Blue fluorescent molecularly imprinted chitosan gel beads for rapid on-site determination of diazinon in environmental water

Biomass-derived blue CDs were immobilized in DZN-imprinted chitosan gel beads. • An IFE-governed fluorescence decrease enabled dual-mode readout by fluorometry and standardized smartphone imaging. • Rapid on-site determination was achieved within ∼10 min over 40–2000 μg/L. • Low detection limits were obtained (8.8 nM by fluorometry; 18.7 nM by smartphone readout). • The method showed good selectivity, matrix robustness, and agreement with an LC-MS reference method in real waters. A portable and environmentally benign sensing method was developed for on-site determination of diazinon (DZN) in environmental waters based on blue fluorescent carbon-dot-embedded molecularly imprinted chitosan gel beads (B-CDs@MIPGB). Biomass-derived blue carbon dots (B-CDs) were synthesized from yellow rose extract and immobilized within a DZN-imprinted chitosan network via a one-pot imprinting–crosslinking strategy followed by coagulation-bath bead formation. DZN binding in the imprinted cavities induced a concentration-dependent fluorescence decrease mainly governed by an inner filter effect (IFE), enabling dual-mode quantification by both fluorometry and standardized smartphone imaging. The method provided a linear response from 40 to 2000 μg/L with detection limits of 8.8 ± 0.09 nM (fluorometry) and 18.7 ± 0.12 nM (smartphone readout). A low-cost imaging box with fixed acquisition settings was employed to minimize variability in smartphone analysis, yielding repeatable G/B ratios with RSD below 3.59%. The beads exhibited high selectivity over common coexisting pesticides and metal ions, and maintained reliable performance under representative matrix interferences including humic acid, turbidity, and mixed major ions. Benchmarked against a reference LC-MS method using identical spiked samples, the developed approach achieved recovery rates of 97.2%–104.4% (fluorescence) and 98.4%–104.8% (smartphone), confirming its accuracy. This bead-based platform integrates selective recognition, rapid operation (∼10 min), and field-deployable readout, offering a practical tool for routine environmental surveillance of organophosphorus pesticide residues. One-pot imprinting embeds yellow-rose-derived B-CDs into chitosan gel beads using DZN as a template. After cross-linking and template removal, DZN-selective cavities enable rebinding/enrichment, producing IFE-dominated fluorescence quenching. Dual readout (fluorometer/smartphone) supports on-site analysis, validated in real waters by LC-MS. Download: Download high-res image (259KB) Download: Download full-size image