Au@ZnO core−shell nanoparticles are efficient energy acceptors with organic dye donors

Abstract

The present study highlights the efficient fluorescence resonance energy transfer from Rhodamine 6G dye to Au@ZnO core−shell nanoparticle by steady state and time-resolved spectroscopy. The calculated energy transfer efficiencies from dye to nanoparticles are 41.3, 52.6, and 72.6% for Au, mixture of Au and ZnO, and core−shell Au@ZnO nanoparticles, respectively. There is a pronounced effect on the PL quenching and a shortening of the lifetime of the dye in the presence of Au@ZnO core−shell nanoparticle which is associated with high charge storage capacity. The nonradiative decay rates are 2.80 × 10⁸, 3.90 × 10⁸ and 7.67 × 10⁸ s^-1 for pure Au, mixture of Au and ZnO and core- shell Au@ZnO nanoparticles, respectively, indicating the resonance energy transfer process. The calculated Förster distances (R₀) are 135.0 and 144.4 Å for Au, and core- shell Au@ZnO nanoparticles, respectively and corresponding the calculated distances (d) between the donor and acceptor are 143.05, and 123.5 Å. Considering the interactions of one acceptor and several donors, the calculated average distances (r_n) between the donor and acceptor are 89.2 and 77.2 Å for Au and core- shell Au@ZnO nanoparticles, respectively. However, the distances between the donor and acceptor are 88.2 and 67.6 Å for Au and core- shell Au@ZnO nanoparticles, respectively, using the efficiency of surface energy transfer which follows a 1/d⁴ distance dependence between donor and acceptor. On the basis of these finding, we may suggest that surface energy transfer process has a more reasonable agreement with experimental finding.