Bulk graphanes synthesized from benzene and pyridine
We report a high-pressure high-temperature synthesis of several millimeter-sized samples of bulk
graphanes with the composition C–HĲD) from benzene and graphene-derivative C–H–N0.2 from pyridine.
X-ray diffraction, transmission electron microscopy, and infrared spectroscopy of the new materials reveal
relatively large (several nanometers in size) crystalline grains of an sp3-bonded graphane lattice (3-cycle-4-
step, the orthorhombic structure (Pbca) with the parameters a = 9.5–9.8 Å, b = 8.9–9.1 Å, and c = 17.1–17.3
Å). The main hydrogen groups in the 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 exhibit a weak absorption maximum at 2.8 eV, which is responsible for the yelloworange
color, the 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 dissolution of metalorganic complexes in benzene and pyridine makes it possible to
obtain doped graphanes, which can have extraordinary electron transport and magnetic properties.