A novel dual-channel Schiff base fluorescent chemo-sensor for Zn2+ and Ca2+ recognition: Synthesis, mechanism and application

A novel multifunctional chemo-sensor (RHCS-NH2), incorporating Schiff base, rhodamine B hydrazide, hydrazine hydrate group into triazine, was successfully designed and synthesized. It was found that the RHCS-NH2 sensor displays immediate multi-response toward Ca2+ in CH3CN-H2O (v/v = 9/1, Tris-HCl pH 7.0) and Zn2+ in DMF-H2O (95/5, v/v). Under the optimized conditions, the linear range of identifing Ca2+ ions are from 0.01 to 10.0 mu M in CH3CN-H2O (v/v = 9/1, Tris-HCl pH 7.0), 0.03-10.0 mu M for Zn2+ ions in DMF-H2O (95/5, v/v), and the detection limit were measured to be 0.10 nM for Ca2+ and 0.14 nM for Zn2+, respectively. The reaction mechanism between RHCS-NH2 and metal ions was investigated in detail based on fluorescence titration, Job's plots and H-1 NMR titration curve, ESI-MS measurement and theoretical calculation respectively. Simultaneously, 3-(4,5)-dimethylthiahiazo(-z-y1)-3,5-di-phenytetrazoliumromide (MTT) assays and inverted fluorescence microscopy imaging also demonstrated that the probe has well cell membrane permeability and hypotoxicity, indicating its potential applicability in vitro.