Graphene Scrolls Research Articles

Tribo-induced photoluminescent behavior of graphene and YSZ:Er/graphene composite films.

In the present work, a novel method was developed to study the evolving surface state of graphene film as it is subject to friction, characterized by photoluminescence properties. We prepared the graphene film (GF) and YSZ:Er (Er3+-Y3+ co-doped ZrO2)/graphene composite films (ZGCF). The Raman spectra and photoluminescence properties of the GF and ZGCF were characterized before and after the sliding friction. A remarkable phenomenon was observed that after friction the GF generated a more pronounced luminescence response than it had prior, apparently due to graphene quantum dots which were found in the wear debris of the GF. Furthermore, the introduction of graphene into YSZ:Er nanoparticles (NPs) resulted in an unmistakable red-shift on the main luminescence bands of ZGCF after the applied friction. This is explained by the formation of considerable graphene scrolls in the wear debris of ZGCF due to the interaction of the graphene and the YSZ:Er NPs. It can be concluded that changes to the configuration of graphene greatly influence the tribo-induced photoluminescence response. Our findings justify further investigation into the composition and morphology of worn surfaces in order to better understand how photoluminescence relates to frictional effects. In addition, this work proposes the in situ fabrication of graphene quantum dots and nanoscale scrolls as a new potential application of the tribo-induced photoluminescence study.

Controllable synthesis of graphene scrolls and their performance for supercapacitors.

A graphene scroll (GSC) is a new type of graphene-derivative material, that has widely attracted attention. However, the controllable preparation of GSCs is a major factor influencing their development and application. In this work, sodium citrate (SC) was added to a graphene oxide (GO) aqueous suspension and GSCs were controllably prepared on a large-scale by a cold quenching method. The results show that the number of scroll layers and the curling degree of the GSCs could be controlled by the quantity of SC added. The diameter of the GSCs increased when SC was added. Compared to the GSC without SC (265 nm), the average diameter of GSC(SC-40) (obtained by adding 40 mg SC to 100 mL GO solution (1 mg mL−1)) is 491 nm. When excessive SC was added, such as 100 mg, the average diameter reached 679 nm. Moreover, these GSCs were used as a supercapacitor electrode material and the electrochemical performance was tested. The specific capacitance of GSC(SC-40) (178 F g−1) is higher than that of the GSC without SC (107 F g−1) at the same current density of 1.0 A g−1. However, when a larger quantity of SC was added, the specific capacitance of the GSCs decreased. So, the number of scroll layers and the curling degree of the GSCs have a significant effect on the electrochemical properties of the supercapacitor.

Graphene scrolls coated Sb2S3 nanowires as anodes for sodium and lithium ion batteries

One-dimensional stibnite (Sb2S3) nanowires templated graphene scrolls (SbGSs) synthesized through two-step wet chemical processes have been applied as anode materials for lithium-ion and sodium-ion batteries (LIB, NIB), where they delivered high reversible capacity of 690 mAh g−1 and 680 mAh g−1 at a current density of 50 mA g−1 without any capacity fading after 50 cycles both in LIB and NIB. Increased current density up to 2000 mA g−1, discharge capacity of 457.6 mAh g−1 in LIB and 444.8 mAh g−1 in NIB can be obtained, indicating that NIB performance is rival to LIB. Further study on optimizing electrolyte manifested that 1 M NaClO4 in ethylene carbonate/dimethyl carbonate (EC/DMC) promoted the electrochemical performance of NIB.

Field Electron Emission From CVD Nanocarbon Films Containing Scrolled Graphene Structures

Electron field emission properties of nanocarbon films produced by plasma‐enhanced chemical vapor deposition (PECVD) were investigated. The films contained nanostructured diamond and graphitic components in different ratios depending on the parameters of the deposition process. Low threshold fields in the range of 1–2 V μm−1 (at 0.1 mA cm−2) are detected for all types of the studied films. It is found that the scrolled graphene structures, contained in the film material, are responsible for the field emission. The individual graphene scrolls show standard Fowler–Nordheim behavior and sustained maximum field emission currents of several microamperes. Long‐time field emission at moderate currents causes partial destruction of the scrolls that significantly changed the threshold field and emission site density of the films. Obtained results show that PECVD growth and post‐treatments allow monitoring of the amount and heights of emission centers providing tailored field emission properties of nanocarbon films for particular applications in vacuum electronic devices.

Synergistic friction-reducing and anti-wear behaviors of graphene with micro- and nano-crystalline diamond films

In present study, a layer of continuous and compact graphene coating was deposited on the surface of microcrystalline diamond (MCD) and nanocrystalline diamond (NCD) film by electrophoretic deposition (EPD) method. The tribological performance of as-deposited films, referred as Gr/MCD and Gr/NCD respectively, was investigated in a set of ball-on-plate reciprocating friction tests in ambient atmosphere (60% RH). Under a normal load of 4N (corresponding to a contact pressure of 770MPa), the stable COF of Gr/MCD film reduced by 60% compared with that of MCD film, which decreased from 0.166 to 0.068; in contrast, the stable COF of Gr/NCD film was comparable with that of NCD film, which were measured as 0.069 and 0.074 respectively. For the Gr/MCD film, the unique surface morphology of underneath MCD film was supposed to play a crucial role on its exceptional friction performance. It produced a plenty of wear particles during the run-in sliding stage and a large portion of these particles were trapped in the sliding interface. During the following stable sliding stage, graphene scrolls formed by graphene sheets wrapping around the wear particles they encountered and attributed to the reduction in friction by decreasing the interfacial contact area and forming an incommensurable contact between the graphene scrolls and counterpart surface. For the Gr/NCD film, in contrast, the absence of wear particles on its sliding interface and structural degradation in its top-layered graphene sheets was supposed to result in its failure in reducing friction. Different from the Gr/MCD film, the residual graphene flakes on the worn surface of Gr/NCD film were transformed to disordered graphitic structures; meanwhile, increased defects and severe oxidation effect were detected in them. Furthermore, due to the exceptional protection effect of graphene coating, the Gr/MCD and Gr/NCD film produced severer wear on the counterface than the MCD and NCD film.

Nitrogen‐Doped Graphene Ribbon Assembled Core–Sheath MnO@Graphene Scrolls as Hierarchically Ordered 3D Porous Electrodes for Fast and Durable Lithium Storage

Graphene scroll is an emerging 1D tubular form of graphitic carbon that has potential applications in electrochemical energy storage. However, it still remains a challenge to composite graphene scrolls with other nanomaterials for building advanced electrode configuration with fast and durable lithium storage properties. Here, a transition‐metal‐oxide‐based hierarchically ordered 3D porous electrode is designed based on assembling 1D core–sheath MnO@N‐doped graphene scrolls with 2D N‐doped graphene ribbons. In the resulting architecture, porous MnO nanowires confined in tubular graphene scrolls are mechanically isolated but electronically well‐connected, while the interwoven graphene ribbons offer continuous conductive paths for electron transfer in all directions. Moreover, the elastic graphene scrolls together with enough internal voids are able to accommodate the volume expansion of the enclosed MnO. Because of these merits, the as‐built electrode manifests ultrahigh rate capability (349 mAh g−1 at 8.0 A g−1; 205 mAh g−1 at 15.0 A g−1) and robust cycling stability (812 mAh g−1 remaining after 1000 cycles at 2.0 A g−1) and is the most efficient MnO‐based anode ever reported for lithium‐ion batteries. This unique multidimensional and hierarchically ordered structure design is believed to hold great potential in generalizable synthesis of graphene scrolls composited with oxide nanowires for mutifuctional energy storage.

3D Hierarchical Anode Configuration Composed of Ultralong N-Doped Graphene Scrolls-Wrapped MnO Nanowires for High-Performance Li-Ion Batteries

Transition metal oxides (TMOs) have been touted as one of the most promising anode materials for next generation lithium ion batteries (LIBs). Yet, how to build energetic TMOs-based electrode architectures by addressing the structural and interfacial stability issues facing TMOs anodes still remains a big challenge. Here, we design and fabricate a novel 3D hierarchical anode configuration composed of ultralong porous MnO nanowires (NWs) wrapped within nitrogen-doped graphene scrolls (GSC) which themselves interlinked and embedded in continuous interconnected networks of nitrogen-doped graphene ribbons (GR). Such a hybrid material (namely, MnO@N-GSC/GR) with plenty of internal void space is totally in an ordered 3D hierarchical porous architecture by taking the advantage of multi-scale and multi-dimensional integration of nanoscaled MnO and graphene building blocks, which can address all the issues related to MnO dissolution, conversion, aggregation and volumetric expansion during the Li+ insertion/extraction. As a result, the 3D hierarchical MnO@N-GSC/GR serves high-performance anode materials for LIBs with a very high reversible specific capacity (as high as 765 mAh g-1 at even 1000 mA g-1) and ultrafast rate capability (349 and 201 mAh g-1 at 8000 and 15000 mA g-1, respectively), as well as excellent discharge and charge capabilities (rapidly charged to 86.7% and 79.9% in 10.5 and 4.6 min, respectively, using the constant current mode). Most importantly, such the robust MnO@N-GSC/GR electrode shows no capacity fading even after 1000 cycles at a high current density of 2000 mA g-1, and no morphology change. The as-built 3D hierarchical MnO@N-GSC/GR is the most efficient MnO-based anode materials ever reported for LIBs.

Graphene-Oxide-Directed Hydrothermal Synthesis of Ultralong M(VO3)n Composite Nanoribbons

New strategies for 1D materials fabrication are of fundamental importance in the advancement of science and technology. Instead of the small organic amine molecule- and the polymer-directed agent, here, we report a unified graphene-oxide-directed agent for the synthesis of a series of nanoribbons with different chemistries and with low dispersity, including V2O5, AgVO3, and Sr(VO3)2. This strategy is based on a general linear growth of vanadate and a splitting mechanism of graphene oxide during the synthesis. We believe our methodology provides a simple and convenient route to a variety of nanoribbon building blocks for assembling materials with novel structure and function in nanotechnology. More important is that graphene is in the middle of the composite structure; while supporting the main structure, it does not affect the mass transfer process. Compared to other composite structures based on graphene, such as graphene scroll and graphene sheet, graphene ribbon is more suitable for lithium-ion battery.

One-Dimensional Nanomaterials for Energy Storage

One-dimensional nanomaterials can offer large surface area, facile strain relaxation upon cycling and efficient electron transport pathway to achieve high electrochemical performance. Hence, nanowires have attracted increasing interest in energy related fields. To increase the stability of Li-ion battery, V3O7 nanowire templated semi-hollow bicontinous graphene scrolls architecture is designed and constructed through “oriented assembly” and “self-scroll” strategy. The V3O7 nanowire templated semi-hollow bicontinous graphene scrolls with interior cavities provide continuous electron and lithium ion transfer channel and space for free volume expansion of V3O7 nanowires during cycling, thus representing a unique architecture for excellent lithium ion storage capacity and cycling performance. Besides, we have designed and synthesized hierarchical MnMoO4/CoMoO4 heterostructured nanowires by combining "oriented attachment" and "self-assembly". The asymmetric supercapacitors based on the hierarchical heterostructured nanowires show a high specific capacitance and good reversibility with a cycling efficiency of 98% after 1,000 cycles. Recently, we also constructed the hierarchical zigzag Na1.25V3O8 nanowires, K3V2(PO4)3 bundled nanowire, and Li3V2(PO4)3 mesoporous nanotubes with enhanced electrochemical performance. Our work presented here can inspire new thought in constructing novel one-dimensional nanostructures and accelerate the development of energy storage appilications.

Symmetric scrolled packings of multilayered carbon nanoribbons

Scrolled packings of single-layer and multilayer graphene can be used for the creation of supercapacitors, nanopumps, nanofilters, and other nanodevices. The full atomistic simulation of graphene scrolls is restricted to consideration of relatively small systems in small time intervals. To overcome this difficulty, a two-dimensional chain model making possible an efficient calculation of static and dynamic characteristics of nanoribbon scrolls with allowance for the longitudinal and bending stiffness of nanoribbons is proposed. The model is extended to the case of scrolls of multilayer graphene. Possible equilibrium states of symmetric scrolls of multilayer carbon nanotribbons rolled up so that all nanoribbons in the scroll are equivalent are found. Dependences of the number of coils, the inner and outer radii, lowest vibrational eigenfrequencies of rolled packages on the length L of nanoribbons are obtained. It is shown that the lowest vibrational eigenfrequency of a symmetric scroll decreases with a nanoribbon length proportionally to L –1. It is energetically unfavorable for too short nanoribbons to roll up, and their ground state is a stack of plane nanoribbons. With an increasing number k of layers, the nanoribbon length L necessary for creation of symmetric scrolls increases. For a sufficiently small number of layers k and a sufficiently large nanoribbon length L, the scrolled packing has the lowest energy as compared to that of stack of plane nanoribbons and folded structures. The results can be used for development of nanomaterials and nanodevices on the basis of graphene scrolled packings.

One-Dimensional Nanomaterial for Energy Storage

One-Dimensional nanomaterials with large surface area, more surface active sites and better permeability can significantly increase the energy density, power density and cycling performance for the energy storage. Such hierarchical structure can also be used as targeted intracellular recording for its facile synthesis route. In our present work, a series of hierarchical nanomaterials have been obtained, including kinked hierarchical nanowires, hierarchical heterostructured nanowires and hierarchical scrolled nanowires which shows great electrochemical. To increase the stability of Li-ion battery, V3O7 nanowire templated semi-hollow bicontinous graphene scrolls architecture is designed and constructed through “oriented assembly” and “self-scroll” strategy. The V3O7 nanowire templated semi-hollow bicontinous graphene scrolls with interior cavities provide continuous electron and lithium ion transfer channel and space for free volume expansion of V3O7 nanowires during cycling, thus representing a unique architecture for excellent lithium ion storage capacity and cycling performance. 1 Besides, we have designed and synthesized hierarchical MnMoO4/CoMoO4 heterostructured nanowires by combining "oriented attachment" and "self-assembly". The asymmetric supercapacitors based on the hierarchical heterostructured nanowires show a high specific capacitance and good reversibility with a cycling efficiency of 98% after 1,000 cycles. 2 Recently, we also constructed the hierarchical zigzag Na1.25V3O8 nanowires, 3 K3V2(PO4)3 bundled nanowire, 4 and Li3V2(PO4)3 mesoporous nanotubes 5 with enhanced electrochemical performance. Our work presented here can inspire new thought in constructing novel nanofiber/nanowire structures and accelerate the development of energy storage appilications. References (1) Yan, M. Y. et al., J. Am. Chem. Soc. 2013, 135, 18176-18182. (2) Mai, L. Q. et al., Nature Commun. 2011, 2, 381. (3) Dong, Y. F. et al., Energy Environ. Sci. 2015, 8, 1267. (4) Wang, X. P. et al., Adv. Energy Mater. 2015, 5(17). (5) Niu, C. J. et al., Nature Commun. 2015, 6, 7402.

Novel scroll peapod produced by spontaneous scrolling of graphene onto fullerene string.

Novel scroll peapods are fabricated simply by utilizing the spontaneous scrolling mechanism of graphene onto fullerene string. The basic interaction between the graphene and the fullerene string is investigated, and the mechanism of the formation of the scroll peapod is explained in particular. The formation of the scroll peapod and its formation time are influenced by the combined effects of fullerene number, diameter and graphene size. It is also worth noting that narrow graphene nanoribbon wrapped onto a C720 bean can form a particular helical peapod. Higher temperature slows the scrolling dynamics, and even hinders the formation of the scroll peapod. This study provides a scientific basis for producing scroll peapods simply, and eventually their applications in various areas.

Facile preparation of nitrogen-doped graphene scrolls via acoustic cavitation as electrocatalyst for glucose biosensing

Nitrogen doping is considered as a promising strategy to tailor and develop the intrinsic properties of graphene. In this work, we report a facile method for preparation of nitrogen-doped graphene scrolls (N-GSS) through acoustic cavitation, which can not only realize graphene nitrogen doping but also simultaneously result in its scrolled topological structure and improvement of reduction degree. As a metal-free electrocatalyst, the prepared N-GSS showed good electrocatalytic activity towards oxidation of hydrogen peroxide with the sensitivity of 87.8 μA mM−1 cm−2. Then N-GSS was employed as a matrix for glucose oxidase (GOD) loading, and the fabricated biosensor also exhibited excellent analytical characteristics, such as a high sensitivity (55.2 μA mM−1 cm−2), wide linear range (2 μM to 3.56 mM, R = 0.999) and low detection limit (1 μM).

Phosphorus Nanoparticles Encapsulated in Graphene Scrolls as a High‐Performance Anode for Sodium‐Ion Batteries

AbstractTwo composites of phosphorus nanoparticles encapsulated in graphene scrolls (P‐G) and phosphorus nanoparticles loaded on planar graphene sheets (P/G) were successfully prepared and applied as anodes for sodium‐ion batteries. Phosphorus nanoparticles (ca. 100–150 nm) were firstly obtained from commercial red phosphorus by using a simple flotation method. P‐G composites with different phosphorus contents (38.6, 52.2, and 62.1 %) were synthesized through a quick‐freezing process. In addition, the P/G composite with a phosphorus content of 50.8 % was prepared for comparison purposes. As a result, the P‐G composites showed a better performance than the P/G composite. Moreover, the P‐G composite with a phosphorus content of 52.2 % showed the best performance, delivering a capacity of 2355 mAh g−1 in the second cycle and 2172 mAh g−1 after 150 cycles at 250 mA g−1 (with a capacity retention of 92.3 %).

Synthesis of FeCo-reduced graphene oxide composite and its magnetic and adsorption properties

The composite of FeCo and reduced graphene oxide (RGO) was synthesized via a facile ultrasonic chemical method. FeCo nanoparticles were firmly dispersed on the surfaces of RGO nanosheets. Interestingly, the graphene scrolls were also observed in the composite. The composite exhibited excellent magnetic property with specific saturation magnetization (Ms) of 78.06emu/g and strong adsorption for Rhodamine-B. The comprehensive properties made the composite have great potential applications in water treatment.

Structure, morphology, and elemental composition of arc discharge evaporation products obtained with a graphite cathode and a composite anode

This paper presents a study of arc discharge sputtering products obtained with metal-graphite anodes. The sputtering products are shown to contain carbides of all the metals studied, except for nickel and copper carbides. Most of the sputtering products contain spheroidal metal or carbide particles, fullerenes, nanotubes, and filaments up to 2 μm in diameter. The surface of the particles is typically covered with carbon multilayers. In some cases, multilayer graphene scrolls are present, which is tentatively attributed to the catalytic effect of the metals or metal carbides. In the case of the C-Nb anode, the sputtering products contain faceted niobium carbide microcrystals up to 300 μm in size.

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.

Ultralow-frequency shear modes of 2-4 layer graphene observed in scroll structures at edges

The in-plane shear modes between neighbor-layers of 2-4 layer graphenes (LGs) and the corresponding graphene scrolls rolled up by 2-4LGs were investigated by Raman scattering. In contrast to that just one shear mode was observed in 3-4LGs, all the shear modes of 3-4LGs were observed in 3-4 layer scrolls (LSs), whose frequencies agree well with the theoretical predication by both a force-constant model and a linear chain model. In comparison to the broad width (about 12cm$^{-1}$) for the G band in graphite, all the shear modes exhibit an intrinsic line width of about 1.0 cm$^{-1}$. The local electronic structures dependent on the local staking configurations enhance the intensity of the shear modes in corresponding 2-4LSs zones, which makes it possible to observe all the shear modes. It provides a direct evidence that how the band structures of FLGs can be sensitive to local staking configurations. This result can be extended to n layer graphene (n > 4) for the understanding of the basic phonon properties of multi-layer graphenes. This observation of all-scale shear modes can be foreseen in other 2D materials with similar scroll structures.

Nanowire Templated Semihollow Bicontinuous Graphene Scrolls: Designed Construction, Mechanism, and Enhanced Energy Storage Performance

Graphene scrolls have been widely investigated for applications in electronics, sensors, energy storage, etc. However, graphene scrolls with tens of micrometers in length and with other materials in their cavities have not been obtained. Here nanowire templated semihollow bicontinuous graphene scroll architecture is designed and constructed through "oriented assembly" and "self-scroll" strategy. These obtained nanowire templated graphene scrolls can achieve over 30 μm in length with interior cavities between the nanowire and scroll. It is demonstrated through experiments and molecular dynamic simulations that the semihollow bicontinuous structure construction processes depend on the systemic energy, the curvature of nanowires, and the reaction time. Lithium batteries based on V3O7 nanowire templated graphene scrolls (VGSs) exhibit an optimal performance with specific capacity of 321 mAh/g at 100 mA/g and 87.3% capacity retention after 400 cycles at 2000 mA/g. The VGS also shows a high conductivity of 1056 S/m and high capacity of 162 mAh/g at a large density of 3000 mA/g with only 5 wt % graphene added which are 27 and 4.5 times as high as those of V3O7 nanowires, respectively. A supercapacitor made of MnO2 nanowire templated graphene scrolls (MGSs) also shows a high capacity of 317 F/g at 1A/g, which is over 1.5 times than that of MnO2 nanowires without graphene scrolls. These excellent energy storage capacities and cycling performance are attributed to the unique structure of the nanowire templated graphene scroll, which provides continuous electron and ion transfer channels and space for free volume expansion of nanowires during cycling. This strategy and understanding can be used to synthesize other nanowire templated graphene scroll architectures, which can be extended to other fabrication processes and fields.

Atomic simulation of the formation and mechanical behavior of carbon nanoscrolls

The process of the formation of a carbon nanoscroll (CNS) from a planar monolayer graphene, initiated by a single-walled carbon nanotube (SWCNT), is investigated by using molecular dynamics simulations. The results show that once the radius of the SWCNT is above a critical value, the SWCNT can activate and guide the rolling of the graphene, and finally form a CNS with the SWCNT inside. During the process of forming the CNS, the van der Waals force plays an important role. The influences of nickel atoms on the formation and mechanical behavior of the CNS are also studied. The results show that there is no appreciable difference between the self scrolling of an ideal graphene (without nickel atoms) and that of a graphene with nickel atoms except for the different times required for the scrolling. The simulations also indicate that adding nickel atoms to two opposite edges (paralleling to the SWCNT axis) of the graphene before rolling is an effective strategy to increase the structural stability and critical buckling load of the CNS.