Interaction Of Graphene Research Articles

Interaction of water with nitrogen-doped graphene

We have studied the interaction of water and graphene doped with nitrogen in different configurations, namely, graphitic and pyridinic nitrogen, by means of the van der Waals density functional. We found that the local nitrogen configuration plays a key role in determining the stable water configuration, while the dispersion force is responsible for the water adsorption. With the graphitic nitrogen, water prefers to orient with its oxygen toward the surface, whereas for the pyridinic nitrogen it prefers to orient with its hydrogens toward the surface, because nitrogen is positively and negatively charged for the former and the latter, respectively. Our results have great implications for the modeling of the interface between water and nitrogen-doped graphitic systems.

Examining the optical model of graphene via the photonic spin Hall effect.

In modern optics, there are two general models to describe the behavior of light in graphene: the zero-thickness model and the slab model. The difference in physical phenomena predicted by the two models is very small, which is hardly distinguished by traditional measurement methods. Therefore, which model can describe the light-matter interaction in graphene more exactly is still a challenging issue. In this work, based on the sensitive optical phenomenon called the photonic spin Hall effect, the small difference can be magnified to a detectable level by the weak-value amplification. The experimental results show that the zero-thickness model can more accurately describe the interaction between light and monolayer or bilayer graphene, while the case of more than two layers, which can no longer be regarded as two-dimensional thickness, should be described by the slab model. Our results may provide information on light interacting with graphene for future investigation in photonics and optoelectronics.

Raman Linewidth Contributions from Four-Phonon and Electron-Phonon Interactions in Graphene.

The Raman peak position and linewidth provide insight into phonon anharmonicity and electron-phonon interactions in materials. For monolayer graphene, prior first-principles calculations have yielded decreasing linewidth with increasing temperature, which is opposite to measurement results. Here, we explicitly consider four-phonon anharmonicity, phonon renormalization, and electron-phonon coupling, and find all to be important to successfully explain both the G peak frequency shift and linewidths in our suspended graphene sample over a wide temperature range. Four-phonon scattering contributes a prominent linewidth that increases with temperature, while temperature dependence from electron-phonon interactions is found to be reversed above a doping threshold (ℏω_{G}/2, with ω_{G} being the frequency of the G phonon).

Investigation of crack detection properties of elastomer-based nanocomposites under cyclic strain loading with graphene and carbon black interaction filler

In this study, the synergistic effect created by adding Graphene (GE) nanoplatelets and carbon black (CB) fillers to the rubber matrix was used to determine the high stretchable sensor properties. GE and CB-filled rubber nanocomposite (HcN) strain sensors have been shown to detect and trace crack initiation and crack propagation of different sizes under cyclic loading. Tests were performed with four different crack sizes (0, 2.5, 5, and 10 mm) at five different strain levels (0%, 5%, 10%, 15%, and 20%) to determine the strain sensing performance of the specimens. The electrical response of HcNs under loading was measured with the four-point probe technique and recorded with a high-performance data acquisition system. The progression of external cracks created by scalpel on HcNs was examined by measuring electrical resistance changes caused by cyclic strain loading between 0% and 20%. The electrical response of 4 phr and 8 phr filled HcNs behaved qualitatively similar to each other, while 1 phr filled HcNs showed a significantly different response in terms of quality and quantity. In 4 phr GE-filled specimens, the resistance increase was changed steadily depending on the crack length, and unstable conditions occurred at 5 and 10 mm crack lengths at 1 and 8 phr GE filler ratios. The flexible and stretchable elastomer-based conductive strain sensing sensors, developed with the synergistic interaction of well-dispersed carbon-based fillers in the matrix, can detect and record damaged conditions caused by cyclic loading in many application areas.

Selective enhancement of Kane Mele-type spin-orbit interaction in graphene

In order to enhance the spin orbit interaction (SOI) in graphene for seeking the dissipationless quantum spin Hall devices, unique Kane-Mele-type SOI and high mobility samples are desired. However, the common external modification of graphene often introduces “extrinsic” Rashba-type SOI, which will destroy the possible topological state, bring a certain degree of impurity scattering and reduce the sample mobility. Here we show that by the EDTA-Dy molecule dressing, the carrier mobility is even improved, and the quantum Hall plateaus are observed more clearly. The Kane-Mele type SOI is mimicked after dressing, which is evidenced by the suppressed weak localization at equal carrier densities and simultaneous Elliot-Yafet spin relaxation. This is attributed to the spin-flexural phonon coupling induced by the enhanced graphene ripples, as revealed by the in-plane magnetotransport measurement.

Polarization-sensitive switchable display through critical coupling between graphene and a quasi-BIC.

Enhanced light-matter interaction of a local field is of prime importance in optics as it can improve the performance of nanophotonic devices. Such enhancement can be achieved by utilizing the optical bound states in the continuum (BICs). In this study, a dielectric metasurface is proposed that could enhance the light-matter interactions in graphene. A symmetry-protected BIC was observed in such a metasurface, which could transform into a quasi-BIC with a high quality (Q-) factor when the in-plane symmetry is broken. As the graphene monolayer was introduced into the system, its absorption was enhanced by the quasi-BIC resonance. By optimizing the graphene Fermi energy and the asymmetry parameter of the metasurface to satisfy the critical-coupling condition, a tunable absorber could be achieved. The absorbing intensity could be efficiently modulated by varying the polarization direction of the incident light, the maximum difference of which was up to 95.4%. Also, further investigation showed that such a feature indicates potential application in digital switches and image displays, which could be switched by incident polarization only, and therefore without dependence on an additional structural change.

The rheological and mechanical properties of natural rubber/graphene composites

This research focuses on the use of graphene as a filler for natural rubber (NR). The purpose of using graphene is to improve the mechanical properties of rubber compounds and their processing characteristics. Graphene (G) consists of carbon atoms and is an essential filler for polymers to enhance electrical and mechanical properties. The addition of graphene to rubber can improve the wear resistance and mechanical strength of rubber products. Thus, the effect of the graphene filler composition is interesting to study. Variety of graphene loads (10, 20, and 30 part hundred rubber (phr)) were combined with a variety of sulfur fillers (S) (10 and 20 phr) and then composited with natural rubber. The effect of variations in a load of graphene and sulfur fillers on the rheological properties, abrasion resistance, and compression set were studied. The results showed that the optimal combination of the G/S load variation was 20/10 phr. It leads to a more extraordinary strengthening ability that is binding rubber molecules so that the interactions occurred, both physical and chemical, could be formed better with the NR molecular chain. This resulted in distinct rheological properties enhancement such as torque modulus and curing time. In contrast, the mechanical properties like abrasion resistance and compression set were still good. The FTIR Spectra of natural rubber-graphene composites confirmed that good filler disperses were obtained due to several intramolecular interactions of carbon graphene with NR molecules. Graphene can be used as a filler for rubber products, mainly rubber, abrasion, and compression resistant, and an alternative for commercial fillers.

Understanding the interaction of N-doped graphene and sulfur compounds in a lithium–sulfur battery: a density functional theory investigation

Pyrrolic N has the strongest adsorption toward Li2Sx mainly via forming the coordination bond of LiN3.

On the effects of induced polarizability at the water-graphene interface via classical charge-on-spring models.

Molecular models of the water-graphene interaction are essential to describe graphene in condensed phases. Different challenges are associated with the generation of these models, in particular π-π and dispersion interactions; thus quantum and classical models have been developed and due to the numerical efficiency of the latter, they have been extensively employed. In this work, we have systematically studied, via molecular dynamics, two polarizable graphene models, denominated CCCP and CCCPD, employing the charge-on-spring model of the GROMOS forcefield, both being compatible with the polarizable water models COS/G2 and COS/D2, respectively. These models were compared with non-polarizable graphene and SPC water models. We focused the study on the water-graphene interface in two distinct systems and under the influence of an electric field: one composed of graphene immersed in water and the other composed of graphene with a water droplet above it. In the former, the orientation of water close to the graphene layer is affected by polarizable graphene in comparison to non-polarizable graphene. This effect is emphasised when an electric field is applied. In the latter, carbon polarizability reduced water contact angles, but graphene retained its hydrophobicity and the computed angles are within the experimental data. Given the significant extra computational cost, the use of polarizable models instead of the traditional fixed-charged approach for the graphene-water interaction may be justified when polarizability effects are relevant, for example, when applying relatively strong fields or in very anisotropic systems, such as the vacuum-bulk interface, as these models are more responsive to such conditions.

Transmissive terahertz amplifier based on optically pumped graphene-dielectric hybrid resonators

Amplification of terahertz radiation is achieved by combining optically pumped graphene with a dielectric resonant cavity through numerical simulation. Graphene is attached to a one-dimensional grating and sandwiched between two distributed Bragg reflectors. The whole cavity enhances the interaction of graphene with the terahertz wave while being transparent to the pump light. When the femtosecond pulse pump light at 1.5 µm with the peak intensity of 8.7 W / m m 2 is considered, graphene is driven to a gain medium. Due to the enhancement of the cavity and the proper complex conductivity of graphene, the amplitude of the transmitted beam is amplified 172 times at 3.82 THz at room temperature, showing great potential in the development of terahertz amplifiers and even lasers.

Broadband high-efficiency near-infrared graphene phase modulators enabled by metal–nanoribbon integrated hybrid plasmonic waveguides

Abstract The phase modulator is a key component in optical communications for its phase modulation functions. In this paper, we numerically demonstrate a variety of ultra-compact high-efficiency graphene phase modulators (GPMs) based on metal–nanoribbon integrated hybrid plasmonic waveguides in the near-infrared region. Benefiting from the good in-plane mode polarization matching and strong hybrid surface plasmon polariton and graphene interaction, the 20 μm-length GPM can achieve excellent phase modulation performance with a good phase and amplitude decoupling effect, a low insertion loss around 0.3 dB/μm, a high modulation efficiency with V π L π of 118.67 V μm at 1.55 μm, which is 1–3 orders improvement compared to the state-of-the-art graphene modulators. Furthermore, it has a wide modulation bandwidth of 67.96 GHz, a low energy consumption of 157.49 fJ/bit, and a wide operating wavelength ranging from 1.3 to 1.8 μm. By reducing the overlap width of the graphene–Al2O3–graphene capacitor, the modulation bandwidth and energy consumption of the modulator can be further improved to 370.36 GHz and 30.22 fJ/bit, respectively. These compact and energy-efficient GPMs may hold a key to various high-speed telecommunications, interconnects, and other graphene-based integrated photonics applications.

Geometric wavefront dislocations of RKKY interaction in graphene

Magnetically doped graphene has great potential for applications in spintronics, in which local magnetic moments are coupled by the Rudermann-Kittel-Kasuya-Yosida (RKKY) interaction. RKKY interaction in graphene has attracted intensive interest. However, previous studies only show the features of the RKKY interaction dictated by energy dispersion, leaving the effect of the geometric nature of electronic structures unexplored. Here, we focus on the short-range oscillation behaviors of RKKY interaction contributed by intervalley scattering. Due to the unique geometric nature of electronic structures, two wavefront dislocations emerge in the RKKY interaction corresponding to winding number 1 of graphene. We further demonstrate the robustness of wavefront dislocations against the doping, trigonal warping, and gap opening of energy bands. This study reveals a unique feature for the RKKY interaction and implies the importance of the geometric nature of electronic structures for magnetism.

Hybrid graphene-based materials and its catalytic activity toward hydrogen sorption

Thanks to unique material's properties, a remarkable research attention has been focused on graphene. In this research work, the Radio frequency (RF) sputtering technique process parameters were varied to achieve the well dispersed nanoparticles onto graphene sheets in the range of 5–10 nm to enhance the hydrogen sorption. On such scale, quantum size effects enter can play lowering the H2 desorption temperature from 400 °C typical of bulk Mg hydrides to 140 °C. In this context, the Magnesium (Mg) nanoparticles were decorated onto graphene sheets by varying the powder vibration frequency during the deposition process. X-ray diffraction (XRD) results demonstrate that the d spacing of graphene sheets was increased with decoration of Mg nanoparticles. Additionally the three characteristic peaks correspond to (001), (002) and (101) planes of hexagonal structure of metallic Mg were also observed. Transmission electron Microscope (TEM) micrographs revealed that the decorated Mg nanoparticles onto graphene at high powder vibration frequency were uniformly distributed over the entire sheet of graphene. Raman spectra showed that with the interaction of graphene with Mg nanoparticles the G and 2D peak were shifted 9.81 cm−1 and 8.2 cm−1 to higher wavenumbers, suggesting p doping of graphene. X-ray Photoemission Spectroscopy (XPS) results revealed that high concentration of Mg nanoparticles was obtained with high powder vibration frequency. The hydrogen up taking capacity for the decorated graphene sheets with Mg nanoparticles was about 6.00 wt% in whole composite. However, the up taking hydrogen storage capacity of the only Mg nanoparticles was 7.4 wt%.

Investigations of thermal and mechanical properties of graphene-silver nanocomposites: a molecular dynamics study

ABSTRACT The effect of graphene silver (GN/Ag) interface is a key factor to understand glides and shuffles dislocations which affect the thermo-mechanical performance. Here, we report the recital optimization of graphene interaction with silver by molecular dynamics (MD) simulation. To analyse the effect of temperature and stress three orientations of Ag ((1 0 0), (1 1 0), and (1 1 1)) attached with monolayer graphene have been chosen. During the heating process apart from interface, edges in graphene can cause dislocation nucleation. The melting temperature of GN/Ag (1 0 0), GN/Ag (1 1 0), and GN/Ag (1 1 1) were observed as 1190, 1150, and 1250 K. The GN/Ag (1 1 0) shows lowest melting temperature indicated least stable structure . GN/Ag (1 1 1) has a higher melting temperature as compared to other samples due to propagation of shuffle dislocations. Furthermore, all samples have been subjected to uniaxial tensile loading. It was calculated that the stress of GN/Ag (1 0 0), GN/Ag (1 1 0), and GN/Ag (1 1 1) increased 341%, 377%, 386.20% along armchair and 1231%, 1000%, 1289% zigzag direction w.r.t silver. Based on the above-mentioned results, GN/Ag nanocomposites is a potential candidate for thermal management applications.

Independently Tunable Dual-Band Perfect Absorption in a Dual-Resonance Hybrid Structure Incorporating Graphene

An independently tunable dual-resonance hybrid structure incorporating graphene is proposed to achieve selective light trapping and response tuning in the visible and near-infrared band. The incident light with different wavelengths are intensely localized in two separated resonant cavities via the synergetic effect of the guided mode resonances (GMRs) and optical Tamm states (OTSs), which leads to the strong enhancement of the light-matter interaction of graphene in different parts of the structure. The dual-band perfect absorption associated with critical coupling is achieved, whereas the two resonant modes can be independently tuned by adjusting the corresponding structural parameters. Furthermore, by dynamically changing the permittivity of the resonant cavities or the chemical potential of graphene, the absorption wavelength can be continuously adjusted and the absorption efficiency can be regulated stepwise.

Atomic-scale perspective of mechanical properties and fracture mechanisms of graphene/WS2/graphene heterostructure

The heterostructures synthesized by vertically stacking two-dimensional (2D) materials exhibit appealing and sophisticated features and functions that are typically missing in single-layer 2D materials. In our present study, the chirality and temperature-dependent mechanical characteristics and fracture process of graphene/h-WS2/graphene (GWG) vertical heterostructure in both armchair and zigzag loading directions are investigated utilizing molecular dynamics (MD) simulations. Our findings reveal that vertically sandwiching h-WS2 between two graphene layers significantly improves the h-WS2 monolayer's mechanical characteristics (Young's modulus and ultimate stress). Young's moduli of the heterostructure are higher than that predicted by the rule of mixture (ROM), especially at high temperatures. This points out a significant enhancement of mechanical properties due to the vertical stacking and strong interlayer interaction of graphene and WS2 layers. Moreover, we have discovered that while armchair loading causes the fracture to begin in the graphene layers, zigzag loading causes the crack to begin in either the WS2 layer or the graphene layers. Finally, this study illustrates an intriguing and thorough characterization of the GWG vertical heterostructures' mechanical properties and fracture mechanisms, as well as their temperature dependence and directional anisotropy, allowing for efficient and versatile application of the material in a variety of fields.

Membrane Fouling: Microscopic Insights into the Effects of Surface Chemistry and Roughness

AbstractFouling is a major obstacle and challenge in membrane‐based separation processes. Caused by the sophisticated interactions between foulant and membrane surface, fouling strongly depends on membrane surface chemistry and roughness. Current studies in the field have been largely focused on polymer membranes. Herein, a molecular dynamics simulation study is reported for fouling on alumina and graphene membrane surfaces during water treatment. For two foulants (sucralose and bisphenol A), it is found that the fouling on alumina surfaces is reduced with increasing surface roughness; however, the fouling on graphene surfaces is enhanced by roughness. It is unravelled that the foulant–surface interaction becomes weaker in the ridge region of a rough alumina surface, thus allowing foulant to leave the surface and reducing fouling. Nevertheless, such behavior is not observed on a rough graphene surface because of strong foulant–graphene interaction. In addition, with increasing roughness, the hydrogen bonds between water and alumina surface are found to increase in number as well as stability. This simulation study reveals that surface chemistry and roughness play a crucial role in membrane fouling, and the microscopic insights are useful for the design of new membranes toward high‐performance water treatment.

Light-matter interactions enhanced by quasi-bound states in the continuum in a graphene-dielectric metasurface.

In this paper, we propose a graphene-dielectric metasurface to enhance the light-matter interactions in graphene. The dielectric metasurface consists of periodically arranged silicon split rings placed on the silica substrate, which supports a symmetry-protected bound state in the continuum (BIC). When perturbation is introduced into the system to break symmetry, the BIC will transform into the quasi-BIC with high quality (Q)-factor. As the graphene layer is integrated with the dielectric metasurface, the absorption of graphene can be enhanced by the quasi-BIC resonance and a bandwidth-tunable absorber can be achieved by optimizing the Fermi energy of graphene and the asymmetry parameter of the metasurface to satisfy the critical coupling condition. By varying the Fermi energy of graphene, the quasi-BIC resonances can be effectively modulated and the max transmission intensity difference is up to 81% and a smaller asymmetry parameter will lead to better modulation performance. Our results may provide theoretical support for the design of absorber and modulator based on the quasi-BIC.

Numerical investigation of fracture behavior by crazing in graphene reinforced polymers

For graphene reinforced polymers, toughness value is found to be scattered and specifically is based on experimental results. Therefore, it is highly desirable to have a proper estimation model for fracture toughness of such composites. In this study a RVE model was proposed to investigate the graphene–craze interaction and fracture behavior of graphene reinforced polymers. A craze presented in polymeric matrix and an interacting graphene platelet randomly located were assumed in the RVE model. Validations were made by both theoretical and experimental results. Parametric studies showed that Young’s modulus ratio of 500 is preferably recommended from the perspective of toughening effect.

Hydrophobic-to-hydrophilic affinity change of sub-monolayer water molecules at water–graphene interfaces

Investigating the interfacial properties between water and graphene is important, as the water–carbon interface influences various applications. Graphene is the fundamental unit of various carbon allotropes and composed of a single atomic species, although slight oxygen groups are normally attached on it. Therefore, adsorption properties on graphene is inevitable to advance fundamental understating on surface sciences. However, the detection of water adsorption on graphene is considerably hard, because amount of water is tiny and mass production of graphene to a detectable level using a standard adsorption apparatus is extremely difficult. We succeeded to detect water vapor adsorption on several layer graphene using lab-made adsorption apparatus with a quartz crystal microbalance technique. This study derives the properties of water on single-, triple-, and six-layer graphene from the contact angles of water droplets and the water vapor adsorption isotherms. The surface hydrophobicity evaluated from the contact angles and water vapor adsorption isotherms decreased in the following order: single-layer graphene > triple-layer graphene > six-layer graphene. At a relative pressure of 0.4 and water surface densities of 0.5–1.5 mg m −2 (corresponding to 2–5 water layers), the water stability was 1.0 kJ mol −1 smaller on single-layer graphene than on triple- and six-layer graphene. The weak interaction between water molecules and single-layer graphene induced slight water adsorption on graphene. As the water amount increased, the water–graphene interaction energy increased with steps of 0.17–0.18 mg m −2 (corresponding to nearly 50% of a water monolayer), and the water structure correspondingly transformed from cluster to layer. The structure transformation of adsorbed water induced the affinity change from hydrophobic to hydrophilic on graphene interfaces. The mechanism of water–graphene interfaces can be exploited in applications of graphene-based carbon nanomaterials. • Water contact angles of graphene were 57–80°, indicating hydrophobic interfaces. • Water vapor on single-layer graphene was rarely adsorbed below P/P 0 = 0.4. • Water-adsorbed structure was changed from cluster to layer form at 0.5 water layer. • Cluster-to-layer transformation triggers affinity change of water on graphene.