Structure and luminescence behaviour of as-synthesized, calcined, and restored MgAlEu-LDH with high crystallinity

Abstract

Highly crystalline Eu(3+)-incorporated MgAl layered double hydroxides (LDHs) were synthesized by the homogeneous precipitation method. For the crystals as-prepared, after their calcination from 200-1000 °C, and, further, after restoration in a Na(2)CO(3) solution, the structural and luminescent changes were investigated for the first time. Eu(3+) ions with a coordination number of, probably, 8, were incorporated into the hydrotalcite layer, which led to a basal spacing (d(basal)) increase, microstrain formation, and crystalline morphology imperfections, while retaining the original lattice symmetry, R3[combining macron]m. In the deconstruction process due to calcination, the Eu(3+) ions restrained the formation of the spinel phase from the layered double oxide (LDO), but did not significantly change the memory effect, by which LDOs can convert to LDHs during the hydration process. For the reversible phase transformation between LDH and LDO, the morphology observation revealed that, in addition to the formation of pores on the surface, nano-slabs were formed, especially for the restored crystals. A layered phase with a d(basal) of 5.8 Å, due to bridging bidentate carbonates with the hydrotalcite layer, was formed in the calcination process at low temperature (300 °C) before the formation of LDO, but could not be restored to a large spacing. Typical (5)D(0) → (7)F(J) (J = 0-4) transitions of Eu(3+) at 579, 593, 615, 653, and 698 nm were observed in the photoluminescence spectra and the intensity of the dominating 615 nm band decreased with the LDH deconstruction and the formation of free water, and then increased with the formation of LDOs in the calcination process, and vice versa in the reconstruction process. The Eu(3+) ions had a probable 9- or 10-coordination mode in addition to the probable 8-coordination mode as the spinel phase appeared.

Anticancer Drug-Incorporated Layered Double Hydroxide Nanohybrids and Their Enhanced Anticancer Therapeutic Efficacy in Combination Cancer Treatment

“…And the size distribution lies in the region of 600–2000, 700–2000, and 600–2000 nm in both deionized water and DMEM. The organic/LDH nanohybrids usually showed formation of agglomerate due to the strong interparticle interaction [59, 60]. However, it did not mean that the primary particles of nanohybrids with ~200 nm lateral size strongly aggregated in the aqueous media, as they can be easily stabilized into small assembly of particles under appropriate treatment of stabilizing agents.…”

Layered Double Hydroxide Materials: Assembly and Photofunctionality

“…It was reported that some rare-earth ions, such as lanthanide Tb 3+ , Eu 3+ , and Nd 3+ , can be doped into the octahedral lattice of the brucite-like layer [27,28]. Incorporation of Tb 3+ has been achieved by coprecipitation method under ambient conditions [29].…”

Luminescent Layered Double Hydroxides Intercalated with an Anionic Photosensitizer via the Memory Effect

“…Synthetic LDHs exhibit a wide flexibility in their composition, as a score of metal cations and polyvalent anions can be introduced in the structure, tuning their chemico-physical properties [1][2][3]. By changing both the interlayer and the metal components, LDHs have been tuned towards different applications, serving as heterogeneous catalysts, catalyst supports [4], water treatment agents [5], luminescent materials [6][7][8][9], etc. Synthetic LDHs exhibit a wide flexibility in their composition, as a score of metal cations and polyvalent anions can be introduced in the structure, tuning their chemico-physical properties [1][2][3].…”

“…Controlled thermal decomposition of LDHs converts their structure into a mixed metal oxyhydroxide phase, before reaching a fully oxidic end product [5,9,19,20]. Starting from the oxyhydroxide phase, the lamellar LDH structure can be recovered by re-hydrating the product in aqueous solutions containing anions, a phenomenon known as the memory effect [5,9,[20][21][22][23]. During this process, selective adsorption of dissolved anionic species A n− can efficiently occur, as indicated by the large anion exchange capacity observed for thermally treated samples [24].…”