A novel fluorescent probe for Cr3 + based on rhodamine–crown ether conjugate and its application to drinking water examination and bioimaging

• A novel rhodamine derivative (RhC) was prepared for Cr3 + detection.
• Sensing mechanism was a complexing one with binding stoichiometry of 2:1 for RhC–Cr3 + complex.
• The probe was successfully applied to drinking water examination and living cell imaging.

A trivalent chromium (Cr3 +) fluorescence probe (RhC) was designed and synthesized via Schiff base reaction based on rhodamine–crown ether conjugate. This probe displayed a favorable selectivity for Cr3 + over a range of other common metal ions in DMF/H2O (3:7, v/v; PBS buffer 50 mmol L− 1; pH = 6.8) solution, leading to prominent fluorescence “OFF–ON” switching of the rhodamine fluorophore. The limit of detection was calculated to be 1.5 μmol L− 1 (S/N = 3). The binding ratio of RhC–Cr3 + complex was determined to be 1:2 according to the Job's plot and HR-MS. The probe was successfully applied to examination of Cr3 + in drinking water spiked samples. The average recoveries ranged from 104.9% to 106.9% at spiked concentration level of 10.00 μmol L− 1, and the obtained results were consistent with those obtained using atomic absorption spectrometry (AAS). Moreover, bioimaging experiments showed that RhC can sense the Cr3 + in living cells with a fluorescence enhancement signal.

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