Luminescence properties of sol-gel derived organic-inorganic composite films dispersed with erbium and neodymium oxalate nanoparticles

Erbium oxalate and neodymium oxalate nanoparticles/titania/organically modified silane composite sol-gel thin films for photonic applications have been prepared by combining an inverse microemulsion technique and the sol-gel technique at low temperature. Transmission electron microscopy observation shows that the size of these oxalate nanoparticles is in the range from 10 to 40 nm. Up-conversion emission properties of these composite thin films on silicon substrates have been studied. A relatively strong room-temperature green up-conversion emission at 544 nm has been measured for the composite films dispersed with erbium oxalate nanoparticles upon excitationat 993 nm. An up-conversion emission in violet (399nm) color from neodymium oxalate nanoparticles upon excitation with a yellow light (587nm) has been observed. In addition to this violet emission, two UV emissions at 341 nm and 376 nm and a weak blue emission at 467 nm have been obtained. The mechanism of the up-conversion emission has been explained by means of an energy level diagram. The lifetimes of the violet emissions have been measured.