Ion Luminescent Micelles: A Surfactant-Mediated Double-End Signal Amplification Strategy for Portable Detection of Phoxim

Residues of organophosphorus pesticides (OPs) raise considerable concern, while achieving high enough detection sensitivity is still a challenge for on-site fluorescence techniques. Herein, we report a “double-end samplification” strategy by encapsulating a low-emission fluorescent ion probe [DCF][P66614]2 into a cetyltrimethylammonium bromide (CTAB) hydrophobic core to form ionic luminescent micelles. At the probe end, ionic liquid micelles locally concentrated the probes, achieving a 350-fold fluorescence enhancement. Benefiting from the strong fluorescence characteristics of DCFP@CTAB, the electron transfer effect between phoxim and DCFP@CTAB, and the fluorescence “turn-off” caused by phoxim, fluorometric and colorimetric methods for simple and sensitive determination of phoxim were proposed. At the analyte end, electrostatic interactions and hydrophobic micellar cavities enhanced phoxim adsorption, improving the fluorescence quenching efficiency by 149%. Under optimized experimental conditions, this sensing platform with a “turn-off” pattern achieves visual limits of detection of 1.7 × 10–7 M and 3.0 × 10–8 M for colorimetric and fluorescence patterns, respectively. Besides, to meet the demand for convenient detection of phoxim, a self-correcting portable paper-based device was constructed, which enabled on-site quantitative analysis of phoxim with a LOD of 0.3 μM. This work represents the first attempt to assemble an ionic liquid with a surfactant, effectively improving the sensitive detection of trace pesticide residues and providing a method for on-the-spot monitoring of food safety.