Ordered Surface Structuring of Spherical Colloids with Binary Nanoparticle Superlattices.

Surface-patterning colloidal matter in the sub-10 nm regime generates exceptional functionality in biology and photonic and electronic materials. Techniques of artificially generating functional patterns in the small nanoscale advanced in a fascinating manner in the last several years. However, they remain often restricted to planar and noncolloidal substrates. Patterning colloidal matter in solution via bottom-up assembly of smaller subunits on larger core particles is highly challenging because it is necessary to force the subunits onto randomly moving objects. Consequently, the non-equilibrium conditions present during nanoparticle self-assembly are difficult to control to eventually achieve the desired material structures. Here, we describe the formation of surface patterns with intrinsic periodic repeats of 8.9 ± 0.9 nm and less on hard, amorphous colloidal core particles by assembling binary nanoparticle superlattices on the curved particle surface. The colloidal environment is preserved during the entire bottom-up crystallization of variable building blocks (here, monodispersed 5 nm Au and 2.4 nm Pd nanoparticles (NPs) and 230 nm SiO core particles) into AB-like, binary, and isotropic superlattice domains on the amorphous cores. The three-dimensional, bottom-up assembly technique is a new tool for patterning colloidal matter in the sub-10 nm surface regime for gaining access to multicomponent metamaterials for bionanoscience, photonics, and electronics.