Quantum Dot-Based Fluorescence Resonance Energy Transfer Through Exciton Dynamics In Sdna-Templated J-Aggregates

Highly efficient and rapid exciton dynamics is crucial for building nanoscale artificial photonic devices with tailored properties for energy related applications. DNA-templated self-assembly of dyes has been shown as a powerful approach to gain controls and optimization of positions, interactions and dynamics of the dyes. The investigation of exciton dynamics in closely packed molecular J-aggregates has gained significant interests because their optical and electronic properties often resemble with those of self-assembled biochemical molecules in nature. Here, J-aggregates of pseudoisocyanine (PIC) dye formed spontaneously on the double stranded DNA template are used to develop a FRET-based donor-J-aggregate-acceptor assembly. In this system highly emissive quantum dot is acting as FRET donor and Alexa Fluor 647 as terminal acceptor. The donor and acceptor are placed in such a geometric arrangement that direct energy transfer from donor to acceptor is prohibited. The photophysical and dynamical properties of the DNA templated J-aggregates, as well as the donor-to-acceptor energy transfer through J-aggregate have been investigated using steady-state fluorescence, time-resolved fluorescence, and pump-probe absorption spectroscopic techniques. The efficiency of this quantum dot-based donor-J-aggregates-acceptor ensemble system has been further investigated by varying the length and structure of the J-aggregate, as well as compared with the system where a molecular dye, ATTO 390 has been used as donor. The detailed fundamental understanding of this system can help develop more complex nanoscale devices using complex DNA origami nanostructures.