Observing plasmonic-molecular resonance coupling on single gold nanorods

Area of Science:

• Plasmonics
• Nanophotonics
• Molecular Spectroscopy

Background:

• Noble metal nanocrystals exhibit plasmonic properties, enabling interactions with organic molecules.
• Plasmonic-molecular resonance coupling is crucial for fundamental studies and applications like sensing and spectroscopy.
• Direct measurement of this coupling on individual nanostructures is challenging.

Purpose of the Study:

• To directly measure plasmonic-molecular resonance coupling in single gold nanorods.
• To investigate the influence of plasmon resonance and molecular absorption on coupling strength.
• To demonstrate the tunability of this coupling phenomenon.

Main Methods:

• Utilizing dark-field scattering spectroscopy to probe single gold nanorods.
• Embedding nanorods in hydrogel for uniform dye adsorption.
• Measuring nanorods before and after adsorbing organic dye molecules with monomer and H-aggregate bands.
• Employing photodecomposition to tune the coupling.

Main Results:

• Observed strong and weak plasmonic-molecular resonance coupling based on nanorod plasmon bands.
• Experimental results showed excellent agreement with analytic theory.
• A unique three-band spectral structure resulting from the resonance coupling was identified.

Conclusions:

• Direct measurement of plasmonic-molecular resonance coupling on single gold nanorods is feasible.
• The coupling strength and spectral features are tunable by altering plasmon resonance and molecular properties.
• This work provides insights into light-matter interactions at the nanoscale.