272
E.F. Sheka
Morphology Empirical experiments reveal a remarkable disordering of the initial graphene structure even by partial oxidation so that the chemically produced
graphene polyoxides (GOs) are highly amorphous (see [66–69] and references
therein).
The performed computational experiment fully supports this finding since none
of the regularly structured GOs has been obtained in the study.
Graphene Oxidation as a Process in General Experimentally was shown that
the oxidation of the graphene proceeds in a rather random manner [66]. The saturated at% ratio of oxygen to carbon is ∼20–45 [69–72]. When GOs are heated to
110 °C, there is still about 5–10 at% oxygen left [71–73].
As shown computationally, the oxidation can be considered as a stepwise addition of oxidants to the pristine graphene molecule subordinated to the algorithm
governed by the list of high-rank atomic chemical susceptibilities N DA . In numerous cases presented in [64, 65], the algorithm action does cause seemingly random
distribution of oxidants over the molecule body in due course of the oxidation process.
The algorithmic approach to the chemical modification of sp 2 nanocarbons does
not impose any restriction on the limit at% ratio of any addend attached to the carbon
skeleton, in general. This was supported by the results of the ‘computational synthesis’ of polyderivatives of fullerene C 60 [5] as well as polyhydrides and polyfluorides
of the (5, 5) NGr molecule [60]. However, the initial radicalization of any pristine
sp 2 molecule, which is provided by N D effectively unpaired electrons, is gradually
suppressed as the chemical reaction proceeds. The molecule chemical reactivity is
little by little worked out approaching zero due to which the reactions stop. This
explains why the hydrogenation and fluorination of fullerene C 60 is terminated at
producing C 60 F 48 and C 60 H 36 polyderivatives, respectively, [59, 62] and why at%
ratio of hydrogen to carbon in the experiment of Elias et al. [61] decreases when
going from graphene polyhydrides formed from two-side, H-accessible, perimeterfixed membranes to one-side, H-accessible ripples [60]. The same regularities govern the (5, 5) NGr molecule oxidation, which, as shown, terminates the oxidation
at achieving ∼67 at% of oxygen when the oxidation is provided by the addition
of either hydroxyls or oxygen atoms. The saturation number involves filling both
edge and basal atoms. Since the pristine (5, 5) NGr molecule is rather small, the
contribution of edge atoms is significant. If the latter is excluded, the basal plane
coverage approaches 48 at% that is quite reasonable and points to a predominant
C 2 O stoichiometry. The earlier mentioned data of ∼20–45 at% are mainly related
to the basal positions of rather big experimental samples for which the contribution
of edge atoms is small.
In contrast, the availability of the remaining oxygen in the reduced GOs (rGOs)
subjected to heating up to 1100 °C, is connected with the edge atoms of the latter. As shown, these atoms, which include not only perimeter atoms of the rGOs
molecules but the atoms framing every defect zone, form a local area with very high
chemical reactivity. The oxidants are strongly coupled with the atoms and can leave
the molecule jointly with the carbon partners. The number of such atoms depends
E.F. Sheka
Morphology Empirical experiments reveal a remarkable disordering of the initial graphene structure even by partial oxidation so that the chemically produced
graphene polyoxides (GOs) are highly amorphous (see [66–69] and references
therein).
The performed computational experiment fully supports this finding since none
of the regularly structured GOs has been obtained in the study.
Graphene Oxidation as a Process in General Experimentally was shown that
the oxidation of the graphene proceeds in a rather random manner [66]. The saturated at% ratio of oxygen to carbon is ∼20–45 [69–72]. When GOs are heated to
110 °C, there is still about 5–10 at% oxygen left [71–73].
As shown computationally, the oxidation can be considered as a stepwise addition of oxidants to the pristine graphene molecule subordinated to the algorithm
governed by the list of high-rank atomic chemical susceptibilities N DA . In numerous cases presented in [64, 65], the algorithm action does cause seemingly random
distribution of oxidants over the molecule body in due course of the oxidation process.
The algorithmic approach to the chemical modification of sp 2 nanocarbons does
not impose any restriction on the limit at% ratio of any addend attached to the carbon
skeleton, in general. This was supported by the results of the ‘computational synthesis’ of polyderivatives of fullerene C 60 [5] as well as polyhydrides and polyfluorides
of the (5, 5) NGr molecule [60]. However, the initial radicalization of any pristine
sp 2 molecule, which is provided by N D effectively unpaired electrons, is gradually
suppressed as the chemical reaction proceeds. The molecule chemical reactivity is
little by little worked out approaching zero due to which the reactions stop. This
explains why the hydrogenation and fluorination of fullerene C 60 is terminated at
producing C 60 F 48 and C 60 H 36 polyderivatives, respectively, [59, 62] and why at%
ratio of hydrogen to carbon in the experiment of Elias et al. [61] decreases when
going from graphene polyhydrides formed from two-side, H-accessible, perimeterfixed membranes to one-side, H-accessible ripples [60]. The same regularities govern the (5, 5) NGr molecule oxidation, which, as shown, terminates the oxidation
at achieving ∼67 at% of oxygen when the oxidation is provided by the addition
of either hydroxyls or oxygen atoms. The saturation number involves filling both
edge and basal atoms. Since the pristine (5, 5) NGr molecule is rather small, the
contribution of edge atoms is significant. If the latter is excluded, the basal plane
coverage approaches 48 at% that is quite reasonable and points to a predominant
C 2 O stoichiometry. The earlier mentioned data of ∼20–45 at% are mainly related
to the basal positions of rather big experimental samples for which the contribution
of edge atoms is small.
In contrast, the availability of the remaining oxygen in the reduced GOs (rGOs)
subjected to heating up to 1100 °C, is connected with the edge atoms of the latter. As shown, these atoms, which include not only perimeter atoms of the rGOs
molecules but the atoms framing every defect zone, form a local area with very high
chemical reactivity. The oxidants are strongly coupled with the atoms and can leave
the molecule jointly with the carbon partners. The number of such atoms depends