The electrochemical deposition of nanostructured cobalt films from lyotropic liquid crystalline media

Lyotropic liquid crystalline phases formed at high concentrations of nonionic surfactants provide a versatile templating medium that can be used to produce nanostructured materials with regular arrays of pores of nanometer dimension and extended periodicity. In this work, we have used this technique to prepare nanostructured cobalt films on gold substrates by electrochemical deposition of cobalt from cobalt acetate dissolved in the aqueous domains of the hexagonal lyotropic liquid crystalline phase of Brij 56(C16EO10). Low angle X-ray and transmission electron microscope studies show that the resulting cobalt films have a regular nanostructure consisting of a hexagonal array of cylindrical pores. The repeat distance for this nanostructure lies in the range of 7-11 nm and can be systematically varied by varying the amount of n-heptane added to the template mixture. Preliminary magnetic measurements on the nanostructured samples suggest that the coercivity (H-c) of these cobalt films is three to five times greater than that for polycrystalline cobalt and that it varies systematically with the size of the pores. (C) 2001 The Electrochemical Society. All rights reserved.