Influence of Magnetic Fe3O4 Nanoparticles on Fluorescence Quenching of Dye Molecules

Magneto-fluorescent nanocomposites possessing both fluorescent and magnetic properties represent an attractive platform for biomedicine and nanotechnology. One of the great challenges facing magneto-fluorescent nanocomposites is understanding the influence of magnetic component on the fluorescence quenching of dye molecules. However, there was still lack of in-depth and quantitative analysis of fluorescence decay for magneto-fluorescent nanocomposites. Herein, fluorescence intensity decay of acridine orange, a model fluorescent dye, was quantitatively determined with magnetic Fe3O4 nanoparticles in various concentrations ranging from 0 to 6250 ng . ml(-1). It was found that when the concentration of Fe3O4 NPs was lower than 0.0625 ng . ml(-1), the fluorescence intensity decreased sharply with increasing concentration of Fe3O4 NPs; when the NP concentrations ranged from 0.0625 ng . ml(-1) to 1.25 ng . ml(-1), the fluorescence intensity of acridine orange decreased linearly with increase of NP concentration; and when the concentration of Fe3O4 NPs exceeded 1.25 ng . ml(-1), essentially no fluorescence can be detected. These findings suggested that magneto-fluorescent composites with optimized fluorescence properties could be obtained by carefully controlling Fe3O4 nanoparticle component, and offered a better understanding of interaction between magnetic NPs and luminescence of fluorescent molecules.