Effect of Temperature and Gold Nanoparticle Interaction on the Lifetime and Luminescence of NaYF4:Yb3+:Er3+ Upconverting Nanoparticles

In this paper, we measured the temperature dependence in the temporal response of the green emission for both the H band (H-2(11/2) -> I-4(15/2) transition) and the S band (S-4(3/2) -> I-4(15/2) transition) for beta-NaYF4 nanocrystals and beta-NaYF4 nanocrystals decorated with 10 nm gold nanoparticles and found that the emission is quenched with temperature. We measured the time -resolved green emission intensity for decorated upconverting nanoparticles (UCNPs) and observed a biexponential decay that has a dominant decay time of similar to 30 pis and a longer decay time of similar to 300 mu s that is similar to the single-exponential decay observed for the undecorated UCNPs. The temperature dependence in the green emission for beta-NaYF4 nanocrystals has a nonradiative quenching rate modeled with activation energy of 700 cm(-1) assigned to multiphonon relaxation to Er3+ lower energy levels. We measured the steady-state emission from the H and S bands for temperatures between 300 and 450 K and obtained a linear relationship between calculated and measured temperatures.