Luminescent layered double hydroxides intercalated with an anionic photosensitizer via the memory effect

Abstract

Layered double hydroxides (LDHs) containing Eu 3+ activators were synthesized by coprecipitation of Zn 2+ , Al 3+ , and Eu 3+ in alkaline NO 3− -rich aqueous solution. Upon calcination, these materials transform into a crystalline ZnO solid solution containing Al and Eu. For suitably low calcination temperatures, this phase can be restored to LDH by rehydration in water, a feature known as the memory effect. During rehydration of an LDH, new anionic species can be intercalated and functionalized, obtaining desired physicochemical properties. This work explores the memory effect as a route to produce luminescent LDHs intercalated with 1,3,5-benzenetricarboxylic acid (BTC), a known anionic photosensitizer for Eu 3+ . Time-dependent hydration of calcined LDHs in a BTC-rich aqueous solution resulted in the recovery of the lamellar phase and in the intercalation with BTC. The interaction of this photosensitizer with Eu 3+ in the recovered hydroxide layers gave rise to efficient energy transfer from the BTC antennae to the Eu 3+ ions, providing a useful tool to monitor the rehydration process of the calcined LDHs.