The present study reports the shell thickness dependence fluorescence resonance energy transfer between Rhodamine 6G dye and Au@SnO2 core-shell nanoparticles. There is a pronounced effect on the PL quenching and shortening of the lifetime of the dye in presence of Au@SnO2 core-shell nanoparticles. The calculated energy transfer efficiencies from dye to Au@SnO2 are 64.4% and 78.3% for 1.5 nm and 2.5 nm thickness of shell, respectively. Considering the interactions of single acceptor and multiple donors, the calculated average distances (r(n)) are 75.8 and 71.5 angstrom for 1.5 nm and 2.5 nm thick core-shell Au@SnO2 nanoparticles, respectively. (C) 2008 Elsevier B.V. All rights reserved.