Applications Of Graphene Nanoribbons Research Articles

Graphene nanoribbons: High-quality conductive additive for high performance aqueous zinc-ion batteries

As an important part of the cathode of aqueous zinc-ion batteries (ZIBs), conductive additive plays an important role in its electrochemical performance. Herein, we initiate graphene nanoribbons (GNRs) as a novel conductive additive for ZIBs, and find that GNRs have satisfactory compatibility with different cathode materials and can form a unique “face-to-face” continuous conductive network within the electrode, thus achieve better comprehensive improvement effect on electrodes' electronic/ionic conductivity compared with traditional carbon black, and significantly improve the rate capability together with cycle stability. To be specific, the GNRs conductive additive successfully increased the specific discharge capacity of ZnxV2O5 from 389.5 mAh g−1 of acetylene black (365.1 mAh g−1 of ketjen black, 377.1 mAh g−1 of super P) to 487.0 mAh g−1 at 0.1 A g−1, and boosted the capacity retention rate from 66.8 % to 104.6 % after 5000 cycles at 5 A g−1. The effect of different amount of GNRs on the electrochemical properties of the cathode is also systematically explored. In addition, the specific discharge capacity of α-MnO2 is also enhanced by about 122 % at 0.1 A g−1. Therefore, the application of GNRs as a novel conductive additive for ZIBs provides an extremely promising path for the development of high-performance ZIBs.

Near infrared photoluminescence of the bottom-up produced 7-armchair graphene nanoribbons

The narrow graphene nanoribbons (GNRs) are carbon based nanomaterials with interesting optical and electronic properties. We studied the photoluminescence properties of narrow graphene nanoribbons synthesized via the chemical vapor deposition method based on the bottom-up approach. The structure and quality of the synthesized GNR films were confirmed by measuring the Raman fingerprints of the 7-armchair graphene nanoribbons. The produced 7-armchair GNRs have a wide optical bandgap with an excitonic photoluminescence peak maximum at 608 nm (2.04 eV). At the same time, the 7-armchair GNR suspension has a bright photoluminescence in the infrared spectrum range with a peak maximum at 910 nm (1.36 eV). The relative intensity of this peak increases upon adding the p-type dopant to the GNR solution. The energy 1.36 eV of this luminescent transition is in good agreement with the theoretically predicted energy of the lowest bright trion state in the freestanding 7-armchair graphene nanoribbons. The demonstrated results can be beneficial for further study of narrow GNRs, especially in optics, and can be useful in applications of GNRs.

Strain modulated carrier mobility and optical properties of graphene nanowiggles

Recently, synthesized Chevron graphene nanoribbons (CGNRs) and its laterally extended counterpart known as extended CGNRs (ECGNR) are constructed by making alternated regular cuts in pristine graphene nanoribbons (GNRs). First-principles calculations demonstrate that these GNRs are super-ductile and possess width-dependent mechanical properties. The Young’s modulus is calculated to be 389.4 GPa and 414.6 GPa for CGNR and ECGNR, respectively. The bandgap of these nanoribbons decreases on the application of tensile strain. The carrier effective masses are found to be highly sensitive towards mechanical strains. The holes (electrons) mobility of ECGNR is calculated to be 7.68 × 104 cm2 V−1 s−1 (1.69 × 104 cm2 V−1 s−1), which is higher than that of CGNR can be further enhanced by elongation. The prominent peaks of the imaginary part of dielectric function and electron energy loss spectra show redshift on increasing the tensile strain. The electron energy loss spectra show intense plasmonic structure in low energy spectrum indicating GNRs to be more sensitive to the visible region than ultra violet spectrum. Our results provide insight about the possible applications of GNRs in the fields of high-speed transistors, sensors, photonics, and optoelectronics.

From graphene to graphene ribbons: atomically precise cutting via hydrogenation pseudo-crack

The properties and applications of graphene nanoribbons (GNRs) depend heavily on their shape and size, making precise design and construction at atomic scale significantly important. Herein, we show that pseudo-cracking is a feasible method for creating atomically precise GNRs. By using molecular dynamics (MD) simulation, we find that hydrogenation can act as a pseudo-crack to trigger the fracture of graphene along the hydrogenation line and cut the graphene into a GNR. Precise GNRs with a desired width, edge type and associated properties can be realized in a controllable way by manipulating the position and dimension of the hydrogenation pseudo-crack. We also find that it is better to use hydrogenation pseudo-cracks along the armchair direction to cut graphene at lower forces into GNRs with smooth edges. Our findings suggest a promising approach to cut graphene and other two-dimensional materials into nanoribbons effectively and accurately.

Synthesis and characterization of graphene nanoribbons on hexagonal boron nitride

Graphene, as a typical representative of the two-dimensional material family, has received a wide attention due to its excellent physical and chemical properties. Graphene nanoribbon (GNR) is graphene in a width of several to a few tens of nanometers. GNRs not only inherit most of the excellent properties of graphene, but also have their own specific properties such as band gap opening and spin-polarized edge states, which make it the potential candidate in graphene based electronics in the future. Hexagonal boron nitride (h-BN), which has similar lattice constant with graphene, normally serves as an ideal substrate for graphene and GNRs. It can not only effectively preserve their intrinsic properties, but also benefit for the fabrication of electrical devices via popular semiconductor processes. In this paper, we reviewed the development history of research of graphene and GNRs on h-BN in recent years. The recent progress of physical properties is also discussed. In order to realize the large scale production of graphene and GNRs on h-BN, high quality h-BN multilayer is necessary. In addition, recent progresses about h-BN preparation methods are presented, and the progresses could pave the way for the further application of GNRs in the electronics. Finally, the research direction of graphene and GNRs on h-BN in the future is discussed.

Zigzag graphene nanoribbons separated by hydrogenation

As the integrated circuits continue to miniaturize, the narrower interconnect matched is needed. Using density functional theory combined with non-equilibrium Green's function, we try to adopt a row or a column of hydrogen atoms adsorbed on the zigzag graphene nanoribbons, which are in the middle parallel or perpendicular to the axial direction to limit the movement of π electron. The utilization of the adsorbed hydrogen row blocks the transport of electrons, zigzag graphene nanoribbons are divided into conductive and non-current part. Physically, the nanoribbons are separated laterally or longitudinally to two strips that contain fewer atoms, preserving the structural integrity of zigzag graphene nanoribbons. According to the transmission pathways after hydrogenation, there is almost no current flowing through the intermediate hydrogenated carbon chains when hydrogenated in the direction of the ribbon axis; while perpendicular to the ribbon axis, except for the loop current among the two edge carbon atoms and the hydrogenated carbon atoms, only a small part of the current flows along the zigzag axial direction. In the application of graphene nanoribbons, we usually want to use semiconductor nanoribbons as devices, and metal nanoribbons for interconnects. Our results indicate that zigzag graphene nanoribbons can be qualitatively separated into two narrower strips by regular adsorption of hydrogen to connect smaller devices.

Electron spin magnetism of zigzag graphene nanoribbon edge states

The electron spin states of zigzag graphene nanoribbon (ZGNR) edge play a pivotal role in the applications of graphene nanoribbons. However, the exact arrangements of the electron spins remain unclear to date. In this report, the electronic spin states of the ZGNR edge have been elucidated through a combination of quantum chemical investigation and previous electron spin resonance experiment observations. An alternating α and β spin configuration of the unpaired electrons along the ZGNR edge is established in ambient condition without any external magnetic field, and the origin of the spin magnetism of the ZGNR edge is revealed. It paves a pathway for the understanding and design of graphene based electronic and spintronic devices.

Synthesis and Application of Graphene Nanoribbons

Graphene, a single-atom-thick planar sheet of graphite with zero-band gap, has great potential applications in nanoelectrics, biosensing, energy storage owing to its unique electrical, mechanical, and physical properties. Graphene nanoribbons (GNRs) are narrow and straight-edged stripes of graphene sheets. They are predicted to exhibit band gaps useful for field-effect transistors with high on/off ratio and carrier mobility. Over the past few years, they have attracted increasing attentions and became the attractive candidates for carbon-based nanoelectronics. This review provides a brief overview on the synthesis, properties and applications of GNRs. The effects of synthetic process on their morphology and electronic properties are discussed in detail. In addition, the applications of graphene nanoribbons in different fields have also briefly presented. Keywords: Graphene nanoribbon, synthesis, application.

Electrical properties of platinum doped armchair graphene nanoribbons

The platinum-doped graphene has been achieved in our previous experiments. To further study the effects of metal doping on the band structures of graphene, and provide theoretical guidance for the next step of the experiment, we analyze the electronic properties of armchair graphene nanoribbons (AGNRs) with platinum atoms doping in the divacancy positions using first principle calculation based on density functional theory. The results show that the band structures of AGNRs can be effectively tailored by controlling the doping position on ribbons. Edge position is the most stable position for platinum atom. The band gaps of edge doped AGNRs can be shown in three curves like that of pristine AGNRs. However, they degenerate into two curves at large width, inhibiting the vibration of band gaps to some extent. In addition, several narrow platinum-doped AGNRs with width index Na = 3p and 3p + 1 have impurity level(s) in the band gap, reducing the large band gap effectively. Furthermore, band characteristics of platinum doped AGNRs are not sensitive to doping concentration, thus reducing the challenge of experimental precision. Our results will promote the application of graphene nanoribbons in the field of nano-electronics.

Twist-enhanced stretchability of graphene nanoribbons: a molecular dynamics study

Graphene nanoribbons (GNRs) have many applications in electronics due to their exceptional mechanical, electronic and thermal properties. In order to utilize GNRs for stretchable electronics, it is an important issue to enhance the stretchability of GNRs. In this work, we report that the stretchability of GNRs can be considerably strengthened by a small twist angle through molecular dynamics simulations. Compared with the tension simulation on untwisted GNRs, twist effect can help the C–C covalent bond go into large nonlinear deformation, when the twisted GNR is under tension. Therefore, the breaking strain of a twisted GNR can be 37.6% larger than that of an untwisted one at room temperature. At the same time, the stiffness of the twisted GNR could also be enhanced. Such results could be useful for further application of GNRs in stretchable electronics with multi-functionality.