A dual-response fluorescent probe for Zn2+ and Al3+ detection in aqueous media: pH-dependent selectivity and practical application

- The probe is structurally simple and easy to synthesize.
- The probe shows pH dependent dual-selectivity for Zn2+ and Al3+ in Tris-HCl buffer.
- The probe has good cell-permeability and selectively sense intracellular Zn2+ and Al3+ by bioimaging at different pH.
- The probe can be used for determination of the analytes in real drug samples.

A Schiff base-type fluorescent probe (1) consist of 2-hydroxynaphthaldehyde and glutamide moieties has been designed and synthesized for detection Zn2+ and Al3+. The probe shows pH dependent dual-selectivity for Zn2+ and Al3+ in Tris-HCl buffer, viz. that can selectively recognized Zn2+ at pH 7.4 and Al3+ at pH 6.0, respectively. From Job's plots and MS data, the stoichiometric ratios of the probe with Zn2+ and Al3+ appeared to be 1:1 and 2:1, respectively. The probe can detect as low as 5.5 × 10−8 M−1 Zn2+ and 1.27 × 10−7 M−1 Al3+, whereas respective association constants are 4.27 × 104 M−1 and 3.50 × 109 M−1. Furthermore, it is also confirmed that the probe has good cell-permeability and could thus be used to selectively sense intracellular Zn2+ and Al3+ by bioimaging in different pH environment. Finally the probe has been used successfully for determination of the analytes in real drug samples.