One-pot synthesis and characterization of rhodamine derivative-loaded magnetic core–shell nanoparticles

Abstract

A new method to produce elaborate nanostructure with magnetic and fluorescent properties in one entity is reported in this article. Magnetite (Fe3O4) coated with fluorescent silica (SiO2) shell was produced through the one-pot reaction, in which one reactor was utilized to realize the synthesis of superparamagnetic core of Fe3O4, the formation of SiO2 coating through the condensation and polymerization of tetraethylorthosilicate (TEOS), and the encapsulation of tetramethyl rhodamine isothiocyanate-dextran (TRITC-dextran) within silica shell. Transmission electron microscopy (TEM), energy dispersive X-ray (EDX) analysis, and X-ray diffraction (XRD) were carried out to investigate the core–shell structure. The magnetic core of the core–shell nanoparticles is 60 ± 10 nm in diameter. The thickness of the fluorescent SiO2 shell is estimated at 15 ± 5 nm. In addition, the fluorescent signal of the SiO2 shell has been detected by the laser confocal scanning microscopy (LCSM) with emission wavelength (λem) at 566 nm. In addition, the magnetic properties of TRITC-dextran loaded silica-coating iron oxide nanoparticles (Fe3O4@SiO2 NPs) were studied. The hysteresis loop of the core–shell NPs measured at room temperature shows that the saturation magnetization (Ms) is not reached even at the field of 70 kOe (7T). Meanwhile, the very low coercivity (Hc) and remanent magnetization (Mr) are 0.375 kOe and 6.6 emu/g, respectively, at room temperature. It indicates that the core–shell particles have the superparamagnetic properties. The measured blocking temperature (TB) of the TRITC-dextran loaded Fe3O4@SiO2 NPs is about 122.5 K. It is expected that the multifunctional core–shell nanoparticles can be used in bio-imaging.