Nanostructured semiconductors templated by cholesteryl-oligo(ethylene oxide) amphiphiles

Lyotropic liquid crystals formed by cholesteryl oligo(ethylene oxide) amphiphiles were used to template the II-VI semiconductor cadmium sulfide. The amphiphiles were synthesized with average chain lengths ranging from 5 to 30 repeats of ethylene oxide and characterized by polarized optical microscopy, differential scanning calorimetry, small-angle X-ray scattering, and mass spectrometry. By varying the ratio of hydrophile coil length to hydrophobe rod length, a transition from lamellar to hexagonal mesophases occurs when the average number of ethylene oxide repeats exceeds 17 units. Inorganic semiconductor templating with these cholesterol-based amphiphiles yields CdS particles with either lamellar or hexagonal nanostructuring. The morphology of the lamellar particles is oblong with lengths of up to 400 nm and widths of 150 nm, whereas that of the hexagonal particles is typically spherical with diameters averaging 200 nm. The nanostructure of the particles consists of either periodic lamellar or hexagonal arranged pores with dimensions similar to those of the organic template.