Macroscopic nanotemplating of semiconductor films with hydrogen-bonded lyotropic liquid crystals

Aqueous gel-like lyotropic liquid crystals with extensive hydrogen bonding and nanoscale hydrophilic compartments have been used to define the growth of macroscopic nanotemplated CdS and CdTe thin films. These mesoporous semiconductor films contain a hexagonal array of 2.5 nm pores, 7 nm center-to-center, that extend in an aligned fashion perpendicular to the substrate. The CdS is deposited on a polypropylene substrate by a reaction between Cd(NO₃)₂ dissolved in the liquid crystal and H₂S transported via diffusion through the substrate. The CdTe is electrodeposited on indium-tin-oxide-coated glass from TeO₂ and Cd(NO₃)₂, both of which are dissolved in the liquid-crystal template. The porous nature of the CdTe films enables chemical transformations of the entire bulk of the film. As electrodeposited, the CdTe films are Te rich and, in contrast to a non-templated film, the excess Te could be removed via a chemical treatment, proving the continuity of the pores in the nanotemplated films. These results suggest that liquid-crystal lithography with hydrogen-bonding amphiphiles may be a useful approach to create materials with nanoscale features over macroscopic dimensions.