Synthesis of monolayer-patched graphene from glucose.

The extraordinary electronic and mechanical properties of graphene have stimulated intense research on developing simple methods for the large-scale synthesis of graphene. High-quality large-area graphene films prepared by the chemical vapor deposition of various carbon-containing molecules on arbitrary substrates could meet the requirements of large-area electronic applications. For the industrial production of conductive graphene powder on the ton scale, 11–13] the chemical exfoliation of graphite minerals still remains the main manufacturing path. On the other hand, the exclusive two-dimensional polymerization of graphene-like structures from simple monomers still presents a challenge for carbon chemists. Further fine-tuning of the Fermi level of graphene by doping offers a way to control the electronic structure of carbonaceous materials and is of major interest for their application in electronics, electrodes, and catalysis. The electronic properties of doped graphene are strongly linked to the dopant concentration, which is only poorly controlled by current methods. It is therefore highly challenging but desirable to develop effective approaches for fabricating graphene that is cheap yet of high quality (e.g. high surface area, high conductivity, doping level, and uniform morphology) in a controlled manner. Herein we report a simple yet versatile approach for the synthesis of two-dimensional (2D) carbon materials ranging from free-standing monolayers to oligolayered graphene by the calcination of glucose, a most abundant, sustainable compound. In this synthesis only dicyandiamide (DCDA) was added for the temporary in situ formation of layered graphic carbon nitride (g-C3N4), which serves as a sacrificial template. This approach is also facile for gradually tuning the concentration of the nitrogen dopant in a broader range without disturbing the morphology of graphene. In a typical synthesis, the two-step heating of a mixture of DCDA and glucose under a protective flow of N2 directly resulted in freestanding graphene with a yield of 28–60% (calculated based on added carbon from glucose). The overall formation process is depicted in Figure 1: Thermal condensation of DCDA creates a layered carbon