On the Mechanical and Electronic Properties of Thiolated Gold Nanocrystals

TL;DR

This study combines experimental and simulation approaches to investigate how alkylthiolated coatings affect the mechanical and electronic properties of gold nanocrystals at the single nanoparticle level, revealing significant changes under strain.

Contribution

It provides a comprehensive analysis of the coupled mechanical and electronic behavior of coated gold nanoparticles using combined experimental and computational methods.

Findings

Young's modulus of NPs is significantly reduced compared to bulk gold

Strain influences the electronic properties of alkylthiolated NPs

Effective tunneling barrier decreases with increased load, boosting tunnel current

Abstract

We present a quantitative exploration, combining experiment and simulation, of the mechanical and electronic properties, as well as the modifications induced by an alkylthiolated coating, at the single NP level. We determine the response of the NPs to external pressure in a controlled manner by using an atomic force microscope tip. We find a strong reduction of their Young modulus, as compared to bulk gold, and a significant influence of strain in the electronic properties of the alkylthiolated NPs. Electron transport measurements of tiny molecular junctions (NP/alkylthiol/CAFM tip) show that the effective tunnelling barrier through the adsorbed monolayer strongly decreases with increasing the applied load, which translates in a remarkable and unprecedented increase of the tunnel current. These observations are successfully explained using simulations based on finite element analysis (FEA) and first-principles calculations that permit to consider the coupling between the mechanical response of the system and the electric dipole variations at the interface.