formation of flower-like crystals of tris(8-hydroxyquinoline)aluminum from 8-hydroxyquinoline on anodic porous alumina

The treatment of anodic porous alumina (APA) plates in heated water containing 8-hydroxyquinoline (HQ) produces crystalline tris(8-hydroxyquinoline)aluminum (Alq3) microbelts about 5–10 μm wide and 5–20 μm long. These microbelts were found to aggregate to form flower-like structures on the surface. X-ray diffraction studies indicated that the Alq3 microbelts are composed of an α-phase having a meridional structure. The Alq3 microbelts exhibited green photoluminescence with a peak at around 520 nm. Scanning electron microscope images and energy dispersive X-ray spectra showed that this reaction is induced at the APA surface by the reaction between the HQ and amorphous Al2O3 species.