A bolaamphiphilic amino acid appended photo-switching supramolecular gel and tuning of photo-switching behaviour

Abstract

Self-assembled bolaamphiphilic perylene bisimide (PBI) containing an amino acid appended fluorescent semiconducting soft material (hydrogel) has been discovered at physiological pH. This new organic material based on self-assembled perylene bisimide appended amino acid-based bolaamphiphile (PBI-C₁₁-Y) has been well characterized using various techniques including UV-Vis, fluorescence, X-ray diffraction, FT-IR, transmission electron microscopic (TEM) and atomic force microscopic (AFM) studies. Interestingly, the UV-Vis absorption properties of the soft-material are dependent on the pH of the medium. This PBI-conjugated amino acid appended gelator molecule contains a centrally located perylene bisimide moiety as well as an aromatic amino acid L-tyrosine at the side chains, which are extremely useful for interacting with the delocalized large π-surface of GO (graphene oxide) or RGO (reduced graphene oxide) to form a GO/RGO containing hybrid hydrogel. Graphene oxide and reduced graphene oxide have been successfully incorporated into the nanofibrillar network structure of the PBI-C₁₁-Y based gel to make nanohybrid systems. The I–V profile of the semiconducting photo-responsive soft-material of the PBI-C₁₁-Y has been successfully tuned upon the incorporation of GO and RGO within the gel-based soft material. This PBI-C₁₁-Y xerogel based structure shows photo-switching behaviour upon exposure to white light. The ON/OFF ratio of the PBI-C₁₁-Y can be modulated upon the inclusion of GO and RGO within the hydrogel matrix. Furthermore, the OFF state stability of the PBI-C₁₁-Y xerogel material has been increased upon the inclusion of RGO. Regulation of the photo-switching behaviour of the PBI-C₁₁-Y based xerogel holds promise for making PBI-containing amino acid appended biomaterials with interesting properties in future.