Molecular-Scale Insights into the Heterogeneous Interactions Between an m-Terphenyl Isocyanide Ligand and Noble Metal Nanoparticles

TL;DR

This study provides detailed molecular-level insights into how m-terphenyl isocyanide ligands interact differently with gold and silver nanoparticles, revealing distinct binding mechanisms and spectroscopic behaviors crucial for nanoparticle functionalization.

Contribution

It offers the first direct visualization and comparison of ligand binding geometries on Au and Ag nanoparticles at the molecular scale, advancing understanding of ligand-metal interactions.

Findings

Ligand extraction efficiency varies between Au and Ag nanoparticles.

Distinct vibrational enhancement factors indicate different binding geometries.

STM imaging visualizes two separate ligand binding mechanisms.

Abstract

The structural and chemical properties of metal nanoparticles are often dictated by their interactions with molecular ligand shells. These interactions are highly material-specific and can vary significantly even among elements within the same group or materials with similar crystal structure. Precise characterization of ligand-metal interactions is crucial for the rational design of ligands and the functionalization of nanoparticles. In this study, we found that the ligation behavior with m-terphenyl isocyanide molecule differs significantly between Au and Ag nanoparticles, with distinct ligand extraction efficiencies and size dependencies. Surface-enhanced Raman spectroscopy measurements revealed unique enhancement factors for two molecular vibrational modes between two metal surfaces, indicating different ligand binding geometries. Molecular-level characterization using scanning tunneling microscopy allowed us to directly visualize these variations between Ag and Au surfaces, which we assign as two distinct binding mechanisms. This molecular-scale visualization provides clear insights into the different ligand-metal interactions, as well as the chemical behavior and spectroscopic characteristics of isocyanide-functionalized nanoparticles.