A Reversibly Responsive Fluorochromic Hydrogel Based on Lanthanide-Mannose Complex.

Fluorochromic materials that are dynamic in response to external stimuli are of great interest for the development of advanced sensors and luminescent materials. Herein, a design based on a lanthanide-containing polymeric hydrogel possessing characteristic emission of lanthanides (Eu and Tb) and showing response to stimuli of metal ions is reported. The fluorochromic hydrogel is prepared using a lanthanide-mannose complex in gelation matrix. The lanthanide-mannose complex shows tunable fluorescent emission in response to Fe2+, due to the inhibition of the "antenna effect" between metal ions and ligands upon stimulation. The fluorescent hydrogel shows reversible "On/Off" fluorochromic response to Fe2+/ethylenediaminetetraacetic acid (EDTA). Remarkably, the fluorescent hydrogel is proven nontoxic and biocompatible; and a proof-of-application as in situ 3D cell culture extracellular matrix with reversible fluorochromic "On/Off" switch upon Fe2+/EDTA is demonstrated. This reversibly responsive fluorochromic hydrogel demonstrates a way to fabricate smart optical materials, particularly for biological-related applications where reversible response is required.