Ligand-Solvent Library Design for Tailoring Interparticle Interactions in Colloidal Nanocrystals

This study explores the critical role of nonpolar ligand-solvent in modulating interparticle interactions in colloidal nanocrystals, which profoundly affects colloidal stability and enables bottom-up precision self-assembly. We created a library comprising 28 distinct ligands and three different solvents to investigate how the position of various modifications—specifically double bond, branched chain, benzene ring, and naphthalene ring—influence ligand crystallinity and interparticle attraction in nonpolar solvents. Through explicit solvent simulations, we demonstrated that placing molecular fragments near the head group or in the midsection of the ligand chain leads to disordered ligand structure, diminishing interparticle attraction, while terminal positioning fosters ordered ligand packing and attractive interactions. By fine-tuning fragment positions or combining two fragments, we achieved control over the crystallinity of ligand bundles, thereby influencing the attraction in the "touch" mode. Additionally, we examine the effects of solvent size on solvation, revealing its potential to independently control attraction in the "lock" mode. These findings enhance our understanding of ligand-solvent dynamics and lay the groundwork for the precise manipulation of nanocrystal self-assembly.