A new composite of graphene and molecularly imprinted polymer based on ionic liquids as functional monomer and cross-linker for electrochemical sensing 6-benzylaminopurine.

Molecularly imprinted polymers prepared using traditional functional monomers and cross-linkers exhibit slow binding kinetics, low electrocatalytic activity and adsorption capacity. Herein, we report a new composite of ionic liquid-based graphene and molecularly imprinted polymer (IL-GR-MIP) with high electrocatalytic activity and adsorption capacity to construct an effective electrochemical sensor for 6-benzylaminopurine (6-BAP). Our objective was to enhance the efficiency of the sensor by incorporating more IL in the MIP framework. We synthesized IL-GR-MIP using ionic liquid 1-vinyl-3-butylimidazolium tetrafluoroborate (IL1) as functional monomer, ionic liquid 1,4-butanediyl-3,3'-bis-l-vinylimidazolium dibromide (IL2) as cross-linker, 6-BAP as template, and GR as supporter. IL-GR-MIP was characterized by Fourier transform infrared spectroscopy, thermal gravimetric analysis, Raman spectroscopy, X-ray photoelectron spectroscopy, and scanning electron microscope. Compared with GR-MIP composites based on methacrylic acid or IL1 as functional monomer, N, N'-methylenebisacrylamide and ethylene glycol dimethacrylate as cross-linker, the IL-GR-MIP (prepared with ionic liquids as functional monomer and cross-linker) sensor exhibited highest peak current for 6-BAP. The results indicate the ability of IL2 as cross-linker to enhance electrocatalytic activity and adsorption capacity for 6-BAP of IL-GR-MIP. Under the optimized conditions, the peak current of IL-GR-MIP sensor was linear to 6-BAP concentration in the range of 0.5-50 µM with a detection limit of 0.2 µM (S/N = 3). The IL-GR-MIP sensor exhibited good selectivity with the anti-interference ability of 1000-fold ascorbic acid in 6-BAP determination. Furthermore, we demonstrated practical applicability of IL-GR-MIP sensor in detecting 6-BAP in real samples with satisfactory results.

Highly sensitive and selective sensor for sunset yellow based on molecularly imprinted polydopamine-coated multi-walled carbon nanotubes.

Polydopamine (PDA) can be formed by monomeric self-polymerization in water. This convenient behavior was exploited to prepare a molecularly imprinted polymer (MIP) layer on the surface of multi-walled carbon nanotubes (MWCNTs) with sunset yellow (SY) as a template molecule. The prepared nanocomposites were characterized, and their electrochemical behavior towards SY was investigated. Under the optimized conditions, a glassy carbon electrode modified with the imprinted nanocomposite showed a highly selective and ultrasensitive electrochemical response to SY compared with the performance of control electrodes and previously reported electrochemical sensors for SY. The improved behavior of the developed sensor can be attributed to its superficial highly matched imprinted cavities on the excellent electrocatalytic matrix of MWCNTs and the electronic barrier of the non-imprinted PDA to outside molecules. The fabricated sensor expressed a linear relationship to SY concentrations from 2.2nM to 4.64µM with a detection limit of 1.4nM (S/N = 3). The sensor also exhibited excellent selectivity for SY over its structural analogs, good stability, and adequate reproducibility. The prepared sensor was successfully used to detect SY in real spiked samples. This methodology has potential application value and may be readily adapted to design other PDA-based MIP sensors.

Electrochemical Molecular Imprinted Sensors Based on Electrospun Nanofiber and Determination of Ascorbic Acid.

In this study, electrochemical molecularly imprinted sensors were fabricated and used for the determination of ascorbic acid (AA). Nanofiber membranes of cellulose acetate (CA)/multi-walled carbon nanotubes (MWCNTs)/polyvinylpyrrolidone (PVP) (CA/MWCNTs/PVP) were prepared by electrospinning technique. After being transferred to a glass carbon electrode (GC), the nanofiber interface was further polymerized with pyrrole through electrochemical cyclic voltammetry (CV) technique. Meanwhile, target molecules (such as AA) were embedded into the polypyrrole through the hydrogen bond. The effects of monomer concentration (pyrrole), the number of scan cycles and scan rates of polymerization were optimized. Differential pulse voltammetry (DPV) tests indicated that the oxidation current of AA (the selected target) were higher than that of the structural analogues, which illustrated the selective recognition of AA by molecularly imprinted sensors. Simultaneously, the molecularly imprinted sensors had larger oxidation current of AA than non-imprinted sensors in the processes of rebinding. The electrochemical measurements showed that the molecularly imprinted sensors demonstrated good identification behavior for the detection of AA with a linear range of 10.0 - 1000 µM, a low detection limit down to 3 µM (S/N = 3), and a recovery rate range from 94.0 to 108.8%. Therefore, the electrochemical molecularly imprinted sensors can be used for the recognition and detection of AA without any time-consuming elution. The method presented here demonstrates the great potential for electrospun nanofibers and MWCNTs to construct electrochemical sensors.

Synthesis, properties and application research of atrazine Fe3O4@SiO2 magnetic molecularly imprinted polymer.

INTRODUCTION: Magnetic Fe3O4 nanoparticles were prepared by coprecipitation and then were coated with SiO2 on the surface. MATERIALS AND METHODS: Fe3O4@SiO2 composite microspheres were modified by KH570. Using molecular imprinting technology, atrazine magnetic molecularly imprinted polymer was prepared by using atrazine as template molecule, methacrylic acid as functional monomer and ethylene glycol dimethacrylate as cross-linkers. The morphology, composition and magnetic properties of magnetic nanoparticles were characterized. The recognition selectivity of polymer was studied for template molecule and simulation by UV spectrophotometry. The adsorption properties and selectivity ability were analyzed by Scatchard analysis. RESULTS: Scatchard linear regression analysis indicated that there are two binding sites of the target molecules. The magnetic molecularly imprinted polymer has been applied to the analysis of atrazine in real samples. CONCLUSION: The results show that: the recovery rates and the relative standard deviation were 94.0∼98.7% and 2.1∼4.0% in corn, the recovery rates and the relative standard deviation were 88.7∼93.5% and 2.8∼7.2% in water.