Liquid dynamics in ZrO2 nanoporous films

Time-resolved Optical Kerr Effect (OKE) measurements were used to det. the orientational dynamics of water and acetonitrile in the bulk and in pores of ZrO2 nanostructured films. The expts. were performed with a home-built OKE microscope, capable of providing the necessary axial resoln. (5 micro m) to exclusively probe the internal vol. of the film. The time consts. obtained for the orientational dynamics of the bulk liqs. agree with the literature. In the pores, both liqs. exhibit slower dynamics, indicating a restricted motion of the mols. at the interface. In the case of water, our data is manifestly incompatible with the existence of a bulk-like population of mols. in the core of the pores, suggesting that the interface induces a long range constraint on the orientational dynamics of the mols. within the nanocavity. The differences obsd. between the two liqs. are interpreted as due to the H-bond character of water, which is absent in acetonitrile.