Optical Detection of λ‑Cyhalothrin by Core–Shell Fluorescent Molecularly Imprinted Polymers in Chinese Spirits

Abstract

In this study, fluorescent molecularly imprinted polymers (FMIPs), which were for the selective recognition and fluorescence detection of λ-cyhalothrin (LC), were synthesized via fluorescein 5(6)-isothiocyanate (FITC) and 3-aminopropyltriethoxysilane (APTS)/SiO₂ particles. The SiO₂@FITC-APTS@MIPs were characterized by Fourier transform infrared (FT-IR), UV–vis spectrophotometer (UV–vis), fluorescence spectrophotometer, thermogravimetric analysis (TGA), confocal laser scanning microscope (CLSM), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The as-synthesized SiO₂@FITC-APTS@MIPs with an imprinted polymer film (thickness was about 100 nm) was demonstrated to be spherically shaped and had good monodispersity, high fluorescence intensity, and good selective recognition. Using fluorescence quenching as the detection tool, the largest fluorescence quenching efficiency (<i>F</i>₀/<i>F</i> – 1) of SiO₂@FITC-APTS@MIPs is close to 2.5 when the concentration of the LC is 1.0 μM L^–1. In addition, a linear relationship (<i>F</i>₀/<i>F</i> – 1= 0.0162<i>C</i> + 0.0272) could be obtained covering a wide concentration range of 0–60 nM L^–1 with a correlation coefficient of 0.9968 described by the Stern–Volmer equation. Moreover, the limit of detection (LOD) of the SiO₂@FITC-APTS@MIPs was 9.17 nM L^–1. The experiment results of practical detection revealed that the SiO₂@FITC-APTS@MIPs as an attractive recognition element was satisfactory for the determination of LC in Chinese spirits. Therefore, this study demonstrated the potential of SiO₂@FITC-APTS@MIPs for the recognition and detection of LC in food