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Versatile Gap Mode Plasmon under ATR Geometry towards Single Molecule Raman, Laser Trapping and Photocatalytic
Masayuki Futamata1, Keitaro Akai, Chiaki Iida
1Graduate School of Science and Engineering, Saitama University.
Summary
Gap mode plasmonics enable highly sensitive Raman scattering detection and precise nanoparticle manipulation. This study demonstrates plasmon-enhanced Raman spectroscopy and photocatalytic oxidation of thiophenol derivatives.
Area of Science:
- Plasmonics
- Nanophotonics
- Surface-enhanced Raman Spectroscopy (SERS)
Background:
- Gap mode plasmons offer unique electromagnetic field confinement.
- Surface-enhanced Raman Spectroscopy (SERS) requires efficient plasmonic substrates.
- Precise control over nanoparticle interactions is crucial for advanced applications.
Purpose of the Study:
- To establish gap mode plasmonics as a versatile analytical tool.
- To investigate Raman scattering enhancement and optical trapping capabilities.
- To explore the photocatalytic activity of plasmon-activated molecules.
Main Methods:
- Utilized attenuated total reflection (ATR) geometry with silver films and silver nanoparticles (AgNPs).
- Employed optical trapping of AgNPs on thiophenol (TP)-covered Ag films under gap mode resonance.
- Analyzed photocatalytic oxidation of p-alkyl thiophenol (TP) derivatives.
Main Results:
- Achieved Raman scattering enhancement factors of 10^7-10^9 for a TP monolayer.
- Demonstrated optical trapping and immobilization of ~20 nm AgNPs at low laser power density (~1 μW/μm^2).
- Confirmed photocatalytic oxidation of p-alkyl TP to p-carboxyl TP, with regioselectivity observed.
Conclusions:
- Gap mode plasmonics provide a powerful platform for ultrasensitive SERS detection.
- Optical trapping of nanoparticles is feasible under gap mode resonance conditions.
- Plasmon-induced photocatalysis offers a selective method for molecular transformation.