Study of reversibility of self-assembly in saponite layered nanoparticles

Abstract

The reversible process of self-assembly involving the rheological motion of 2-dimensional nanosheets with the aid of water molecules was studied for saponite inorganic layered nanoparticles by dilatometry and positronium lifetime spectroscopy. The two nanosheet insertion type local molecular structure, dominant in the dehydrated state, was not fully reproducible upon dehydration for the self-assembled sample. The two nanosheet insertion type local structure could thus disappear when saponite goes through self-assembly several times. It was furthermore found that a local structure with a void size slightly larger than that in the two nanosheet insertion type structure exists before self-assembly. This structure, presumably due to curved nanosheets, is metastable and gradually disappears during self-assembly.