Yin Wei

Design of L -Cysteine Functionalized Au@SiO 2 @Fe 3 O 4 /Nitrogen-doped Graphene Nanocomposite and Its Application in Electrochemical Detection of Pb 2+

A novel magnetic electrochemical sensor was designed for determination of lead ions based on gold nanoparticles(AuNPs)@SiO2@Fe3O4/nitrogen-doped graphene(NG) composites functionalized with L-cysteine. The Au@SiO2@Fe3O4/NG was synthesized by the electrostatic adsorption between AuNPs and SiO2-coated Fe3O4 NPs(SiO2@Fe3O4) and the amide bond between Au@SiO2@Fe3O4 and NG. L-Cysteine was successfully functionalized on the surface of Au@SiO2@Fe3O4/NG nanocomposites via the S―Au bond between L-cysteine and AuNPs. Owing to numerous active sites in L-cysteines and high conductivity of Au@SiO2@Fe3O4/NG composites, the proposed electrochemical sensor exhibited a well-distributed nanostructure and high responsivity toward Pb(II). The sensor linearly responded to Pb2+ concentration in the range of 5―80 μg/L with a detection limit of 0.6 μg/L, indicating that this L-cysteine functionalized Au@SiO2@Fe3O4/NG composite could be a promising candidate material for the detection of Pb2+.

A Dual Read-out Molecularly Imprinted Composite Membrane Sensor Based on Zinc Porphyrin for the Detection of Dimethyl Methylphosphonate

Molecularly imprinted membrane-zinc porphyrin-mathacrylate(MIM-Zn-MAA), a dual read-out sensor based on a molecularly imprinted membrane, was developed to recognize and detect dimethyl methylphosphonate (DMMP) as an intermediate molecule of organophosphorus pesticides. The membranes were prepared via thermal polymerization of two functional monomers(zinc porphyrin and mathacrylate) on the surface of a glass slide functionalized with ethylene glycol dimethacrylate and azobisisobutyronitrile. The morphology of the as-synthesized MIM-Zn-MAA was determined with scanning electronic microscopy. The composite membranes exhibited macrovoid morphologies, which were affected by the functional monomers. These membranes were selectively adsorbed onto the template molecule and displayed higher adsorbing capacity toward DMMP compared with their structural analogs. Changes in the fluorescent spectra were qualitatively and quantitatively monitored via fluorescence photometry. Difference maps were also obtained using colorimetry before and after the reaction between MIM-Zn-MAA and DMMP at various concentrations. The maps showed a wide linear range varying from 0.1 µmol/L to 10 mmol/L with a low detection limit of 0.1 µmol/L. These preliminary results demonstrate that the as-fabricated dual read-out sensor displays good sensitivity and selectivity toward DMMP, indicaing its considerable potential in DMMP detection in real applications.