25 June 2014 Non-classical light from a bacterial light-harvesting complex

Light-harvesting complex at nanoantenna hotspot

Strong antenna-enhanced fluorescence of a single light-harvesting complex in Nature Communications In a recent study Emilie Wientjes and colleagues of the Molecular NanoPhotonics group led by ICREA Professor at ICFO Niek van Hulst have coupled light harvesting complexes to plasmonic antennas to obtain sufficiently strong emission enhancement to scrutinize the photon statistics of the individual photosynthetic complexes. The work was published in Nature Communications.

Plants, bacteria and algae collect sunlight to store energy and synthesize high energy molecular species to power life. The photosynthetic light-harvesting complexes transfer energy very efficiently, potentially exploiting quantum coherence. Unfortunately such complexes are not designed to emit light and thus are difficult to study. Now Emilie Wientjes and colleagues have coupled single LH2 complexes resonantly to a gold nanoantenna. This way the fluorescence decay speeds up to 20 ps, quantum efficiency is enhanced and 500 times more emission is collected. Using the bright photon emission, they revealed that the LH2 complex with 27 bacteriochlorophylls coordinated in two rings of chromophores shows photon anti-bunching at ambient conditions, i.e. a bacterial complex acting as a non-classical single-photon emitter.