AIE-active naphthyl-hydrazine Schiff base chemosensor and its multi-ion sensing activities in the living cells

1-[(2-Hydroxy-4-methoxy-benzylidene)-hydrazonomethyl]-naphthalen-2-ol (H₂L), a tetradentate ONNO Schiff base, structurally established by Single Crystal X-ray Diffraction measurement, shows Aggregation Induced Emission (AIE) in 80 % H₂O: DMSO mixture (4:1, v/v) and has been investigated by the change in the FESEM images. The emission intensity in DMSO solution only is enhanced by Zn²⁺ (LOD(Zn²⁺) 0.18 μM) in presence of fifteen interfering metal ions which may be due to the chelation enhancement of fluorescence (CHEF) mechanism. The emission of H₂L in DMSO is also enhanced by CN^- (LOD(CN^-), 0.94 μM) in presence of eleven invading anions by suppressing the ESIPT process. The emission in AIE phase of H₂L in H₂O: DMSO mixture (4:1, v/v) has been quenched by Fe³⁺ (LOD(Fe³⁺), 3.92 μM) and Cu²⁺ (LOD(Cu²⁺), 0.17 μM). The FESEM images and EDX analysis of H₂L and analyte support the binding of the ions. Use of H₂L has been demonstrated through a paper strip soft disposable device for the determination of CN^- in daily consumed fresh food samples. The plausible sensing mechanism with the analyte is evaluated through ¹H NMR titration, FTIR spectra and has also been explained by the DFT computation. The MTT assay establishes the non-toxicity of H₂L in cells upto a concentration of 100 μM. Intracellular imaging obtained through fluorescence microscopy demonstrates the sensing behaviour of H₂L in the MDA-MB 231 cells in presence of Zn^2+, Fe³⁺, Cu²⁺ and CN^- ions.