Photoluminescence of bound rare earth nanoscale complexes

The photoluminescent properties of the nanoscale rare earth ceramic clusters (THF)14Er10S6Se12I6 (THF = tetrahydrofuran), (THF)8Nd8O2Se2(SePh)16, and the molecular thiolates (DME)2X(SC6F5)3 (DME = 1,2-dimethoxyethane, X = Er or Nd) are studied by optical absorption and photoluminescence. From the Judd-Ofelt (JO) analysis of the absorption spectra and the measured decay time of the photoemission it is found that the Er complexes show high quantum efficiencies whereas the Nd complexes not. The differences are explained in terms of energy transfer processes among the corresponding active ions. It is found that the Nd thiolate present the most drastic quenching in spite that the energy transfer processes are driven only by multipolar interactions whereas for the other complexes, there is evidence of migration for the Nd one and upconversion for the Er complex.