Control of Depletion Interactions in Nanoplatelets via Ligand-Shell Engineering to Enhance Colloidal Stability and...

Depletion interactions play a critical role in colloidal stability, yet their behavior in ligand-coated, anisotropic nanocrystals remains poorly understood due to the limitations of hard-particle assumptions at soft interfaces. In two-dimensional (2D) nanoplatelets (NPLs), atomically flat surfaces amplify excluded-volume overlap, leading to strong depletion-driven aggregation in multicomponent environments. Here, we show that the nanoscale configuration of the ligand shell serves as a key parameter governing depletion interactions in 2D nanocrystals. By tuning ligand-shell compactness through partial substitution with short-chain spacers, we introduce controlled free volume within the organic shell, thereby reducing excluded-volume overlap and weakening depletion attraction. This interfacial modification suppresses aggregation and enables stable NPL dispersions without altering their intrinsic geometry and optical properties. Notably, this mechanism persists across diverse co-dispersion environments, including small molecules, liquid crystals, and polymers, where interparticle interactions are strongly perturbed. As a result, ligand-shell engineering modulates depletion interactions to enable robust solution-phase dispersion and its direct translation into uniform composite materials, establishing a practical strategy for controlling colloidal interactions and improving the processability of anisotropic nanocrystals in complex media.