Metasurface-Enhanced Raman Spectroscopy (mSERS) for Oriented Molecular Sensing

Area of Science:

• Plasmonics
• Nanotechnology
• Spectroscopy

Background:

• Surface-enhanced Raman spectroscopy (SERS) offers ultrasensitive chemical detection.
• Plasmonic nanogaps enhance SERS signals but are sensitive to molecular orientation.
• Nanoparticle aggregation often leads to signal instability in colloidal SERS platforms.

Purpose of the Study:

• To develop a nanoparticle-on-metal metasurface platform for enhanced Raman detection of highly oriented molecular analytes.
• To overcome challenges of nanoparticle aggregation and signal fluctuation in SERS.
• To demonstrate a metasurface-enhanced Raman spectroscopy (mSERS) platform for quantitative molecular detection.

Main Methods:

• Fabrication of a nanoparticle-on-metal metasurface using colloidal Langmuir-Schaefer deposition.
• Design for near-perfect optical absorption and high surface coverage of nanogaps.
• Integration of local electric field simulations and experimental characterization of mSERS signals.

Main Results:

• Achieved up to 32% surface coverage density of nanogaps.
• Demonstrated quantitative detection of polybrominated diphenyl ether (BDE-15) at 0.25 μM.
• mSERS platform showed comparable detection limits to other SERS sensors at significantly lower laser power.

Conclusions:

• The developed mSERS platform effectively detects highly oriented molecular analytes.
• This platform overcomes aggregation issues, providing stable and sensitive Raman signals.
• mSERS shows significant promise for nondestructive, low-level analyte detection in various applications.