Longcheng Xu

Preparation of molecularly imprinted nanoparticles with superparamagnetic susceptibility through atom transfer radical emulsion polymerization for the selective recognition of tetracycline from aqueous medium.

In the work, we reported an effective method for the preparation of molecularly imprinted nanoparticles with superparamagnetic susceptibility through atom transfer radical emulsion polymerization (ATREP), and then as-prepared magnetic molecularly imprinted nanoparticles (MMINs) were evaluated as adsorbents for selective recognition of tetracycline (TC) molecules from aqueous medium. The resulting nanoparticles were characterized by FT-IR, TGA, VSM, SEM and TEM. The results demonstrated MMINs with a narrow diameter distribution were cross-linked with modified Fe3O4 particles, composed of imprinted layer and exhibited good magnetic sensitivity, magnetic and thermal stability. Batch rebinding studies were carried out to determine the specific adsorption equilibrium, kinetics, and selective recognition. The estimated adsorption capacity of MMINs towards TC by the Langmuir isotherm model was 12.10 mgg(-1) at 298 K, which was 6.33 times higher than that of magnetic non-molecularly imprinted nanoparticles (MNINs). The kinetic property of MMINs was well-described by the pseudo-second-order rate equation. The results of selective recognition experiments demonstrated outstanding affinity and selectivity towards TC over competitive antibiotics. The reusability of MMINs showed no obviously deterioration at least five repeated cycles in performance. In addition, the MMINs prepared were successfully applied to the extraction of TC from the spiked pork sample.

Magnetic ZnO surface-imprinted polymers prepared by ARGET ATRP and the application for antibiotics selective recognition

This paper reports a molecularly imprinted polymers (MIPs) based fluorescence sensor which is synthesized by grafting MIP layers on the surface of ZnO nanorods embedded γ-Fe2O3 nanoparticles via activators regenerated by electron transfer atom transfer radical polymerization (ARGET ATRP). Methacrylic acid (MAA, functional monomer), 3-(trimethoxysilyl)propyl mathacrylate (MPS) modified γ-Fe2O3 (γ-Fe2O3/MPS, assistant magnetic monomer) and ethylene glycol dimethacrylate (EGDMA, cross-linking monomer) were co-polymerized in anisole at 313 K in the presence of sulfamethazine as a template molecule. Sulfamethazine was then solvent-extracted to obtain ZnO-grafted molecularly imprinted polymers (ZnO-MIPs). ZnO-MIPs were characterized by FE-SEM, TEM, FT-IR, TGA/DSC, VSM, fluorescence spectroscopy and Raman spectroscopy. It was observed that sulfamethazine can quench the luminescence of ZnO-MIPs in a concentration-dependent manner that can be described by a Stern–Volmer-type equation. ZnO-MIPs were used to determine sulfamethazine in a spiked pork sample with good recognition ability. This study therefore demonstrates the potential application in the recognition and separation of antibiotics based on molecularly imprinted polymers.

Removal of cefalexin using yeast surface-imprinted polymer prepared by atom transfer radical polymerization.

The first use of yeast as a support in the molecular imprinting field combined with atom transfer radical polymerization was described. Then, the as-prepared molecularly imprinted polymers were characterized by Fourier transmission infrared spectrometry, scanning electron microscope, thermogravimetric analysis, and elemental analysis. The obtained imprinted polymers demonstrated elliptical-shaped particles with the thickness of imprinting layer of 0.63 μm. The batch mode experiments were adopted to investigate the adsorption equilibrium, kinetics, and selectivity. The kinetic properties of imprinted polymers were well described by the pseudo-second-order kinetic equation, indicating the chemical process was the rate-limiting step for the adsorption of cefalexin (CFX). The equilibrium data were well fitted by the Freundlich isotherm, and the multimolecular layers adsorption capacity of imprinted polymers was 34.07 mg g(-1) at 298 K. The selectivity analysis suggested that the imprinted polymers exhibited excellent selective recognition for CFX in the presence of other compounds with related structure. Finally, the analytical method based on the imprinted polymers extraction coupled with high-performance liquid chromatograph was successfully used for CFX analysis in spiked pork and water samples.

Selective recognition of 4-nitrophenol from aqueous solution by molecularly imprinted polymers with functionalized tetratitanate whisker composites as support.

Three kinds of molecularly imprinted polymers (MIPs) were obtained with surface molecular imprinting technique on functionalized potassium tetratitanate whisker (F-PTW). The results of adsorption experiments indicated that MIP prepared using PTW modified with N-(2-aminoethyl)-3-(trimethoxysilyl)propylamine (AAPTS) (F-PTW A) as support [MIP(1)] was superior to the other two polymers, then MIP(1) was selected to analyze the 4-nitrophenol (4-NP) adsorption process from aqueous solution in this study. AAPTS offered hydrophilic exterior that allowed to self-assemble with the template 4-NP through intermolecular interaction rather than based on the interactions between the functional monomers and template. Equilibrium adsorption data were analyzed by the Langmuir and Freundlich isotherm models at various temperatures. Kinetic properties were successfully investigated by pseudo-first-order model, pseudo-second-order model, intraparticle diffusion equation, initial adsorption rate, half-adsorption time. A diffusion-controlled process as the essential adsorption rate-controlling step was also proposed. The performance of such imprinted polymer was further demonstrated by high-performance liquid chromatography, and the results showed that the selectivity of MIP(1) exhibited higher affinity for template 4-NP over competitive phenolic compounds than that of non-imprinted polymer NIP(1). MIP(1) could be reused four times without significant loss in the adsorption capacity.