Synthesis of Graphene and Graphene Films with Minimal Structural Defects

Graphene is a carbon material with extraordinary properties that has been drawing a significant amount of attention in the recent decade. High-quality graphene can be produced by different methods, such as epitaxial growth, chemical vapor deposition, and micromechanical exfoliation. The reduced graphene oxide route is, however, the only current approach that leads to the large-scale production of graphene materials at a reasonable cost. Unfortunately, graphene oxide reduction normally yields graphene materials with a high defect density. Here, we introduce a new route for the large-scale synthesis of graphene that minimizes the creation of structural defects. The method involves high-quality hydrogen functionalization of graphite followed by thermal dehydrogenation. We also demonstrated that the hydrogenated graphene synthesis route can be used for the preparation of high-quality graphene films on glass substrates. A reliable method for the preparation of these types of films is essential for the widespread implementation of graphene devices. The structural evolution from the hydrogenated form to graphene, as well as the quality of the materials and films, was carefully evaluated by Raman spectroscopy.

Interaction studies of propylene and butadiene on tricycle graphane nanosheet - A DFT outlook

In this research work, we employed a tricycle graphane nanosheet as a chemical sensor to monitor the toxic hydrocarbon molecules, namely propylene, and 1,3-butadiene, which are emitted from automobile industries. At first, the structural stability and dynamical permanency of tricycle graphane is ascertained based on cohesive energy and phonon-band-spectrum. Sequentially, the electronic properties of tricycle graphane are conferred with the results of the projected density of states spectrum and band structure. The computed band gap of tricycle graphane is 5.53 eV. Chiefly, the adsorption behaviour of target propylene and 1, 3-butadiene on tricycle graphane is explored by determining adsorption energy, relative band gap variation, and Mulliken population analysis. Furthermore, the range of adsorption energy magnitudes (-0.16 eV to -1.03 eV) demonstrates that the target hydrocarbon molecules are physically adsorbed on tricycle graphane material. The overall outcome endorses that the tricycle graphane can be utilised as a prominent sensor to sense the hydrocarbon molecules released from automobiles and monitor air pollutants.

First-Principles Study of the Optical Dipole Trap for Two-Dimensional Excitons in Graphane

Recent studies on excitons in two-dimensional materials have been widely conducted for their potential usages for novel electronic and optical devices. Especially, sophisticated manipulation techniques of quantum degrees of freedom of excitons are in demand. In this Letter we propose a technique of forming an optical dipole trap for excitons in graphane, a two-dimensional wide gap semiconductor, based on first-principles calculations. We develop a first-principles method to evaluate the transition dipole matrix between excitonic states and combine it with the density functional theory and GW+BSE calculations. We reveal that in graphane the huge exciton binding energy and the large dipole moments of Wannier-like excitons enable us to induce the dipole trap of the order of meV depth and μm width. This Letter opens a new way to control light-exciton interacting systems based on newly developed numerically robust ab initio calculations.

Fluorographene and Graphane as an Excellent Platform for Enzyme Biocatalysis

The application of enzymes is a crucial issue for current biotechnological application in pharmaceutical, as well as food and cosmetic industry. Effective platforms for enzyme immobilization are necessary for their industrial use in various biosynthesis procedures. Such platforms must provide high yield of immobilization and retain high activity at various conditions for their large-scale applications. Graphene derivatives such as hydrogenated graphene (graphane) and fluorographene can be applied for enzyme immobilization with close to 100 % yield that can result to activities of the composites significantly exceeding activity of free enzymes. The hydrophobic properties of graphene stoichiometric derivatives allowed for excellent non-covalent bonding of enzymes and their use in various organic solvents. The immobilized enzymes retain their high activities even at elevated temperatures. These findings show excellent application potential of enzyme biocatalysts immobilized on graphene stoichiometric derivatives.

Hydrogenation of Fluorographite and Fluorographene: An Easy Way to Produce Highly Hydrogenated Graphene

Fluorographene is an excellent precursor for the synthesis of graphene derivatives. Relative to pure graphene, fluorographene possesses higher reactivity and, in comparison with graphene oxide, is also homogenous in composition, which enables the preparation of well-defined materials. Recently, it has been shown that several graphene derivatives can be synthesized from fluorographene, thus yielding various products such as graphene acid or alkylated graphene. This study focuses on the hydrogenation of fluorographene by using various hydrogenation reactions, including the use complex hydrides and solvated electrons in different media. In addition, a comparison of these reactions shows that fluorinated graphite has significantly lower reactivity than fluorographene. The conversion rates of these reactions are higher when fluorographene is used relative to fluorographite. These reactions can be used to tune the hydrogen/fluorine composition on a graphene backbone.

Chemistry of Graphene Derivatives: Synthesis, Applications, and Perspectives

The chemistry of graphene and its derivatives is one of the hottest topics of current material science research. The derivatisation of graphene is based on various approaches, and to date functionalization with halogens, hydrogen, various functional groups containing oxygen, sulfur, nitrogen, phosphorus, boron, and several other elements have been reported. Most of these functionalizations are based on sp³ hybridization of carbon atoms in the graphene skeleton, which means the formation of out-of-plane covalent bonds. Several elements were also reported for substitutional modification of graphene, where the carbon atoms are substituted with atoms like nitrogen, boron, and several others. From tens of functional groups, for only two of them were reported full functionalization of graphene skeleton and formation of its stoichiometric counterparts, fluorographene and hydrogenated graphene. The functionalization of graphene is crucial for most of its applications including energy storage and conversion devices, electronic and optic applications, composites, and many others.

Synthesis and properties of phosphorus and sulfur co-doped graphene

The derivatisation of graphene significantly extends its application potential beyond just a highly conductive material.

Planar Polyolefin Nanostripes: Perhydrogenated Graphene

Graphene hydrogenation gives an opportunity to introduce a band gap into the graphene electronic structure. Complete hydrogenation may lead to the graphane, a fully hydrogenated counterpart of graphene. However, pure graphane has not been successfully prepared to this day. Here, we show that hydrogenation of single-walled carbon nanotubes by means of Birch reduction leads to graphene-based carbon nanostripes with uniform dimensions. Such a material exhibits interesting electrocatalytic and magnetic properties as well huge potential for hydrogen storage since the weight concentration of hydrogen is 8.78 wt.% corresponding to the composition of C₁ H_1.22 O_0.05 and thus exceeding the theoretical concentration in pure graphane (7.74 wt.%). The obtained concentration of hydrogen is the highest value ever reported for any graphene-based material and significantly exceeds the ultimate goal of the U.S. Department of Energy for a hydrogen storage material of 7.5 wt.%.

Towards stoichiometric analogues of graphene: graphane, fluorographene, graphol, graphene acid and others

Stoichiometric derivatives of graphene, having well-defined chemical structure and well-defined chemical bonds, are of a great interest to the 2D materials research.

Characterization of hydrogenated graphite powder by X-ray photoelectron spectroscopy and time-of-flight secondary ion mass spectrometry

Hydrogenated graphite powder was obtained through Birch reduction of graphite powder and characterized by X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS) at 500 °C.

Toward graphene chloride: chlorination of graphene and graphene oxide

Chlorinated graphene derivates with chlorine concentration exceeding 11 at% were synthesized by high temperature exfoliation in chlorine atmosphere. Halogen graphenes have a great potential for electronic and electrochemical devices.