Design And Sensing Application Research Of Novel Polymer-based Nanocomposites

In recent years, composites consisted of conducting polymers, novel carbon nanomaterials and metal nanoparticles have become a focus accompanied with the development of conducting polymer. Generally, these composites possess excellent physical and chemical properties, good catalytic activity, biocompatibility and conductivity, which are ideal functional materials for electrode modification of electrochemical sensors. In this thesis, we aim to combine the functional nanomaterials with a controllable structure and morphology with the electrochemical analysis technology which has high sensitivity and high selectivity. A series of nanocomposites based on conducting polymers have been prepared to construct various electrochemical sensors. The electrochemical properties and application of these sensors in the aspects of quantitative detection for medicine, pollutants and small biomolecules were also explored.1. A poly(glutamic acid) film modified glass carbon electrode (GCE) was fabricated through a simple and efficient electro-polymerization method. The electrochemical properties of modified electrode were investigated by electrochemical impedance spectroscopy (EIS) and chronocoulometry. The kinetics and reaction mechanism of acetaminophen at the interface of modified electrode were also explored. The studies showed that a strong interaction existed between the carboxyl of molecular segments of poly(glutamic acid) and the target molecules, which could enhance the catalytic activity of modified electrode obviously. Under the optimized conditions, the quantitative detection of acetaminophen was achieved with a detection limit of 0.02 μM based on the current-time (i-t) curve. The proposed sensor was successfully applied to validate its capability for the analysis of acetaminophen in two kinds of commercial medicine in tablet and capsule.2. An novel modified electrode based on the composite consisted of gold nanoparticles and poly(glutamic acid) film was developed by using an electro-deposition method and followed an electro-polymerization method. It was characterized by cyclic voltammetry(CV) and and chronocoulometry. The effects of scanning rate and pH of buffer solution on the electrode reaction was also investigated. It is found that the modified electrode based on the poly(glutamic acid) composite with gold nanoparticles could efficiently distinguish the redox peaks of dihydroxybenzene isomers due to the signal amplification from gold nanoparticles, which realized the simultaneous determination of three isomers. The result showed that the constructed sensor could achieve a high sensitive detection of one isomer in presence of the others, with the detection limit of 0.38 μM for hydroquinone,0.56 μM for catechol and 0.92 μM for resorcinol, respectively. This proposed method has been applied to simultaneous determination of dihydroxybenzene isomers in real river water and tap water samples.3. The large-scale synthesis of ternary nanocomposite hemin-graphene sheets/poly(3,4-ethylenedioxythiophene) (H-GNs/PEDOT) was achieved via a microwave-assisted method. The morphology and structure of the as-prepared nanocomposites were characterized by transmission electron microcopy, Fourier-transform infrared spectroscopy, and ultraviolet-visible absorption spectroscopy. The H-GNs/PEDOT nanocomposite combined the excellent properties of three components, maintaining the peroxidase-like activity of hemin, and displaying a high-speed electron transfer ascribed to the presence of PEDOT and graphene sheets. The H-GNs/PEDOT exhibited remarkable electrocatalysis toward the reduction of hydrogen peroxide (H2O2) due to the direct electron-transfer of hemin. The novel biomimetic H2O2 biosensor based on the well-designed ternary hybrid H-GNs/PEDOT had a low detection limit (0.08 μM).4. Based on the electrostatic interaction of positively charged polyaniline (PANI) and negatively charged graphene oxide (GO), (PANI/GO)n multilayer films were prepared via layer-by-layer assembly method on the activated GCE. The proposed (PANI/RGO)n/hemin/GCE sensor was further obtained by electrochemical reduction of GO and drop casting of hemin on the (PANI/GO)n film. The results demonstrated that the conductivity of the multilayer film increased gradually with the number of its bilayers and it possessed the largest response current at 7 bilayers. The designed sensor exhibited remarkable catalytic activity toward the reduction of H2O2 with a determination limit of 0.04 μM. This method was successfully used to the selective detection of H2O2 in the commercially available contact lens cleaning solution.