Probing Adsorption Configurations and Reaction Selectivity in Plasmon-Induced Reactions at the Nanoscale via...

Area of Science:

• Surface science
• Nanoscale photocatalysis
• Plasmonics

Background:

• Plasmon-induced reactions are key for nanoscale photocatalysis.
• Surface-enhanced Raman spectroscopy (SERS) and tip-enhanced Raman spectroscopy (TERS) probe these reactions.
• Molecular orientation's role in reaction selectivity is not well understood.

Purpose of the Study:

• Investigate how molecular adsorption orientation affects plasmon-driven reactions.
• Examine reactions of 4-BTP on silver and gold surfaces.
• Determine the influence of substrate and molecular packing on reaction pathways.

Main Methods:

• Utilized high-resolution tip-enhanced Raman spectroscopy (TERS).
• Studied 4-BTP reactions on polycrystalline Ag, polycrystalline Au, and single-crystal Au(111).
• Compared reactions on ordered and disordered self-assembled monolayers.

Main Results:

• Observed distinct reaction pathways based on substrate and molecular assembly.
• Identified hydrodebromination to thiophenol (TP) and C-C coupling to 4,4'-biphenyldithiol (BPDT) as competing pathways.
• Found that steric constraints from molecular packing and orientation govern reaction selectivity.

Conclusions:

• Established a clear molecular-level structure-selectivity relationship in plasmon-driven reactions.
• Demonstrated that steric engineering of molecular assembly can control surface reaction pathways.
• Highlighted steric control as a complementary strategy to electronic control for tailoring surface chemistry.