Increase of SERS Signal Upon Heating or Exposure to a High-Intensity Laser Field: Benzenethiol on an AgFON Substrate

TL;DR

Heating and high-intensity laser exposure enhance the SERS signal of benzenethiol on AgFON substrates by converting molecules from a precursor to a chemisorbed state, revealing a new method to boost signal strength.

Contribution

This study demonstrates that thermal and laser-induced effects can significantly increase SERS signals by facilitating molecular state transitions on plasmonic substrates.

Findings

SERS signal increased by ~100% with heating at 100°C and 125°C.

Additional ~80% increase after 10 sec laser exposure at 3.2 kW/cm^2.

Signal enhancement linked to conversion of molecules from precursor to chemisorbed state.

Abstract

The surface-enhanced Raman scattering (SERS) signal from an AgFON plasmonic substrate, recoated with benzenethiol, was observed to increase by about 100% upon heating for 3.5 min at 100C and 1.5 min at 125C. The signal intensity was found to increase further by about 80% upon a 10 sec exposure to a high-intensity (3.2 kW/cm^2) 785-nm cw laser, corresponding to 40 mW in a 40+/-5-um diameter spot. The observed increase in the SERS signal may be understood by considering the presence of benzenethiol molecules in an intermediate or 'precursor' state in addition to conventionally ordered molecules forming a self-assembled monolayer. The increase in the SERS signal arises from the conversion of the molecules in the precursor state to the chemisorbed state due to thermal and photo-thermal effects.