Competition-Driven Ligand Exchange for Functionalizing Nanoparticles and Nanoparticle Clusters without Colloidal Destabilization

We present a novel and scalable approach to tailored ligand exchange in stable suspensions of nanoparticles and nanoparticle clusters which is applicable to a wide range of nanoparticle types. Competition-driven ligand exchange (CDLE) uses a substrate with a higher affinity for the primary ligand to "activate" the dispersed nanoparticles for functionalization with a secondary ligand (which itself is not subject to substrate competition and which cannot exchange in the absence of the substrate). This approach allows ligand replacement without destabilization of the colloid. Ligand exchange while maintaining colloidal stability and hydrodynamic particle size is demonstrated for iron oxide nanoparticles and nanoparticle clusters in suspension, and a range of ligand types are used to impart new functionality, demonstrating the general applicability of the approach. Time-dependent attenuated total reflectance-infrared spectroscopy is used to investigate the nature and dynamics of the critical interfacial interactions that take place within the colloidal system and govern the CDLE process. Novel CDLE reactors applicable to suspensions of dispersed nanoparticles and monodisperse nanoparticle assemblies are described.