A multi-stimuli responsive metallosupramolecular polypseudorotaxane gel constructed by self-assembly of a pillar[5]arene-based pseudo[3]rotaxane via zinc ion coordination and its application for highly sensitive fluorescence recognition of metal ions

Abstract

A novel metallosupramolecular polypseudorotaxane has been successfully prepared via a pillar[5]arene-based pseudo[3]rotaxane and zinc ion coordination. The obtained metallosupramolecular polypseudorotaxane could self-assemble to form a fluorescent metallosupramolecular polypseudorotaxane gel at a high concentration. Interestingly, by taking advantage of the dynamic nature of metal–ligand bonds, host–guest interactions and hydrogen bonding interactions, the multiple stimuli-responsive gel–sol phase transitions of such a polypseudorotaxane gel were successfully realized under different stimuli, such as temperature, sulfide, formaldehyde, competitive guests, etc. Moreover, this metallosupramolecular polypseudorotaxane gel could effectively sense Fe³⁺ and Cu²⁺via fluorescence. It is worth noting that this metallosupramolecular polypseudorotaxane gel could be used as an ultrasensitive fluorescent sensor for detecting Fe³⁺ with a fluorescence spectrum detection limit of 0.893 nM. Meanwhile, the detection limit was 45.7 nM for Cu²⁺, also indicating the superior sensitivity of the gel to Cu²⁺. Moreover, thin films based on this metallosupramolecular polypseudorotaxane gel were prepared, which could act as convenient test kits for detecting Fe³⁺ and Cu²⁺.