Graphite oxide (GO) and its derivatives have been studied using
13C and 1H NMR. NMR spectra of
GO
derivatives confirm the assignment of the 70 ppm line to C−OH groups
and allow us to propose a new
structural model for GO. Thus we assign the 60 ppm line to epoxide
groups (1,2-ethers) and not to 1,3-ethers, as suggested earlier, and the 130 ppm line to aromatic entities
and conjugated double bonds. GO
contains two kinds of regions: aromatic regions with unoxidized
benzene rings and regions with aliphatic
six-membered rings. The relative size of the two regions depends
on the degree of oxidation. The carbon
grid is nearly flat; only the carbons attached to OH groups have a
slightly distorted tetrahedral configuration,
resulting in some wrinkling of the layers. The formation of phenol
(or aromatic diol) groups during
deoxygenation indicates that the epoxide and the C−OH groups are very
close to one another. The distribution
of functional groups in every oxidized aromatic ring need not be
identical, and both the oxidized rings and
aromatic entities are distributed randomly.
Graphite oxide is an inorganic multilayer system that preserves the layered structure of graphite but not the conjugated bond structure. In the past few years, detailed studies of the static structure of graphite oxide were carried out. This was mainly done by NMR investigations and led to a new structural model of graphite oxide. The layer distance of graphite oxide increases with increasing humidity level, giving rise to different spacings of the carbon layers in the range from 6 to 12 A. As a consequence, different types of motions of water and functional groups appear. Information about the mobility of the water molecules is not yet complete but is crucial for the understanding of the structure of the carbon layers as well as the intercalation process. In this paper, the hydration- and temperature-dependent dynamic behavior of graphite oxide will be investigated by quasielastic neutron scattering using the time-of-flight spectrometer NEAT at the Hahn-Meitner-Institut Berlin. The character of the embedded water does not change over a wide range of hydration levels. Especially the interlayer water remains tightly bound and does not show any translational motion. In samples with excess water, however, the water is also distributed in noninterlayer voids, leading to the observation of additional motions of bulklike or confined water. The dynamic behavior of hydrated graphite oxide can be described by a consistent model that combines two two-site jump motions for the motions of the water molecules and the motions of OH groups.
Graphite oxide (GO) and its derivatives have been studied using
13C and 1H NMR. The 13C NMR
lines at
60, 70, and 130 ppm are assigned to C−OH, C−O−C, and >CC<
groups in the bulk of the material,
respectively. The >CC< double bonds are relatively stable,
while C−OH groups may condense to form
C−O−C (ether) linkages. There are at least two magnetically
inequivalent C−OH sites, and the structure
does not necessarily possess long-range order. Water molecules
interact very strongly with the structure.
The results reveal a number of new structural
features.
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