Well crystallized nanoplates of the (Y0.95−xGdxEu0.05)2(OH)5NO3·nH2O ternary layered rare-earth hydroxides (LRHs), synthesized hydrothermally, have been investigated with emphasis on the effects of Gd3+ substitution for Y3+ on the structural features and optical properties. Characterizations of the materials were achieved by the combined techniques of XRD, FT-IR, TEM, DTA/TG, and optical spectroscopies. The results showed that Gd3+ substitution leads to linearly expanded ab plane, shortened interlayer distance (c/2), and reduced hydration (smaller n value) of the crystal structure. As a consequence, the Ln3+ partially shifts from the C4v to C1 site symmetries and thus leads to systematically altered photoluminescence behaviors. Under the 7F0→5L6 transition excitation of Eu3+ at 394 nm, both the 5D0→7F2 to 5D0→7F4 and the 595 nm 5D0→7F1 to 590 nm 5D0→7F1 intensity ratios linearly increase towards a higher Gd3+ content. The incorporated Gd3+ cations selectively sensitize emission from the C1-site Eu3+ and produce a new charge transfer (CT) excitation band at ∼254 nm. With this, the desired 615-nm red emission is obtainable either under intra-4f6 transition excitation of Eu3+ or by exciting the CT band. The materials have similar fluorescence lifetimes of 0.85 ± 0.05 ms for the 615-nm emission, irrespective of the Gd3+ content and excitation wavelength.
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