Why Is Surface-Enhanced Raman Scattering Insensitive to Liquid Water?

Area of Science:

• Analytical Chemistry
• Physical Chemistry
• Surface Science

Background:

• Surface-enhanced Raman scattering (SERS) is a powerful technique for detecting trace organic molecules in aqueous systems.
• SERS usually exhibits negligible spectral interference from water.
• However, SERS sensitivity to water is observed under specific electrochemical conditions, with the underlying cause remaining unclear.

Purpose of the Study:

• To elucidate the mechanism behind SERS sensitivity to liquid water under specific conditions.
• To identify the factors that enable SERS detection of water in aqueous systems.
• To provide a new perspective for in situ SERS investigations in aqueous environments.

Main Methods:

• Investigated the role of water's hydrogen-bond networks in SERS enhancement.
• Examined the influence of local defects in hydrogen-bond networks on SERS signals.
• Studied SERS behavior around hydration shells of solute ions and on polarized electrode surfaces.

Main Results:

• Demonstrated that hydrogen-bond networks of water are crucial for the loss of SERS enhancement.
• Showed that SERS detection of water requires local defects in these networks.
• Identified hydration shells of ions and polarized electrode surfaces as sources of these defects.

Conclusions:

• The hydrogen-bond network structure of water dictates its SERS detectability.
• Local disruptions in water's hydrogen-bond network are necessary for SERS detection.
• This research offers a novel understanding for in situ SERS applications in electrochemistry and biological studies.