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The photophysical properties of the triple-stranded dimetallic helicates [Ln 2 (L C -2H) 3 ]‚H 2 O (Ln ) Nd, Sm, Dy, Yb) are determined in water and D 2 O solutions, and energy transfer processes are modeled for Sm III . The luminescence of Nd III , Sm III , and Yb III is sensitized by (L C -2H) 2-, but the energy transfer from the ligand to the Ln III ions is not complete, resulting in residual ligand emission. The luminescence of the Nd III helicate is very weak due to nonradiative de-excitation processes. On the other hand, the Yb III and Sm III helicates exhibit fair quantum yields, 1.8% and 1.1% in deuterated water, respectively. The energy transfer rates between (L C -2H) 2-and Sm III levels are calculated by direct and exchange Coulomb interaction models. This theoretical modeling coupled to numerical solutions of the rate equations leads to an estimate of the emission quantum yields in H 2 O and D 2 O, which compares favorably with experimental data. The main component of the ligandto-metal energy transfer (97.5%) goes through a 3 ππ* f 5 G 5/2 (1) path, and the operative mechanism is of the exchange type. For the Yb III helicate, minor effects of oxygen on the sensitization of Yb III and nanosecond time-resolved spectroscopy point to the energy transfer mechanism being consistent with a recently proposed pathway involving fast electron transfer and Yb II . No up-conversion process could be identified. Ligand-field splitting of the 2 F 5/2 (3E 1/2 + E 3/2 ) and 2 F 7/2 (2E 1/2 + E 3/2 ) levels of Yb III is consistent with D 3 symmetry.

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Figure 6. Schematic geometric structures (top panels) and SEM/TEM images (bottom panels) of various plasmon-coupled UCNPs. (a) UCNP@Au. (b) GNR@SiO 2 −UCNP. (c) UCNP@Ag. (d) Multilayer design of Au nanodisks, SiO 2 nanopillars, Au backplanes, and UCNPs. (e) UCNP-deposited Au square/annular. (f) UCNP-deposited Ag nanocraters. (g) UCNP-deposited Ag nanopillars fused with silica. (h) Sandwiched design of Ag nanocube, UCNPs, and Au film. Reprinted from ref 62.

Non-doped as well as titanium and lutetium doped zirconia (ZrO 2 ) materials were synthesized via the sol-gel method and structurally characterized with X-ray powder diffraction. The addition of Ti in the zirconia lattice does not change the crystalline structure whilst the Lu doping introduces a small fraction of the tetragonal phase. The UV excitation results in a bright white-blue luminescence at ca. 500 nm for all the materials which emission could be assigned to the Ti 3+ e g  t 2g transition. The persistent luminescence originates from the same Ti 3+ center. The thermoluminescence data shows a well-defined though rather similar defect structures for all the zirconia materials. The kinetics of persistent luminescence was probed with the isothermal decay curve analyses which indicated significant retrapping. The short duration of persistent luminescence was attributed to the quasi-continuum distribution of the traps and to the possibility of shallow traps even below the room temperature. 1076-1078 (2000). 13. R. C. Garvie, R. H. Hannink, and R. T. Pascoe, "Ceramics steel," Nature 258(5537), 703-704 (1975)