Sulfonate substituted rhodamine hydrophilic fluorescent probes: Application to specific detection of Fe3+ and imaging in living fish.

Two Sulfonate substituted rhodamine hydrophilic fluorescent probes RbS1 and RbS2 were designed and synthesized for specific detection of Fe3+. It was found that the probe RbS2 was stronger than RbS1 in the water solubility test. Both of them displayed responses to Fe3+ with a apparent fluorescence enhancement at 585 nm, accompanied with a distinct fluorescence change to pink. Upon addition of Fe3+ ions (0-16 μM), the emission intensity of RbS1 and RbS2 increased to 40 and 70 fold, which exhibited a good linear relationship with the concentration of Fe3+. The detection limits of RbS1 and RbS2 for sensing Fe3+ were 0.64 μM and 0.56 μM, respectively. The binding ratios of the RbS1 and RbS2 to Fe3+ were 1:1 and the recycling ability for Fe3+ was reasonable. RbS1 and RbS2 have been successfully applied to the determination of Fe3+ in real water samples with satisfactory recovery and accuracy. In further living fish imaging test, the probe RbS2 was distributed into abdomen, which exhibited better fluorescence imaging ability than that of RbS1.