Synthesis of cubic and hexagonal NaYF sub(4):Er super(3+)

Up-conversion luminescence process, which is related to absorption of several light photons (usually infrared) followed by emission of light in the visible or even ultraviolet spectral regions, has attracted interest of scientists due to its potential practical use in various applications including biolabels, temperature sensors, light sources etc. Although observable in d- and f-ions doped materials, the highest efficiency of up-conversion luminescence is usually attained in lanthanides doped hosts. Among huge variety of materials suitable as up-conversion hosts the most prominent is considered to be NaYF sub(4), both due to its low phonon energy and multisite nature of the crystalline lattice. In the present report erbium doped NaYF sub(4) nanomaterial has been synthesized by a novel molten salt method. Depending on the synthesis temperature the structure of the material varied from solely cubic to exclusively hexagonal. It was found that the intensity of the up-conversion luminescence increased drastically as the structure of NaYF sub(4):Er super(3+) changed from cubic to hexagonal.