Combined SPR and SERS microscopy in the Kretschmann configuration

Area of Science:

• Spectroscopy
• Microscopy
• Surface Science

Background:

• Surface-enhanced Raman scattering (SERS) offers high sensitivity for molecular detection.
• Surface plasmon resonance (SPR) is a label-free technique for monitoring surface binding events.
• Combining SPR and SERS can potentially enhance analytical capabilities.

Purpose of the Study:

• To develop and demonstrate a novel hybrid spectroscopic technique integrating SPR and SERS microscopy.
• To investigate the excitation of surface plasmon-polaritons (SPPs) in a modified Raman microscope.
• To explore the trade-offs between optimal plasmon coupling and spatial resolution in the hybrid system.

Main Methods:

• Modification of a standard Raman microscope to incorporate SPR excitation in the Kretschmann configuration.
• Utilizing a high numerical aperture oil immersion objective for both SPP excitation and SERS emission collection.
• Recording angular dispersion of plasmon resonance in reflectivity and simultaneous SERS spectra from adsorbed Nile Blue molecules.

Main Results:

• Successful integration of SPR excitation with SERS microscopy on flat metallic surfaces.
• Demonstration of simultaneous measurement of SPR reflectivity and SERS spectra.
• Identification of a trade-off between optimum SPP coupling conditions and the resulting spot size, impacting spatial resolution.

Conclusions:

• The developed hybrid SPR-SERS microscopy technique enables uniform signal enhancement on flat surfaces.
• This approach opens new avenues for advanced SERS microscopy applications.
• The identified trade-off provides crucial insights for optimizing experimental parameters in hybrid spectroscopy.