Self-Assembled Thifensulfuron-Methyl Surface Molecular Imprinting Material on Silica Nanoparticles for Electrochemiluminescence Immunosensor

Using thifensulfuron-methyl (TFM) as the template and α-methacrylic acid (MMA) as the functional monomer, a novel surface molecular imprinting material electrochemiluminescence (ECL) immunosensor was prepared by self-assembled TFM molecular imprinting film on the surface of silicon oxide (SiO₂) nanoparticles. The experimental conditions for self-assembly were optimized by combining scanning electron microscopy and ultraviolet spectroscopy analysis. 100 mg of the prepared SiO₂ nanoparticles was taken and dispersed in 50 mL of anhydrous toluene by ultrasonic. And then 0.8 mL of (3-aminopropyl) triethoxysilane (APTS) was added fast and refluxed at 130 ℃ for 24 h under nitrogen protection to obtain surface modified nano silica oxide product (APTS-SiO₂), followed by washing three times with anhydrous ethanol and acetonitrile, and drying for 24 h. 20 mg of APTS-SiO₂ was taken, and dispersed in 50 mL of acetonitrile by ultrasonic. 0.1 mmol of TFM, 0.4 mmol of MAA, 1.6 mmol of ethylene glycol methacrylate (EGDMA), and 15 mg of initiator 2,2-azodiisobutyronitrile (AIBN) were added for polymerization reaction. The origin TFM molecules in the polymer (the template molecules) were eluted by 50 mmol · L⁻¹ NaOH-CH₃OH solution. After washing and centrifugation, a neutral molecular imprinting material TFM@Si-MIP was obtained. The TFM@Si-MIP disperse solution was immobilized at a surface polished glassy carbon electrode (GCE), and a sensor modified with TFM molecular imprinting material TFM@Si-MIP-ECL was got after drying with an infrared lamp. The TFM@Si-MIP-ECL combined with Luminol system achieved highly sensitive detection of TFM. As shown by the results, this molecular imprinting electrochemiluminescence immunosensor had strong selectivity for target molecules, effectively avoiding interference from other components. Linear relationship between logarithm of TFM concentration and logarithm of electrochemiluminescence signal intensity was found in the range of 1.0×10⁻¹⁰−1.0×10⁻⁷ mol · L⁻¹, with detection limit (3S/N) of 8.6×10⁻¹¹ mol · L⁻¹. Test for recovery was made on the environmental water sample by the standard addition method, giving results of in the range of 94.1%−109%, with RSDs of the determined values (n=7) less than 5.0%.