Exploring Rotational Diffusion with Plasmonic Coupling

Area of Science:

• Nanoscience
• Biochemistry
• Optical Methods
• Plasmonics

Background:

• Optical methods for real-time orientation dynamics of nanoparticles and nonfluorescent molecules are challenging.
• Optoplasmonic sensing offers a potential solution for these measurement difficulties.

Purpose of the Study:

• To examine optoplasmonic sensing for measuring nanoparticle orientation dynamics.
• To use rotational diffusion of plasmonic nanorods as an experimental model.
• To achieve real-time observation of single nanorod rotational motion.

Main Methods:

• Monitoring dark-field scattering of a large gold nanorod (GNR) sensor.
• Observing smaller plasmonic nanorods diffusing in the GNR's near field.
• Utilizing a time resolution of approximately 50 ns for motion tracking.

Main Results:

• Plasmonic coupling significantly enhances the scattering signal of small diffusing gold nanorods.
• Improved angular sensitivity was observed with plasmonic coupling compared to free diffusion.
• Simultaneous translational and rotational diffusion reduced angle sensitivity compared to simulations.

Conclusions:

• Optoplasmonic sensing with plasmonic coupling is effective for studying nanoparticle rotational dynamics.
• Achieving full angular sensitivity requires a plasmonic assembly with nearly fixed positions and orientations.
• This technique advances the capability to measure orientation dynamics in nanoscience and biochemistry.