Förster Energy Transfer in Core–Shell Nanoparticles: Theoretical Model and Monte Carlo Study

The model of Förster excitation energy transfer on a spherical core–shell nanoparticle was presented. A general expression for fluorescence intensity decay was obtained for an arbitrary number of acceptors linked chemically to the shell. It was found that the dynamical behavior of the system is extremely sensitive to the number of acceptors and the size of the nanoparticle. Monte Carlo simulations performed for the energy transfer parameters taken from an independent experiment show excellent agreement with the model for donor fluorescence decay and its mean lifetime. The original model was then extended to the common experimental case of core–shell nanoparticle size distribution, assuming the Gaussian distribution function of their radii. This effect leads to slower fluorescence decays and longer mean fluorescence lifetimes, as revealed by Monte Carlo simulations.