Graphene oxide exhibits extensive disorder with a multitude of functional groups and holes making its structure an abstract concept. Multiple structural models make it a dark horse and hamper its utility despite its synthetic ease, maneuverability, and promising applications. Here we probe the impact of the epoxidation process, which is arguably the first kinetic step in graphene oxidation, to identify the induced vulnerabilities of its backbone and to cognize possible pathways for further oxidation. Probing the topological and geometrical variations in the distribution of epoxide on the graphene lattice, we find that the conformational entropy, driven by the combinatorial growth of isomers, aids and abets disorder. Graph theoretical enumeration gives 16 distinct epoxide environments within symmetrically equivalent epoxides. Their stability is primarily influenced by the steric repulsion between the oxygen lone pairs and overlap compatibility of the interepoxy C–C bond. Avoiding steric repulsion either by topology or by equatorial splaying of oxygens leads to stability, without which the network is weakened either by elongation of C–C bonds or by axial splaying of oxygens leading to uneven C–O bonds. The proposed unzipping of the underlying epoxy C–C bond through the cooperativity of strain from three-membered rings and conjugative stabilization from residual sp2 character are found to be incongruous. With an improved bonding model of epoxide, we account for the observed variations in C–C bond lengths and energetics of epoxides in different environments that facilitate strategic mechanistic control for further oxidation.

Strategic perturbations on the graphene framework to inflict a tunable energy band gap promises intelligent electronics that are smaller, faster, flexible, and much more efficient than silicon. Despite different chemical schemes, a clear scalable strategy for micromanaging the band gap is lagging. Since conductivity arises from the delocalized π-electrons, chemical intuition suggests that selective saturation of some sp 2 carbons will allow strategic control over the band gap. However, the logical cognition of different 2D π-delocalization topologies is complex. Their impact on the thermodynamic stability and band gap remains unknown. Using partially oxidized graphene with its facile and reversible epoxides, we show that delocalization overwhelmingly influences the nature of the frontier bands. Organic electronic effects like hyperconjugation, conjugation, aromaticity, etc. can be used effectively to understand the impact of delocalization. By keeping a constant C 4 O stoichiometry, the relative stability of various πdelocalization topologies is directly assessed without resorting to resonance energy concepts. Our results demonstrate that >C�C< and aromatic sextets are the two fundamental blocks resulting in a large band gap in isolation. Extending the delocalization across these units will increase the stability at the expense of the band gap. The band gap is directly related to the extent of bond alternation within the π-framework, with forced single/double bonds causing the large gap. Furthermore, it also establishes the ground rules for the thermodynamic stability associated with the π-delocalization in 2D systems. We anticipate that our findings will provide the heuristic guidance for designing partially saturated graphene with the desired band gap and stability using chemical intuition.

No abstract

Strategic perturbations on graphene framework to inflict a tunable energy bandgap promises intelligent electronics that are smaller, faster, flexible, and much more efficient than silicon. Despite different chemical schemes, a clear scalable strategy for micromanaging the bandgap is lagging. Since conductivity arises from the delocalized π-electrons, chemical intuition suggests that selective saturation of some sp2 carbons will allow strategic control over the bandgap. However, the logical cognition of different 2D π-delocalization topologies is complex. Their impact on the thermodynamic stability and bandgap remains unknown. Using partially oxidized graphene with its facile and reversible epoxides, we show that delocalization overwhelmingly influences the nature of the frontier bands. Organic electronic effects like hyperconjugation, conjugation, aromaticity, etc., can be used effectively to understand the impact of delocalization. By keeping a constant C4O stoichiometry, the relative stability of various π-delocalization topologies is directly assessed without resorting to resonance energy concepts. Our results demonstrate that >C=C< and aromatic sextets are the two fundamental blocks resulting in a large bandgap in isolation. Extending the delocalization across these units will increase the stability at the expense of the band gap. The bandgap is directly related to the extent of bond alternation within the π-framework, with forced single/double bonds causing the large gap. Furthermore, it also establishes the ground rules for the thermodynamic stability associated with the π-delocalization in 2D systems. We anticipate our findings will provide the heuristic guidance for designing partially saturated graphene with desired bandgap and stability using chemical intuition.

No abstract