Graphene Scrolls Research Articles

Metallic-nanowire–induced spontaneous scrolling of graphene nanostructures

Molecular-dynamics simulations have been performed to investigate metallic-nanowire (NW) induced spontaneous scrolling of single-layered graphene (SLG) nanostructures. This unique behavior is attributed to the van der Waals attraction between the SLG and NW and theπ-π stacking effect between SLG layers. The scrolling velocity shows a nonlinear dependence on time. Such self-scrolling of SLG is hindered by the surface roughness and especially the oxygen concentration of NW. SLGs with arbitrary sizes and shapes can wrap onto NW to form various configurations. The proposed discoveries eventually provide a powerful way to fabricate nanoscale composite materials and devices and tune their properties.

Hydrogenation enabled scrolling of graphene

Hydrogenation of graphene leads to local bond distortion of each hydrogenated carbon atom. Therefore, programmable hydrogenation of graphene can open up new pathways to controlling the morphology of graphene and therefore enable the exploration of graphene-based unconventional nanomaterials. Using molecular dynamics simulations, we show that single-sided hydrogenation can cause the scrolling of graphene. If a proper size of the graphene is hydrogenated on one side, the graphene can completely scroll up into a carbon nanoscroll (CNS) that remains stable at room temperature. We perform extensive simulations to delineate a diagram in which three types of scrolling behaviour of partially single-sided hydrogenated graphene are identified in the parameter space spanned by the hydrogenation size and the graphene size. Such a diagram can serve as quantitative guidelines that shed important light on a feasible solution to address the challenge of fabricating high-quality CNSs, whose open topology holds promise to enable novel nanodevices.

Supercapacitors based on high-quality graphene scrolls

High-quality graphene scrolls (GSS) with a unique scrolled topography are designed using a microexplosion method. Their capacitance properties are investigated by cyclic voltammetry, galvanostatic charge-discharge and electrical impedance spectroscopy. Compared with the specific capacity of 110 F g(-1) for graphene sheets, a remarkable capacity of 162.2 F g(-1) is obtained at the current density of 1.0 A g(-1) in 6 M KOH aqueous solution owing to the unique scrolled structure of GSS. The capacity value is increased by about 50% only because of the topological change of graphene sheets. Meanwhile, GSS exhibit excellent long-term cycling stability along with 96.8% retained after 1000 cycles at 1.0 A g(-1). These encouraging results indicate that GSS based on the topological structure of graphene sheets are a kind of promising material for supercapacitors.

Facile Preparation of High‐Quality Graphene Scrolls from Graphite Oxide by a Microexplosion Method

High-quality graphene scrolls with several possible conformations are designed using a facile microexplosion method under an ultrasonic reaction between MnO2 and H2O2. The as-obtained graphene scrolls exhibit a tubular structure. The methodology successfully realizes the transformation from a 2D material to a nearly 1D material.

Epoxy/graphene platelets nanocomposites with two levels of interface strength

Graphene platelets (GP) are a novel class of nanofillers due to its good compatibility with most polymers, high aspect ratio, high absolute strength and cost-effectiveness. We in this study synthesised two types of epoxy/GP nanocomposites with different interface strength using the combination of sonication and chemical modification. Although the surface-modified graphene platelets (m-GP) formed clusters, a higher degree of dispersion and exfoliation of graphene was observed in each cluster owning to the improved interface by modification. The scrolling of graphene was found predominantly in the interface-modified nanocomposite. At 4 wt%, the modified nanocomposite shows fracture energy release rate G1c 613.4 J m−2, while the unmodified nanocomposite indicates 417.3 J m−2, in comparison with neat epoxy G1c 204.2 J m−2. The interface modification enhanced the glass transition temperature of neat epoxy from 94.7 to 108.6 °C, 14.7% increment. Toughening mechanisms are attributed to the voiding, microcracking and breakage of GP, while matrix may not consume as much fracture energy as m-GP do.

Observations of the electrical behaviour of catalytically grown scrolled graphene

Carbon nanoscrolls, made of rolled up graphene, are expected to show unique electronic properties different from those of nested multi-wall tubes. Here we report in situ TEM observations and electrical measurements of the transport and breakdown behaviour of catalytically grown, multi-turn monochiral graphene scrolls, 30–65 nm in outer diameter. Generally, the low-bias IV region proved strictly linear Ohmic behaviour, non-linear increase in conductance occurred beyond an applied voltage of ∼0.4 V. Excellent maximum conductance values up to G ∼ 63 G 0 and sustainable current-carrying capacities up to J = 8.5 × 10 8 A/cm 2 were found in the most successful samples right before electric breakdown. Inferior values are ascribed to defect-rich or semiconducting scrolls. This study emphasizes the promising nature of carbon nanoscrolls for a number of electronic device applications.

Conformation Transition of Single-Layer Graphene and Its Raman Spectroscopy

In this work, we report conformation transitions of pristine exfoliated graphenes after they are coated with a layer of polymethyl methacrylate and baked at 180 degrees C. Optical microscopes, scanning electron microscope are used to characterize the morphology changes. In the meantime, the characteristics of their Raman spectra are also studied before and after the conformation transition. After the transition, D-phonon mode in the Raman spectroscopy appears; G- and 2D-phonon modes show blue shift as well as broadening. It is suggested that the scrolling and curvature of graphene are responsible for these Raman characteristics. These results indicate the modification of the intrinsic properties of single-layer graphene during the standard device fabrication processes.