Preparation and Luminescence Properties of Neodymium(III) Oxide Nanocrystals Dispersed in Sol-gel Titania/ (γ-glycidoxypropyl)Trimethoxysilane Composite Thin Films

Neodymium(III) oxide nanocrystals prepared by an inverse microemulsion technique have been dispersed in sol-gel titania/(γ-glycidoxypropyl)trimethoxysilane composite thin films at low temperature. Transmission electron microscopy and x-ray diffraction were used to characterize the phosphor nanoparticles and show that the neodymium(III) oxide nanoparticles have a nanocrystal structure and the size of the nanoparticles is in the range from 5 to 60 nm. An intense up-conversion emission in violet (399 nm) color from neodymium(III) oxide nanocrystals upon excitation with a yellow light (577 nm) has been observed. Two ultraviolet emissions at 347 and 372 nm and a blue emission at 466 nm have also been observed, and those are assigned to electronic transitions appropriately. A relatively strong room-temperature photoluminescence emission at 1064 nm corresponding to the ⁴F_3/2 → ⁴I_11/12 transition of neodymium ion has been measured as a function of the heat treatment temperature. In addition to this emission, two other emissions at 890 and 1336 nm have also been observed. Especially, a clear shoulder peak at 1145 nm, which could probably be resulting from the host matrix, was observed in all measured samples, and this shoulder peak reached a maximum intensity after a heat treatment at 300 °C.