs. In the 0.1 M PBS pH 7 electrolyte, the AuPd/NPGA electrode displays a linear response towards H2O2 reduction in the range of 1–1000 μM, high sensitivity of 12,235 μA mM−1 cm−2, low LOD 0.038 μM (S/N = 3) and quick response time (<1 s). This nonenzymatic H2O2 sensor was also displays satisfying selectivity, good reproducibility, and excellent long-term stability. In addition, the AuPd/NPGA electrode can also be employed for H2O2 detection in human serum samples. These results confirm that the AuPd/NPGA composite would be a promising catalytic material to construct sensors in different fields.

3D nitrogen-doped porous graphene aerogel as high-performance electrocatalyst for determination of gallic acid

In this work, three-dimensional nitrogen-doped porous graphene aerogel (NPGA) was easily synthesized via one-step hydrothermal reduction by mixing graphene oxide (GO) with p-phenylenediamine (PPD) and ammonia solution and then followed by freeze-dried. The NPGA sample was studied by different techniques such as SEM, TEM, nitrogen adsorption-desorption isotherms, XRD, XPS, and electrochemical measurements. NPGA composite exhibits a microporous with 3D structure, a large specific surface area and exposes edge plane like-sites/defects which lead to high electrical conductivity and facilitate electrons transfer towards the probe. The appropriate experimental conditions such as supporting electrolyte, pH value and scan rate were optimized before applying NPGA electrode to determine gallic acid (GAL) using differential pulse voltammetry (DPV) method. NPGA electrode shows superior electrochemical performance compared to the previous studies with regard to the limit of detection (0.067 μmol/L) and linear range (2.5–1000 μmol/L). The NPGA electrode provides a new way for GAL concentration determination with high selectivity, excellent stability, and good reproducibility. In addition, it is highly suitable for the detection of GAL concentration in real samples with excellent reliability.

PVP-assisted laser ablation growth of Ag nanocubes anchored on reduced graphene oxide (rGO) for efficient photocatalytic CO2 reduction

Metallic nanoparticles loaded graphene nanocomposites have been widely studied for various scientific and technological applications. In this study, a facile method was reported to realize a straightforward growth of shape and size-controllable of metallic nanoparticles, and the subsequent hybridization with graphene in solution by strategically coupling wet-chemical route and laser ablation. By mixing graphene oxide (GO) with a tunable concentration level of polyvinylpyrrolidone (PVP) in aqueous solution, Ag nanocubes with a face-centered cubic crystal structure were generated by pulsed laser ablation and then mounted on GO nanosheets with the assistance of PVP. The preferential adsorption of PVP to Ag (100) crystal face led to the production of Ag nanocubes with exposed (100) facet. The result showed that the morphological yield of spherical particles decreased with the increase in PVP concentration. X-ray diffraction (XRD) and UV–visible spectroscopy analyses confirmed that GO was partially reduced. In the reduction of CO2 gas, the photocatalytic conversion rate could achieve 133.1 μmol g−1 h−1 in 6 hrs for cubic Ag-loaded reduced GO composites.

Ambient Synthesis of Single-Atom Catalysts from Bulk Metal via Trapping of Atoms by Surface Dangling Bonds.

Single-atom catalysts (SACs) feature the maximum atom economy and superior performance for various catalysis fields, attracting tremendous attention in materials science. However, conventional synthesis of SACs involves high energy consumption at high temperature, complicated procedures, a massive waste of metal species, and poor yields, greatly impeding their development. Herein, a facile dangling bond trapping strategy to construct SACs under ambient conditions from easily accessible bulk metals (such as Fe, Co, Ni, and Cu) is presented. When mixing graphene oxide (GO) slurry with metal foam and drying in ambient conditions, the M0 would transfer electrons to the dangling oxygen groups on GO, obtaining Mδ+ (0 < δ < 3) species. Meanwhile, Mδ+ coordinates with the surface oxygen dangling bonds of GO to form MO bonds. Subsequently, the metal atoms are pulled out of the metal foam by the MO bonds under the assistance of sonication to give M SAs/GO materials. This synthesis at room temperature from bulk metals provides a versatile platform for facile and low-cost fabrication of SACs, crucial for their mass production and practical application in diverse industrial reactions.

Effect of reduced graphene oxide load into TiO2 P25 on the generation of reactive oxygen species in a solar photocatalytic reactor. Application to antipyrine degradation

TiO2-based photocatalysis is intensively investigated for efficient degradation of emerging environmental contaminants, but the generation of reactive oxygen species during such photocatalytic reactions is often underresearched. In this paper, we study the formation of reactive oxygen species under real solar irradiation on TiO2 P25 loaded with reduced graphene oxide (rGO). TiO2/rGO composites were prepared by mixing graphene oxide and TiO2 P25, followed by hydrothermal treatment. The band gap of TiO2 was not affected in the composites but the optical properties of the systems changed due to the morphology and presence of rGO. When these composites were studied under solar irradiation, the generation rate of hydroxyl HO radicals under solar light was higher in pure TiO2 than in TiO2/rGO, but also their decay with time, so TiO2/rGO eventually presented higher HO concentration at longer times. Moreover, adding rGO to TiO2 also affected the concentration of superoxide O2− and singlet oxygen 1O2 radicals, which we assign to the charge transfer between TiO2 and rGO and the presence of remaining holes on the surface. The amount of generated hydrogen peroxide H2O2 and consumed in these systems was practically the same, so its concentration remained low. The catalytic systems developed were tested in the solar photocatalytic degradation of antipyrine, demonstrating the relationship between the evolution of generated reactive oxygen species along the reaction time and the consumption of antipyrine. The TiO2 valence band holes were also found to be the responsible primary species along the course of reaction especially in the final mineralization step.

The preparation and research of reduced graphene oxide/glass composite fiber

In this article, reduced graphene oxide/glass composite fiber was prepared from mixing graphene oxide and glass powder by ultrasonic dispersion, planetary grinding, high-temperature sintering, and melting wire drawing. The effects of reduced graphene oxide content on the mechanical and electrical properties of the fiber were investigated. Thermal gravimetric analyzer, differential scanning calorimeter, x-ray diffraction, and energy-dispersive x-ray spectroscopy analysis revealed that the graphene oxide was reduced to reduced graphene oxide in the sintering process and the performances of the composite fiber were improved. The tensile strength of reduced graphene oxide/glass composite fiber was 20% higher than the pristine glass fibers by the addition of 0.5 wt% of reduced graphene oxide. Reduced graphene oxide content was positively correlated with composites conductivity, and according to the percolation theory, the percolation threshold of reduced graphene oxide/glass composite fiber was about 0.5 wt%, and the conductivity of the composite fibers was increased by four orders of magnitude compared to the pristine glass fibers when the content of reduced graphene oxide was 0.5 wt%.

Preparation of graphene oxide/cellulose composites in ionic liquid for Ce (III) removal

An environmental friendly adsorbent was prepared by mixing graphene oxide (GO) and cellulose in 1-butyl-3-methylimidazolium chloride ionic liquid. The characterization of GO/cellulose composite films (CGC) was carried out by Fourier-transform infrared spectroscopy, scanning electron microscopy, thermogravimetric analysis and X-ray photoelectron spectroscopy (XPS). The Ce (III) adsorption on CGC was evaluated systematically, revealing that the adsorption equilibrium could be achieved within 40 min. The adsorption behavior was well fitted to the pseudo-second-order kinetic model and the Langmuir adsorption model. The XPS analysis indicated that two peaks attributing to Ce3d nearly disappeared after desorption in NaCl, which confirmed the ion exchange mechanism. Furthermore, the CGC adsorbent had a high adsorption capacity of Ce (III) in a wide pH range of 3–8 with a theoretical maximum adsorption capacity of Ce (III) 109.1 mg g−1. This work indicated that as-prepared CGC is a promising adsorbent for removing rare earth ions pollutants from wastewater.

Free-standing, layered graphene monoliths for long-life supercapacitor

Fabricating free-standing film/paper or 3D material without additive binder is of great importance to maintain its original architectures and properties. Here, we for the first time introduce a simple, facile approach to fabricate a free-standing, layered N-doping reduced graphene oxide (NRGO) monolith for supercapacitor, firstly mixing graphene oxide (GO) with urea, and lastly taking a short-term flame bath. It is found that urea is a key sacrificial grasper, which can effectively prevent reduced GO (RGO) sheets from being peeled off in flame bath. Moreover, 3.5–7.0 at.% of N elements are successfully introduced into RGO skeleton. These structural characteristics are translated into high specific capacitance (323.7 F g−1 at 1 A g−1, higher than RGO powder (252.1 F g−1)), ultra-high coulombic efficiency (125% at 1 A g−1) and superior cycle performance with a 9.2% improvement in specific capacitance after 50,000 cycles at 30 A g−1. Relatively, only 69.3% of the specific capacitance for RGO powder remains after 10,000 cycles at 30 A g−1. Compared with RGO powder, NRGO shows obviously improvement in coulombic efficiency, energy efficiency, and especially in cycle stability. Thus, this layered NRGO not only shows a high energy storage capacity, but also successfully solves the stability problem in the long-term charge/discharge cycle. This provides a novel clue for designing long-life graphene-based electrode materials for supercapacitor.

Graphene oxide-loaded shortening as an environmentally friendly heat transfer fluid with high thermal conductivity

Graphene oxide-loaded shortening (GOS), an environmentally friendly heat transfer fluid with high thermal conductivity, was successfully prepared by mixing graphene oxide (GO) with a shortening. Scanning electron microscopy revealed that GO particles, prepared by the modified Hummer?s method, dispersed well in the shortening. In addition, the latent heat of GOS decreased while their viscosity and thermal conductivity increased with increasing the amount of loaded GO. The thermal conductivity of the GOS with 4% GO was higher than that of pure shortening of ca. three times, from 0.1751 to 0.6022 W/mK, and increased with increasing temperature. The GOS started to be degraded at ca. 360?C. After being heated and cooled at 100?C for 100 cycles, its viscosity slightly decreased and no chemical degradation was observed. Therefore, the prepared GOS is potentially used as environmentally friendly heat transfer fluid at high temperature.

Enhancements of thermal insulation and mechanical property of silica aerogel monoliths by mixing graphene oxide

In order to improve the thermal insulation and mechanical property of silica (SiO2) aerogels, the graphene oxide (GO), as nanofillers, was added into SiO2 matrix to prepare the SiO2/GO composite aerogel monoliths on the basis of sol-gel technology and submitted to supercritical drying. The results showed that the monoliths were maintained and GO was well-distributed in the aerogel, due to the interfacial interaction between GO nanosheets and SiO2 matrix. The thermal insulation property of composite aerogels was improved in contrast with that of pure aerogel. The experimental results suggested that the thermal conductivity was lowered from 0.0089 W/mK to 0.0072 W/mK. A possible mechanism was analyzed to explain this result in virtue of GO loadings. The mechanical strength of aerogels was enhanced. It was found that with the loading of GO from 0.0 wt% to 5.0 wt%, the compressive modulus was enhanced from 0.238 MPa to 0.394 MPa, which was a significant improvement for low-solid-content silica aerogels. Moreover, the composite aerogels exhibited some toughness compared to the fragility of pure aerogel.

Synergetic effect in the multifunctional composite film of graphene-TiO2 with transparent conductive, photocatalytic and strain sensing properties

In this study, reduced graphene oxide-TiO2 (rGO-T) composite films fabricated by a spray coating method are proposed to develop a multifunctional material with transparent conductive, photocatalytic and strain sensing properties. In the presence of SDBS, well-dispersed reduced graphene oxide solutions were prepared by mixing graphene oxide dispersions with hydrazine hydrate. A drastic synergetic effect was found simply by mixing reduced graphene oxide dispersions with TiO2 solutions. The obtained multifunctional rGO-T composite films showed relatively high optical transmittance, excellent strain sensing property with tunable gauge factors (GF) of 11–21 and enhanced photocatalytic property. The remarkable performance could be attributed to the combination of the excellent electrical and mechanical properties of graphene nanosheets and photocatalytic performance derived from TiO2 nanoparticles. Overall, this work could provide new insights into the research of the graphene-TiO2 composite materials and facilitate their application in a broad range.

The preparation of reduced graphene oxide-TiO2 composite materials towards transparent, strain sensing and photodegradation multifunctional films

In this study, reduced graphene oxide-TiO2 (rGO-T) composite films fabricated by a spray coating method are proposed to develop a multifunctional material for the application of strain sensing and photodegradation. This work provides a simple and versatile approach to prepare rGO-T as a multifunctional material. The drastic synergy effect was found simply by mixing graphene oxide with TiO2. The obtained multifunctional rGO-T composite films showed relatively high optical transmittance (around 60% at a 550 nm wavelength), excellent strain sensing property with gauge factors (GF) of 12–23 and enhanced photocatalytic property. The remarkable performance could be attributed to the combination of electrical and mechanical properties of rGO nanosheets and photocatalytic performance derived from TiO2 nanoparticles. Overall, this work could provide new insights into the research of the graphene-TiO2 composite materials and facilitate their application in a broad range.