Cu2+-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 2+ -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 4 :Yb20 %,Er2 %@NaYF 4 :Yb10 %,Nd10 % (UNs), utilizing 808 nm excitation and 655 nm upconversion emission to circumvent pigment interference. Cu 2+ quenches the upconversion luminescence by forming a CyPh complex; subsequent Gly addition restores luminescence through competitive Cu 2+ 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 2+ 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.