Maliwan Amatatongchai a,b,⁎ , Suphatsorn Thimoonneea, Purim Jarujamrusa, Duangjai Nacapricha b,c , Peter A. Lieberzeitd a Department of Chemistry and Center of Excellence for Innovation in Chemistry, Faculty of Science, Ubon Ratchathani University, Ubon Ratchathani 34190, Thailand b Flow Innovation-Research for Science and Technology Laboratories (FIRST Labs), Thailand c Department of Chemistry and Center of Excellence for Innovation in Chemistry, Faculty of Science, Mahidol University, Bangkok 10400, Thailand d University of Vienna, Faculty for Chemistry, Department of Physical Chemistry, 1090 Vienna, Austria

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.