Europium-doped Zn-Al-LDH intercalated with 4-biphenylcarboxylate anion and undoped Zn-Al-LDH intercalated with its anionic Eu(III) complex: Structural and UV or X-ray excited luminescence properties

Undoped and doped layered double hydroxides (LDH) were obtained by coprecipitation and the bca (biphenyl-4-carboxylate) anion or [Eu(bca)4]- intercalation by solvothermal post treatment. The three systems, (i) [Zn2Al1-xEux]NO3-LDH x = 0.1 at.%, (ii) [Zn2Al1-xEux]bca-LDH x = 0.1 at.% and (iii) [Zn2Al][Eu(bca)4]-LDH are compared by XRD, FTIR, Zeta Potential, PLS and XEOL characterizations. The luminescent properties are exciting. The bca intercalation/coordination increases the luminescence intensity of the doped LDH because decreases the –OH groups, luminescence suppressors by multi-phonon process, and increases the ligand to Eu3+ energy transfer processes. The luminescence in the (iii) system is less intense than the (ii) system but more intense than (i) system and the Eu3+ symmetry in the intercalated complex is different from the free one. X-ray excited optical luminescence occurs on all systems with different radiation damage. The intense luminescence remarks the Eu3+ as an excellent spectroscopic probe, as dopant in the brucite-like layers and in the interlayer space as anion complex. Finally, the LDH host structure acts as a protective environment for the luminescence properties of intercalated species. Thus, LDH systems become potential candidates combining the inorganic and organic properties for promising emission materials.