Synthesis And Characterization Of CaF2:Yb,Er(CORE) /CaF2(SHELL) Up-Conversion Nanoparticles

Abstract

The synthesis of monodispersed CaF2:Yb,Er up-conversion nanoparticles (particle size ~ 5.4 nm ? 0.9 nm) using thermolysis of precursors in oleylamine at 340 oC was studied. These nanoparticles were characterized using TEM, XRD, FTIR, Zeta potential, DTA/TGA and XPS.

An undoped CaF2 shell was subsequently deposited on the doped core nanoparticles to form the CaF2:Yb,Er(core)/CaF2(shell) structure in order to improve the emission intensity. The critical shell thickness was determined to be ~ 2.5 nm which improved the emission intensity by more than 20 times. Both core and core/shell nanoparticles were stable in solvents such as chloroform and hexane.

Amorphous silica coating on CaF2:Yb,Er(core)/CaF2(shell) UCNPs was also achieved to demonstrate the potential for bio-application.

CaF2:Yb,Er(core)/CaF2(shell) up-conversion nanoparticles showing strong red emission, with its longer wavelength and penetration distance compared with that of shorter wavelengths of green and blue lights, may find promising potential applications.