Pyrene-based fluorescent supramolecular hydrogel: scaffold for energy transfer

Abstract

The self-assembled gelation of an amino-acid-based low molecular weight gelator having a pyrene moiety at the N terminus and a bis-ethyleneoxy unit linked with succinic acid at the C terminus is reported. This amphiphile is capable of gelating binary mixtures (1/3 v/v) of CH₃CN/water, DMSO/water, and DMF/water, and the minimum gelation concentration (MGC) varied from 0.2 to 0.3 % w/v. The sodium salt of the amphiphile efficiently gelates water with an MGC of 1.5 % w/v. The participation of different noncovalent interactions in supramolecular gelation by formation of fibrillar networks was investigated by spectroscopic and microscopic methods. High mechanical strength of the supramolecular gels is indicated by storage moduli on the order of 10³ Pa. The hydrogel was utilized for energy transfer, whereby inclusion of only 0.00075 % w/v of acridine orange resulted in about 50 % quenching of the fluorescence intensity of the gel through fluorescence resonance energy transfer.