Photophysics of Self-Assembled PHE-PHE/PVK Systems Studied by FLIM.

Diphenylalanine (Phe-Phe) dipeptide can self-assemble into distinct structures, depending on the preparation conditions, which also influence its photophysical behavior. Therefore, to better understand the energy transfer processes to which those structures are subject and aim an application, it is crucial to find the best techniques that are able to explore the reasons for such distinct behavior. In this work, the photophysical properties of a functional luminescent system composed of self-assembled Phe-Phe distinct nanostructures combined to polyvinylcarbazole (PVK) are studied. Through Fluorescence Lifetime Imaging Microscopy (FLIM), the intermolecular interactions that are explored in the self-assembling supramolecular strategy to render nanotubes and nanovesicles, as well as to combine PVK, and the unique photophysical properties presented by the resulting materials are scrutinized. FLIM was able to evidence the local fluorescence steady-state and time-resolved behavior, the role of electronic excited states in the efficiency of the energy transfer processes that are enabled by the materials combination and the influence of the intermolecular interactions that result in distinct self-assembled Phe-Phe structures. The results show that these systems present modulated fluorescence emission and enhanced energy transfer efficiency, which turn them into interesting alternatives for application in photoluminescent and photovoltaic devices.