Graphene, a carbon allotrope consisting of one atom thickness of planar sheets of sp2-bonded carbon atoms, has become the focus of considerable research attention because of its high conductivity, 2D structure, and superior mechanical properties. Site-specific patterning on graphene can increase the bandgap of this material for applications in integrated optics and electronics, and the immobilization of soft organic and biologically active materials is necessary for the fabrication of graphene-based sensors. While the adaptation of conventional lithographic processing to graphene is being pursued for the fabrication of integrated electronics, many of these potential applications can only be realized through the combination of organic reactions on graphene with molecular printing techniques. However, a consequence of the stabilizing conjugation of graphene is that the basal plane is resistant to chemical functionalization, so carrying out site-specific organic reactions on graphene is challenging. Consequently, this extended conjugation provides thermal stability and resistance to chemical functionalization that would perturb the stabilizing delocalization that extends along the basal plane. For this reason, the basal plane of graphene is significantly less reactive than other fullerene carbon allotropes.
Functional molecules such as methoxide have been shown to be anchored to graphene using noncovalent interactions onto the basal plane or coupling to oxidized defect sites and edges (see FIG. 18). Alternatively, photochemical, dipolar-cycloadditions, and diazonium salt reactions are known to couple organics directly to the basal plane of graphene; however the requisite input of energy would denature or destroy soft matter, and thus such methods are not compatible with molecular patterning techniques.
There remains, therefore, a need for reliable, scalable and commercially applicable techniques for immobilization of soft organic and biologically active materials via site-specific patterning on the basal plane of graphene for use in integrated optics and electronics.