| Biomolecules play important role in metabolism and other important physiologicalproeesses, which are charaeteristics of electron transfer between their oxidation andreduction states. Therefore, to study the proeess of life is to investigate the electrontransmition in essence. Electrochemical methods are applied widely in life scienceresearches to research the electron transfer process among the biomolecules, which notonly can obtain the basic thermodynamics and dynamics parameters, and show theelectron transfer mechanism as well. This is significant to understand the life process, andprepare the electrochemical biosensors to meet the needs of the biomedical, environmentaltest and rapid analysis of industrial.Due to their special physical and chemical properties, nanosturctured materials canactivate while active electrode surface, and promote the direct electron transfer betweenthe active center in biomolecule and the electrode surface. Therefore, the application ofNano-technology on electrochemical analysis of biological molecules is a promising aera.and conducive to the establishment of some new theories, new technologies and newmethods.In this thesis, some novel biosensors were constructed based on CdTe quantum dot(QD), CdSe QD and Platinum nanoparticle, and the electrochemical properties andcatalytic effects were studied. The main contents and results are summarized as follows:(1) Water-soluble CdTe nanoparticles and hemoglobin (Hb) were immobilized on aglassy carbon (GC) electrode with Nafion. The direct electrochemistry and the catalytickinetics of Hb on this surface were studied by cyclic voltammetry (CV) and current-timeamperomeric method. The results indicated that CdTe nanoparticles could effectivelypromote the direct electron transfer of Hb at the interface of a electrode. Theheterogeneous electron transfer rate constant, k, was calculated as 0.068 s-1 and thetransfer coefficient,α, was 0.59. The immobilized Hb still kept its catalytic activity toH2O2 reduction. The apparent Michaelis-Menten constant was calculated to be 17.7μM. Itwas also found that the modified electrode could be used as a sensor for H2O2; the linearrange of detection was 5.0×10-6～4.5×10-5 M, with a detection limit of 8.4×10-7 M. The sensor exhibited high sensitivity, reproducibility and stability.(2) Horseradish peroxidase (HRP) and lipophilic CdSe/ZnS QD were incorporatedonto the surface of GC electrodes in various ways. It was found that HRP transferselectron directly onto the GC electrode only when the electrode was modified with QDthrough evaporative deposition. The heterogeneous electron transfer rate constant k was5.80±0.70 s-1. Absorption spectra and Fourier-transform infrared spectra showed that theconformation of HRP immobilized on the electrode has no obvious change. Further studiesindicated that immobilized HRP retains excellent catalytic activity to H2O2. The apparentMichaelis-Menten constant was calculated as 0.152 mM. It was also found that themodified electrode could be used as a sensor for H2O2, and the linear range of detectionwas 5.0×10-6～1.0×10-4 M, with a detection limit of 2.84×10-7 M. The sensor exhibitedreproducibility, stability and relatively high sensitivity. The result indicated that core-shellQD could promote the direct electron transfer between protein and electrode, but theelectrochemical behavior strongly depend on modify method of QD.(3) Evaporative deposition of lipophilic CdSe/ZnS QD was characterized by variousways, the influence of deposition time and deposition temperature on the catalytic activeof HRP were studied. The results indicated that the direct electron transfer of HRP couldbe promoted preferably when QD was deposited 7 hours at 35℃. Under these conditions,the average coverages of QD and HRP on the electrode surface were 5.56×10-8 mol/cm2and 6.47×10-11mol/cm2 respectively, and the heterogeneous electron transfer rate constantk of HRP is 6.01 s-1.(4) Laccase was immobilized on an electrode modified with a cysteineself-assembled monolayer and coated with functionalized quantum dots. The directelectrochemistry and the catalytic kinetics of Laccase on this surface was studied by CVand current-time amperomeric method. The immobilized laccase is capable of directlytransferring an electron, the heterogeneous electron transfer rate constant, k, wascalculated as 21.7 s-1 and the transfer coefficient,α, was 0.47. Immobilized laccaseretained its activity to oxidize ascorbic acid (AA), and the apparent Michaelis-Mentenconstant was found to be 0.47 mM. The modified electrode was used to linearlysense AA in the 1.0×10-5～1.4×10-4 M concentration range, with a detection limitation of 1.4×10-6 M.(5) Pt nanoparticle was deposited on the Pt electrode by electro-chemical deposition,the prepared PNP/Pt electrode had good electrocatalytic oxidation response to salicylicacid (SA), and could detect SA in weak alkali condition, the response current was 9.2times that of Pt electrode, and the linear range of detection was 2.0×10-5～5.0×10-4 M. ThePNP/Pt electrode has low detection limit, high repeatability and stability as SA sensor, canapplicate on the detection of salicylic acid reliably.
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