Anodic construction of lamellar structured ZnO films using basic media via interfacial surfactant templating

Zinc oxide films with ordered lamellar structures were anodically deposited in basic media using an interfacial surfactant templating method. Sodium dodecyl sulfate (SDS) and lauric acid served as efficient structure-directing agents and incorporated a lamellar structure with d(001) = 3.5 and 2.8 nm, respectively, into ZnO films. When 0.03 M cetyltrimethylammonium bromide (CTAB) or tetramethylammonium bromide (TAB) was added as supporting electrolytes, the amount of SDS required to template the lamellar structures was decreased from 10 to 5 wt % and the basal spacing of the resulting lamellar structure was decreased to 3.1 nm. The effects created by the addition of CTAB and TAB are identical, indicating that the amphiphilic nature of CTAB does not play a major role in altering SDS assemblies. Investigation of the effect of various supporting cations and anions (e.g., NaCl, NaBr, NaI, Na2SO4) demonstrated that the effect seen with the addition CTAB and TAB is primarily due to the cationic groups reducing the repulsion of SDS head groups and enhancing interactions between anionic inorganic species (i.e., [Zn(OH)4]2-) and anionic SDS. Br- and I- ions also appear to have a slight effect on improving the ordering of interfacial SDS assemblies, while no apparent changes were observed when NaCl and Na2SO4 were added. These results indicate that it is not the increase in concentration of any salts but the specific type of cations and anions that can alter the interfacial SDS assemblies.