Design of a surface-immobilized 4-nitrophenol molecularly imprinted polymer via pre-grafting amino functional materials on magnetic nanoparticles

• A new surface imprinting method by template immobilizing strategy.
• Michael addition of EGDMA and amino functional groups on the magnetic surface.
• High adsorption capacity, proper selectivity and fast kinetic binding were achieved.
• Magnetic sorbent was utilized for selective determination of 4-nitrophenol.

In order to resolve the low adsorption capacity of the surface molecularly imprinting methods, an approach was developed for the preparation of magnetic imprinted polymers by pre-grafting the amino functional material, 3-aminopropyltriethoxysilane (APTES), on the surface of the silica coated magnetic substrate. APTES was used for amino functionalization of the silica coated Fe3O4 nanoparticles. Amino groups were used for immobilization of the template molecules on the magnetic surface and additionally to react with the terminal vinyl groups of cross-linker, ethylene glycol dimethacrylate (EGDMA), by the Michael addition reaction. In this way, the imprinting sites of the analytes formed on the substrate were increased. The sorbent was synthesized in the presence of 4-nitrophenol (4-NP) and EGDMA as the template and cross-linker, respectively. Different parameters affecting the adsorption, such as pH, desorption solvent type and adsorption time were evaluated and optimized. The prepared magnetic molecularly imprinted polymer (MMIP) showed high adsorption capacity and proper selectivity for the template molecule. The kinetic adsorption curve indicated that 90 min was sufficient to achieve the adsorption equilibrium for MMIP. The maximum adsorption capacity was 129.1 mg g−1. The experiments exhibited a linear range of 10–3000 μg L−1 for 4-NP with the correlation coefficient (R2) of 0.997. The results of the real sample analysis confirmed the applicability of the proposed MMIP for quantitative analysis of 4-NP in the aqueous samples.