| Abstract
| - Energy transfer is characterized in the layered compounds Tb[Ag(CN)2]3 and Tb[Au(CN)2]3 through both steady-state and time-resolved luminescence. In both compounds, excitation of the donor leads to sensitized luminescence of the acceptor. However, the sensitized luminescence is much stronger in Tb[Ag(CN)2]3 than in Tb[Au(CN)2]3 due to stronger spectral overlap between the donor and the acceptor. Analysis of the donor luminescence decay indicates that the energy transfer follows the Dexter exchange mechanism.
- A temperature-dependent photoluminescence study is reported for single crystals of M[Au(CN)2]3 and M[Ag(CN)2]3 (M = Tb; Gd; Y). The results indicate that in both Tb[Au(CN)2]3 and Tb[Ag(CN)2]3 exclusive excitationof the donor leads to sensitized luminescence for the acceptor, characteristic of the 5D4 → 7FJ (J = 0−6) transitionof Tb(III). However, the sensitized luminescence is much stronger in Tb[Ag(CN)2]3 than in Tb[Au(CN)2]3 due toa larger spectral overlap between the [Ag(CN)2-] emission and the Tb(III) absorption. Upon increasing thetemperature, energy transfer is enhanced in Tb[Ag(CN)2]3 but inhibited in Tb[Au(CN)2]3. In Tb[Ag(CN)2]3, alarge spectral overlap exists between the [Ag(CN)2-] donor emission and the Tb(III) acceptor absorption at alltemperatures. The Tb(III) sensitized emission is strong at all temperatures and is enhanced upon a temperatureincrease while the [Ag(CN)2-] emission is quenched. An activation energy of 53.7 cm-1 (±2.5 cm-1) has beencalculated for the energy transfer process in Tb[Ag(CN)2]3. In Tb[Au(CN)2]3, the Tb(III) sensitized luminescencedecreases upon increasing the temperature. The [Au(CN)2-] emission is strong and does not undergo a completequenching as the temperature increases toward room temperature. The [Au(CN)2-] emission undergoes a redshift upon cooling, which leads to an increased spectral overlap with the 5D4 → 7F6 absorption band of Tb(III);thus energy transfer is tuned by controlling the temperature. The sensitized luminescence intensity of Tb(III) inTb[Au(CN)2]3 is directly proportional to the numerical value of the donor−acceptor spectral overlap, in agreementwith the theory of radiationless energy transfer.
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