Design of a highly sensitive and selective bulk optode based on fluorescence enhancement of N,N′-bis-(1-hydroxyphenylimine)2,2′-pyridil Schiff base: Monitoring of zinc(II) ion in real samples and DFT calculation

Abstract

A novel highly sensitive and selective optical chemical sensor (optode) was fabricated for the determination of Zn2+ ion. The optical sensor was prepared by incorporating recently synthesized ionophore, HPP: N,N′-bis-(1-hydroxyphenylimine)2,2′-pyridil, sodium tetraphenylborate (NaTPB) as an anionic additive, dibutyl phthalate (DBP) as a plasticizer in a poly(vinylchloride) membrane. The novel ionophore was synthesized by conventional condensation reaction between 2,2′-pyridil and 2-aminophenol and characterized using different spectroscopic techniques. The response of the sensor is based on the strong fluorescent emission enhancement of ionophore HPP upon binding to Zn2+ ions. This can be correlated to the efficient Zn2+ binding of HPP which promotes a good chelation-enhanced fluorescence (CHEF) effect and prevents the photoinduced electron transfer (PET) effect. The effect of several parameters in determining Zn2+ were studied and optimized. Under the optimum conditions, a good linear relationship between the fluorescence response and concentration of Zn2+ was achieved with high sensitivity within a wide range from 1.0×10−10 to 1.0×10−2M and a limit of detection (LOD) 6.3×10−11M. Furthermore, the present probe exhibited a high selectivity for Zn2+ over other metal ions and was successfully assessed for determination of Zn2+ ions in real samples including some food and biological samples with satisfactory results. Theoretical calculations were employed to support the sensing mechanism of the sensor toward Zn2+.