A multifunctional fluorescent sensor for sequential off-on-off visual detection of Zn2+ and glyphosate in food and biological matrices and efficient removal of Zn2+ from aqueous media.

BACKGROUND

Zinc ions (Zn2+) are essential trace elements that play crucial roles in numerous physiological processes. However, their imbalance can induce harmful effects. This dual nature renders the monitoring and removal of Zn2+ critical for public health. In addition, the widespread use of glyphosate (Glyp) pesticide in the environment poses a serious threat to the eco-system. Therefore, developing integrated platforms that combine precise tracking with efficient absorption of Zn2+/Glyp from environmental and food matrices is essential for ensuring food safety and safeguarding public health.

RESULTS

Herein, we developed a high-performance Zn2+ chemosensor, X6, via one-step condensation of pyridoxal hydrochloride and 1H-indole-2-carbohydrazide. X6 rapidly (within 30 s) and selectively reacted with Zn2+ to form a stable 1:1 complex (X6-Zn2+), accompanied by a distinct colorless-to-yellow color change and an immediate fluorescence "turn-on" response. Meanwhile, the resulting metal complex, X6-Zn2+, demonstrated high performance in glyphosate (Glyp) detection within 20s, achieving a detection limit of 33.6 nM. Taking advantage of the three-dimensional network structure of polyvinyl alcohol (PVA) for controlled loading and release, X6 was embedded into a PVA hydrogel, enabling both dual-signal sensing and efficient removal of Zn2+ from aqueous environments. For practical applications, X6-based test strips were integrated with smartphone-assisted analysis, enabling real-time visual and sequential detection of Zn2+ and Glyp residues in complex matrices. Moreover, X6 was successfully applied to the qualitative detection of Zn2+ and Glyp residues in food and biological samples.

SIGNIFICANCE: This work presents a multifunctional sensor platform for Zn2+ that integrated rapid visual detection, quantitative analysis, efficient removal, and bioimaging capabilities. Furthermore, this platform also provided a versatile strategy for monitoring Glyp residues, demonstrating considerable potential for applications in environmental monitoring, food safety, and biological imaging.