Photoluminescence of Eu³⁺and Tb³⁺ ions adsorbed on oxide nanosheets

Photoluminescence properties of TiO (Ti1.825O4) and NbO (Nb6O17) nanosheets adsorbed with Ln3+ ions were studied comparing with those of photoluminescent GdEuTiO and LaTbTaO perovskite nanosheets. Intense emissions of Ln3+ (Eu3+ and Tb3+) ions adsorbed on TiO and NbO (Ln3+/MO) nanosheets were observed during UV light illumination. The photoluminescence results from the energy transfer from the band gap excitation of the nanosheets to the adsorbed Ln3+. Coadsorbed H2O increased the emission intensities of the adsorbed Ln3+ for the Ln3+/MO samples. On the other hand, no effect of adsorbed H2O on the emission intensities of the photoluminescent perovskite nanosheets was observed because of the presence of Ln3+ on the inside of the nanosheets. Hydrogen-bonding networks between O21 ions of the nanosheet surface and the adsorbed H2O surrounding Ln3+ will promote the energy transfer for the Ln3+/MO samples. Recombination and photoreaction of the produced electron and hole of the nanosheet, and a phonon due to the adsorbed H2O suppress the emission, according to the analyses of effects of pH, adsorbed ions and D2O on the emission.