The results lay the groundwork for the design and application of graphene-based functional materials through oxidation control methods; in other words, by altering the epoxidation density and arrangement patterns. Understanding the structural property relation is also critical for preparing graphene-related materials such as graphene oxide papers through chemical exfoliation methods. Furthermore, with the ability to control the oxidation and reduction process – for example, to modify the structure of graphene by oxidation in specific regions – one can expect to fabricate tunable graphene-related nanodevices, such as chemical sensors or patternable nanoelectric circuits.

To study the system, the researchers built an atomistic model of graphene epoxide where oxygen atoms bind on top of sp2 carbon bonds and form epoxy groups. The team performed first-principles calculations based on density functional theory and conducted a series of simulations for various epoxy symmetries and densities.

For graphene functionalized by very high-density epoxy groups (the ratio between carbon and oxygen atoms is 4:1), a clamped phase is observed that is stabilized by an energy barrier of 0.58 eV. In less-dense graphene oxide, the unzipped phase becomes the only possibility where the sp2 bond in the epoxy group is broken.

The effect of oxidation on the electronic and mechanical properties of graphene has been studied systematically. The bendable epoxy triangle leads to a half loss of Young's modulus of graphene, while leaving the tensile strength unaffected. It also changes the band structure remarkably, from semiconductor with a bandgap depending on oxidation density to flatband magnetism when the epoxy groups bind anti-symmetrically on both sides of graphene. These results have implications for applications such as graphene-based nanocomposites and tunable electronic devices.

Full details can be found in the journal Nanotechnology.