Stimuli-Sensitive Pyrenylated Hydrogels as Optical Sensing Platform for Multiple Metal Ions

In the present work, we report a thermoresponsive hydrogel formed by the self-assembly of compounds 1 and 2 Milli Q water. Both hydrogels showed thixotropic behavior. Atomic force microscopy (AFM) studies confirm the fiber-like microstructure of compounds 1 and 2, but denser fibers were observed in the case of compound 1. The hydrogel formed by compound 1 detected Cu2+, Fe3+, and Hg2+, whereas the hydrogel of 2 showed a change in the optical signal, specifically upon adding Cu2+ and Hg2+. Mechanistically, adding metal ions to the hydrogel resulted in the formation of a (1:1) complex with Fe3+ and Hg2+ and (2:1) with Cu2+. The detection of metal ions has also been achieved in real-life samples, such as in tap water. Low-cost portable gel-coated paper strips have also been developed for the onsite detection of these metal ions.