Effect of various surfactants on changes in the emission color chromaticity in upconversion YVO4: Yb3+, Er3+ nanoparticles.

YVO 4 : Yb 3+ ,Er 3+ upconverting nanocrystals were synthesized via a hydrothermal method using different compounds as surfactants. Structure and morphology of the nanocrystals were investigated by X-ray diffraction and transmission electron microscopy. Tetragonal crystal structure of the nanocrystals appeared irrespective of the type of surfactant used. The average crystallite size was estimated by TEM images. The obtained products were composed of small nanoparticles, in the size range of 10–60 nm, depending on the surfactant used. The morphology of the nanoparticles was also regulated by the type of surfactant. Spectroscopic analysis of the materials obtained was carried out by measuring the emission and excitation spectra and the intensity of luminescence as a function of laser energy and luminescence decays. The nanocrystals prepared exhibited a green upconversion emission attributed to the 2 H 11/2 → 4 I 15/2 and 4 S 3/2 → 4 I 15/2 transitions of Er 3+ , under NIR (985 nm) pulse laser irradiation, and their emission lifetimes were in the range 3.84–4.90 μs. On the basis of the spectroscopic investigation, the upconversion mechanism was proposed and chromaticity coordinates were calculated. Surfactants were found to influence on chromaticity of luminescence. [ABSTRACT FROM AUTHOR]