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@SiO ₂ 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.