Novel amino-containing molecularly-imprinted polymer coating on magnetite-gold core for sensitive and selective carbofuran detection in food

Abstract

We report a novel and facile method for synthesis of amino-containing molecularly-imprinted coatings on magnetite-gold nanoparticle cores (Fe3O4@Au-MIP-NH2) for constructing robust and sensitive carbofuran sensors. Fe3O4@Au-MIP-NH2 nanoparticles were synthesized by successive self-assembly of organic thiols, 11–mercaptoundecanoic acid, on magnetite-gold core surfaces, followed by coupling with an amino-containing molecularly-imprinted polymer (MIP-NH2) shells. The MIP-NH2 nanocomposite was synthesized via two polymerization steps to form carbofuran imprinted pre-polymer nanoparticles and then terminating the surface with amino-containing polymer. The synthesized pre-polymer nanoparticles possess a large surface-to-volume ratio. This approach allows for increased numbers of carbofuran template molecules to attach to the polymer surface to form larger recognition sites. We constructed the highly sensitive and selective carbofuran amperometric sensor by coating the surface of a glassy carbon electrode with Fe3O4@Au-MIP-NH2 coupled with a simple flow-injection system. Morphological and structural characterization reveals that the coupling of the MIP-NH2 on the Fe3O4@Au core surface significantly increases the recognition surface area and electron transfer efficiency to provide improved selectivity and sensitivity. The MIP-NH2 modified electrode shows substantially enhanced carbofuran current response, which is by a factor of about twenty times that of the non-imprinted polymer electrode. The modified electrode provides fast response with good selectivity when applied to carbofuran detection by amperometry. The carbofuran oxidation-current signal appears at + 0.50 V vs Ag/AgCl, using 0.1 M phosphate buffer (pH 7.0) as the carrier solution. The designed Fe3O4@Au-MIP-NH2 sensor provides a linear response over the range 0.01–100 µM (r2 = 0.9967) with a low detection limit of 1.7 nM. The intraday and inter-day precision (%RSD) of 5 µM CBF are 1.4% and 1.8%, respectively. We demonstrate the successful application of the sensor to the detection of CBF in fruit and vegetable samples.