Dec 8, 2010
Pulse anodization of aluminium delivers tailor-made pore structures
Nanoporous anodic aluminum oxide (AAO) formed by anodization of aluminum has become a popular template system for fabricating various one and two-dimensional functional nanostructures from organic and inorganic materials. AAO membranes with a tailor-made internal pore structure could provide not only a new degree of freedom in template-based fabrication of advanced functional materials, but also a model system for investigating the separation of particles and adsorption characteristics of molecules.
In a recent study, published in the journal Nanotechnology, W Lee and J C Kim present a generic method for the preparation of highly ordered nanoporous anodic alumina with a pattern-addressed pore structure, in which the diameters of oxide nanopores are modulated with designated patterns.
The approach is based on pulse anodization of aluminum employing a series of potential waves that consist of two or more different pulses with designated periods and amplitudes, and provides a unique way of tailoring the internal pore structure of anodic alumina. Pores of the resulting AAO exhibit a high degree of directional coherency along the pore axes without any bifurcations (that is, branching of pores).
Anodic alumina membranes formed by the new pulse anodization method can be readily utilized as templates for developing novel nanowires or nanotubes, the diameters of which are modulated in controlled manners along their axes, and hence will enable not only the investigation of topography-induced various physical properties, but also could provide particle scaffolds for multiplexed bioassays.
The evolution of the internal pore structures of the pulse anodized sample was also investigated as function of pulse parameters. It was revealed that the effective electric field strength across the barrier oxide layer is a key controlling parameter governing the size of the pores and also the detailed geometry of the barrier layer. The study will shed light on the mechanism responsible for the self-organized growth of oxide nanopores during anodic oxidation of aluminum.
Additional information can be found in the journal Nanotechnology.
About the author
Woo Lee is a leader of Nanostructured Materials Research Laboratory (NMRL) at Korea Research Institute of Standards and Science (KRISS) and a professor at the department of Nano Science, University of Science and Technology (UST) in Daejeon, Korea. Mr. Jae-Cheon Kim is working on microscopic analysis of low-dimensional nanostructures as a staff researcher at KRISS.