Structure Evolution of Binary Ligands on Nanoparticles Triggered by Competition Between Adsorption Reaction and Phase Separation.

Abstract

The ligand shell of a nanoparticle (NP) determines most of the interfacial properties through its composition and structure. Despite widespread study over the years, the factors impacting the ligand shell structures, especially the effects of ligand adsorption kinetics in solution, are still not clear and even conflict with each other. We have developed an adsorption-migration reaction model to study the dynamic evolution processes of binary ligands on NP surfaces during adsorption reaction. Apparent dependence of the structure of ligand shells on ligand-adsorption and phase-separation rates has been found, which induces the formation of different shell patterns, including Janus, patchy, stripe and island patterns. The formation process of these patterns accords with different reaction kinetic pathways, depending on the nature of ligands. Further screening the role of the NPs curvature reveals that it can indirectly influence the ligand-adsorption and phase-separation kinetics. As the NPs curvature increases, an accelerated ligand adsorption and phase-separation process on NPs will happen, resulting in the preferential formation of more ordered Janus or stripe patterns. These results suggest that controlling the reaction kinetics is key to effectively regulate the composition and morphology of binary ligands on NPs. They also provide principles for guiding the experimental studies to fabricate novel NPs with functional surface for use in broad nanoscience fields.