The Preparation And Its Application Of Nanomaterials Chemically Modified Carbon Paste Electrode

In recent years, the preparation, characterization, future development andapplication in life science, environmental monitoring, food and drug analysis ofCarbon Paste Electrode (CPE) were researched by the scientific workers detailedly.And the development prospect of CPE was also discussed. The characteristics, suchas: a low cost, high sensitivity, easy to update, renewable surface, low residual currentand simple fabrication method, make CPE play an important role in elecctroanalyticalchemistry. Chemical Modified Carbon Paste Electrode (CMCPE) extended theapplication range of carbon paste electrode.Carbon is the "myth" of scientific community, and the carbon nanomaterials isnew trend in recent years. The available of carbon nanotubes (CNTs), Graphene (Gr)and Graphene Oxidation (GO) result in heated discussions of carbon nanomaterials.Numerous studies showed that the large specific surface area, low cost and excellentcatalytic performance of CNTs laid a solid foundation for their application in the fieldof voltammetric sensor.Quantum dots (QDs) is a kind of semiconductor nanomaterials. QDs hasincomparable advantage over other materials in terms of chemical modificationbecause of the small size, large specific surface area and good biocompatibility. Sothe research and application QDs in field of chemical and biological sensors isincreasing rapidly.On the basis of previous studies, this thesis adopted the nano materials (QDs,CNTs) as the main modifier to doping the carbon paste electrode. The main contentsare shown below:(1) In this part, bare carbon paste electrode (CPE) and multi-walled carbonnanotubes doped carbon paste electrode (MWCNTs/CPE) were fabricated and used asthe voltammetric sensor. The mix proportion of carbon nanotubes and graphitepowder was optimized in advance. The electrochemical response characteristics ofcolchicine on different electrodes was investigated using various electrochemicalmethods, and the electrode reaction mechanism of colchicine were discussed on the basis of the previous reports. Results showed that the doped MWCNTs could greatlypromote the electrochemical response of colchicine. Under optimum conditions,differential pulse voltammetry was adopted to established the standard curve ofcolchicine. The oxidation current of colchicine was proportional to the concentrationof colchicine in a wide linear range from1.0×10-8to2.5×10-5mol/L with a lowdetection limit8.0×10-9mol/L. The newly-recommended sensor showed severalmerits including extreme simplicity, wide linear range, low detection limit, goodstability and reproducibility. Furthermore, it was successfully employed for thedetermination of colchicine in pharmaceutical formulations with satisfactory results.(2) The polyvinyl pyrrolidone cladding CdS quantum dots (PVP-CdS) wasprepared and characterized with transmission electron microscopy(TEM), ultravioletspectrum (UV-Vis) and infrared spectrum(IR). Then, the PVP-CdS was doped in CPEto construct a facile and highly sensitive electrochemical sensor (PVP-CdS/CPE) forkaempferol. The PVP-CdS/CPE accelerated the redox of kaempferol obviously. Then,the electrochemical behaviors and kinetic parameters of kaempferol were investigatedand the electrode reaction mechanism of kaempferol discussed. The oxidationcurrents were linearly relationship with kaempferol in two concentration intervals:one was6.0×10-8to2×10-6mol/L and the other was5.0×10-6to2.5×10-5mol/L,and the quantitation limit was6.0×10-8mol/L. The PVP-CdS/CPE was successfullyapplied to determine the kaempferol in tablets.(3) On the basis of previous studies, the Ethylenediamine (En) and GrapheneOxide (GO) was fixed on the CPE orderly with the method of self-assembly. A facileand highly sensitive electrochemical sensor (GO/En/CPE) for malachite green wasconstructed successfully. As a control, CPE, GO/CPE, En/CPE were prepared. Theelectrochemical responses of malachite green at the four sensors were investigated indetail and results showed that the proposed GO/En/CPE exhibited the bestelectrochemical response with a linearity for malachite green over the range from8.0×10-9to8.0×10-7mol/L, and the detection limit of5.0×10-9mol/L. Finally, thepractical application was proved by spiking malachite green standards to lake waterwith recoveries of ranged from98.80%to101.10%, showing a satisfactory result.