Effects of heat treatment temperature on up-conversion luminescence properties of titania/γ-glycidoxypropyltrimethoxysilane composite thin films dispersed with neodymium oxalate nanoparticles

Neodymium (III) oxalate nanoparticles prepared by the microemulsion technique are dispersed in sol-gel titania/γ-glycidoxypropyltrimethoxysilane composite thin films. Up-conversion emission of the composite thin films heated at different heat treatment temperatures is studied. A relatively strong room-temperature violet up-conversion emission at 399 nm (4D3/2→4I13/2) is measured from the composite thin film heated at 100 °C upon excitation at a yellow light of 587 nm. In addition to this violet emission, an UV emission at 376 nm and a blue emission at 467 nm are also observed. With an increase of heat treatment temperature, except mentioned emissions above, a relatively weak emission at about 349 nm can be also observed from the thin films heated at 500 and 600 °C. The lifetime of the violet emission is measured. The mechanism of the up-conversion emission is proposed. Thermal gravimetric analysis and atomic force microscopy are also employed to characterize the effect of heat treatment temperature on up-conversion emission properties of the thin films.