Selective detection of terminal alkyne acaricide <i>via</i> click-reactive carbon dots: applications in food safety monitoring

Propargite is a widely used organosulfur acaricide employed for controlling mites in citrus fruits and tea cultivation, necessitating a sensitive analytical method for residue monitoring. This study presents a novel fluorescence detection strategy leveraging azide-functionalized carbon dots (Az-CDs) as highly selective and responsive probes for propargite determination in food matrices. The novelty lies in the specific chemical interaction between the azido groups on the CD surface and the terminal alkyne moiety present in propargite's molecular structure. This molecular interaction induces a measurable fluorescence quenching effect through dual mechanisms involving aggregation-caused quenching and photoinduced electron transfer. The method demonstrates exceptional analytical performance with high sensitivity (LOD = 0.35 ng mL^-1) and a wide linearity range (1.0-100.0 ng mL^-1), with excellent correlation (<i>R</i>² = 0.9965). The mechanism of detection and comprehensive characterization of the prepared Az-CDs were thoroughly investigated using TEM, FTIR, XPS, UV-visible, and fluorescence spectroscopy. Selectivity studies demonstrated negligible interference from common agricultural compounds, natural fruit constituents, and structurally related pesticides due to the bioorthogonal nature of the click chemistry reaction. The method was successfully applied to citrus fruit and tea leaf samples, achieving excellent recovery values (95.20-97.60%) with low relative standard deviations (<3.66%), demonstrating its capability for monitoring pesticide residues in agricultural commodities. By offering high sensitivity, chemical specificity, and minimal sample preparation, this strategy introduces a practical alternative for pesticide monitoring in food safety analysis applications.