Fabrication And Electrochemical Activation Of Enzyme-free Sensor Based Carbon Nanotubes

This dissertation focuses on the fabrication of enzyme-free sensor based on carbon nanotubes’(CNTs) and the promotion effect of electrochemical activation on electrochemical performance of the sensor. Kinds of composites based on CNTs were prepared and used to fabricate sensitive enzyme-free sensors with different fabrication method including casting, electro-polymerization, self-assembly. Subsequently, electrochemical activation was taken on these sensors to promote the sensitivity. Transmission electron microscopy (TEM), scanning electron microscopy (SEM), and electrochemical techniques are used to study the properties of the interface. Fabrication and detecting conditions were optimized. And, the application of as-prepared enzyme-free sensors in bioactive substance was discussed systematically. The main works and achievements were as followed:1. Multi-walled carbon nanotubes (MWNTs) composites prepared based on electrostatic effect between carboxyl MWNTs and cationic polyeelectrolytes (PEs). The enzyme-free sensors were fabricated by casting the composites on electrode. The influence of electro-chemical activation on sensor was discussed. The result showed that only when the CNTs modified with PEs, the electrochemical activation could influence the performance of the sensor. The signal to DA at the activated sensor was improved. The signal of the as-prepared sensors could keep about95%of the original signal within30days, which stated that sensor achieved an excellent stability. The experiment on determination to DA and anti-interference indicated that the as-prepared senors had good response to DA. For instance, the linear range of DA at PEI-MWNTs modified electrode was0.08×10-6to6×10-6mol L-1with a detect limitation of0.05×10-6mol L"1. The as-prepared sensor could be applied in determination of DA in dopamine injection.2. By means of the force between Au and the long pair electrons of N in PEI, Au nanoparticals (AuNPs) were in-situ synthesized on the surface of PEI-MWNTs. The enzyme-free sensors were fabricated by casting the composites on electrode and subsequently activated by electro-chemical activating. SEM, TEM and CV were used to characterize the differents of surface morphology and electrochemical properties before and after electrochemical activation. The result indicated when the PEI-MWNTs-AuNPs was electrochemical activated, some edge were appeared on in the surface of polyelectrolyte wrapped CNTs and the polymer film thinned. The anti-interference experiment showed that the signal of the as-prepared sensors could keep about95%of the original signal within60days. The study on DA detection in complicated system stated that the enzyme-free sensor had a good selectivity to DA and could be applied in real samples. The detection range included the normal concentration of DA in human blood (<1μM).3. An alternate strategy of electro-polymerization and self-assembly was developed to fabricated a stable sensor which can be used in simultaneous determination of dopamine and uric acid. First, a layer of poly-Chrome black T (poly-EBT) was electro-polymerized onto the surface of glassy carbon electrode. Experiment results indicated that the enzyme-free sensor could detect DA and UA simultaneously and its signal could keep about93%of the original signal within30days. The sensitivity of the sensor to DA was11.03μA L mol-1, which increased nearly ten times compared with other sensors. The as-prepared sensor has obvious advantages and application potential and it can appllied in detecting DA and UA with the normal concentration in human bodies.