A Versatile Silica Functionalization Strategy for Nanomaterials

Chemical interactions between nanoparticles and their surroundings are governed by their surface chemistry, and thus a versatile strategy for surface functionalization compatible with a variety of particle compositions would empower nanotechnology research. Although silica coating offers a promising approach, common protocols are often impeded by inconsistent reproducibility, non-uniform thicknesses, difficulty in producing thin coatings, and particle aggregation during functionalization. Here, we demonstrate that these challenges can be overcome by adding additional surface ligands to stabilize the particle cores during the silica growth process. The inclusion of excess ligands alters the nanoparticles’ surface chemistry such that particle aggregation is suppressed, even for thin silica coatings (<1 nm) and coatings on a wide range of nanoparticle compositions, sizes, and shapes. The versatility and reproducibility of this approach is illustrated through its application to isotropic magnetite nanoparticles with diameters between 20-28 nm, anisotropic magnetite nanodiscs >200 nm in diameter, and CdS/ZnS quantum dots. These silica-coated nanomaterials retain their functional properties, and the silica shell can be further modified with application-specific organic moieties. Being agnostic to the nanomaterials shape and composition, this approach is enabling to nanomaterials applications demanding precise control over their surface chemistry independent of their functional properties.