Utilizing homogenous FRET to extend molecular photonic wires beyond 30 nm (Presentation Recording)

Molecular photonic wires (MPWs) present interesting applications in energy harvesting, artificial photosynthesis, and nano-circuitry. MPWs allow the directed movement of energy at the nanoscopic level. Extending the length of the energy transfer with a minimal loss in efficiency would overcome an important hurdle in allowing MPWs to reach their potential. We investigated Homogenous Förster Resonance Energy Transfer (HomoFRET) as a means to achieve this goal. We designed a simple, self-assembled DNA nanostructure with specifically placed dyes (Alexa488-Cy3-Cy3.5-Alexa647-Cy5.5) at a distance of 3.4 nm, a separation at which energy transfer should theoretically be very high. The input of the wire was at 466 nm with an output up to 697 nm. Different structures were studied where the Cy3.5 section of the MPW was extended from one to six repeats. We found that though the efficiency cost is not null, HomoFRET can be extended up to six repeat dyes with only a 22% efficiency loss when compared to a single step system. The advantage is that these six repeats created a MPW which was 17 nm longer, almost 2.5 times the initial length. To confirm the existence of HomoFRET between the Cy3.5 repeats fluorescence lifetime and fluorescence lifetime anisotropy was measured. Under these conditions we are able to demonstrate the energy transfer over a distance of 30.4 nm, with an end-to-end efficiency of 2.0%, by utilizing a system with only five unique dyes.