Preparation of Eu(iii) acetylacetonate-doped well-defined titania particles with efficient photoluminescence properties.

The aggregation/dispersion of luminescent species is a critical factor that determines their luminescence properties. In this study, europium(iii) acetylacetonate (Eu(acac)) was doped into a titania matrix to form Eu(acac)-doped titania particles with well-defined size and shape through a microreactor-based sol-gel approach. The morphology and structure of the as-synthesized products were characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, scanning transmission electron microscopy and X-ray diffraction measurements. The Eu/Ti value of the products varied in the range from 0.125 to 5.0 and the resulting luminescence properties were examined. It should be noted that there was an optimum Eu/Ti value that exhibited the strongest luminescence. A possible reason for this phenomenon can be explained on the basis of a balance between the inter-molecular distance of Eu(acac) and its doped amount. The effects of the crystal phase of the titania matrix on luminescence behavior were also investigated. As a result, Eu(acac)-doped amorphous titania demonstrated more efficient luminescence than that after calcined at 550 °C for 6 h to convert amorphous to anatase probably because of the aggregation of Eu species on the crystallite surface. The stability of the present Eu(acac)-doped titania was confirmed by preparing thin films on a glass substrate and by applying UV/ozone treatment. As compared to bare Eu(acac), degradation in luminescence was suppressed in the case of Eu(acac)-doped titania. Thus, the present titania-based hybrid with controlled Eu(acac) doping is useful as a stable, luminescent material for optical, biological and environmental applications.