Rapid Detection of Methyl Parathion Based on SiONPs-Eu³⁺ Dual-Emitting Fluoroprobe and Its On-Site Application

Herein, we pioneered an innovative methodology for the rapid identification and quantitation of methyl parathion (MP) residues, overcoming the drawbacks of existing methods such as poor selectivity, high costs, and intricate operational procedures. A dual-emitting fluoroprobe SiONPs-Eu³⁺ was engineered based on silica oxide nanoparticles (SiONPs) conjugated with Eu³⁺, and the synthetic conditions were meticulously optimized to ensure exceptional sensitivity and selectivity to 4-nitrophenol (4-NP), one of the MP hydrolytic products. Upon excitation at 317 nm, the blue fluorescence of SiONPs at 400 nm was quenched, while the red fluorescence of Eu³⁺ at 616 nm remained nearly unchanged, constituting a ratiometric fluorescent change that significantly enhanced the detection stability. The fluoroprobe rapidly detected 4-NP at concentrations below 80 μM within 10 s and gave a limit of detection (LOD) as low as 0.16 μM, markedly lower than the allowable residue limit of MP in China food safety standards. Also, it exhibited excellent anti-interference properties in complex matrices, remaining unaffected by common amino acids, cations, and pesticides. The underlying mechanism of the fluoroprobe was elucidated through time-dependent density functional theory (TD-DFT) calculations. Under optimized hydrolysis conditions, the detection of MP in real rice samples was successfully achieved. Furthermore, the self-developed and dual-channel portable device was conducive to on-site fluorescence detection of 4-NP, offering enhanced stability in contrast to traditional photography-based methods.