Synthesis of anisotropic silica nanoparticles by organic amine with diverse structures

Herein, we synthesized anisotropic silica nanoparticles (AISNPs) with organic amines with different structures. Monoamines and diamines with distance between amine groups shorter than<i>ca.</i>4 Å have been observed to facilitate the formation of isotropic silica nanoparticles (ISNPs). AISNPs were synthesized with diamines with distance between amine groups longer than<i>ca.</i>4 Å and linear structures of triamines. Non-linear structures with amine groups positioned in a triangular configuration and the cage-like structure of tetra-amines directed the formation of ISNPs. It has been speculated that the formation of AISNPs would be due to the spherical primary particles connecting by organic amines with two or more amine groups with distances between them longer than<i>ca.</i>4 Å. On the contrary, the formation of ISNPs would be attributed to the adsorption of two amine groups on the same primary particles, or to steric hindrance that prevent their connection.