Graphene Nanoscrolls Research Articles

Erratum to: Analytical investigation of carrier concentration effect on one-dimensional graphene nanoscroll

Erratum to: Analytical investigation of carrier concentration effect on one-dimensional graphene nanoscroll

Experimental Evidence and Theoretical Analysis of Nanobubble Stability Within Graphene Nanoscrolls.

In this study direct observation and dynamics of nanoscale water and nanobubbles within graphene nanoscrolls were reported. The life time of these nanobubbles is much higher than expected, which we propose is due to the combination of several factors including localized heating and surface charge. The stability of the nanobubbles within graphene nanoscrolls has been theoretically analyzed. The nanobubbles inside these nanoscrolls reveal a wide distribution of graphene-water contact angles. Bubble dynamics within these graphene nanochannels was directly observed and recorded.

Preparation of graphene nanoscroll/polyaniline composites and their use in high performance supercapacitors

The graphene nanoscroll is a kind of tubular graphene with an open end and a helical nanostructure. Different amounts of polyaniline were formed on the surface of the nanoscroll by the in-situ polymerization of aniline. SEM observation shows that the polyaniline nanoparticles are evenly distributed on the nanoscrolls and the number of free polyaniline clusters increases with the amount of monomer used. The electrochemical performance of three composites with different polyaniline/graphene nanoscroll ratios was evaluated. The best specific capacitance of the composites reaches 320 F/g at 1 A/g and a 92.1% retention capacitance rate is obtained at 100 A/g, indicating that the composite has a rate performance as good as graphene nanoscrolls and a higher specific capacitance.

Graphene-cellulose tissue composites for high power supercapacitors

Flexible supercapacitors have aroused a great deal of interest for their integration in portable, flexible and wearable electronic devices. In this context, graphene has emerged as an excellent building block for the fabrication of flexible electrodes. However, free-standing graphene films suffer from a certain lack of mechanical resistance, which limits their use. In this paper, we report on the fabrication of free-standing and flexible composites with enhanced robustness, consisting of a graphene layer deposited over a porous cellulose tissue. The coated graphene consists of two types of holey graphene units (i.e. wrinkled graphene sheets and graphene nanoscrolls) that produce closely interconnected and porous 3D graphene architectures. The graphene-tissue composites developed here have a thickness of around 60µm and areal densities in the 0.6–2.4mgcm−2 range. These composites have a very open structure that provides easy access to the electrolyte, thereby guaranteeing high ion-transport rates. In consequence, they show a remarkable capacitive performance in both liquid (1M H2SO4) and solid (PVA-H2SO4) electrolytes. The supercapacitors assembled with these materials possess an areal capacitance of up to ~80mFcm−2 at low rates in both kinds of electrolyte and around 60mFcm−2 at 500mAcm−2 in H2SO4 and 54mFcm−2 at ca. 80mAcm−2 in a gel electrolyte. What is more, these SCs are able to deliver ca. 9µWhcm−2 of energy at a high power density of 100mWcm−2.

Analytical investigation of carrier concentration effect on one-dimensional graphene nanoscroll

In recent years, carbon nanoscrolls (CNSs) that have a tubular structure similar to that of the open multi-wall carbon nanotube have received significant attention. Graphene nanoscrolls (GNSs) have also attracted significant attention, owing to their unique properties. These nanoscrolls are obtained by systematically winding graphene sheets into a spiral, and are expected to have high mechanical strength, high carrier mobility, and high thermal conductivity. In the present work, an analytical model was used to determine the band energy of (16,0) GNS, and the normalized Fermi energies in the degenerate and non-degenerate regimes are modeled. The model revealed that degenerate and non-degenerate approximations can be used for normalized Fermi energies higher than 3 and lower than −3, respectively.

Evaluation of carbon nanoscroll materials for post-combustion CO2 capture

Carbon nanoscrolls are similar to multi-walled carbon nanotubes but constructed from rolled graphene sheets into papyrus-like structures. In this work, molecular simulations are used to evaluate the post-combustion CO2 capture properties of nanoscrolls made of graphene, α-, β-, and γ-graphyne, boron nitride, and three types of carbon nitride. The CO2 uptake capacity, CO2/N2 selectivity and CO2 working capacity were computed with grand canonical Monte Carlo simulations at conditions relevant to post-combustion CO2 capture. The interlayer spacing of the nanoscrolls was optimized for each property and sheet material. For graphene nanoscrolls, the optimal interlayer spacing of 7.3 Å was identified for both the CO2 uptake and selectivity, while for working capacity the optimal interlayer spacing was determined to be 8.6 Å. It was found that the CO2 uptake capacity of the materials correlated to the density of the sheets from which they were formed. Nanoscrolls made from graphene and boron nitride, which have the highest number of atoms per unit area, also showed the highest CO2 uptakes. At 0.15 bar CO2, 313 K, graphene and boron nitride nanoscrolls exhibited exceptional CO2 uptake capacities of 7.7 and 8.2 mmol/g, respectively, while also exhibiting high CO2/N2 selectivities of 135 and 153, respectively. Molecular dynamics simulations were used to examine the adsorption kinetics. The simulations showed that an empty graphene nanoscroll with a roll length of 200 Å could adsorb CO2 into the center of the roll within 10 ns. Materials with pores that can allow CO2 to pass through, such as graphynes, showed much faster adsorption times.

Mass production of graphene nanoscrolls and their application in high rate performance supercapacitors.

The output of graphene nanoscrolls (GNSs) has been greatly enhanced to the gram-level by using an improved spray-freeze-drying method without damaging the high transforming efficiency (>92%). The lowest bulk density of GNS foam reaches 0.10 mg cm(-3). Due to the unique morphology and high specific surface area (386.4 m(2) g(-1)), the specific capacitances of the GNSs (90-100 F g(-1) at 1 A g(-1)) are all superior to those of multiwalled carbon nanotubes meanwhile maintaining excellent rate capabilities (60-80% retention at 50 A g(-1)). For the first time, all-graphene-based films (AGFs) are fabricated via the intercalation of GNSs into graphene layers. The AGF exhibits a capacitance of 166.8 F g(-1) at 1 A g(-1) and rate capability (83.9% retention at 50 A g(-1)) better than those of pure reduced graphene oxide (RGO) films and carbon nanotubes/graphene hybrid films (CGFs).

Dual coexisting interconnected graphene nanostructures for high performance supercapacitor applications

A high-quality hierarchical carbon nanostructure consisting of graphene nanosheets and nanoscrolls can be synthesized by a facile and scalable molten salt method. This carbon nanostructure is here proposed as a high-performance supercapacitor electrode material.

Band structures of graphene nanoscrolls and their dispersion relation near the Fermi point

We studied the physical structure and band structure of different types of graphene nanoscrolls.

Atomic layer deposition of TiO2and Al2O3on nanographite films: structure and field emission properties

Atomic layer deposition (ALD) of metal oxides (MO) was used to modify the properties of nanographite (NG) films produced by direct current plasma–enhanced chemical vapor deposition technique. NG films consist of a few layers of graphene flakes (nanowalls) and nanoscrolls homogeneously distributed over a silicon substrate with a predominantly vertical orientation of graphene sheets to the substrate surface. TiO2 and Al2O3 layers, with thicknesses in the range of 50 to 250 nm, were deposited on NG films by ALD. The obtained NG-MO composite materials were characterized by scanning electron microscopy, energy dispersive x-ray analysis, and Raman spectroscopy. It was found that ALD forms a uniform coating on graphene flakes, while on the surface of needle-like nanoscrolls it forms spherical nanoparticles. Field emission properties of the films were measured in a flat vacuum diode configuration. Analysis based on obtained current–voltage characteristics and electrostatic calculations show that emission from NG-TiO2 films is determined by the nanoscrolls protruding from the TiO2 coverage. The TiO2 layers with thicknesses of <200 nm almost do not affect the overall field emission characteristics of the films. At the same time, these layers are able to stabilize the NG films’ surface and can lead to an improvement of the NG cold cathode performance in vacuum electronics.

Analytical Modeling and Artificial Neural Network (ANN) Simulation of Current-Voltage Characteristics in Graphene Nanoscroll Based Gas Sensors

Graphene nanoscrolls (GNSs) as a new category of quasi one-dimensional (1D) belong to the carbon-based nanomaterials, which have recently captivated the attention of researchers. The latest discoveries of outstanding characteristics of GNSs in terms of structural and electronic properties such as high mobility, controllable band gap, and tunable core size. Previous studies have shown the fact that graphene different structures such as carbon nanotube (CNT), bilayer graphene (BLG) and GNS experience changes in the electrical conductivity when expose to various gases. Therefore, these materials are proposed as a promising candidate for gas detection sensors. These are typically constructed on a field effect transistor (FET) based structure in which the GNS is employed as the channel between the source and the drain. In this study, an analytical model has been proposed and developed with the initial assumption that the gate voltage is directly proportional to the gas concentration as well as its temperature. The effect of gas adsorption on GNS surface makes the changes in GNS conductance which leads to the changes in the current of sensor consequently. This phenomenon is considered as sensing mechanism with proposed sensing parameters. Using the corresponding formula for GNS conductance, the proposed mathematical model is derived. Also, artificial neural network (ANN) algorithms have also been incorporated to obtain other models for the current-voltage (I-V) characteristic in which the analytical data extracted from current and previous related works has been used as the training data set. The comparative study of the results from ANN and the analytical models with the experimental data in hand shows a satisfactory agreement which validates the proposed models.

Friction. Macroscale superlubricity enabled by graphene nanoscroll formation.

Friction and wear remain as the primary modes of mechanical energy dissipation in moving mechanical assemblies; thus, it is desirable to minimize friction in a number of applications. We demonstrate that superlubricity can be realized at engineering scale when graphene is used in combination with nanodiamond particles and diamondlike carbon (DLC). Macroscopic superlubricity originates because graphene patches at a sliding interface wrap around nanodiamonds to form nanoscrolls with reduced contact area that slide against the DLC surface, achieving an incommensurate contact and substantially reduced coefficient of friction (~0.004). Atomistic simulations elucidate the overall mechanism and mesoscopic link bridging the nanoscale mechanics and macroscopic experimental observations.

CVD nanographite films covered by ALD metal oxides: structural and field emission properties

AbstractNanographite films produced by direct current plasma enhanced chemical vapour deposition technique were covered by metal oxides TiO2 and Al2O3 using atomic layer deposition. Nanographite films are composed of few‐layer graphene nanowalls and nanoscrolls, which are mostly oriented perpendicular to the silicon substrate surface. The nanographite and nanographite‐metal oxide composite film materials, with oxide layer thickness between 50 nm and 250 nm, were characterized by scanning electron microscopy, energy dispersive X‐ray analysis, thermal gravimetric analysis, and Raman spectroscopy. We demonstrate that the metal oxide deposit homogenously covers graphene nanowalls and forms individual spherical particles on the surface of needle‐like nanoscrolls. Field emission properties of the samples were measured in a flat vacuum diode configuration. It was found that the metal oxide layers thinner than 200 nm do not significantly affect the field emission characteristics of the nanographite. At the same time, metal oxides form a passivation shell which may improve the nanographite film performance as cold cathode in vacuum electronic devices. (© 2015 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)

Fabrication of high-quality graphene oxide nanoscrolls and application in supercapacitor.

We reported a simple and effective way of fabricating one-dimensional (1D) graphene oxide nanoscrolls (GONS) from graphene oxide (GO) sheets through shock cooling by liquid nitrogen. The corresponding mechanism of rolling was proposed. One possibility is the formation of ice crystals during the shock cooling process in liquid nitrogen to be the driving force. The other might be due to the uneven stress of the sheets inside or outside ice during the lyophilization. After reducing, graphene nanoscrolls (GNS) exhibited good structural stability, high specific surface area, and high specific capacitance. The capacitance properties were investigated by cyclic voltammetry, galvanostatic charge-discharge, and electrical impedance spectroscopy. A specific capacity of 156 F/g for the GNS at the current density of 1.0 A/g was obtained comparing with the specific capacity of 108 F/g for graphene sheets. Those results indicated that GNS-based rolling structure could be a kind of promising electrode material for supercapacitors and batteries.

Molecular dynamics simulation on the fabrication of graphene nanoscrolls with ferromagnetic nanowire templates

Graphene nanoscrolls (GNSs) have attracted more and more attention both in theory and experiments for their unique and excellent fundamental properties and the wide range of potential applications. In this paper, the fabrication of GNSs with different ferromagnetic nanowire (FNW) templates has been studied by molecular dynamics (MD) method. We have presented convincing explanations on the GNS formation mechanism and a thorough analysis about the differences between varying FNWs. Moreover, a distinctive deformation behavior in the Ni nanowire oriented in [001] axis direction was observed and deeply investigated. And the influence of nanowire lengths on the fabrication of GNS is also studied. Our theoretical results will provide researchers a powerful guide and helpful assistance in designing better targeted programs in experiments.

Sensitivity Modelling of Graphene Nanoscroll-Based NO2 Gas Sensors

Graphene nanoscrolls (GNSs) as a new category of quasi one-dimensional (1D) belong to the carbon-based nanomaterials, which have recently captivated the attention of researchers. The latest discoveries of exceptional structural and electronic properties of GNSs like high mobility, controllable band gap, and tunable core size have become a great stimuli for graphene researchers. Due to the importance and critical role of nanoscale sensors and biosensors in medical facilities and human life, using a promising material like graphene has been widely studied to achieve better accuracy and sensitivity in these devices. Up until now, the majority of surveys conducted previously have focused on experimental studies for sensors family. Therefore, there is lake of analytical models in comparison to experimental surveys. In order to start and understand about the modelling of gas sensors structure, the field effect transistor(FET)-based structure is employed as a basic. In this study, graphene nanoscroll conductivity has been evaluated under the impacts which is induced by the adsorption of different values of NO2 gas concentration on GNS surface. So that, when GNS-gas sensor is exposed to NO2 gas molecules, the carrier concentration of GNS is changed which leads to the changes in the conductance, and consequently, in the current, this phenomenon is considered as sensing mechanism. The I–V characteristic of graphene nanoscroll-based gas sensor has been considered as a criterion to detect the effect of gas adsorption. In order to verify the accuracy of the proposed model, the results have been compared with the existing experimental works.

Analytical Study of Electronic Structure in Archimedean Type-Spiral Zig-Zag Graphene Nanoscroll

The semiconducting electronic properties of graphene nanoscroll (GNS) are very much related to its geometric structure. The aim of this study is to construct a GNS energy dispersion model within low-energy transport of 1 eV in identifying its electronic properties and carrier statistics. Non-parabolic energy dispersion is used to incorporate the Archimedean type-spiral model, and the band gap is assessed based on chirality and geometry effects. The energy band within low-energy transport indicates that GNS can achieve a quantum conductance limit of ~6.45 kΩ for ballistic transport. On the other hand, the numbers for three minimum sub-bands are attained based on non-parabolic energy dispersion, and the semi-metallic zig-zag GNS is found at chirality (3j + 1, 0). This work consistently predicts the semiconducting properties of the tight-binding model from previous work. The GNS overlapping region strongly affects its electronic properties. Constantly increasing the length of the overlapping region decreases the band gap exponentially, whilst semimetallic GNS forms when the overlap reaches a certain limit. The carrier density with temperature dependence is subsequently assessed at the intrinsic level, and found that the number of carriers in GNS shows a higher rate of increment (exponentially) compared to carbon nanotubes (CNT), in accordance to their diameter. The results are very useful in giving an intuitive understanding on GNS carrier statistics as subject to geometry changes.

Hydrogen microexplosion synthesis of platinum nanoparticles/nitrogen doped graphene nanoscrolls as new amperometric glucose biosensor

Platinum nanoparticles/nitrogen doped graphene nanoscrolls (Pt/N-GSS) nanocomposites were prepared by hydrogen microexplosion method. Based on the fantastically scrolled structure, N-doping and high reduction degree properties of N-GSS as catalyst support for Pt nanoparticles, Pt/N-GSS nanocomposites exhibit excellent electrocatalytic activity towards the oxidation of H2O2 with the sensitivity of 25.26μAmM−1 and good linear response from 2μM to 16.57mM. Additionally, taking glucose oxidase (GOD) as the model, the resulting glucose amperometric biosensor not only presents good analytical performance such as a wide linear range (10μM–12.55mM), a high sensitivity (6.36μAmM−1), but also possesses low detection limit of 1μΜ and long-term stability for detection.

Highly Efficient Synthesis of Neat Graphene Nanoscrolls from Graphene Oxide by Well-Controlled Lyophilization

Graphene nanoscroll (GNS) is an important one-dimensional tubular form of graphitic carbon with characteristic open topology. It has been predicted to possess extraordinary properties that are significantly different from the analogical multiwalled carbon nanotubes. However, comprehensive experimental investigations on its properties and applications are still hindered by the lack of its reliable synthesis in high yield. To efficiently transform the scalable graphene oxide sheets into GNSs, here, we proposed a well-controlled lyophilization that comprises four sequential steps: chemical reduction of giant GO, freezing isolation of reduced graphene sheets, freeze-drying, and thermal annealing. The combined method has an extremely high efficiency, up to the record 92%. Systemic control experiments and cryo-SEM inspections revealed that the topological transformation from 2D sheet to 1D scroll is the sublimation-induced scrolling of individually confined graphene sheets in ice, which was controlled by chemic...

Facile preparation of large-scale graphene nanoscrolls from graphene oxide sheets by cold quenching in liquid nitrogen

Graphene nanoscrolls (GNSs) are receiving intense interest because they are expected to possess some peculiar properties quite distinct from both graphene and carbon nanotubes. Research on GNS, however, has been hindered by limitations of the available preparation methods. Here we demonstrate a novel strategy for the large-scale preparation of GNSs from graphene oxide (GO) sheets by cold quenching, freeze-drying and subsequent thermal reduction. When a plastic box with a heated GO aqueous suspension is immersed in liquid nitrogen, GO sheets are able to roll up and most GNSs have diameters ranging from 200 to 600nm. More interestingly, these GNSs connect each other to form a 3D network. The structural conversion is closely correlated with the initial temperature of GO suspension, the size of GO sheets and the immersion way. The liquid nitrogen cold quenching is a simple and controllable method for large-scale preparation of GNSs. The liquid nitrogen cold quenching is a simple and controllable method for large-scale preparation of GNSs.