| Glucose monitoring has been of great interests for clinical analysis, food industry, biotechnology, and so forth. Glucose oxidase-based biosensors have been developed greatly for this mission due to their high selectivity. However although glucose oxidase is quite stable compared with other enzymes, the biocomponent-based biosensors still suffer from the influences of various environmental factors such as temperature, oxygen, pH, humidity, detergents, organic reagents and toxic chemicals due to the inherent instability of enzyme molecules, which accordingly affects their stability, sensitivity and reproducibility. The immobilization of enzyme on the surface of transducers also further complicates the fabrication procedures and thus affect their final performance. Thermal and chemical instability of glucose oxidase prevents the fabricated enzymatic biosensors from being used for continuous monitoring in fermentation processes or in human bodies requiring sterilization. Non-enzymatic amperometric sensor for direct determination of glucose is an attractive alternative technique to solve the disadvantages of enzymatic biosensors. They have received continuously increasing interest in the recent years. Especially, many efforts have been tried for the development of non-enzymatic glucose sensors using various nanostructures of metal (Pt, Au, Cu, Ni), metal alloys (Pt-Pb, Pt-Ru, Pt-Au, Ni-Pd), metal oxides (CuxO, RuO2, NiO, CoO, MnO2, Co3O4), carbon nanotubes and graphene as novel electrocatalytical materials. Although these non-enzymatic sensors for glucose determination are somewhat nonselective toward other carbohydrates, such as fructose and sucrose, and need to be operated in an alkaline media, they display a lot of advantages of faster response, higher sensitivity, lower detection limit, better stability and lower cost than glucose oxidase-based biosensors.This thesis comprises four parts, as follows:1. The development of electrochemistry glucose sensors was summarized:from glucose oxidase-based biosensors to non-enzymatic glucose sensors. The nanostructure materials was applied in the field of sensors was described in detail, providing the theory support for electrodes modified with nanostructure materials such as transition metal oxides (NiO) and transition metal (Au) nanocomposite was used to detect glucose.2. In the preliminary studies, we tried to modify the carbon paste electrodes with several transition metal oxides to fabricate electrochemical non-enzymatic glucose sensors. After compared, we found that only the electrode modified with nano NiO has obvious response current to glucose. Enzymatic-free electrochemical oxidation of glucose is greatly enhanced at Ni, NiO or Ni(OH)2based electrodes due to the existence of the redox couple of Ni(OH)2/Ni00H formed on the electrode surface in alkaline medium. The oxidation of glucose is catalyzed by the high-valent, oxyhydroxide species NiOOH. So we start to investigate non-enzymatic glucose sensors modified with nano NiO.3. Enzymatic-free electrochemical oxidation of glucose is greatly enhanced at Ni, NiO or Ni(OH)2based electrodes due to the existence of the redox couple of Ni(OH)2/NiOOH formed on the electrode surface in alkaline medium. Nano NiO modified carbon paste electrodes were fabricated to develop non-enzymatic sensors for glucose determination where an electrochemical technique of potential scan up to high potential was employed to process the prepared electrodes with the purpose of enhancing their electrochemical performance and determination sensitivity.4.3-methylthiophene react with HAuCl4to form nano Au and Poly(3-methyl thiophene)(PMTh). Here we describe a strategy of preparation and self-assembly of Au-PMTh nanocomposites induced by PMTh at a particular concentration. The shapes of the nanocomposites are very uniform, and the reaction solution became more stable. This material was used to modify carbon glassy electrode to detect glucose enhancing their electrochemical performance and determination sensitivity. |
PDF Full Text Request