Nanocomposites and nanomaterials
Synthesis and characterization of hybrid inorganic (LDH)-organic (terephthalate) nanostructures

Smalenskaite A., Beganskiene A., Skaudzius R., Kareiva A.
Department of Inorganic Chemistry, Institute of Chemistry, Vilnius University, Naugarduko 24, LT 03225, Vilnius, Lithuania
E-mail: aurelija.smalenskaite@chf.vu.lt

       Layered double hydroxides (LDHs) are compounds composed of positively charged brucite-like layers with an interlayer containing anions and water molecules ([M2+1-xM3+x (OH)2]x+(Ay−) x/y·zH2O, where M2+and M3+ are divalent and trivalent metal cations and Ay− is an intercalated anion). In the composition of LDH materials the M2+ and M3+ cations can be substituted or partly replaced by other cations and the interlayer anion can also be replaced by other anions, modifying their chemical and physical properties.
         Considerable attention has been focused on incorporating rare earth elements into LDH host layers to develop new functional materials, which resemble designed optical properties [1, 2]. Many investigations of luminescent materials based on aromatic carboxylates of lanthanides have related to their use in analytical chemistry, biology, medical diagnostics, and environmental monitoring.
        LDHs doped with Eu3+, Yb3+, Tb3+ and Nd3+ were prepared through the microemulsion method [3]. It was concluded that the lanthanide content in the LDH samples depends on the ionic radius of the lanthanide cation and on fabrication conditions. Eu3+ and Nd3+ were incorporated also into hydrocalumite and mayenite [4]. The Zn/Al/Eu LDHs were reported as perspective and efficient luminescent materials [5].
      The organic-inorganic hybrid phosphors have been designed and assembled by the intercalation of salicylic acid, as sensitizer, into the layered lanthanide hydroxides with the compositions of Gd/Tb/Eu/OH/NO3/H2O through ion-exchange reaction under hydrothermal condition [6]. Luminescent ordered multilayer transparent ultrathin films based on inorganic rare earth elements doped layered double hydroxides Mg/Al/Eu nanosheets and organic ligand were recently fabricated via layer-by-layer assembly method [7].
       In this work, the LDHs with the metal cation composition of Mg3Al1-xLnx (Ln = Nd, Sm, Eu, with the Ln3+substitution rate from 1 to 10 mol%) were synthesized using a novel sol-gel method. The main aim of this study was to investigate the effect of Ln3+ substitution on structural features of the obtained layered double hydroxides with intercalated terephthalate anions and estimate the luminescent properties of the hybrid inorganic-organic LDHs samples.
     Acknowledgments
    This research was funded by a grant SINALAN (No. S-LU-18-13) from the Research Council of Lithuania.

1.	Binnemans K. Lanthanide-based luminescent hybrid materials // Chem Rev.-2009.-109. P.4283-4374.
2.	Yagami T., Hagiwara M., Fujihara S. Fabrication of luminescence-sensing films based on surface precipitation reaction of Mg–Al–Eu LDHs // J Sol Gel Technol.-2017.- 82.-P. 380–389.
3.	Posati T., Costantino F., Latterini L., Nocchetti M., Paolantoni M., Tarpani L. Hydrotalcite-like materials as precursors of catalysts to produce hydrogen from methanol // Inorg Chem.-2012.- 51.-P. 13229–13236.
4.	Domínguez M., Pérez-Bernal M.E., Ruano-Casero R.J., Barriga C., Rives V., Ferreira R.A.S., Carlos L.D., Rocha J. Multiwavelength luminescence in lanthanidedoped hydrocalumite and mayenite // Chem Mater. -2011.-23.-P. 1993–2004.
5.	Gao X.R., Lei L.X., Kang L.W., Wang Y.Q., Lian Y.W., Jiang K.L. Synthesis, characterization and optical properties of a red organic-inorganic phosphor based on terephthalate intercalated Zn/Al/Eu layered double hydroxide // J Alloys Compd.-2014.- 585.-P. 703–707.
6.	Liu L.L., Xia D., Liu W.S., Tang Y. Initial theoretical evaluation of pore structure for metal-organic frameworks // Chinese J Inorg Chem.-2013.-29.-P. 1663–1667. 
7.	Zhang W.J., Li Y.L., Fan H.X. Lanthanide luminescence for biomedical analyses and imaging. Opt Mater. -2016.-51.-P. 78–83.