Tunable photoluminescence of europium-doped layered double hydroxides intercalated by coumarin-3-carboxylate

We report a highly tunable photoluminescence of rare-earth (europium, Eu3+) doped layered double hydroxides (LDHs) intercalated by an organic photofunctional anion, courmarin-3-carboxylate (C3C). Novel Eu3+-doped LDHs intercalated by C3C (ZnAlEu-LDH-C3C) with high purity and crystallinity have been successfully synthesized via an interlayer ion exchange process using Eu3+ doped LDH (ZnAlEu-LDH-NO3) as a precursor. A bilayer arrangement with nearly perpendicular orientation was deduced for the C3C anions in the LDH interlayer space. Compared with the precursor, ZnAlEu-LDH-C3C shows a strong UV absorbance and an interesting photoluminescence function, possibly due to an interfacial energy transfer process between the interlayer C3C anions and the Eu3+ within the LDH lattices. The photoluminescent spectra denote a lower symmetry of the coordinating environment around Eu3+ within ZnAlEu-LDH-C3C. More importantly, the photoluminescence of ZnAlEu-LDH-C3C could be highly tuned by simply adjusting the structural constituents (including the content of Eu3+ or C3C) or the excited wavelength. These findings open new avenues to prepare tunable photoluminescent materials and further have potential applications for optical devices.