A highly sensitive and selective fluorescent probe for trivalent aluminum ion based on rhodamine derivative in living cells

A rhodamine spirolactam derivative (1) is developed as a colormetric and fluorescent probe for trivalent aluminum ions (Al³⁺). It exhibits a highly sensitive “turn-on” fluorescent response toward Al³⁺ with a 70-fold fluorescence intensity enhancement under 2 equiv. of Al³⁺ added. The probe can be applied to the quantification of Al³⁺ with a linear range covering from 5.0 × 10⁻⁷ to 2.0 × 10⁻⁵ M and a detection limit of 4.0 × 10⁻⁸ M. Most importantly, the fluorescence changes of the probe are remarkably specific for Al³⁺ in the presence of other metal ions, which meet the selective requirements for practical application. Moreover, the experiment results show that the response behavior of 1 towards Al³⁺ is pH independent in neutral condition (pH 6.0–8.0) and the response of the probe is fast (response time less than 3 min). In addition, the proposed probe has been used to detect Al³⁺ in water samples and image Al³⁺ in living cells with satisfying results.