Fabrication of magnetic surface molecularly imprinted polymers via semi-covalent imprinting strategy for selective recognition of bisphenol A

The magnetic responsiveness could endow material with excellent separation performance. In this work, magnetic surface molecularly imprinted polymers (MIPs) were prepared by a semi-covalent imprinting strategy. Firstly, a covalent template-monomer complex was synthesized through the reaction of bisphenol A (BPA) and 3-isocyanatopropyltriethoxysilane (IPTS). Secondly, Fe
3
O
4
nanoparticles were prepared through the co-precipitation of Fe
2+
and Fe
3+
. Thirdly, the gelation of template-monomer complex (BPA-IPTS) and tetraethoxysilane was performed on the surface of Fe
3
O
4
magnetic cores. After the removal of BPA by the thermal cleavage, Fe
3
O
4
@MIPs with core-shell structure were obtained. BPA-IPTS was characterized by Fourier transform infrared spectroscopy (FTIR) and
1
H NMR. Fe
3
O
4
@MIPs were detected by FTIR, X-ray diffraction (XRD) and transmission electron microscopy (TEM). The spectra of FTIR and
1
H NMR indicate that BPA-IPTS has been synthesized successfully. The TEM images show that Fe
3
O
4
@MIPs possess a typical core-shell structure with the diameter range from 25 to 40 nm. The XRD patterns indicate that the presence of MIPs shell layer does not affect the crystal structure of Fe
3
O
4
nanoparticles. The FTIR spectrum of Fe
3
O
4
@MIPs indicates that BPA-IPTS has been coated on the surface of Fe
3
O
4
nanoparticles. The successful building of imprinted sites on the shell layer was validated by a series of binding experiments, including binding kinetics, binding isotherm and binding selectivity. Due to the presence of Fe
3
O
4
cores, the imprinted sites are distributed in the external shell layer, which decreases the mass transfer resistance significantly. The results show that Fe
3
O
4
@MIPs have fast binding rate with the equilibrium binding time of 60 min, which is consistent with the expected result. Besides, Fe
3
O
4
@MIPs appear considerable binding affinity and high selectivity towards BPA, the binding capacity is apparently higher than that of Fe
3
O
4
@NIPs with the imprinting factor of 1.74. The experiment results indicate that Fe
3
O
4
@MIPs are promising material for the separation of BPA. This study provides an alternative strategy for the building of magnetic surface MIPs.