Luminescent amorphous alumina nanoparticles in toluene solution

We report on blue luminescence from alumina nanoparticles suspended in toluene solution. They were fabricated through ultrasonic treatment of porous anodic alumina membrane. The photoluminescence in the suspension of alumina nanoparticles shows considerable blueshift as larger particles precipitate. Transmission electron microscopy observations confirm the occurrence of the precipitation. A mixed mechanism combining the surface bonding states with widened bandgaps of alumina nanoparticles by the quantum confinement effect is presented. It agrees well with the observed photoluminescence results.