Highly selective recognition of acetate and bicarbonate by thiourea-functionalised inverse opal hydrogel in aqueous solution.

We have synthesised an inverse opal hydrogel functionalised with a thiourea moiety as an anion recognition site. The resulting hydrogel showed remarkable changes of its structural colour with respect to acetate and bicarbonate ions selectively in aqueous solution, indicating a potential as colorimetric sensing materials for hydrophilic anions.