Molecularly imprinted polymers coated on multi-walled carbon nanotubes through a simple indirect method for the determination of 2,4-dichlorophenoxyacetic acid in environmental water

A new and facile method was presented to graft molecularly imprinted polymers (MIPs) on carbon nanotubes (CNTs) for 2,4-dichlorophenoxyacetic acid (2,4-D) analysis. In brief, CNTs were firstly coated with a layer of vinyl group modified silica, followed by a common precipitation polymerization with 2,4-D as the template, ethylene glycol dimethacrylate (EGDMA) as the crosslinker and 2,2-azobisisobutyronitrile (AIBN) as the initiator. The imprinted effects obtained by using different monomers were investigated, and the results showed that acrylamide (AM) and styrene as mixed monomers was the best choice. This functionalized material was characterized by Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM) and thermogravimetry (TG), which demonstrated a successful polymerization reaction on CNTs with MIPs grafting ratio of about 80%. The results of static adsorption experiments indicated the imprinted material possessed fast kinetics and good selectivity for 2,4-D molecules. A corresponding analytical method was developed and demonstrated to be applicable for the determination of 2,4-D in environmental water. The recoveries were in the range from 74.6% to 81.2% with relative standard deviation below 7.0%. To be emphasized, the method for MIPs coating proposed herein also provides a significant reference for other radical polymerization reactions based on CNTs.