How gold inclusions increase the rate of fluorescein energy homotransfer in silica beads

Self-quenching, that limits the luminescence of silica particles containing fluorophores, can be reduced by the presence of gold inclusions within silica. This reduction originates from a dramatic decrease of the non-radiative decay rate, the presence of metal impeding energy transfers to fluorescein quenchers. This Letter describes the modification of energy transfers induced by gold by performing systematic steady-state and time-resolved anisotropy measurements. For the lowest dyes concentration, gold accelerates by one order of magnitude the rate of fluorescein energy homotransfer. The hopping time is then unexpectedly found to be independent of the distance between the fluorophores.