Determining molecular orientation via single molecule SERS in a plasmonic nano-gap

Area of Science:

• Plasmonics
• Nanotechnology
• Spectroscopy

Background:

• Surface-Enhanced Raman Scattering (SERS) is a powerful technique for molecular detection.
• Plasmonic nano-gaps offer significant signal amplification for SERS.
• Controlling nano-gap properties is crucial for optimizing SERS performance.

Purpose of the Study:

• To fully optimize plasmonic nano-gaps for single molecule SERS.
• To investigate the influence of particle size and molecule orientation on SERS signals.
• To elucidate the interplay between excitation and emission enhancement in nano-gaps.

Main Methods:

• Fabrication and optimization of silver nanoparticle-silver film plasmonic nano-gaps.
• Experimental SERS measurements on single molecules.
• Finite Difference Time Domain (FDTD) simulations for optical properties.
• Density Functional Theory (DFT) for molecular orientation analysis.

Main Results:

• SERS signal intensity is highly dependent on nano-gap particle size.
• Molecule orientation relative to the nano-gap field significantly impacts SERS.
• FDTD simulations revealed the complex relationship between particle size and enhancement effects.
• DFT calculations allowed for the determination of individual molecule orientations.

Conclusions:

• Optimized plasmonic nano-gaps are effective for single molecule SERS.
• Understanding particle size and molecule orientation is key to maximizing SERS sensitivity.
• Integrated simulation and experimental approaches provide comprehensive insights into SERS mechanisms.