Synthesis and Characterization of Core@shell Β-NaYF4 to Yb3+/Ho3+@SiO2 with Different Ratios of Fluorine to Yttrium

Fluorescent beta-NaYF4 to Yb3+/Ho3+@SiO2 nanoparticles with variations in the ratios of fluorine and yttrium 4:1, 12:1, and 20:1, respectively, have been synthesized using the solvothermal method at a temperature of 200 celcius and reaction time of 8 h and coated with SiO2 by the inverse microemulsion method. The obtained nanoparticles were characterized by XRD, UV-Vis, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and fluorescence spectroscopy. The characterizations show that at a ratio of 20:1 a hexagonal crystalline phase develops, with an absorption band centered at 980 nm, an upconversion fluorescence spectrum with centric peaks at 541 nm corresponding to green, and at 643 nm corresponding to red light; likewise, they present spherical morphologies and an average size of 80 nm with a core-shell coating thickness of 10 nm. Furthermore, these nanoparticles were found to possess a high upconversion of luminescence intensity compared to 4:1-cubic crystalline and 12:1-mixed (cubic and hexagonal) nanoparticles. On the other hand, it was shown that the SiO2 coating decreases the luminescence intensity. The results obtained go towards the continuation of research in a biomedical application with highly stable nanoparticles by silica coating.

Automated summary

Fluorescent beta-NaYF4 to Yb3+/Ho3+@SiO2 nanoparticles with variations in the ratios of fluorine and yttrium have been synthesized and characterized. The results show that nanoparticles with a 20:1 ratio have a hexagonal crystalline phase and higher upconversion luminescence intensity compared to other ratios. However, the luminescence intensity is decreased with SiO2 coating.