Sensitive Fluorescent Probe for Al³⁺, Cr³⁺ and Fe³⁺: Application in Real Water Samples and Logic Gate

Construction of single probes for simultaneous detection of common trivalent metal ions has attracted much attention due to higher efficiency in analysis and cost. A naphthalimide-based fluorescent probe K1 was synthesized for selective detection of Al³⁺, Cr³⁺ and Fe³⁺ ions. Fluorescence emission intensity at 534 nm of probe K1 in DMSO/H₂O (9:1, v/v) was significantly enhanced upon addition of Al³⁺, Cr³⁺ and Fe³⁺ ions while addition of other metal ions (Li⁺, Na⁺, K⁺, Ag⁺, Cu²⁺, Fe²⁺, Zn²⁺, Co²⁺, Ni²⁺, Mn²⁺, Sr²⁺, Hg²⁺, Ca²⁺, Mg²⁺, Ce³⁺, Bi³⁺ and Au³⁺) did not bring about substantial change in fluorescence emission. The calculated detection limits were 0.32 µM, 0.81 µM, and 0.27 µM for Al³⁺, Cr³⁺, and Fe³⁺, respectively. Probe K1 displayed strong anti-interference ability, a large Stokes shift, rapid response, and applicability in a wide pH range for the simultaneous detection of Al³⁺, Cr³⁺ and Fe³⁺ in real water samples. Job's plot test showed that the stoichiometric ratio of the complexes formed between probe K1 and the trivalent metal ions was 1:1. The reversible application of probe K1 was realized by addition of Na₂EDTA. A molecular logic gate was built based on the input-output information. This approach may provide a basis for highly selective and sensitive detection of common trivalent cations and for design of memory devices.