Strong electro-optic effect in self assembled peptide nanofibers

Low-cost biocompatible nanomaterials with opto-electronic properties are highly desirable as they may open avenue onto new biomedical imaging or sensing technologies. It was recently unveiled that short peptides self-assemble into various micro- and nano-structures including tubes, tapes and fibrils. These structures were found to possess striking mechanical, electrical and optical properties, which are rarely seen in organic materials. Here, we focus on the electro-optic (EO) properties of di- and tri-phenylalanine self-assembled peptide fiber structures and characterize them by using a home built EO phase microscope (PLEOM). This prototypal set-up is based on a highly sensitive interferometric scheme allowing to detect electric-field driven optical phase shifts at the focal point of the microscope objective. The Pockels effect requires a breaking of centro-symmetry, which is intrinsic to the ferroelectric phase in oxide crystals or to molecular crystals of adequate symmetry, or also in statistically oriented molecular assemblies such as biological tissues or membranes.