Vortex fluidic mediated transformation of graphite into highly conducting graphene scrolls

Two-dimensional graphene has remarkable properties that are revolutionary in many applications. Scrolling monolayer graphene with precise tunability would create further potential for niche applications but this has proved challenging. We have now established the ability to fabricate monolayer graphene scrolls in high yield directly from graphite flakes under non-equilibrium conditions at room temperature in dynamic thin films of liquid. Using conductive atomic force microscopy we demonstrate that the graphene scrolls form highly conducting electrical contacts to highly oriented pyrolytic graphite (HOPG). These highly conducting graphite-graphene contacts are attractive for the fabrication of interconnects in microcircuits and align with the increasing interest in building all sp²-carbon circuits. Above a temperature of 450 °C the scrolls unravel into buckled graphene sheets, and this process is understood on a theoretical basis. These findings augur well for new applications, in particular for incorporating the scrolls into miniaturized electronic devices.

Evolution of magnetism by rolling up hexagonal boron nitride nanosheets tailored with superparamagnetic nanoparticles

Controlling tunable properties by rolling up two dimensional nanomaterials is an exciting avenue for tailoring the electronic and magnetic properties of materials at the nanoscale. We demonstrate the tailoring of a magnetic nanocomposite through hybridization with magnetic nanomaterials using hexagonal boron nitride (h-BN) templates as an effective way to evolve magnetism for the first time. Boron nitride nanosheets exhibited their typical diamagnetism, but rolled-up boron nitride sheets (called nanoscrolls) clearly have para-magnetism in the case of magnetic susceptibility. Additionally, the Fe₃O₄ NP sample shows a maximum ZFC curve at about 103 K, which indicates well dispersed superparamagnetic nanoparticles. The ZFC curve for the h-BN-Fe₃O₄ NP scrolls exhibited an apparent rounded maximum blocking temperature at 192 K compared to the Fe₃O₄ NPs, leading to a dramatic increase in T_B. These magnetic nanoscroll derivatives are remarkable materials and should be suitable for high-performance composites and nano-, medical- and electromechanical-devices.

Evolution of a high local strain in rolling up MoS2 sheets decorated with Ag and Au nanoparticles for surface-enhanced Raman scattering

We report that a high local strain was obtained for multilayer MoS₂ nanoscrolls decorated with noble nanoparticles (Ag and Au NPs) using a rolling process beyond breaking or slipping of MoS₂. The local strain was estimated through the bending strain in the nanoscrolls and the extent of coverage of Ag and Au NPs decorated on MoS₂, exhibiting magnified surface-enhanced Raman scattering. TEM images showed that the MoS₂-Ag and MoS₂-Au nanoscrolls have a tube-like morphology decorated with NPs on the inner and outer sides of the MoS₂ nanoscrolls. In the Raman spectra, we confirmed the red shift and broadness of the FWHM for nanoscrolls in the eigenvectors of the [Formula: see text] and [Formula: see text] modes. From the Grüneisen parameter γ and the shear deformation potential β, we obtained peak shifts of ∼4.9 cm^-1/% at [Formula: see text] and ∼1.1 cm^-1/% strain at [Formula: see text] for free-standing MoS₂. According to the obtained relationship of the Raman shift and the induced uniaxial tensile strain, the [Formula: see text] and [Formula: see text] peaks shifted upwards to around -12.8 cm^-1 and -2.9 cm^-1, respectively, and can be converted to an induced uniaxial tensile strain of about 2.6% for MoS₂-Ag nanoscrolls.

Highly thermal-stable paramagnetism by rolling up MoS2 nanosheets

Controlling phase transitions through local strain engineering is an exciting avenue for tailoring the electronic and magnetic properties of materials at the nanoscale. Herein, we demonstrate a tunable semiconducting to metallic phase transition of two-dimensional transition metal dichalcogenides using strain engineering through rolled up MoS₂ sheets (named as MoS₂ scrolls). A phase incorporated structure for MoS₂ nanoscrolls containing the maximum concentration of 1T phase (∼58%) with high thermal stability up to 473 K can be produced by a gliding-rolling process for the S plane. These phase transitions are irreversible by virtue of the van der Waals interaction between the layers of the nanoscrolls, which is relatively stronger than the bending strain. A high concentration of the 1T phase can tune the bandgap through temperature, and also the magnetic property from nonmagnetic to paramagnetic MoS₂. This study, which is able to control phase transitions by strain engineering in the field of 2D materials, proves an exciting avenue for tailoring the novel functional properties of low-dimensional materials.

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).