Studies Of Carbon Nanotubes Modified Catechol Sensors

This dissertation constructed novel types of carbon nanotube film modified electrodes, multi-walled carbon nanotubes/chitosan multilayer modified electrode(GC/MWNT-CHI) and ionic liquids ([BDmim]PF6) multi-walled carbon nanotubes/chitosan multilayer modified electrode(GC/MWNT-CHI-IL), studied their electrochemical behaviors, and successfully used them for the determination of catechol with satisfactory results.The main contents of the dissertation were as follows:1. Constructed the multi-walled carbon nanotubes/chitosan multilayer modified electrode (GC/MWNT-CHI). The GC/MWNT-CHI was constructed by dropping the modified solution, which was prepared with the modified method of carbon nanotubes dispersion in the solution of chitosan, on the surface of the electrode. The optimum compositions and volume of the modified solution, MWNT: CHI: alcohol=1mg: 1mL: 0.5mL and 2μL, was chosen by orthogonal experiments. Its CV behaviors and EIS in the solution of K3[Fe(CN)6] were thoroughly studied. Experimental results showed that the electrochemical response was enhanced; the sensitivity and the reversibility of the electrode were improved with the increase of the modified layers of the electrode. Moreover, the 5 modified layers of the electrode revealed the best performance.2. The response of CAT on GC/MWNT-CHI. The modified electrode showed a high sensitive response to CAT in the solution of PBS (pH=6.8) when the scan rate was 200mV/s. Under the optimum conditions, the oxidative current increase were linear with the concentrations of CAT in the range of 3.99×10-6~9.09×10-4mol/L, while the detection limits was of 2.39×10-6mol/L (S/N=3). The recoveries of CAT in the artificial waste water sample were satisfied. In addition, RSD(n=10) was 2.1% and the response current was only decreased 1.9% after 15 weeks when the modified electrode was used to detect 4×10-5mol/L CAT , which showed that the proposed modified electrode had excellent stability.3. Constructed the ionic liquids ([BDmim]PF6) multi-walled carbon nanotubes/chitosan multilayer modified electrode(GC/MWNT-CHI-IL). The optimum compositions of the modified solution, MWNT:CHI:IL=1.3mg:0.5mL: 20mg, was chosen by orthogonal experiments. The electrochemical behaviors of the electrode were studied with CV, chronoamperometry and EIS in the solution of K3[Fe(CN)6]. Experimental results illustrated that GC/MWNT-CHI-IL showed higher sensitive and better reversible than that of GC/MWNT-CHI . Because of the existence of IL in the modified layers, the electron transmission in the membrane was enhanced and the impedance of the electron transfer was reducd. Moreover, a large number of surface defects in the membrane of electrode could reduce the impedance of the solution. Therefore, the procese of electrode reaction was controlied by diffusion. Howevere, IL in the membrane showed good capacitive characters during the circulation of charge and discharge, which induced the increase of the background currents and the augment of the impedance of the interface of electrode/solution. So, the CPE contained a certain of capacitive characters. 4. The response of CAT on GC/MWNT-CHI-IL. The modified electrode showed a high sensitive response to CAT in the solution of PBS (pH=6.8) when the scan rate was 200mV/s. Under the optimum conditions, the oxidative current increase were linear with the concentrations of CAT in the range of 3.99×10-6~8.00×10-4mol/L, while the detection limits was of 1.01×10-6mol/L (S/N=3). The regression equation was Ipa(μA)=3.8365c+6.3352 (R2=0.9876) In addition, RSD(n=10) was 2.6% and the response current was only decreased 1.5% after 3 weeks when the modified electrode was used to detect 4×10-5mol/L CAT, which showed that the proposed modified electrode was stable. In addition, GC/MWNT-CHI-IL was used to determine the trace amounts of CAT in practical environmental water samples with satisfactory results.