Multifunctional Fe-doped carbon dots and metal-organic frameworks nanoreactor for cascade degradation and detection of organophosphorus pesticides

Organophosphorus pesticides (OPs) are the most widely used pesticides, hence it is crucial to effectively prevent and control OPs residues for agricultural product safety and ecological development. In this work, the nanoreactor consisting of Fe-doped carbon dots (Fe-CDs) and metal-organic framework (MOF-808) were developed for selective degradation as well as sensitive detection of paraoxon and parathion. MOF-808 was selected as the host and used to rapidly degrade paraoxon due to its excellent organophosphorus hydrolase activity. Fe-CDs were severed as guest molecules not only for photocatalytic degradation of parathion, but also for sensing to detect OPs. Through host–guest interaction, Fe-CDs/MOF-808 and Fe-CDs@MOF-808 were synthesized for cascade degradation and detection of paraoxon and parathion, respectively. Paraoxon and parathion were detoxified by catalytic hydrolysis and photocatalytic degradation by Fe-CDs/MOF-808 and Fe-CDs@MOF-808, respectively. Meanwhile, the fluorescence of the nanocomposites was quenched by the internal filtering effect with 4-nitrophenol (4-NP), the degradation product of OPs. Fe-CDs/MOF-808 has a wide linear range for detection of paraoxon from 0.001 to 360 μM, with a limit of detection (LOD) as low as 0.3 nM. Fe-CDs@MOF-808 exhibited a linear range of 0.01–100 μM for parathion, with an LOD about 3.3 nM. The reliability of the nanoreactor was verified by testing the recovery rate of OPs spiked water sample. Meanwhile, the nanoreactors were applied for degradation and detection of OPs in pakchoi. The OPs in pakchoi can be fully degraded within 5 min, and the analytical results are consistent with those by standard method (HPLC). Therefore, the proposed nanoreactor provides a feasible alternative for effective degradation and timely detection of OPs during agricultural production.