Study On Nanoparticles Enhanced Electrochemical Enzymebiosensors

One of chief challenges in direct electrochemistry field is to find the suitablematerials to enhance the direct electron transfer between the electrode and redox protein.Nanomaterials have attracted much interest due to their desired physical and chemicalproperties. In this dissertation, H₂O₂biosensors were constructed using ITO electrodemodified with ZrO₂and Si-doped-TiO₂nanomaterials, respectively. Theelectrochemical behaviors of H₂O₂at the as-prepared biosensors were detailedinvestigated and the mechanism was also discussed. The main work could besummarized as follows:Firstly, Si-doped TiO₂nanocomposites were synthesized by two phasehydrothermal method and the as-prepared samples were characterized by SEM, XRD,UV-Vis, and IR. It was found that the Si-doping has a suppressive effect on the crystalgrowth of TiO₂and resulted in smaller crystalline size. A Si-doped TiO₂（TiO₂:0.2Si）nano-composite modified glassy carbon electrode （Si-TiO₂/GC） was constructed for thedetermination of tryptophan （Trp）. It was interesting that the electro-oxidation peakcurrent of Trp at the Si-TiO₂/GC was obviously higher than those on the bare and TiO₂nanoparticle modified GCE, suggesting the enhanced electrochemical properties ofTiO₂:0.2Si. Under the optimum experimental conditions the Si-TiO₂/GC displayed agood electrocatalytic oxidation of Trp with a linear range of1.0×10^-6-4×10^-4M anda detection limit of5.0×10^-7M （S/N=3）. The electrochemical sensor proposed hereinis easy to prepare, and exhibit good reproducibility and long-term stability. Furthermore,it was successfully employed to determine Trp in pharmaceutical samples.Secondly, the Si-doped TiO₂nanocomposites were employed to immobilize HRP for the construction of H₂O₂biosensor. A biosensor with good response to H₂O₂hasbeen prepared by using the above-mentioned composite material and Chitosan. Theexperiment conditions have been optimized, according to the influence of thepercentage of doped Si and synthesis condition. All results show that thebio-compatibility of the material is enhanced after doping with Si into TiO₂nanoparticles, as a result the performance of the biosensor is improved.Lastly, H₂O₂biosensors were prepared using ZrO₂nanoparticles annealed atdifferent temperature. It was interesting that the annealing temperature can exertsignificant effect on the biosensing properties. A biosensor with good response to H₂O₂has been prepared by using the composite material, ZrO₂nanoparticles and Chitosan, asthe immobilizing matrix. The conclusion can be draw as that annealing process canfacilitate the conductivity and catalytic activity of the nanomatrials.600°C is the besttemperature to achieve better performance of ZrO₂nanoparticles and ZrO₂nanoparticlesmodified biosensor. The bioensor has a good response sensitivity and low detectionlimit, and the linear range is5.0×10^-6M-9.5×10-3M, detection limit is5.0×10^-7M,response time is less than10s, while Km=6.07mM.