Phys. Rev. Lett. (In the press); (2012)

Since the early work of Edward Purcell it has been recognized that the electromagnetic environment affects the spontaneous emission rate of individual excited atoms and molecules. Much less studied is the effect that the environment has on the energy transfer rate between pairs of closely spaced molecules. Previous studies indicated that this rate depends strongly on the environment, while others reported weak or no dependence at all. In an elegant work, Christian Blum and colleagues now provide strong evidence that the energy transfer rate between molecules is not affected by the nanophotonic environment. The researchers attached energy donor and acceptor molecules at the two ends of a DNA strand of a precisely defined length (6.8 nm). The energy transfer pairs were then positioned with nanometre precision close to a metallic mirror. The researchers found that although the environment did not seem to affect the energy transfer rate, it could dramatically change the efficiency of the transfer, essentially between 0 and 100%.