Self-assembled Au nanoparticles as substrates for surface-enhanced vibrational spectroscopy: optimization and...

Area of Science:

• Materials Science
• Nanotechnology
• Spectroscopy

Background:

• Development of nanostructured metallic substrates is crucial for enhancing vibrational spectroscopy techniques.
• Self-assembly offers a scalable method for fabricating complex nanostructures.

Purpose of the Study:

• To fabricate three-dimensional (3D) nanostructured metallic substrates using self-assembly.
• To investigate the suitability of these substrates for surface-enhanced polarization modulation infrared reflection-absorption spectroscopy (PM-IRRAS) and surface-enhanced Raman scattering (SERS).
• To optimize the nanostructure fabrication for maximum SERS efficiency.

Main Methods:

• Fabrication of nanostructures via self-assembly of gold nanoparticles (Au NPs) on gold films.
• Characterization using Atomic Force Microscopy (AFM) and UV/Vis reflection-absorption spectroscopy.
• Evaluation of spectroscopic performance using 4-hydroxythiophenol as a probe molecule for PM-IRRAS and SERS, including in situ electrochemical measurements.

Main Results:

• Surface-enhanced PM-IRRAS was observed, but limitations for this technique were identified.
• Surface-enhanced Raman scattering (SERS) was successfully observed.
• SERS signal intensity maximized at 11 depositions of Au NPs, with reproducible intensities (within 20%).
• The nanostructured substrates demonstrated electrochemical stability between -800 and +200 mV.

Conclusions:

• Three-dimensional nanostructured gold substrates fabricated by self-assembly are effective for SERS.
• The number of nanoparticle depositions significantly influences SERS efficiency, with an optimum found at 11 depositions.
• These substrates offer a stable and reproducible platform for in situ electrochemical SERS applications.