Gradient SERS Substrates with Multiple Resonances for Analyte Screening: Fabrication and SERS Applications.

Area of Science:

• Materials Science
• Spectroscopy
• Nanotechnology

Background:

• Surface-enhanced Raman spectroscopy (SERS) relies heavily on substrate properties for signal enhancement.
• Developing substrates with tunable plasmonic properties is crucial for improving SERS performance.
• Current methods often lack the ability to provide multiple resonance conditions within a single sample.

Purpose of the Study:

• To develop a facile method for fabricating a non-uniform SERS substrate.
• To create a substrate with tunable plasmonic resonances and varying gap sizes.
• To demonstrate the substrate's utility for correlating SERS enhancement with surface morphology and for rapid analyte screening.

Main Methods:

• Fabrication of a non-uniform SERS substrate via annealing a thin gold film.
• Characterization using Scanning Electron Microscopy (SEM) to analyze morphology and gap sizes.
• Analysis of plasmonic properties using extinction spectroscopy.
• Testing with analytes 1,2-bis(4-pyridyl) ethylene (BPE) and methylene blue (MB) to evaluate SERS enhancement.

Main Results:

• The annealed gold film exhibited particle-like and island-like morphologies with varying gap sizes.
• Extinction spectra confirmed continuous tuning of plasmonic resonance across the substrate.
• Maximum SERS enhancement for different analytes (BPE, MB) occurred at distinct lateral positions.
• A correlation was established between SERS enhancement, surface morphology, and plasmonic resonance.

Conclusions:

• The developed non-uniform SERS substrate offers a facile and chemically stable platform with reproducible plasmonic responses.
• The substrate's ability to provide multiple resonances and gap sizes within one sample facilitates rapid analyte screening.
• This approach allows for direct correlation between SERS enhancement and substrate morphology, advancing SERS applications.