Nitrogen-doped carbon dots/glutathione-iron nanoflower enhanced fluorescent/photothermal dual-modal sensor for...

The reliable detection of glyphosate (Gly) in complex samples remains a critical challenge due to inevitable interference of matrices and unpredictable factors. Conventional single-signal sensors are often susceptible to environmental fluctuations, leading to false-positive or false-negative results. This study aimed to develop a novel fluorescent/photothermal dual-modal sensor based on N-CDs/GSH-Fe nanoflower as the signal probe for the sensitive and accurate detection of Gly in complex matrices. A dual-modal sensing strategy was established by integrating fluorescence and photothermal signals into a single nanoprobe, enabling self-validation and mutual calibration between the two detection modes. Nitrogen-doped carbon dots (N-CDs) were synthesized via a hydrothermal method and subsequently complexed with glutathione-iron (GSH-Fe) to construct the N-CDs/GSH-Fe nanoflower probe, which exhibited excellent fluorescence and photothermal responses. The detection mechanism was investigated, and the analytical performance of both modes was evaluated under optimized conditions. Medicinal and edible malt and ginger were used as representative real samples to validate the practical applicability of the sensor. In the presence of Gly, the fluorescence signal of the nanoprobe was effectively quenched through a dynamic mechanism, while a distinct temperature change was simultaneously generated by the photothermal effect. Under optimized conditions, the fluorescent mode exhibited a linear range of 10-250 ng/mL with a limit of detection (LOD) of 2.34 ng/mL, whereas the photothermal mode achieved a broader linear range of 10-2000 ng/mL with a LOD of 3.68 ng/mL. The spiked recovery rates for the fluorescent mode ranged from 97.02% to 113.26%, while the photothermal mode achieved recoveries between 93.94% and 106.06% in medicinal and edible malt and ginger samples. The proposed dual-modal sensor offered high sensitivity, strong anti-interference capability, and operational simplicity, providing a promising strategy for the rapid and accurate detection of trace Gly residues in complex matrices and holding significant value for ensuring food quality and safety.