Two organic sensitisers 4-biphenylcarboxylate (BPC) and terephthalate (TA) were intercalated into the gallery of layered europium hydroxide (LEuH). PL spectra tests indicated that BPC markedly enhanced the red luminescence of Eu(3+) due to efficient energy transfer between BPC and Eu(3+), forming a contrast to intercalated TA and the starting NO(3)(-) anions in the gallery. The energy level matching of the organic guests and Eu(3+) was also discussed to explain the energy transfer from sensitiser to Eu(3+).

The NO3–‐type Eu3+‐doped layered gadolinium hydroxide (NO3–LGdH:Eu) was prepared by a developed homogeneous precipitation method through hexamethylenetetramine (HMT) hydrolysis with hydrothermal treatment. Two amino acid anions, phenylalanine (Phe) and tyrosine (Tyr), were intercalated into LGdH:Eu to form composites Phe–LGdH:Eu and Tyr–LGdH:Eu. Photoluminescence studies show that the incorporation of Phe and Tyr into the host layer can sharply quench the Eu3+ luminescence. This simple method is expected to be applied in biological systems for detecting amino acids.

The structural control involving staging formation was studied in the nanocomposites of macrocyclic tetraazacrown ether carboxylic acid derivative (TECA) and layered double hydroxide (LDH) obtained by an osmotic swelling/restoration process. After NO(3)-type MgAl-LDH was osmotically swollen in formamide, TECA was added, leading to a restoration of the LDH sheets and formation of TECA-LDH nanocomposites. In the wet state, the structure of the composites was homogenous, and the basal spacings of ∼2.0 or 1.8 nm were not changed by the water-washing process that removed formamide and caused the replacement of NO(3)(-) by CO(3)(2-). However, in the drying process, both the orientation of TECA in the interlayer and the formed staging structure varied with the TECA content. The TECA orientation changed from horizontal to tilted/twisted and finally to vertical with interlayer TECA density. The staging structure occurred for samples with both TECA and small inorganic guests coexisting in the interlayer. Third-staging, second-staging, and homogenous structures were observed at TECA/LDH weight ratios of low (0.125 and 0.25), medium (0.5) and large (1 and 2) values, respectively. The decrease of negative charge of TECA ions from -4 to -1 led to the co-existence of small ions (NO(3)(-)) with TECA in the gallery and the formation of a NO(3)(-)-containing staging structure, even at a high TECA/LDH ratio of 2. The study of the influence of CO(3)(2-) on the composite structure indicates that a TECA/CO(3)(2-) ion exchange progressed reversibly and the staging structure formed is thermodynamically stable, depending mainly on the chemical composition of the interlayer guests. The staging formation could be explained by the Daumas-Hérold model, which differs markedly from the Rüdorff model previously proposed for the LDH system. The treatment in formamide of the composite such as T2L+Na(2)CO(3) with staging structure shows that the transformation process is reversible, and these kinds of composites may be used as an adsorbent for some harmful organic solvents.

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.

The organic sensitizer terephthalic acid and its anion terephthalate (TA) were introduced into the galleries of europium‐doped layered yttrium hydroxide (LYH:Eu). In contrast to using water as solvent, the use of formamide resulted in the introduction of more organic guests and markedly enhanced the Eu3+ luminescence. Formamide prevented water from entering the system, leading to an excess of terephthalic acid molecules, and more efficient coordination of the TA guest with the Eu3+ in the layers of the composite, all of which may have contributed to the enhanced Eu3+ luminescence.