Ligand Interactions and Nanoparticle Shapes Guide the Pathways toward Interfacial Self-Assembly

Area of Science:

• Materials Science
• Nanotechnology
• Computational Chemistry

Background:

• Self-assembly of nanoparticles (NPs) into ordered structures is crucial for advanced materials.
• Controlling NP shape and surface ligands is key to directing assembly.
• Understanding the dynamics of NP assembly at interfaces is challenging.

Purpose of the Study:

• To investigate the driving forces behind the formation of ordered superlattices of polyhedral NPs at fluid-fluid interfaces.
• To elucidate the role of NP shape, ligand density, and solvation on assembly mechanisms.
• To develop novel order parameters for tracking NP assembly dynamics.

Main Methods:

• Non-equilibrium molecular dynamics simulations were employed.
• Coarse-grained ligands capping the NP surface were explicitly modeled.
• Novel order parameters were developed to measure local orientation alignment.

Main Results:

• Different NP shapes and time-dependent ligand densities lead to distinct transformation mechanisms.
• Solvation environment significantly impacts inter-particle interactions, reversibility, and superlattice coherence.
• Cuboctahedral NPs formed intermediate clusters before achieving a square lattice, while truncated octahedral NPs showed a rhombic-to-square transition driven by ligand clustering.

Conclusions:

• NP shape and ligand dynamics are critical determinants of interfacial superlattice formation.
• The simulation protocols provide a framework for exploring NP interfacial self-assembly.
• This work advances the understanding of directed nanoparticle assembly for material design.