Application And Detection Of Small Molecules On Nanomaterial Modified Carbon Ionic Liquid Electrode

Owing to the small size effect, quantum size effects, surface effects resulted from its unique structure, nano-materials have shown distinctive function in many field such as optical, electronic, adsorption, catalysis and so on. By using of the nano-materials modified electrode, the electrode surface increases rapidly, which would provide more active sites for the further modification. In addition, when the nano-materials were used to modify electrode, both of their own physical and chemical properties had also been introduced to the electrode surface, and the electrochemical active of the electrode would be greatly strengthened. In the paper, the CILE was prepared by using ionic liquid N-hexylpyridinium hexafluorophosphate (HPPFe) as the binder, we have studied the effect of the nano-materials modified electrode (CILE) to the electrical activity of small molecules and sample.The thesis can be summarized as follows:1. Direct electrochemistry and electrocatalytic activity of rutin were study with an electrode (CILE) modified with a composite made from oxidation graphene (GO) and multi-walled carbon nanotubes (MWCNTs).The modified electrode was denoted as GO-MWCNTs/CILE. The resulted electrode showed excellent electrochemical performances due to the formation of high conductive oxidation graphene (GO) and multi-walled carbon nanotubes (MWCNTs) film on the CILE surface. Electrochemical behaviors of rutin on the GO-MWCNTs/CILE were carefully investigated with a pair of well-defined redox peaks appeared in pH=2.0phosphate buffer solution (PBS) by cyclic voltammetry. Under the optimal conditions, the redox peak current was linear. The reduction peak currents showed good linear relationship with the rutin concentration in the range from0.080to80μmol L-1with the detection limit as2.0×10-8mol L-1(3a). The GO-MWCNTs/CILE showed the advantages such as excellent selectivity, improved performance, good stability and it was further applied to the rutin tablets sample detection with satisfactory results.2. A voltammetric sensor was fabricated by applying a chitosan (CTS) and LiFePO4nanoparticles composite film on the surface of a carbon ionic liquid electrodes(CILE). The electrochemical behaviors of rutin on the CTS/LiFePO4/CILE were investigated in pH2.5phosphate buffer solution (PBS). Rutin showed an reversible diffusion-controlled redox reaction with enhanced electrochemical response on the modified electrode, which was due to the presence of high conductive LiFePO4on the CILE surface. The electrochemical parameters of rutin eletro-redox reaction were calculated and the experimental conditions such as potential, solution pH were optimized. Under the optimal conditions, the redox peak currents was linear to rutin concentration over the range from4.0×10-8～1.0×10-4mol/L with the detection limit estimated to be8.0×10-9mol/L (3a). The modified electrode showed good stability and selectivity without the interferences from various foreign substances. It was further applied to the rutin tablets sample detection with satisfactory results.3. A chitosan (CTS) and unchinlike MnO2nanoparticles composite was further cast on the CILE surface to get a modified electrode denoted as CTS/MnO2/CILE. The fabricated electrode showed strong electrocatalytic ability to the bisphenol A (BPA) with a well-defined anodic peak appeared in pH8.0Britton-Robinson buffer solution, which was attributed to the electrooxidation of BPA on the modified electrode. The electrochemical parameters of BPA on the modified electrode were calculated with the results of the charge transfer coefficient (a) as0.657and the apparent heterogeneous electron transfer rate constant (ks) as5.03×10-1s-1. Under the optimal conditions, a linear relationship between the oxidation peak current of BPA and its concentration can be obtained in the range from0.4μmol/L to800.0μmol/L with the limit of detection as3.16×10-8mol/L (3σ). The CTS/MnO2/CILE was applied to the detection of BPA content in plastic products with satisfactory results.4. Graphene(GR) and cobalt(Co) nanoparticles modified carbon ionic liquid electrode (CILE). Scanning electron microscopy and electrochemical techniques were used for the characterization of the composite material which is very uniform and forms a kind of nanoporous structure. Electrochemical experiments showed that the modified electrode exhibited excellent electrocatalytic properties for nitrite. The electrochemical parameters of nitrite on the modified electrode were calculated with the results of the charge transfer coefficient (a) as0.50and the apparent heterogeneous electron transfer rate constant (ks) as1.87s’1. cyclic voltammetry revealed a good linear relationship between peak current and nitrate concentration in the0.4to80μM range with a detection limit of0.2μM (S/N=3). The method has been applied to the detection of nitrite in real samples. The modified electrode displays good stability, reproducibility, and selectivity for a promising practical application.