General synthesis of monodisperse metal oxide nanoparticle clusters

Nanoparticle clusters (NPCs) consisting of multiple nanoparticles are of great scientific and technological importance; however, there is a lack of a generic method for synthesizing NPCs in a controllable manner. We present a general approach for crafting monodisperse metal oxide NPCs (MONPCs) via a small-ligand and polymer co-mediated hydrolysis method. The small ligands such as citrates and cyanides coordinating with metal ions dramatically reduce the concentrations of free metal ions, slowing down the hydrolysis rate and providing sufficient time for the formed nanoparticles to assemble into spherical clusters induced by the water-soluble polymethacrylate coating on the nanoparticles. This strategy enables us to produce a large variety of phase-pure MONPCs with controlled compositions including high-entropy MONPCs of up to 13 metal elements, tunable dimensions from tens to hundreds of nanometers, and controllable core-shell heterostructures, which provides a versatile platform for manipulating the physical properties of MONPCs for applications in various fields.