Cu-activated dye-sensitized upconversion nanoprobe: Overcoming pigment interference for ultrasensitive glyphosate detection in plant-derived foods and live-cell imaging.

The development of universal methods for pesticide residue detection in plant-derived foods is significantly impeded by strong UV-visible absorption from natural pigments. These pigments induce inner filter effects that distort fluorescence signals and compromise the accuracy of conventional sensing platforms. In this study, we developed a Cu-activated dye-sensitized upconversion nanoprobe for ultrasensitive glyphosate (Gly) detection in pigment-rich plant-derived foods. The probe integrates near-infrared cyanine dye (CyPh) with core-shell upconversion nanoparticles β-NaYF:Yb20 %,Er2 %@NaYF:Yb10 %,Nd10 % (UNs), utilizing 808 nm excitation and 655 nm upconversion emission to circumvent pigment interference. Cu quenches the upconversion luminescence by forming a CyPh complex; subsequent Gly addition restores luminescence through competitive Cu chelation. Owing to efficient Förster resonance energy transfer from CyPh to UNs, the nanoprobe demonstrated high sensitivity with a detection limit of 19.01 nM in aqueous solutions, along with rapid response characteristics. Spike recovery experiments conducted with dark matrix samples yielded Gly recovery rates of 97.0-104.0 %, accompanied by relative standard deviations below 2.95 %. To enable field applications, a semi-quantitative analysis system based on smartphone color recognition was developed for rapid on-site Gly screening through fluorescence color changes. Notably, the probe exhibited excellent biocompatibility and enabled simultaneous imaging of Cu and Gly in live cells. This work presents a powerful tool for the rapid and accurate detection of Gly in both complex environmental and biological matrices.