Dispersion and stability of gold nanorods prepared by anodized aluminum oxide (AAO) templates in alkaline solution

Template-based nanorods prepared by anodized aluminum oxide templates have been utilized in a variety of fields as hot spots for surface-enhanced Raman scattering, self-assembling components, molecular electronic junctions, and elements for plasmon coupling. An important requirement for nanorods used in these fields is that they are stably dispersed in solution. Despite the importance of this research, these properties have not been extensively studied either experimentally or theoretically. Herein, the required conditions (concentration and surface potential) for the stable dispersion of template-based nanorods were theoretically investigated using DLVO (Derjaguin-Landau-Verwey-Overbeek) theory, and experimentally examined for the nanorods with different radii (175 and 22.5 nm), but the same length (750 nm). Contrary to the results expected from DLVO theory, only the thin nanorods were stably dispersed in solution. The difference in stability between the thin and thick nanorods under the same conditions was explained by their different surface potentials, which resulted from the different degrees of surface coverage by the adsorbates (2-mercapto ethane sulfonate).