Two phosphorescent iridium(III) complexes conjugated to a lipophilic triphenylphosphonium cation moiety, IrMitoOlivine and IrMitoNIR, were synthesized. The complexes show high mitochondria-specificity and relatively lower cytotoxicity. Time-lapse confocal imaging indicates that both complexes exhibit an excellent anti-photobleaching capability under continuous laser irradiation.

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 Fe 3 O 4 nanoparticles in various concentrations ranging from 0 to 6250 ng · ml −1 . It was found that when the concentration of Fe 3 O 4 NPs was lower than 0.0625 ng · ml −1 , the fluorescence intensity decreased sharply with increasing concentration of Fe 3 O 4 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 Fe 3 O 4 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 Fe 3 O 4 nanoparticle component, and offered a better understanding of interaction between magnetic NPs and luminescence of fluorescent molecules.