A facile method to synthesize superparamagnetic and up-conversion luminescent NaYF4:Yb, Er/Tm@SiO2@Fe3O4 nanocomposite particles and their bioapplication

This paper presents a facile method for the fabrication of core-shell-structured NaYF4:Yb, Er/Tm@SiO2@Fe3O4 nanocomposite particles (NCPs). In this approach, when the EDTA-capped NaYF4:Yb, Er/Tm nanoparticles were mixed with the oleic acid-modified magnetic Fe3O4 nanoparticles in isopropyl alcohol, followed by addition of TEOS and ammonium hydroxide, core-shell NaYF4:Yb, Er/Tm@SiO2@Fe3O4 NCPs were directly yielded; neither surface modification nor high temperature was needed. The obtained NCPs have very good superparamagnetic and luminescent properties. Preliminary investigation of incubating with HeLa cells displays that the NCPs are easily swallowed and can be used in bioimaging.