Assembly of Colloidal Nanoparticles into Anodic Aluminum Oxide Templates by Dip-Coating Process

In this paper, the assembly behavior of colloidal nanoparticles into anodic aluminum oxide (AAO) templates is investigated. Approximately 20-nm-diameter iron oxide (Fe₂O₃) particles stabilized by oleic acid and 5-nm-diameter CdSe coated by thin ZnS and stabilized by trioctylphosphine oxide and dispersed in octane solvent are integrated into AAO pores with an average pore diameter of ~30-100 nm by dip-coating process. The particles assemble selectively at the bottom of pores. Also, the multiple stacks of particles are obtained selectively inside the pores by sequentially repeating dip coating and removing the surfactants (oleic acid) from the particle layer. The nanoparticles integrated into nanometer-scale AAO templates produce the nanostructures for potential applications such as high-density patterned magnetic media, patterned nanoparticle layers for memory device, seeds for nanowire growth, and so on.