| Popis: |
Sensitized photol uminescence in zeolites has been studied to provide information on the nature, lifetimes, and energy transfer from excited states of intra-zeolitic cations. The decay time analysis of the 540 nm luminescent emission due to Cu+ activator ions in Type Y and Z zeolites in the absence and in the presence of Ni2+, Co2+, or Mn2+ sensitizers resulted in the determination of critical transfer radii for the dipole-dipole transfer mechanism. The largest transfer radius, 2.4 nm, occurred between the Cu+/Co2+ pairs, indicating an efficient sharing of excitation energy at distances far exceeding the dimensions of a single sodalite cage. A continuum treatment of exchanged ion site occupancy by the co-exchanged ions was used to calculate predicted decay curves and quantum efficiencies, and a good agreement was obtained between experimental data and the Foerster-Dexter theory of resonant energy transfer. |
