Seung Hyeon (Sarah) Ko,* Kan Du,* J. Alexander Liddle
(*: equal contribution)
The ability to organize nanostructures of disparate types and materials – such as metal nanoparticles and semiconductor quantum dots – is challenging but essential for the creation of novel materials and devices. Metal nanoparticles (NPs) have interesting individual plasmonic properties and can be organized to exhibit useful collective responses. Quantum dots (Qdots) provide a powerful means to optically access the nanoscale. Bringing the two together in a well-controlled manner can create structures with interesting properties such as fluorescence enhancement/quenching and high efficiency Förster resonance energy transfer.
Here we report a novel, flexible approach to fluorescence lifetime engineering of CdSe/ZnS (core/shell) Qdots by controlling their coupling to adjacent gold nanoparticles (AuNPs) at geometrically different locations on the DNA origami. To examine these constructs in their native state in solution, we use a three-dimensional (3D), real-time, single-particle tracking system. We determine the influence of AuNPs on Qdot fluorescence lifetime by systematically varying the location, number, and size of AuNPs as well as interparticle distance and spectral overlap between AuNP and Qdot. The DNA origami serves as a programmable nano-pegboard for heterogeneous integration of Qdots and AuNPs wherein complex geometries are created by using modified staple strands on the DNA origami to capture specific nanoparticles. In this work, we manipulate and control the average photon count rate and lifetime of Qdots by varying the geometrical configuration of Qdot-AuNP conjugates on DNA origami and observe good agreement between theory and measurement.