- Peptide fibril nanostructures have been advocated ascomponents of future biotechnology and nanotechnologydevices. However, the ability to exploit the fibril functionalityfor applications, such as catalysis or electron transfer, dependson the formation of well-defined architectures. Fibrils made ofpeptides substituted with aromatic groups are describedpresenting efficient electron delocalization. Peptide self-assem-bly under various conditions produced polymorphic fibrilproducts presenting distinctly different conductivities. Thisprocess is driven by a collective set of hydrogen bonding,electrostatic, and p-stacking interactions, and as a result it canbe directed towards formation of a distinct polymorph by usingthe medium to enhance specific interactions rather than theothers. This method facilitates the detailed characterization ofdifferent polymorphs, and allows specific conditions to beestablished that lead to the polymorph with the highestconductivity.