Rhodamine-B decorated superparamagnetic iron oxide nanoparticles: preparation, characterization and their optical/magnetic properties

The paper reports on covalent clicking of rhodamine-B (RhB) bearing a terminal azide group to alkyne-terminated silica coated superparamagnetic iron oxide nanoparticles via the copper(I)-catalyzed Huisgen azide-alkyne 1,3-dipolar cycloaddition (CuAAC) reaction. The course of the reaction was followed the use of powder X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectroscopy, fluoroscopy, and magnetics. The RhB labelled Fe3O4@SiO2 nanoparticles exhibit stable fluorescence and no detectable leakage of the fluorescent dye because the resulting 1,4-disubstituted 1,2,3-triazole ring formed via click reaction is thermally stable and relatively inert to hydrolysis, oxidation, and reduction. Due to the superparamagnetic property of the Fe3O4 and the RhB molecule covalently decorated in the Fe3O4@SiO2 framework, the nanoparticles are endowed with properties of a contrast agent in magnetic resonance imaging (MRI) and optical imaging modality. The cytotoxicity tests indicate the bifunctional nanoparticles could be applied in biomedical or bioengineering field.