A furano-ortho-vanillin conjugate for fluorogenic ratiometric and selective Zn²⁺ sensing: theoretical insights and...

A fluorescent sensor BFC was designed and synthesized in order to identify the selective fluorescence recognition of Zn²⁺ in semi-aqueous environments. BFC notably displayed ratiometric red-shifted, twelve-fold fluorescence "turn-on" enhancement when exposed to Zn²⁺ at 490 nm with an isoemission point at 440 nm and a detection limit of 0.65 µM, which is considerably below the WHO (World Health Organisation) recommended value of Zn^2+. The binding constant of BFC with Zn²⁺ was determined as 4 × 10⁴ M^-1. The fluorescence enhancement of BFC in the presence of Zn²⁺ is attributed to the enhancement of charge transfer leading to high fluorescence via the CHEF mechanism. The binding interaction between BFC and Zn²⁺ was elucidated using UV-vis and fluorescence spectroscopy, supported by Job's plot analysis and theoretical insights from DFT calculations. For biological applications, BFC has been employed in plant-based cell imaging to monitor Zn²⁺ accumulation in Lathyrus sativus L. (grass pea). Overall, BFC presents a simple, effective, and promising fluorescent probe for ratiometric Zn²⁺ detection in diverse fields such as a versatile tool for Zn²⁺ detection in different applications like detoxification and marker molecules for bioabsorption.