Temperature and pH dual-responsive supramolecular hydrogels based on riboflavin sodium phosphate and 2,6-Diaminopurine with thixotropic and fluorescent properties

Abstract

A novel temperature and pH dual-responsive supramolecular (TPS) hydrogels based on riboflavin sodium phosphate (RP) and 2,6-Diaminopurine (DAP) were fabricated and investigated. In this study, the TPS hydrogels were fabricated under different molar ratios of RP to DAP and analyzed with theoretical chemical calculations. These TPS hydrogels can form gels at room temperature and acidic conditions, and convert to sols at higher temperature and alkaline conditions. Thermal studies indicated that TPS hydrogels have thermally reversible properties. Rheological experiments related to frequency sweep experiment proved the formation of the TPS hydrogel. Time sweep experiments show the thixotropic properties of the gel. XRD pattern and SEM confirm that these complexes formed a new crystal structure. FTIR spectra show that the DAP and RP self-assemble through the H-bonding interaction. The UV–vis spectra show that in the visible region, the peaks of TPS hydrogel are red shift compared with TPS sol and RP solution. The fluorescence lifetime of TPS hydrogel increased to 4.1 ns longer than that of RP solution 2.6 ns.