Supraballs as spherical solid 3D superlattices of hydrophobic nanocrystals dispersed in water: nanoarchitectonics and properties.

Herein, we use a water-dispersive 3D suprastructure of ferrite (Fe 3 O 4 ) nanocrystals called supraballs. They are solid spherical assemblies of hydrophobic nanocrystals with a rather low Young's modulus compared to similar 3D superlattices deposited on a substrate. Using atomic force microscopy methods, their nanomechanical properties are measured, which show small flexibility and deformation. This suprastructure behaves as a nanoheater and remains self-assembled after internalization in cancer cells. Furthermore, when subjected to light, the percentage of dead cells compared to the nanocrystals used as building blocks and dispersed in the solution increases.