Super metal hydrogels constructed from a simple tripodal gelator and rare earth metal ions and its application in highly selective and ultrasensitive detection of histidine

Abstract

A series of stable super metal hydrogels (TP-Ms, M = Tb³⁺, Eu³⁺, La³⁺ and Ce³⁺) with a low critical gelation concentration (2.28 × 10⁻³ M, 0.1%) was successfully constructed by forming hierarchical assemblies of a tripodal gelator (TP) with rare earth metal ions (Tb³⁺, Eu³⁺, La³⁺ and Ce³⁺). Interestingly, the super metal hydrogels TP-Eu and TP-La show a specific and ultrasensitive response to histidine (His). The addition of a series of amino acids into the metal hydrogels TP-Eu and TP-La showed that only His could induce distinct fluorescent enhancement for TP-Eu and TP-La, while other amino acids did not significantly interfere with the His sensing process. The LODs of super metal–hydrogel TP-Eu and TP-La for His are (1.83–1.94) × 10⁻⁹ and (1.83–1.85) × 10⁻⁹ M, respectively. In addition, constructing super supramolecular metal hydrogels by hierarchical assemblies of an easily synthesized tripodal gelator and rare earth metal ions is a novel and efficient approach to the design and development of multi-functional super supramolecular metal hydrogel-based materials.