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Functionalization of Graphite and Graphene
Published in Titash Mondal, Anil K. Bhowmick, Graphene-Rubber Nanocomposites, 2023
Akash Ghosh, Simran Sharma, Anil K. Bhowmick, Titash Mondal
Fluorination is another widely used method to prepare fluorographene. Baraket et al. were first to report the fluorination of CVD-based graphene on Cu foil. Graphene was exposed to XeF2 in an inert environment at 30°C to form single-sided fluorinated graphene (Baraket et al. 2010). Nair et al. followed the same protocol to prepare the fluorographene using SiO2/Si substrate. The results suggested double-sided fluorination of graphene with a stoichiometry of C1F1. The obtained material was stable and inert in the air up to 400°C like Teflon. On fluorination, the graphitic sp2 carbons transform into sp3 states in fluorinated graphene that results in a drastic change in electrical and optical properties. Modified graphene becomes an electrical insulator with its resistance value in the order of 1012 Ω. Apart from XeF2, fluorine gas is another fluorinating agent which can be used to functionalize graphene at different conditions (Nair et al. 2010). Mazanek et al. reported mass production of fluorinated graphene oxide using fluorine gas in an autoclave. Stoichiometric composition was found to be around C1F1.05 that exhibited high hydrophobicity and controlled luminescence properties (Mazánek et al. 2015). Jankovský et al. (2014) utilized fluorine gas to prepare fluorinated graphene oxide and further reduced it to fluorographene. The fluorographene was water soluble with tunable luminescence property.
Quantum Mechanics of Graphene
Published in Andre U. Sokolnikov, Graphene for Defense and Security, 2017
Figure 4.5 illustrates a transformation from metallic to semiconductor bonds. Graphane is a two-dimensional polymer that consists of carbon and hydrogen. The formula of the molecule is (CH)n and n is large. Graphane usually alternates the hydrogen atoms in A and B sublattices sides, we receive a diamond-like structure. The graphane lattice constant, a = 0.244 nm (graphene a = 0.242 nm). The crystalline structure of graphene may be easily transformed into that of graphene by the process of annealing in the atmosphere of Ar at 450°C for 24 hours. Another version of graphene was suggested in 201011. Fluorographene is a derivative of graphene which is a fluorocarbon in chemical terms. It is a two-dimensional carbon structure that consists of sp3 hybridized carbons where every carbon atom is bound with one fluorine atom. The chemical formula, (CF)n, is close to that of Teflon (chemical formula (CF2)n) which has carbon chains: each carbon is connected with two fluorines. In contrast, graphene is unsaturated (sp2 hybridized). Fluographene has a hexagonal lattice with one fluorine at each carbon atom and lattice constant of 0.248 nm. Fluographene’s mechanical properties are similar to those of graphene. The bandgap of 3 eV modes fluorographene makes it a good isolator. Fluorine (F) is a chemical element which is the lightest halogen with the atomic number 9. Fluorine is the most electronegative element and is extremely reactive forming bonds almost with all other elements with the exception of noble gases. Fluorographene can be produced from graphite monofluoride (CF)n that has layers of weakly band stacks of fluorographene. Its most stable formation consists of an infinite array of trans-linked cyclohexane chains that have covalent C – F bonds in an AB-stacking sequence.
Introduction
Published in Satyendra Mishra, Dharmesh Hansora, Graphene Nanomaterials, 2017
Satyendra Mishra, Dharmesh Hansora
Graphene-based carbon NMs [28, 64, 65] mainly include (i) graphene oxide (GO), (ii) doped graphene (iii) derived graphene nanoribbons (GNRs), (iv) graphane, (v) fluorographene, (vi) graphyne (vii) graphdiyne, (viii) graphone and (ix) porous graphene. Graphene is a semimetal with zero band gap, i.e. conduction and valence bands meet at the Dirac point. A zero band gap can be easily tuned by doping and cutting the 2D graphene into form of 1D GNRs [20, 66]. GO is an oxidised and functionalised derivative and it has been reported as hydrophilic material because it has ability of water dispersion. GO adheres on interfaces due to its lower interfacial energy, so it has been widely used as surfactant for emulsification of organic solvents in water. It has been used for the dispersion of insoluble graphite and CNTs in water. This capability strengthens it for development of graphene and P-conjugated systems-based functional hybrid NMs [66, 67]. Graphane is hydrogenated form of graphene sheet. It is a non-magnetic semiconductor having an energy gap due to hydrogenation. Graphane is a hydrocarbon with a stoichiometry formula unit of CH, i.e. extended 2D polymer form of carbon. It generally adds a wealth to the carbon-based NMs useful for hydrogen storage and nanoelectronic applications. Generally, the hydrogen atoms alternate the directions along with the graphane sheet and transform the carbon lattice from sp2 to sp3 hybridisation. Graphane can be easily transformed back into original graphene sheets by annealing process. Fluorographene, with stoichiometric formula of CF, is an another important structure of graphene. Fluorographene has a geometric structure and sp3 bonding configuration similar to graphane with each carbon attached to one fluorine atom. Fluorographene has been used as a solid lubricant for developing the batteries under extreme conditions. Graphyne and graphdiyne are another non-natural carbon allotropes, which have better potential than graphene due to their unique structures, electronic and intriguing properties. Graphyne is a one-atom-thick planar sheet of sp- and sp2-bonded carbon atoms arranged in a crystal lattice form. Graphydine has acetylenic linkages connecting the hexagons of graphene. Graphone, is known as a semi-hydrogenated derivative of graphene, having stoichiometric formula of C2H [65]. In graphone structure, hydrogen atoms are attached on either side of the carbon sheet and graphone is also known as a hybridised mixture of sp2 and sp3 carbon atoms. A porous graphene is a another new class of light weight carbonaceous material. It has a distributed structure within the covalent p-electronic framework of graphene sheet.
The simple preparation of superhydrophobic sponge with fluorinated graphene and carbon nanotube
Published in Journal of Dispersion Science and Technology, 2023
Xiangyuan Ye, Meigui Wang, Mingjin Fan
Among the porous materials, polyurethane sponges are popular materials to absorb liquid due to their low density, high void content, and high resilience.[17–19] However, the hydrophilicity of the polyurethane sponges causes poor selectivity in separating oil/water mixture. In order to enhance the oil/water separating efficiency, the polyurethane sponges should endow with the better hydrophobic property.[20–22] Until now, the two-dimensional carbon nanomaterials, graphene with large specific surface area and strong adsorbability has been widely used to improve the hydrophobic property of the polyurethane sponges.[14,23–34] Kinds of graphene modified polyurethane sponges have achieved the function to separate the oil/water mixture, but most of them need use the expensive perfluoroalkyl groups. However, recent study shows that organic adsorbates have higher affinities to fluorographene than to graphene.[35] A large number of fluorine atoms emerged on the surface of the graphene not only bring the lower surface energy, but also endow the strong adsorbability of organic adsorbates to the fluorographene.[15,36]