Effects of dodecyl sulfate anionic surfactants on the crystal growth of ZnO through hydrothermal process

Abstract

The effects of dodecyl sulfate anionic surfactants (on the synthesis of ZnO nanostructures were investigated at low temperature hydrothermal conditions in an aqueous solution. We used anion surfactants which have the same length of alkyl chain with different counter-ions, such as sodium dodecyl sulfate (NaDS), ammonium dodecyl sulfate (NH4DS) and lithium dodecyl sulfate (LiDS) as additives. As a result, single-crystalline ZnO nanorods with various morphologies, sizes and aspect ratios were synthesized depending on the different counter ions of the surfactants. From the series of experiments, it was observed that the anionic surfactants affect the surface energy of ZnO crystal faces by adsorption of their hydrated counter-ions on negatively charged zinc hydrate precursor (Zn(OH)(4)(2-)), and this phenomenon continuously occurs through the whole crystal growth process. So, it promotes the control of the crystal growth along a specific direction. The various ZnO morphologies depending on the type of dodecyl sulfate surfactants were explained by the differences in electrostatic interaction between the surface charge of ZnO and the counter-ions of the surfactant molecules.