Novel pH Induced Reversible Luminescent Lanthanide Hydrogels

Two lanthanide complexes were encapsulated into silica matrix (aminopropyltriethoxysilane, APTS) via a mild sol-gel technique, resulting in two luminescent xerogels. Subsequently two novel luminescent polymeric hydrogels were successfully fabricated by incorporating these two lanthanide xerogels into the poly(acrylamide) matrix. The europium-ion-containing hydrogel can be sensitized by visible light (408 nm). More interestingly, the emissions of the Ln(III)-containing hydrogel can be switched on-and-off reversibly by a change of the pH value. The resulting color change can easily be observed by naked eyes. These luminescent hydrogels exhibited high stabilities in comparison with xerogels in aqueous media.