Temperature-controlled reversible exfoliation-stacking of titanate nanosheets in an aqueous solution containing tetraalkylammonium ions

Exfoliation and stacking of titanate nanosheets dispersed in aqueous solutions containing tetraalkylammonium ions can be reversibly controlled by adjusting the solution temperature as a tunable physical parameter. That is, the transparent colloidal solution of exfoliated titanates is clouded on the basis of spontaneous stacking of multiple nanosheets when heated at a certain temperature, and cooling of the clouded solution causes regeneration of the original exfoliated state. This cycle repeatedly and rapidly occurs according to the temperature fluctuation. The origin of behavior is qualitatively interpreted with a temperature-dependent variation in the Debye screening length of negatively charged nanosheets that affects the dispersibility of nanosheets.