Bulk graphanes synthesized from benzene and pyridine

Abstract

The discovery of graphene stimulated an intensive search for its analogs and derivatives. One of the most interesting derivatives is hydrographene called graphane. Calculations indicate that bulk graphane is thermodynamically more favorable than all CH hydrocarbons including benzene. At the same time, pressureinduced polymerization of hydrocarbons and their derivatives at room temperature leads to the formation of amorphous products or poorly ordered one-dimensional products such as polyacetylene and benzene-derived carbon nanothreads.Here, we report a high-pressure high-temperature synthesis of several millimetersized samples of bulk graphanes with the composition C-H(D) from benzene and graphene-derivative C-H-N 0.2 from pyridine. X-ray diffraction, transmission electron microscopy, and infrared spectroscopy of new materials reveal relatively large (several nanometers in size) crystalline grains of an sp 3 -bonded graphane lattice (3-cycle-4step, the orthorhombic structure with P bca space-group and parameters a = 9.5-9.8Å, b = 8.9-9.1Å, c = 17.1-17.3Å). The main hydrogen groups in samples are C-H groups connected by aliphatic bonds. The synthesized graphanes at atmospheric pressure are stable up to 500 • C. The macroscopic density of CH samples is 1.5-1.57 g cm −3 and the refractive index is 1.78-1.80. The absorption spectra of samples with a high degree of crystallization exhibits a weak absorption maximum at 2.8 eV, which is responsible for the yellow-orange color, large absorption maximum at 4 eV and an absorption edge associated with the width of the optical gap at 5.2 eV. The bulk modulus (30-37 GPa) and shear modulus (15-18 GPa) of the fabricated samples, as well as their hardness (1-1.5 GPa), are about twice as high as the respective values for polycrystalline graphite. The solution of metalorganic complexes in benzene and pyridine makes it possible to obtain doped graphanes, which can have extraordinary electron transport and magnetic properties.arXiv:1608.07221v1 [cond-mat.mtrl-sci]

Chemistry of Graphene Derivatives: Synthesis, Applications, and Perspectives

“…A completely different approach was used by Brazhkin et al., who prepared graphane by high temperature (700–1200 K) and high pressure (<10 GPa) synthesis from benzene. The synthesis also allowed the production of nitrogen‐doped graphane by the use of a benzene/pyridine mixture …”

“…The synthesis also allowed the production of nitrogen-doped graphane by the use of a benzene/pyridine mixture. [76] In contrast, the wet chemistry processes based on dissolving metals,s uch as alkali metals,i nl iquid ammonia, whichs erve as as ource of solvated electrons, prove to be very useful in the production of highly hydrogenated graphenes by Birch-type reactions. [77] It has been demonstratedt hat single-layer graphene is hydrogenated uniformly,b ut graphene with more layers and sealed edges is not,w hich supports the idea that hydrogenation occurs from the edges of graphene by intercalation of alkali metal into the structure, where the defects are located.…”

Pressure‐Induced Diels–Alder Reactions in C6H6‐C6F6 Cocrystal towards Graphane Structure

“…[2c] Recently,i tw as reported that aniline forms diamond-like polyaniline under external pressure and the hydrogen bond between the NH 2 groups is believed to be responsible for better crystallinity. [4] Ther eaction mechanism of these pressure-induced polymerizations (PIPs) was explored from various perspectives. [4] Ther eaction mechanism of these pressure-induced polymerizations (PIPs) was explored from various perspectives.…”

“…[2d] Besides the one-dimensional structure, the graphane structure was also obtained by compressing the aromatics under high-pressure and high-temperature conditions. [4] Ther eaction mechanism of these pressure-induced polymerizations (PIPs) was explored from various perspectives. Va rious possible connections between benzene molecules were theoretically proposed, and the energies of the formed dimers were examined to evaluate the corresponding reactions.…”

High-pressure elastic properties of polycyclic aromatic hydrocarbons obtained by first-principles calculations

“…При этом учитывались различные конфигурации веществ в зависимости от соединения бензольных колец. Предыдущие исследования касались фазовой диаграммы, РТусловий диссоциации и определения стабильных фаз бензола при давлениях до 30 ГПа (Thiery, Leger, 1988;Ciabini et al, 2005;2007;Kondrin et al, 2017;Chanyshev et al, 2018). Теоретический расчет фазовых преобразований бензола проведен до давлений 200 ГПа (Wen et al, 2011).…”