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There are mines of elemental carbon such as graphite. It is the most stable form of elemental carbon at 25°C, under 1 atm (Section 3.7). A second form of pure or nearly pure elemental carbon is represented by diamonds (Section 3.12). Other forms of elemental carbon are produced by combustion or heat treatment of wood (Section 3.6), bio-polymers such as paper, cotton (cellulose), or synthetic polymers such as viscose (Section 11.10.1) and polyacrylonitrile (Section 8.2.7). Nanoparticles such as graphene (Section 3.7), fullerenes (Section 3.8), nanotubes (Section 3.9), and quantum dots of carbon (Section 3.10) are available that find biomedical applications and are used in the manufacture of nanometric objects useful for electronics, optoelectronics, photophysics, energy and the environment protection. Nanoparticles must be handled with care as they can be toxic…

The application areas of two-dimensional (2D) materials, their hetero-structures and composites are rapidly expanding — thanks to their extraordinary mechanical, optical, electronic and thermal properties. The family of 2D materials, which are finding a use in applications, is rapidly growing, and now includes graphene, graphene oxide, hexagonal boron nitride and transition-metal dichalcogenide, as well as the recently obtained chemical derivatives, physically modified hybrids and allotropes. New applications also trigger the development of new and more e±cient methods for the synthesis of 2D materials and the formulation of composites. In this paper, we focus on the relation between the structure of the 2D materials and their heterostructures on the one hand and their properties on the other, summarize recent improvements in the synthesis approaches and discuss the perspectives in applications. We highlight existing applications in electronics, optoelectronics, electrocatalysis and energy storage and discuss new potential areas such as functional coatings and biomedical materials and devices.

Convergent beam electron diffraction (CBED) performed on two-dimensional (2D) materials recently emerged as a powerful tool to study structural and stacking defects, adsorbates, atomic 3D displacements in the layers, and the interlayer distances. The formation of the interference patterns in individual CBED spots of 2D crystals can be considered as a hologram, thus the CBED patterns can be directly reconstructed by conventional reconstruction methods adapted from holography. In this study, we review recent results applying CBED to 2D crystals and their heterostructures: holographic CBED on bilayers with the reconstruction of defects and the determination of interlayer distance, CBED on 2D crystal monolayers to reveal adsorbates, and CBED on multilayered van der Waals systems with moiré patterns for local structural determination.

Reduced graphene oxide (rGO) has attracted interest in its potential application in large area photodetectors owing to its ease of manufacture and wideband optical absorbance. Here, we report that thin rGO films produced via vacuum filtration of GO followed by reduction by immersion in L-ascorbic acid are capable of sensing light through a bolometric mechanism. The photoresponse of these rGO thin films can be further enhanced by dropcasting graphene quantum dots (GQDs) on the rGO surface. These GQDs were observed to increase the opacity of the rGO film and hence its absorptivity of light, thereby enabling a significant increase in the photoresponse of the device.

The Casimir effect in graphene systems is reviewed with a emphasis made on the large thermal correction to the Casimir force predicted at short separations between the test bodies. The computational results for the Casimir pressure and for the thermal correction are presented for both pristine graphene and real graphene sheets, which possess nonzero energy gap and chemical potential, obtained by means of exact polarization tensor. Two experiments on measuring the gradient of the Casimir force between an Au-coated sphere and graphene-coated substrates performed by using a modified atomic force microscope cantilever-based technique are described. It is shown that the measurement data of both experiments are in agreement with theoretical predictions of the Lifshitz theory using the polarization tensor. Additionally, several important improvements made in the second experiment, allowed to demonstrate the predicted large thermal effect in the Casimir interaction at short separations. Possible implications of this result to the resolution of long-term problems of Casimir physics are discussed.

The adsorption of manganese and chromium on graphene is investigated using first principles based on density functional theory. The binding energy, optimal geometric structures, band structure, density of states, charge density, and charge density difference, spin distribution, and magnetic moment of each adatom-adsorbed graphene system are calculated in detail. The calculated results show that the most stable adsorption positions of both Mn and Cr on graphene are hollow sites. The calculated adsorption of all systems illustrates strong hybridization between transition metal adatoms and graphene, as well as metallic behavior. Besides, the positive magnetic moment shows that the Mn- and Cr-adsorbed graphenes have ferromagnetic configurations. The electronic and magnetic properties of Mn- and Cradsorbed graphenes reveal that the transition metal-adsorbed graphene systems have potential for applications in the future.

Lanthanum (La) and cerium (Ce) atom-adsorbed graphene systems are investigated for a thorough understanding of the strongly coupling effects associated with the very complicated quasi-particle 4f orbital charges and spin configurations, such as the significant covalent bonds of C-sp3 and La-5d5/Ce-4f7 orbitals and their non-magnetic/ferromagnetic spin configurations. Their quasi-particle behaviors are expected to present a sharp contrast with those observed in alkalizations, oxidations, and halogenations.

Through the quasi-particle framework implemented using VASP calculations, the structural, electronic, and optical properties of 4d transition-metal intercalated graphite were investigated and discussed.

While the Association of Southeast Asian Nations (ASEAN) is a leading contributor of greenhouse gases (GHGs) due to its dependency on fossil fuels, a sudden transition to renewable energy would be costintensive and difficult due to a lack of infrastructure. Carbon Capture, Utilization, and Storage (CCUS) can be implemented to combat carbon dioxide (CO₂) emissions. Membrane technology offers to lower CCUS costs and is made more viable by incorporating advanced materials, such as graphene-based materials (GBM) and other 2D substances, to improve carbonaceous-based gas separation and selectivity. Herein, we develop the GBM membrane, evaluating its membrane structure through material characterization and its sensing performance on gaseous compounds. We also investigate the prospects, utilization, and challenges of membrane technology in CCUS, particularly in ASEAN and Indonesia. Scanning electron microscopy (SEM) examinations show that the GBM has a porous layered structure and performs its sensing character of carbonaceous-based gases. This study shows that membrane technology could be implemented and would fulfill ASEAN demands as well as meet carbon neutrality targets with government policy and infrastructure support.

Graphene is a fascinating material for exploring fundamental science questions as well as a potential building block for novel electronic applications. In order to realize the full potential of this material the fabrication techniques of graphene devices, still in their infancy, need to be refined to better isolate the graphene layer from the environment. We present results from a study on the influence of extrinsic factors on the quality of graphene devices including material defects, lithography, doping by metallic leads and the substrate. The main finding is that trapped Coulomb scatterers associated with the substrate are the primary factor reducing the quality of graphene devices. A fabrication scheme is proposed to produce high quality graphene devices dependably and reproducibly. In these devices, the transport properties approach theoretical predictions of ballistic transport.

The functional integral has many triumphs in elucidating quantum theory. But incorporating charge fractionalization into that formalism remains a challenge.

The special surface activity and structural characteristics make Titanium dioxide (TiO₂) an ideal candidate for high-rate anode material. However, because of poor electron conductivity, small diffusion coefficient of lithium ions and the tendency of nanoparticle to aggregate, the full electrochemical performance of TiO₂ as Lithium-ion batteries (LIBs) anode have not been reached. Uniform TiO₂ nanosheets on graphene templates in a sandwich-like configuration with variable content of graphene were synthesized by a hydrothermal treatment and heating reduction continuous process. The TiO₂/graphene nanosheets with about 5 wt% graphene content provided a very high first discharge capacity of 315 mAh g-1 at a rate of 0.2C. When graphene content was increased to 11 wt%, the TiO₂/graphene nanosheets delivered a discharge capacity of 93 mAh g-1 at a rate of 50C. We hence proved that TiO₂/GNS is an excellent anode material for high power lithium storage, with high rate capacity and excellent cycle durability. This sandwich-like TiO₂/graphene architecture is a promising anode material with very high lithium storage capacity and desirable cycling stability.

More and more scholars were committed to loading the iron oxide nanoparticles on the graphene. Shown in the studies, there were many nucleation sites on the graphene for the Fe₃O₄ particles, meanwhile, the distance between the graphene was lengthened due to the magnetic Fe₃O₄ particles, and the reunion of the graphene could be avoided. The excellent performance of the two materials was combined perfectly in this way. To facilitate the researchers work better in the future, in this paper, the synthesis of Fe₃O₄/graphene were reviewed from its applications such as waste water treatment, magnetic targeting drugs, biosensor, and the anode materials for lithium-ion battery. Simultaneously, the prospects of the composite material were discussed.

Proximity induced spin-orbit coupling effects in graphene on transition-metal dichalcogenides (TMD) have potential to bring graphene spintronics to the next level. Here we discuss electronic structure of graphene on monolayer MoS₂, MoSe₂, WS₂ and WSe₂. The Dirac electrons of graphene lie within the semiconducting gap and exhibit a giant global proximity spin-orbit coupling, without compromising the semimetallic character. We found that graphene on MoS₂, MoSe₂, and WS₂ has a topologically trivial band structure, while graphene on WSe₂ exhibits inverted bands. Within the inverted regime the graphene zigzag nanoribbon hosts protected helical edge states demonstrating the quantum spin Hall effect, which opens a new route to access topological states of matter in graphene-based systems. Additionally the use of graphene/TMD vertical heterostructures serve as a promising platform for optospintronics, in particular for optical spin injection into graphene.

Experimental measurements of photoresistivity under terahertz (THz) radiation in low magnetic fields at conditions of cyclotron resonance (CR) in two-dimensional electron system (2DES) of GaAs/AlGaAs nanostructures are presented and discussed. We report the experimental discovery of “CR-vanishing effect” (CRV) in GaAs/AlGaAs heterostructures with high mobility as a well-defined gap on CR-line that is independent on incident THz power. Our analysis shows that the CRV may appear in systems with well correlated state of 2D electrons such as plasma waves and others. Fundamental nature of these correlated states of electrons in 2DES is discussed. Future THz detectors utilizing the new correlated states in 2DES may expand horizons for supersensitive detection in sub-THz and THz frequencies ranges.

We present a kinetic transport model describing the transport of charge carriers and optical phonons in graphene. The Boltzmann transport equations are solved numerically by a set of deterministic methods. Our simulations provide a deep insight into the coupled dynamics of electrons and phonons including features unique to graphene. We demonstrate the importance of such effects when turning to the high field transport regime.

We study the two-dimensional Ising model with competing nearest-neighbour and diagonal interactions and investigate the phase diagram of this model. We show that the ground state at low temperatures is ordered either as stripes or as the Néel antiferromagnet. However, we also demonstrate that the energy of defects and dislocations in the lattice is close to the ground state of the system. Therefore, many locally stable (or metastable) states associated with local energy minima separated by energy barriers may appear forming a glass-like state.

We discuss the results in connection with two physically different systems. First, we deal with planar clusters of loops including a Josephson π-junction (a π-rings). Each π-ring carries a persistent current and behaves as a classical orbital moment. The type of particular state associated with the orientation of orbital moments in the cluster depends on the interaction between these orbital moments and can be easily controlled, i.e. by a bias current or by other means. Second, we apply the model to the analysis of the structure of the newly discovered two-dimensional form of carbon, graphene. Carbon atoms in graphene form a planar honeycomb lattice. Actually, the graphene plane is not ideal but corrugated. The displacement of carbon atoms up and down from the plane can be also described in terms of Ising spins, the interaction of which determines the complicated shape of the corrugated graphene plane.

The obtained results may be verified in experiments and are also applicable to adiabatic quantum computing where the states are switched adiabatically with the slow change of coupling constant.

The unusual quantum Hall effect (QHE) in graphene is often discussed in terms of Dirac fermions moving with a linear dispersion. A new theory describing the same phenomena is presented in terms of the more traditional composite bosons. The "electron" (wave packet) is shown to move easier in the direction [110] ≡ [110 c-axis] of the honeycomb lattice than perpendicular to it, while the "hole" moves easier in [001]. Since "electrons" and "holes" move in different channels, the number densities can be very high especially when the Fermi surface has "necks". The strong QHE at filling factor ν = 2 arises from the "neck" Fermi surfaces.

We adopt the Dirac model for graphene and calculate the Casimir interaction energy between a plane suspended graphene sample and a parallel plane ideal conductor. We employ both the Quantum Field Theory (QFT) approach, and the Lifshitz formula generalizations. The first approach turns out to be the leading order in the coupling constant of the second one. The Casimir interaction for this system appears to be rather weak but experimentally measurable. It exhibits a strong dependence on the mass of the quasi-particles in graphene.

Electrons and holes in clean, charge-neutral graphene behave like a strongly coupled relativistic liquid. The thermo-electric transport properties of the interacting Dirac quasiparticles are rather special, being constrained by an emergent Lorentz covariance at hydrodynamic frequency scales. At small carrier density and high temperatures, graphene exhibits signatures of a quantum critical system with an inelastic scattering rate set only by temperature, a conductivity with a nearly universal value, solely due to electron-hole friction, and a very low viscosity. In this regime one finds pronounced deviations from standard Fermi liquid behavior. These results, obtained by Boltzmann transport theory at weak electron-electron coupling, are fully consistent with the predictions of relativistic hydrodynamics. Interestingly, very analogous behavior is found in certain strongly coupled relativistic liquids, which can be analyzed exactly via the AdS-CFT correspondence, and which had helped identifying and establishing the peculiar properties of graphene.