Sensitization effects of supramolecular assemblies on the luminescence of terbium-ion prulifloxacin complexes

Luminescence enhancement of terbium-ion prulifloxacin complexes (Tb(III)–PUFX) in supramolecular hydrogels formed by assembly of 1,3:2,4-di-O-benzylidene-D-sorbitol (DBS) was investigated by steady-state fluorescence, varying temperature fluorescence and time-resolved fluorescence. The luminescence images show that Tb(III)–PUFX were dispersed in the DBS gels. The luminescence intensity of Tb(III)–PUFX in the DBS gels was significantly increased in comparison with that in corresponding aqueous solutions. The varying temperature fluorescent spectra show that the luminescence intensity of Tb(III)–PUFX decreased with an increase in the temperature. This implies that the luminescence enhancement of Tb(III)–PUFX is related to the dissociation and the formation of the DBS assemblies. Time-resolved fluorescence measurements show slower rotational motion in DBS gels in comparison with that in the corresponding aqueous solutions. This may be ascribed to a unique microstructure of three-dimensional network formed by DBC aggregates, resulting in deactivation of the nonradiative relaxation. The images of field emission scanning electron microscopy and polarized optical microscopy indicate that the morphology of the DBS assemblies was not influenced upon addition of Tb(III)–PUFX to the DBS gels.