Molecular interaction between asymmetric ligand-capped gold nanocrystals

Area of Science:

• Nanoscience and Nanotechnology
• Computational Chemistry
• Materials Science

Background:

• Understanding interactions between functionalized nanoparticles is crucial for designing advanced materials.
• Gold nanocrystals (NCs) capped with alkylthiols are model systems for studying nanoparticle assembly.
• The potential of mean force (PMF) quantifies interaction energies between nanoscale objects.

Purpose of the Study:

• To investigate the influence of size and capping ligand length on the PMF between asymmetric gold nanocrystals (NCs) in a vacuum.
• To develop predictive models for the equilibrium distance and interaction potential of capped NC dimers.

Main Methods:

• Atomistic molecular dynamics (MD) simulations were employed.
• The PMF was calculated for various combinations of gold NC sizes and alkylthiol ligand lengths.
• Analysis focused on ligand interdigitation and its effect on inter-NC forces.

Main Results:

• Potential well depth scales linearly with the total ligand length, independent of NC size.
• Equilibrium distance increases linearly with total NC size and slightly with total ligand length.
• Ligand interdigitation significantly influences inter-NC forces and equilibrium separation.

Conclusions:

• A simple formula was derived to estimate the equilibrium distance between asymmetric capped gold NCs.
• An empirical two-body potential was proposed for interactions between such NCs.
• Simulation results provide fundamental insights into the assembly of functionalized nanoparticles.