Graphene Nanoscrolls Research Articles

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.

Inclusion and exclusion of self-assembled molecules inside graphene scrolls and control of their inner-tube diameter

Graphene nanoscrolls (GNSs) have a unique structure and properties different from those of graphene and carbon nanotubes. Nanoscrolls of graphene are first synthesized by a simple solution process. Using N-(2-aminoethyl)-3α-hydroxy-5β-cholan-24-amide (LCA), as a bile acid derivative and self-assembling material, the inner-tube diameter of GNSs can be controlled by adjusting the diameter of LCA fibers grown by self-assembly. TEM and SEM images show that the GNSs have a tube-like morphology with various inner diameters of 2–12 nm and up to 250 nm achieved through growth and inclusion of LCA fibers. Finally, open cylindrical GNSs with a hollow core were obtained by solvent dissolution and thermal degradation of LCAs.

Graphene nanoscrolls encapsulated TiO2 (B) nanowires for lithium storage

Graphene nanoscrolls encapsulated TiO2 (B) nanowires have been fabricated through a self-scrolling and template-free process for the first time. Transmission electron microscope images reveal that graphene tightly encompassed TiO2 (B) nanowires to construct nanoscrolled architectures. Cyclic voltammetry demonstrates that pseudocapacitive behavior dominates fast lithium storage rather than diffusion-controlled insertion in the hybrids. Galvanostatic cycling tests show that the reversible specific capacity of the hybrids remains 153 mAh g−1 after 300 cycles at 10 C with capacity retention of 94%. The excellent lithium storage performance can be attributed to the unique nanoscrolled structure, which provides abundant channels for lithium ions transport, as well as accommodates volume variation during fast lithiation and delithiation.

Facile preparation of one-dimensional wrapping structure: graphene nanoscroll-wrapped of Fe3O4 nanoparticles and its application for lithium-ion battery.

Graphene nanoscroll (GNS) is a spirally wrapped two-dimensional (2D) graphene sheet (GS) with a 1D tubular structure resembling that of a multiwalled carbon nanotube (MWCNT). GNS provide open structure at both ends and interlayer galleries that can be easily intercalated and adjusted, which show great potential applications in energy storage. Here we demonstrate a novel and simple strategy for the large-scale preparation of GNSs wrapping Fe3O4 nanoparticles (denoted as Fe3O4@GNSs) from graphene oxide (GO) sheets by cold quenching in liquid nitrogen. When a heated aqueous mixed suspension of GO sheets and Fe3O4 nanoparticles is immersed in liquid nitrogen, the in-situ wrapping of Fe3O4 nanoparticles with GNSs is easily realized. The structural conversion is closely correlated with the initial temperature of mixed suspension, the zeta potential of Fe3O4 nanoparticles and the immersion way. Remarkably, such hybrid structure provides the right combination of electrode properties for high-performance lithium-ion batteries. Compared with other wrapping structure, such 1D wrapping structure (GNSs wrapping) effectively limits the volume expansion of Fe3O4 nanoparticles during the cycling process, consequently, a high reversible capacity, good rate capability, and excellent cyclic stability are achieved with the material as anode for lithium storage. The results presented here may pave a way for the large-scale preparation of GNS-based materials in electrochemical energy storage applications.

Analytical prediction of liquid-gated graphene nanoscroll biosensor performance

The latest discovery of the graphene nanoscroll has provided enormous new stimuli to carbon nanoresearch. Due to its one-dimensional structure and tunable core size, the graphene nanoscroll is suitable for nanoscale applications such as in nanotransistors, and biosensor devices. DNA sensing is critical in the identification of the genetic risk factors associated with complex human diseases, and continues to have an emerging role in therapeutics and personalized medicine. This paper presents the analytical model of liquid-gated field effect transistors (LGFETs) for zig-zag graphene nanoscrolls (ZGNSs) inspired by carbon nanotube behavior when exposed to DNA molecules. First of all, in order to gain physical insight into GNS-based devices, the conductance of GNSs is analytically modelled. Based on the sensing mechanism of the DNA sensor, GNS controlling elements (ηGNS and eGNS) are proposed and the behavior of LGFETs-based GNS nanomaterial in the presence of DNA molecules is predicted to get a greater insight into the rapid development of DNA sensors and their application. Because of the channel-doping effect due to the adsorption of the DNA molecules, the conductance of the channel is altered. On the other hand, the applied voltage effect in the form of tilted electron energy levels is utilized in the form of normalized Fermi energy variation which is used in the sensor modelling. This study emphasizes the promising nature of carbon nanoscrolls for a number of electronic device applications.

Carrier Statistics and Quantum Capacitance Models of Graphene Nanoscroll

As a new category of quasi‐one‐dimensional materials, graphene nanoscroll (GNS) has captivated the researchers recently because of its exceptional electronic properties like having large carrier mobility. In addition, it is admitted that the scrolled configurations for graphene indicate larger stability concerning the energy, as opposed to their counterpart planar configurations like nanoribbon, nanotube, and bilayer graphene. By utilizing a novel analytical approach, the current paper introduces modeling of the density of state (DOS), carrier concentration, and quantum capacitance for graphene nanoscroll (suggested schematic perfect scroll‐like Archimedes spiral). The DOS model was derived at first, while it was later applied to compute the carrier concentration and quantum capacitance model. Furthermore, the carrier concentration and quantum capacitance were modeled for both degenerate and nondegenerate regimes, along with examining the effect of structural parameters and chirality number on the density of state and carrier concentration. Latterly, the temperature effect on the quantum capacitance was studied too.

An ice-templated, pH-tunable self-assembly route to hierarchically porous graphene nanoscroll networks.

Porous graphene nanostructures are of great interest for applications in catalysis and energy storage. However, the fabrication of three-dimensional (3D) macroporous graphene nanostructures with controlled morphology, porosity and surface area still presents significant challenges. Here we introduce an ice-templated self-assembly approach for the integration of two-dimensional graphene nanosheets into hierarchically porous graphene nanoscroll networks, where the morphology of porous structures can be easily controlled by varying the pH conditions during the ice-templated self-assembly process. We show that freeze-casting of reduced graphene oxide (rGO) solution results in the formation of 3D porous graphene microfoam below pH 8 and hierarchically porous graphene nanoscroll networks at pH 10. In addition, we demonstrate that graphene nanoscroll networks show promising electrocatalytic activity for the oxygen reduction reaction (ORR).

Formation of nitrogen-doped graphene nanoscrolls by adsorption of magnetic γ-Fe2O3 nanoparticles

Graphene nanoscrolls are Archimedean-type spirals formed by rolling single-layer graphene sheets. Their unique structure makes them conceptually interesting and understanding their formation gives important information on the manipulation and characteristics of various carbon nanostructures. Here we report a 100% efficient process to transform nitrogen-doped reduced graphene oxide sheets into homogeneous nanoscrolls by decoration with magnetic γ-Fe2O3 nanoparticles. Through a large number of control experiments, magnetic characterization of the decorated nanoparticles, and ab initio calculations, we conclude that the rolling is initiated by the strong adsorption of maghemite nanoparticles at nitrogen defects in the graphene lattice and their mutual magnetic interaction. The nanoscroll formation is fully reversible and upon removal of the maghemite nanoparticles, the nanoscrolls return to open sheets. Besides supplying information on the rolling mechanism of graphene nanoscrolls, our results also provide important information on the stabilization of iron oxide nanoparticles.

Geometry Effect on Graphene Nanoscrolls Band Gap

Geometry Effect on Graphene Nanoscrolls Band Gap

QUANTUM CAPACITANCE EFFECT ON ZIG-ZAG GRAPHENE NANOSCROLLS (ZGNS) (16, 0)

Miniaturization of electronic devices carries them to the quantum limits which mean quantum effect will be dominant in nano-size device characterization. A first band analytical model of the quantum capacitance for (16, 0) zig-zag graphene nanoscroll (ZGNS) is presented. The behavior of the quantum capacitance within the degeneracy limits is approximated using the Maxwell–Boltzmann approximation within a range of E - EF > 3KBT. The quantum capacitance is subsequently derived from the carrier density of the ZGNS due to its significance within one-dimensional (1D) devices by employing the Taylor's series expansion for parabolic energy band structure approximation. Additionally, the quantum capacitance analytical derivation in term of ZGNS physical form considering the Archimedean spiral-type structure is modeled. Because of its unique geometry structure which provides high area for intercalation, it is expected that ZGNS structure (length and interlayer distances) will alter the quantum capacitance. We also report that at first sub-band of (16, 0) ZGNS the quantum capacitance reach degenerate limit at approximately of ≅ 0.49 × 10-10 F/m @ 49 pF/m .

Preparation of Graphene Dispersion and Carbon Nanoscrolls

Abstract A novel versatile approach for the bulk and facile preparation of graphene dispersion with high concentration is developed, via sonication of graphite that is intercalated by a mixture of benzene derivative and N-methyl-2-pyrrolidone (NMP). Subsequently, graphene nanoscrolls, a new structure between graphene and nanotubes are obtained by heat treatment of graphene sheets.

Unique synthesis of graphene-based materials for clean energy and biological sensing applications

Graphene has unique physical properties, and a variety of proof-of-concept devices based on graphene have been demonstated. A prerequisite for the application of graphene is its production in a controlled manner because the number of graphene layers and the defects in these layers significantly influence transport properties. In this paper, we briefly review our recent work on the controlled synthesis of graphene and graphene-based composites, the development of methods to characterize graphene layers, and the use of graphene in clean energy applications and for rapid DNA sequencing. For example, we have used Auger electron spectroscopy to characterize the number and structure of graphene layers, produced single-layer graphene over a whole Ni film substrate, synthesized well-dispersed reduced graphene oxide that was uniformly grafted with unique gold nanodots, and fabricated graphene nanoscrolls. We have also explored applications of graphene in organic solar cells and direct, ultrafast DNA sequencing. Finally, we address the challenges that graphene still face in its synthesis and clean energy and biological sensing applications.

A novel synthesis of graphene nanoscrolls with tunable dimension at a large scale

Graphene nanoscrolls which could overcome the chirality dependence of metallic or semiconducting behavior in carbon nanotubes have been recently investigated and proposed for a wide variety of applications. In order to further improve their practical applications, a variety of synthetic approaches have been widely explored but with various limitations. For instance, it remains challenging to produce graphene nanoscrolls with tunable dimensions and high quantity, which greatly hinders their potential applications. Herein, we report a new and general approach to synthesize graphene nanoscrolls with accurately tunable widths and lengths at a large scale. The resulting high-quality graphene nanoscrolls show promising applications in a wide variety of electronic devices.

Nuclear spin–lattice relaxation and paramagnetic defects in carbon nanomaterials

We review recent nuclear spin–lattice relaxation studies of carbon nanomaterials, such as nanodiamonds, carbon onions, activated carbon fibers, graphene and carbon nanoscrolls. We show that a significant reduction in the relaxation time in nanoparticles compared with that in the bulk compounds and a stretched exponential magnetization recovery are caused by the interaction of nuclear spins with unpaired electron spins of paramagnetic defects, which creates an effective channel for the nuclear relaxation. We present a theoretical approach for such kind of relaxation in static and magic angle spinning regimes and explain a difference in the data received in these regimes. We also extend our approach for the case of additional contributions to the relaxation resulting from interaction of nuclear spin with conduction electrons and with adsorbed paramagnetic oxygen molecules. The developed approach allows correct interpreting of the NMR relaxation data and receiving useful information on properties of nanomaterials from the NMR measurements.

Self-Assembly of Graphene Nanoribbons with Unsaturated Edges

ABSTRACTWe studied the self-assembly mechanisms of Graphene Nanoribbon (GNR) with unsaturated edges and demonstrated the ability of GNR to self-assemble into novel stable structures. We proposed three mechanisms which dictate the self-assembly evolution of GNR with unsaturated edges. Using the Adaptive Intermolecular Reactive Empirical Bond-Order (AIREBO) potential, we performed molecular dynamics simulations on initially-planar GNRs with unsaturated edges. The simulation results showed that the self-assembly mechanisms and final conformations of the GNRs correlate well with the proposed GNR self-assembly mechanisms. Furthermore, the simulations also showed the ability of a narrow GNR to self-assemble into various nanostructures, such as tapered graphene nano-rings and graphene nanoscrolls with an embedded nanotube.

Fabrication of Carbon Nanoscrolls from Monolayer Graphene Controlled by P-Doped Silicon Nanowires: A MD Simulation Study

It is demonstrated using molecular dynamics (MD) simulations that P-doped silicon nanowires (Si NWs) can activate graphenes self-scrolling onto Si NWs and thus produce new kinds of graphene nanoscroll (NS)/Si core/shell heterojunctions. The simulations show that graphene sheets can fully self-scroll onto Si NWs when the Si NW radius is larger than a threshold of about 5 Å, forming a stable core/shell structure. It is the van der Waals force that plays a primary role in the self-scrolling process. The configuration of the graphene–Si heterojunction depends significantly on the diameter of the Si NWs. The final NS becomes multiwalled with increasing graphene length when the diameter of the Si NWs is larger than a threshold of about 6 Å. The zigzag NS is proved to be the most stable, while the chiral NSs are unstable and tend to evolve into zigzag NS and a model is set up to interpret the tendency from the standpoint of bond. It is demonstrated that the graphene width has no influence on the self-scrolling process at all. Compared with the conventional fabricating method, the new self-assembling one occurs at room temperature and the thickness of the NSs can be controlled accurately. Besides, the unique structure of the graphene/Si core/shell heterojunctions will significantly enhance their applications in nanoelectronic devices, hydrogen storage, solar cells, chemical or biological sensors, and energy storage in supercapacitors or batteries.

Fabrication of Carbon Nanoscrolls from Monolayer Graphene

A simple way of synthesizing carbon nanotube (CNT)/graphene (GN) nanoscroll core/shell nanostructures is demonstrated using molecular dynamics (MD) simulations. The simulations show that GN sheets can fully self-scroll onto CNTs when the CNT radius is larger than a threshold of about 10 A, forming a stable core/shell structure. Increasing the length of the GN sheet results in multilayered carbon nanoscroll (CNS) shells that exhibit a tubular structure similar to that of multiwall CNTs. The distances between the CNT and the GN wall or adjacent GN walls are about 3.4 A. It is found that the van der Waals force plays an important role in the formation of the CNT/GN nanoscroll core/shell-composite nanostructures. However, the chirality of the CNT and the GN sheet does not affect the self-scrolling process, which thus provides a simple way of controlling the chirality and physical properties of the resulting core/shell structure. It is expected that this preparation method of CNT/GN nanoscroll core/shell composites will lead to further development of a broad new class of carbon/carbon core/shell composites with enhanced properties and even introduce new functionalities to composite materials.