A Novel Ferrocene-Derivative-Based Dual-Response Chemosensor for Selective Al³⁺ Detection: Fluorescence and Electrochemical Signaling

Abstract A new Chemosensor, 5-ferrocenylsalicylaldehyde-2-pyridinehydrazone (SP-Fc), was designed and synthesized by condensing 5-ferrocenylsalicylaldehyde with 2-hydrazinopyridine. Its structure was characterized by ¹H NMR, ¹³C NMR and HRMS. SP-Fc could be used to identify Al³⁺ through dual optical and electrochemical responses. Upon addition of Al³⁺, the sensor exhibited a significant fluorescence enhancement attributed to CHEF and the inhibition of both PET and ESIPT processes. The sensor showed a high selectivity for Al³⁺ in DMSO solution at pH = 6 and was not disturbed by other competing metal ions. In additon, the detection limit for Al³⁺ was observed as 1.30 × 10⁻ ⁷ M. Job’s plot analysis and NMR titration experiment confirmed 1:1 stiochiometry between Al³⁺ and probe through phenolic oxygen, imine nitrogen and pyridine nitrogen atoms. Moreover, the electrochemical signals of SP-Fc in the presence of the Al³⁺ was shifted significantly compared with those of the other metal cations tested, indicating SP-Fc could be used to be a dual-response chemosensor for Al³⁺ with excellent sensitivity and selectivity both in optical and electrochemical ways. Also, Confocal fluorescence microscopy imaging demonstrated that SP-Fc can monitor Al³⁺ in living MCF-7 cells with low cytotoxicity.