Characterization of Patchy Polymer Grafted Nanocube Transformations in Air and Water with Atomic Force Microscopy

Surface grafting polymer onto nanoparticles is widely used to enable greater functionality and stability. Many different systems have been developed, including nanoparticles with chemically and topographically patterned surfaces, referred to as patchy nanoparticles. These nanoparticles display spatial heterogeneity in functionalization across the nanoparticle surface. It has proven difficult, however, to fully characterize the surface of individual nanoparticles with high spatial resolution in a liquid environment. Atomic force microscopy (AFM) is a highly useful tool for characterizing nanoparticle surfaces in different environments, but it requires firmly immobilized nanoparticles for high resolution liquid imaging. By immobilizing patchy polymer-grafted Ag nanocubes in a polymer substrate, we can directly observe surface heterogeneities within a liquid environment using AFM. Formation of patches was observed depending on environmental conditions, either in air or water. It was also found that polymer-grafted nanocube surfaces that were previously assumed to be homogeneous show complex surface patterning. Furthermore, immobilization in a polymer substrate enabled in-situ imaging of nanoparticle surface transformations in a liquid environment.