A composition of graphene-based nanomaterials and a method of preparing the composition are provided. A carbon-based precursor is dissolved in water to form a precursor suspension. The precursor suspension is placed onto a substrate, thereby forming a precursor assembly. The precursor assembly is annealed, thereby forming the graphene-based nanomaterials. The graphene-based nanomaterials are crystallographically ordered at least in part and configured to form a plurality of diffraction rings when probed by an incident electron beam. In one aspect, the graphene-based nanomaterials are semiconducting. In one aspect, a method of engineering an energy bandgap of graphene monoxide generally includes providing at least one atomic layer of graphene monoxide having a first energy bandgap, and applying a substantially planar strain is applied to the graphene monoxide, thereby tuning the first energy band gap to a second energy bandgap.