Transformation of anodic aluminum oxide to nanoporous α-Al2O3, ruby and Ti-sapphire micropatterns

Anodic aluminum oxide (AAO) stands in the forefront of the most important materials in modern nanotechnology. Its regular nanoporous structure is widely used for template assisted nanopatterning, optical applications, membrane science and plenty more. Our study presents an enhancement on the potential application of AAO by exploiting its inherent nature of polymorphism. Amorphous AAO is selectively transformed to α-Al2O3 by a laser-induced photo-thermal process. Carbon nanotubes (CNT) are employed as a sacrificial laser light absorber to accomplish the phase transformation of AAO to α-Al2O3. Doping of the evolving α-Al2O3 with Cr or Ti enables preparation of free designable photoluminescent surface patterns. The superior properties of α-Al2O3 are utilized to create hierarchically structured systems for optical, biomedical and lithographic applications.