Assembling nonspherical 2D binary nanoparticle superlattices by opposite electrical charges: the role of Coulomb forces.

Abstract

High-quality approximately 16 nm c-In2O3 nanoctahedra and approximately 6 nm Pd spherical nanoparticles were synthesized via a high-temperature wet-chemical approach, and their electrophoretic mobilities in toluene were investigated, respectively. Opposite electrical charge-induced 2D binary nanoparticle superlattice patterns containing two such nanocomponents were prepared, for the first time. Three types of c-In2O3-skeleton-structure-contained assembly patterns were identified as well. It was further observed that the vertices of c-In2O3 nanoctahedra could have higher electrical charge density than that on edge or plane and the small Pd nanoparticles were "suspended" on the middle plane of the c-In2O3 nanoctahedra, apparently well above the substrate surface (support film) rather than sitting on it. The assembly structure study indicates that Coulomb forces resulted from the opposite electrical charges are the dominative driving forces to induce the formation of such nanoctahedra-nanospheres 2D binary nanoparticle superlattices.