Improving energy transfer in QD-DNA photonic networks

There is considerable research in the area of manipulating light below the diffraction limit, with potential applications ranging from information processing to light-harvesting. In such work, a common problem is a lack of efficiency associated with non-radiative losses, e.g., ohmic loss in plasmonic structures. From this point of view, one attractive method for sub-wavelength light manipulation is to use Förster resonance energy transfer (FRET) between chromophores. Although most current work does not show high efficiency, biology suggests that this approach could achieve very high efficiency. In order to achieve this goal, the geometry and spacing of the chromophores must be optimized. For this, DNA provides an easy means for the self-assembly of these complex structures. With well established ligation chemistries, it is possible to create facile hierarchical assemblies of quantum dots (QDs) and organic dyes using DNA as the platform. These nanostructures range from simple linear wires to complex 3-dimensional structures all of which can be self-assembled around a central QD. The efficiency of the system can then be tuned by changing the spacing between chromophores, changing the DNA geometry such that the donor to acceptor ratio changes, or changing the number of DNA structures that are self-assembled around the central QD. By exploring these variables we have developed a flexible optical system for which the efficiency can be both controlled and optimized.