Integrated colorimetric and fluorometric sensor for the detection of Cu2+ and glyphosate in food samples and bioimaging

Rapid and reliable monitoring of Cu²⁺ and glyphosate levels is important owing to their widespread use and associated health risks in food systems. Herein, we developed a multifunctional fluorescent sensor, (E)-2-(benzothiazol-2-yl)-3-(8-((tert-butyldimethylsilyl)oxy)-julolidin-9-yl)acrylonitrile (LCY), via a straightforward Knoevenagel condensation reaction for sequential detection of Cu²⁺ and glyphosate. The sensor LCY exhibited exceptional sensitivity, achieving remarkably low limits of detection of 148 nM for Cu²⁺ and 53.8 nM for glyphosate, levels that are well-suited for food safety monitoring. On binding Cu²⁺ in 1:1 stoichiometry, LCY underwent an instantaneous color change from yellow to purple-red and a fluorescence “turn-off” response driven by chelation-enhanced quenching. These interactions were systematically investigated using ¹H nuclear magnetic resonance titration, infrared spectroscopy, and computational modeling. Crucially, LCY demonstrated reversible binding, enabling the detection of glyphosate through a competitive displacement assay involving HPO₄²⁻. To validate its real-world food safety applications, LCY was integrated into test strips for rapid, on-site, naked-eye detection of Cu²⁺ ions in food samples. Furthermore, a smartphone-assisted platform was developed for user-friendly, low-cost, and accurate detection of both analytes in food and environmental matrices. This dual-mode sensing approach offers a portable and efficient tool for food quality control, contributing to public health protection and regulatory compliance.