An efficient iodide ion chemosensor and a rewritable dual-channel security display material based on an ion responsive supramolecular gel

Abstract

By introducing multi-self-assembly driving forces, coordination binding sites and signal groups into the same molecule, a well designed functional gelator G1 was synthesized. The gelator G1 could form a stable Pb²⁺-coordinated supramolecular metallogel (PbG) accompanied with aggregation-induced fluorescence emission (AIE). PbG shows the reversible selective fluorescent response for I⁻ under a gel–gel state. The detection limit of PbG for I⁻ is 1.0 × 10⁻⁷ M. The AIE fluorescence of PbG could be reversibly switched “on–off–on” under gel–gel states via alternatively adding I⁻ and Pb²⁺ water solution into PbG. Other anions could not induce similar stimuli-response for PbG. Interestingly, when a writing brush dipped in I⁻ water solution was used to write on the xerogel film of PbG, the film did not show any color changes. However under UV at 365 nm, a clear dark writing image appeared. This dark writing could be erased by brushing Pb²⁺ on the film. More interestingly, when the PbG film containing the invisible I⁻ writing was exposed to iodine vapor, a clear brown writing appeared on the film. However, when this film was placed under the room atmosphere for one minute, the brown writing gradually disappeared. Therefore, the PbG film could act as not only a convenient reversible I⁻ detection test kit, but also an erasable dual-channel security display material.