Through the application of mechanochemistry, controlled forces may be used to drive specific reactions by altering reaction states and pathways. Graphene, a two-dimensional (2D) material, can serve as a model platform for studying the impact of mechanical forces on chemical reactivity, as the single layer of sp2-hybridized C atoms provides a means of seeing how applied forces are distributed across a well-organized atomic lattice. Using Raman micro-spectroscopy and first-principles calculations, we have elucidated the influence strain has on a radical addition reaction of graphene with 4-nitrobenzenediazonium tetrafluoroborate (4-NBD). With increased out-of-plane distortion (transitioning the C atoms from sp2 to sp3 electronic states), the reactivity increases, where greater out-of-plane distortions leading to greater reactivity. Through density functional theory (DFT), it is revealed that the increase in graphene curvature decreases the activation barrier and increases the thermodynamic favorability of 4-NBD functionalization. Additionally, we find that the orientation of the graphene 2pz orbitals are influenced by the lattice curvature, and relate the thermodynamic feasibility of the reaction with the orbital orientation. These studies serve as an example of the influence that precise application of forces can have on directing C-C bond forming reactions with graphene and has significant implications for controlling the electronic structure of graphene in a well-defined fashion.

Studies of the reactivity of graphene driven by mechanical distortions

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