A Study On Alcohol Sensor Based On Composite Film Modified ITO Electrode

The detection of C₂H₅OH is very important in medical domain,forensic medicine and food security. And drunk driving is gradually increasing with development of economics, so importance of fast and quantificational detection for alcohol concentration in blood is more and more important. Electrochemical biosensor for alcohol testing have high sensitivity,broad linearity rage and fast response time, then this method become hot research in the field now.MWCNTs is a nano-scale material with metallicity and semiconductor featrue. The material is wildly used for electron mediated transport as it's good conductivity of electricity,big specific area and excellent catalysis. Its electrontransport activity had been confirmed by some experiments in electrochemical biosensor. PB nano particles have nano size effect and can decrease over potential of oxidation-reduction process in particular redox process of super-oxider; PB's chemical structure is stabilization and PB have excellent catalysis and nice reversible electron tansport effect. ITO electrode is a special electrode which surface coated by indium tin oxid, its chemical structure is stable and it is produced easily, meanwhile it have good electrical conductivity and nice catalysis. A novel alcohol sensor was made by using indium tin oxides(ITO) electrode's surface modified by carboxylated multi-walled carbon nanotubes(MWCNTs) which absorbed a thin Prussia blue film as electron mediator. By this method we not only achieve electrochemical catalysis for alcohol and amplify of current response signal, but also established foundation for exploring new electrochemical test method of alcohol concentration in body blood.Methods(1)Cutting a glass of ITO to even oblong ITO electrode.(2)We supersonic dispersed 5mg pured MWCNTs for 10 minutes in 50mL DMF and finally got 1.0mg/mL injectable suspension solution of MWCNTs. And then dripping and daubing 20μL suspension solution on ITO electrode surface(0.6×0.6cm²) for electrode(MWCNT/ITO) which were modified by MWCNTs. After that we scanned it in PBS buffer solution(pH=7.0) by cyclic voltammetry method, at the same time analysised characters of ITO electrode which has been decorated by MWCNTs.(3)Adding slowly the 5mmol/L K₃Fe(CN)₆ solution into the 100mL 5mmol/L FeCl₃(pH=1)solution which was stirring by magnetic stirring apparatus, we got Nano-PB colloid solution after 3 hour. We soaked the prepared MWCNTs/ITO electrode into the nano-PB solution, and got homogeneous PB film on surface of the ITO electrode. To test the best characters and the detective conditions of the electrode, we scanned in PBS buffer and PBS+C₂H₅OH mixed solution by cyclic voltammetry respectively.(4)Exploring the performance of the MWCNTs/PB/ITO composite electrode by parallel compare between electrochemical biosensor method and GC method.ResultsWe slef-assembly decorated MWCNTs on the surface of ITO electrode, after that it had adsorbed a piece of nano-PB film because of electrostatic adherence effect, and finally produced a good alcohol biosensor. The made biosensor obviously have electrochemical properties for alcohol, that sensor exhibited a linear range of 0.5～10mmol/L with a correlation coefficient of 0.9968. In the case of S/N=3, the detection limit was 0.07mmol/L , the 95% response time of stable state is less than 15s.We taken out the MWCNTs/ITO electrode which immersed in the nano-prussian blue solution respectively after 2,4,8,16 hours. We scanned some prepared MWCNTs/PB/ITO electrodes in the 0.02mol/L PBS buffer by cyclic voltammetry, meanwhile we found the response current increased with increasing soaked time, and the response current became steady after 8 hours. At the same time we demonstrated that 25℃is the best temperature,optimum pH =7 and the best scan rate is 50mv/s by checking the prepared electrodes with different temperature,pH and scan rat. The alcohol biosensor have good catalysis, low detection limit and fast time of test ,so we are satisfied with these results when checking the real samples with alcohol biosensor.ConclusionIn experiments a novel alcohol sensor was first made by using indium tin oxides(ITO) electrode's surface modified by carboxylated multi-walled carbon nanotubes(MWCNTs) which absorbed a thin Prussia blue film as electron mediator. This sensor have facile preparation, reliable, good catalysis, fast detection time and accurate results, so it will be good future of development and practice.