Graphene Nanosheets In Water Research Articles

Low-temperature decomposable industrial surfactant for stabilization of few-layered graphene in water

Surface-active agents, such as surfactant molecules, are essential for stabilizing liquid-exfoliated graphene and other 2D nanosheets in water through electrostatic or steric repulsion. It is important to note that surfactants are no longer necessary for solutions converted into thin films for electronic devices, sensors, and composite applications. High-temperature (∼400–500 °C) thermal annealing is one of the performed methods to remove surfactant molecules. However, the surfactant residues present on the graphene nanosheets by post-annealing may adversely impact the electronic properties of the graphene film, potentially resulting in additional doping and defects. To address this challenge, we report a low-temperature decomposable (∼320 °C), eco-friendly and industrially viable surfactant, i.e., coco-glucoside, for the efficient liquid-phase exfoliation and stabilization of graphene nanosheets in water. Compared with the well-studied surfactants in liquid exfoliation such as sodium dodecyl benzene sulphonate (SDBS) and sodium cholate (SC), ∼90 % of this surfactant molecules completely decomposed at ∼320 °C in an air atmosphere for coco-glucoside. Electrical conductivity studies suggested that annealing at 320 °C enhanced the conductivity by 15 times for the coco glucoside-stabilized graphene film; however, marginal change in the conductivity was observed for the SDBS and SC-stabilized graphene film. To demonstrate the viability of the concept, a wallpaper-based rapid fire alarm application utilizing coco glucoside-stabilized graphene/cellulose paper was demonstrated.

Massive laser pulling of graphene nanosheets in water.

Light manipulation of graphene-based materials attracts much attentions. As a new light manipulation concept, optical pulling develops rapidly in the past decade. However, optical pulling of graphene in liquid is rarely reported. In this work, laser pulling of graphene nanosheets (GN) in pure water by using common gauss beams is presented. This phenomenon holds for multiple incident laser wavelengths including 405 nm, 488 nm, 532 nm and 650 nm. A particle image velocimetry software PIVlab is adopted to analyze the velocity field information of GN. The laser pulling velocity of the GN is approximately ∼ 0.5 mm/s corresponding to ∼ 103 body length/s, which increases with an increase of the incident laser energy. This work presents a contactless mothed to massively pull microscale graphene materials in simple liquid, which supplies a potential manipulation technique for micro-nanofluidic devices and also provides a platform to investigate laser-graphene interaction in a simple liquid phase medium.

A sustainable reduction route of graphene oxide by industrial waste lignin for versatile applications in energy and environment

The high toxicity of chemical reducing agents for graphene oxide (GO) and the high-polluting emission of industrial waste lignin as black liquor are always the two troubling issues in clean production. Herein, we reported a sustainable win-win route to utilize waste lignin as a green reducing agent of GO through hydrothermal method. Various hydrothermal conditions were investigated to reveal the reduction capability and mechanism of lignin towards GO. Results indicated that lignin could repair the conjugated structure of GO, while the hydroxyl ions in water could cause the decarboxylation of GO. The lignin-reduced GO composites (LRGOs) prepared at acidic and neutral pHs tended to form hydrogels, while the alkaline LRGOs were monodispersed graphene nanosheets in water. The alkaline LRGO suspensions exhibited reversible sol-gel transition by adding acid/base, and irreversible gelation by metal ions chelation. Besides, they could self-assemble into a robust film with excellent mechanical properties (306.7 ± 47.9 MPa in tensile strength, 135.2 ± 45.3 GPa in modulus) and electrical conductivity (399.5 ± 58.3 S/cm) through vacuum filtration and annealing. The freeze-dried LRGO aerogels and their carbonized products showed excellent absorption capacities for various organic solvents. As electrode materials, the LRGO aerogels also displayed a high pseudo-capacitance of 213.8 F/g at 1 A/g. These findings of LRGOs showed a huge application potential in clean energy and environmental pollution treatment.

High Performance Na-O2 Batteries and Printed Microsupercapacitors Based on Water-Processable, Biomolecule-Assisted Anodic Graphene.

Integrated approaches that expedite the production and processing of graphene into useful structures and devices, particularly through simple and environmentally friendly strategies, are highly desirable in the efforts to implement this two-dimensional material in state-of-the-art electrochemical energy storage technologies. Here, we introduce natural nucleotides (e.g., adenosine monophosphate) as bifunctional agents for the electrochemical exfoliation and dispersion of graphene nanosheets in water. Acting both as exfoliating electrolytes and colloidal stabilizers, these biomolecules facilitated access to aqueous graphene bio-inks that could be readily processed into aerogels and inkjet-printed interdigitated patterns. Na-O2 batteries assembled with the graphene-derived aerogels as the cathode and a glyme-based electrolyte exhibited a full discharge capacity of ∼3.8 mAh cm–2 at a current density of 0.2 mA cm–2. Moreover, shallow cycling experiments (0.5 mAh cm–2) boasted a capacity retention of 94% after 50 cycles, which outperformed the cycle life of prior graphene-based cathodes for this type of battery. The positive effect of the nucleotide-adsorbed nanosheets on the battery performance is discussed and related to the presence of the phosphate group in these biomolecules. Microsupercapacitors made from the interdigitated graphene patterns as the electrodes also displayed a competitive performance, affording areal and volumetric energy densities of 0.03 μWh cm–2 and 1.2 mWh cm–3 at power densities of 0.003 mW cm–2 and 0.1 W cm–3, respectively. Taken together, by offering a green and straightforward route to different types of functional graphene-based materials, the present results are expected to ease the development of novel energy storage technologies that exploit the attractions of graphene.

Scotch-tape-like exfoliation effect of graphene quantum dots for efficient preparation of graphene nanosheets in water

As a simple and eco-friendly strategy, the production of graphene nanosheets (GNs) by liquid-phase exfoliation (LPE) faces a challenge to the improvement of exfoliation yield for scalability, as well as the stable dispersibility for application. Herein, we electrochemically prepare a kind of graphene quantum dots (GQDs) with undestroyed crystalline structure on basal plane and a number of hydrophilic functional groups at edge, to exfoliate and disperse GNs in water with a high yield of 89–100%. The obtained GNs show a conductivity of 1.2 × 105 S m−1 and water dispersibility of 1.0 mg mL−1 for over one month, due to the firm adsorption of amphiphilic GQDs, which have non-covalent π-π bond interaction with graphene basal plane and strong H-bonds with water. The lateral size, functional groups and defect nature of GQDs have great influence on GNs and a scotch-tape-like exfoliation mechanism is proposed. GQDs as green stabilizer and exfoliation agent can effectively acquire the high-quality GNs and promote their potential application.

Pulsed Nd:YAG laser assisted fabrication of graphene nanosheets in water

AbstractGraphene nanosheets were prepared by pulsed Nd:YAG laser ablation of graphite target in H2O under ambient conditions. The synthesized graphene nanosheets were characterized by high resolution transmission electron microscope (HRTEM), X-ray diffraction (XRD), Raman spectroscopy and Selected Area Electron Diffraction (SAED). The obtained structural and morphological analysis confirmed that the graphene nanosheets could be formed in an aqueous medium via one step method where a nanosecond pulsed near-infrared (NIR) laser (λ = 1064 nm) is used to ablate the surface of a pure graphite target. Compared to other used chemical methods to synthesis graphene nanosheets, laser ablation is an easy, versatile, environmental friendly and rapidly growing method for the synthesis of nanostructured materials such as graphene nanosheets. This technique showed normal operation in liquid medium (i.e. water or organic) under ambient conditions. Our study confirmed the great potential of laser ablation in liquid method for the fabrication of graphene nanosheets based nanofluids wich has a potential applicatiuon as a heat transfer fluid.

Green synthesis of water-soluble graphene nanosheets under solvent-free condition and in-situ anchored with MnO2 as supercapacitor

Since the direct dispersion of hydrophobic graphene nanosheets (GNS) in water without the assistance of dispersing agents such as polymeric or surfactant stabilizers are generally considered as an insurmountable challenge, current research aims to develop GNS using a green and solvent-free method. This method is an environmental eco-friendly approach and lets GNS get produced directly from graphite in simple conditions without using any toxic acids and reagents. This method is implemented at the shortest possible time without high temperatures and long synthesis times by using green and non-toxic citric acid as a cheap and eco-friendly intercalation agent at 100 °C without any need for any additional purification. This procedure is a promising route for the generation of stable GNS in water. In the second step, we utilized in-situ synthesis through a green method to develop graphene-MnO2 nanocomposite by anchoring MnO2 nanoflowers on graphene sheets. In this approach, there is no need for any additional purification or adding any materials or catalysis. The specific capacitance of 213 F g−1 was obtained for the graphene-MnO2 nanocomposite at a scan rate of 10 mV s−1.which makes it a great candidate for supercapacilator applications. In addition, the synthesized nanocomposite retained 90.25% of the initial capacitance after 500 cycles of charge–discharge at a current density of 40 A g−1. The work provides a new approach for synthesized GNS with the functional group without needing reduction agent and in situ anchored GNS with MnO2 nanoflowers nanocomposite at a green and eco-friendly condition, suggesting GNS and its nanocomposite have potential uses in many different areas of research.

Preparation of water-soluble graphene nanoplatelets and highly conductive films

This paper tackles the challenge of preparation stable, highly concentrated aqueous graphene dispersions. Despite tremendous recent interest, there has been limited success in developing a method that ensures the total dispersion of non-oxidized, defect-free graphene nanosheets in water. This study successfully demonstrates that few-layer graphene nanoplatelets (GNPs) can form highly concentrated aqueous colloidal solutions after they have been pretreated in a low-concentration inorganic sodium-hypochlorite and sodium-bromide salted aqueous solvent. This method retains the graphitic structure as evidenced by nuclear magnetic resonance spectroscopy, X-ray photoelectron spectroscopy, and Raman spectroscopy. Vacuum-filtrated freestanding films demonstrate an electrical conductivity as high as 3000 S m−1. This dispersion technique is believed to be applicable not only for GNPs, but also for dispersing other types of graphitic materials, including fullerenes, single/double/multi-walled carbon nanotubes, graphene nanoribbons and etc.

Nonlinear optical properties of the mixture of ZnO nanoparticles and graphene nanosheets

In this work, the experimental investigation of the nonlinear response of the mixture of ZnO nanoparticles and graphene nanosheets as a function of volumetric ratio of ZnO and graphene colloidal suspensions has been reported. The colloidal ZnO nanoparticle and graphene were synthesized by nanosecond pulsed laser ablation of Zn and graphite target in water, respectively. The X-ray diffraction pattern, transmission electron microscopy, Raman spectrum and linear absorption properties of ZnO nanoparticle and graphene nanosheets were used to characterize the ablation products. D band and G band of Raman shift at 1325 and 1580 cm−1, respectively, confirmed the formation of graphene nanosheets in water. Results show that the bandgap energy of mixtures decreased noticeably with increasing the amount of graphene in the suspensions. The nonlinear optical properties of the mixture of ZnO nanoparticles and graphene nanosheets were also investigated using open and close z-scan experiments. The positive nonlinear refractive index and absorption coefficient of the mixture of graphene nanosheets and ZnO nanoparticles were increased with increasing the concentration of graphene in the mixtures.

碳纳米管制备蓝光石墨烯量子点及其在柔性有机存储器上的应用

We presented a facile method to prepare uniform size and stable property graphene quantum dots( GQDs) from chemical cutting the double-walled carbon nanotube with blue light emission in a chlorobenzene solution. The double-walled carbon nanotube was firstly cut into graphene nano sheets( GNSs) in acidic in the condition of heating and stirring,then chlorobenzene was used to separate GQDs from GNSs in water. The chlorobenzene solvent enabled the preparation of GQD-PVK hybrid nanocomposite. Nonvolatile rewritable memory effect was observed for the GQD-based nanocomposite,suggesting the promising applications of GQDs in data storage. Moreover,due to the easy solution process,we demonstrated the design and realization of flexible GQD-based memory device. The memory has performance as follow: low driving-voltage,high ON / OFF ratio,high cycles,high repeatability and stability. This work may expand the application of GQDs to the portable electronic devices.

The synthesis of xanthenes and benzoxanthenes on graphene oxide and sulfated graphene nanosheets in water

A practical and green method for the synthesis of xanthenes and benzoxanthenes by the reaction of 1-naphthol, 2-naphthol or 1,3-diketones with a wide range of aldehydes and 1,3-diketones, using graphene oxide or sulfated graphene nanosheets as two recyclable solid acid catalysts in water, is described. The best results were obtained with sulfated graphene.

Pulse Microwave Deposition of Cobalt Oxide Nanoparticles on Graphene Nanosheets as Anode Materials for Lithium Ion Batteries

We report the high capacity, superior rate capability, and excellent cyclic stability of graphene nanosheets (GNs) decorated with Co3O4 nanoparticles as anodes in Li-ion batteries. A pulse microwave-assisted (MA) polyol method (total period: 30 min) is adopted to deposit cobalt oxides onto the GNs in water and ethylene glycol (EG), forming two types of Co3O4@GN hybrids. The selection of solvent in the MA process plays a central role in affecting the crystallinity, dispersion, and particle size of cobalt oxide particles. The resulting Co3O4@GN hybrid, prepared by the MA method in EG, shows a homogeneous dispersion of Co3O4 nanocrystals with an average size of 10 nm. The Co3O4@GN hybrid displays advantages of high reversible capacity, excellent cycleability, and high rate capability. This improved cyclic performance can be attributed to the formation of a three-dimensional GN framework decorated with Co3O4 nanocrystals, leading to fast diffusion of Li ions (diffusion coefficient: 5.82 × 10–12 cm2 s–1) and l...