Modular modification of the two-dimensional electronic properties of graphene by bio-inspired functionalization

Graphene is emerging as a promising 2D material in a variety of advanced electronic and optoelectronic devices. For optimization of the performance of the devices, tuning the work function of the graphene is crucial. This work presents a modular yet straightforward way to modulate the work function of single-layer graphene using specifically designed peptides with varied amounts of amine and indole groups assembled from an aqueous solution. Molecular doping of the graphene layer and the formation of a permanent dipole at the graphene interface led to either decreasing or increasing the work function, depending on the peptide sequence. Overall, the peptide modification increases the conductivity of the graphene layer with hardly compromising its transparency. Consequently, the modification of graphene by peptides emerges as a powerful low-cost and environmentally friendly tool to control 2D materials' electronic properties. The modularity of peptides provides a simple way to tune the electronic properties by peptide design.