Experimental variation of the volume ratio (filling factor: i.e., volume of nanoparticles (NPs) compared with that of medium) of nanocomposite materials with doped lanthanide ions demonstrates that it has a significant affect upon local field effects. Lanthanum orthophosphate NPs are doped with Eu and/or Tb and immersed in organic solvents and lead borate glasses for Tb D lifetime measurements. For media with a refractive index (n ) less than that of LaPO (n = 1.79), the D emission decay rate increases with increasing volume ratio of the NPs, whereas for n > 1.79, the decay rate decreases with increasing volume ratio. Fitting with the model of Pukhov provides an estimation of the radiative lifetime of D and the quantum yield. Energy transfer (ET) from Tb to Eu occurs in co-doped LaPO NPs with excitation into a Tb absorption band. The ET rate is independent on n and the energy transfer efficiency decreases with an increase in n . The behavior of ET rate with regard to the local field is consistent with the Dexter, but not Förster, equation for ET rate involving the electric dipole-electric dipole mechanism. This has consequences when using the spectroscopic ruler approach to measure distances between donor-acceptor chromophores.
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