Tuning Optical Absorption and Emission Using Strongly Coupled Dimers in Programmable DNA Scaffolds

Area of Science:

• Molecular nanotechnology
• Biophysics
• Materials science

Background:

• Nanoscale integration of electronically active subunits is crucial for advanced molecular materials.
• Tuning optical properties often relies on complex chemical modifications.
• Developing facile methods for controlling photophysics is essential for applications in light harvesting, computing, and imaging.

Purpose of the Study:

• To introduce a simple method for tuning optical absorption and emission properties of molecular materials.
• To demonstrate control over photophysics by altering the geometry of coupled chromophores.
• To explore the potential of DNA nanostructures for creating tunable molecular materials.

Main Methods:

• Utilizing double-crossover (DX) DNA tiles to position a Cy3 dimer.
• Adjusting the length of complementary DNA strands to induce geometric changes in the dimer.
• Analyzing changes in photophysical properties, including optical absorption, emission, and fluorescence lifetime.
• Observing photophysics at both ensemble and single-molecule levels.

Main Results:

• Geometric manipulation of the Cy3 dimer on the DNA tile significantly altered its optical absorption and emission.
• DNA strand length tuning induced dramatic changes in photophysics, including distinct fluorescence lifetimes.
• Separable lifetimes and environmental sensitivity were observed, indicating potential for fluorescence probes.
• The study established a framework for geometrically controlled photophysics in coupled chromophores.

Conclusions:

• Geometric control of coupled chromophores on DNA nanostructures offers a facile way to tune photophysical properties.
• These Cy3-DX tile constructs show promise as fluorescence probes for multiplexed imaging.
• The developed framework has broad implications for light-harvesting devices and molecular electronics.