Unusually stable ∼100-fold reversible and instantaneous swelling of inorganic layered materials

Abstract

Cells can swell or shrink in certain solutions; however, no equivalent activity has been observed in inorganic materials. Although lamellar materials exhibit increased volume with increase in the lamellar period, the interlamellar expansion is usually limited to a few nanometres, with a simultaneous partial or complete exfoliation into individual atomic layers. Here we demonstrate a large monolithic crystalline swelling of layered materials. The gallery spacing can be instantly increased ∼100-fold in one direction to ∼90 nm, with the neighbouring layers separated primarily by H 2 O. The layers remain strongly held without peeling or translational shifts, maintaining a nearly perfect three-dimensional lattice structure of >3,000 layers. First-principle calculations yield a long-range directional structuring of the H 2 O molecules that may help to stabilize the highly swollen structure. The crystals can also instantaneously shrink back to their original sizes. These findings provide a benchmark for understanding the exfoliating layered materials. © 2013 Macmillan Publishers Limited. All rights reserved.