Crystallization of amorphous tris(8-hydroxyquinoline)aluminum nanoparticles and transformation to nanowires

Amorphous tris(8-hydroxyquinoline)aluminum (AlQ(3)) nanoparticles can be grown directly into alpha-phase crystalline nanowires in a one-step heat treatment. At the most appropriate Ar pressure, heating time. and heating temperatures (between 150 and 190 degrees C), fine and long nanowires are obtained. The growth of the nanowires is dictated by the anisotropic bonding in alpha-AlQ(3) crystals. The growth mechanism is illustrated by the concept of nucleation and molecular migration. Two exotherms are revealed, from differential scanning calorimetry analyses, in the transformation process of AlQ(3) amorphous nanoparticles to crystalline nanowires. The first exotherm is the transition from amorphous nanoparticles to the gamma-phase, and the second exotherm is the transition from the gamma- to the gamma-phase. By means of Kissinger plots, the activation energies for the crystallization of the gamma-phase and the transition from the gamma- to the alpha-phase are calculated, for the first time, to be 9.7 and 12.1 kJ mol(-1), respectively. A blue-shift and higher intensity of photoluminescence after heat treatment are also demonstrated.