Preventing Memory Effects in Surface-Enhanced Raman Scattering Substrates by Polymer Coating and Laser-Activated...

Area of Science:

• Chemical Sensing
• Materials Science
• Spectroscopy

Background:

• Continuous monitoring requires in situ sensors for real-time chemical analysis.
• Surface-enhanced Raman scattering (SERS) is a noninvasive technique for detecting low concentrations of chemicals.
• A major challenge in SERS is the "memory effect" caused by irreversible analyte adsorption on plasmonic substrates, hindering accurate time-series measurements.

Purpose of the Study:

• To develop a novel plasmonic substrate that mitigates the SERS memory effect for reliable continuous monitoring.
• To control analyte adsorption on SERS substrates and enable sequential measurements at specific times.

Main Methods:

• Designed plasmonic substrates coated with a nonpermeable poly(lactic-co-glycolic acid) (PLGA) thin layer.
• Utilized laser irradiation at higher fluence to locally degrade the PLGA layer, creating micrometer-sized windows for analyte access.
• Employed surface-enhanced Raman scattering (SERS) spectroscopy for in situ chemical analysis.

Main Results:

• Demonstrated the ability to perform over 10,000 consecutive measurements using a single SERS substrate.
• Successfully achieved accurate continuous monitoring of analytes in microfluidic channels and biological systems.
• The PLGA layer effectively controlled analyte adsorption, preventing interference between successive measurements.

Conclusions:

• The developed PLGA-coated SERS substrates provide a robust solution to the memory effect, enabling precise real-time chemical sensing.
• This technology facilitates accurate continuous monitoring in complex environments, including microfluidics and biological systems.
• The laser-degradable polymer layer offers a controllable method for sequential SERS measurements, advancing in situ chemical analysis.