The Fabrication And Application Of Screen Printed Electrodes Modified By Carbon Nanoparticles And Their Composites

Electrochemical sensors are the“core”of electroanalytical chemistry and the main research objects of electrochemical workers.Screen-printed electrodes are favored by electrochemical researchers because of their simple fabrication,low cost,fast detection,convenient use and easy commercialization.The main research works of this dissertation were to prepare a new type of carbon nano-organic modified silica sol composite conductive carbon paste for screen printing,and to synthesize nitrogen-doped graphene and nitrogen-doped graphene-gold nanocomposite composites.They were used to measure the oxidation induction time of vegetable oil and to detected the three isomers of hydroquinone in water simultaneously.The main research contents and results were as follows:1.Preparation of carbon nano-organic modified silica sol composite conductive carbon paste for screen printing.Based on the characteristics of Sol-gel technology and screen printing,the formulation of organically modified silica sol binder for screen printing was optimized.The experimental resultsshowedthattheoptimumvolumeratioofeachmaterialwas KH560:KH570:TEOS:EtOH:H₂O:HCl?1mol/L?:H₂O=1:1:8:8:2:2:0.17,thehydrolysis temperature of silane was 60°C,the hydrolysis time was 1 h and the curing temperature was60°C.The adhesive force of the prepared gel film to the PC plate was strong and the film layer was in a good state.And then,it was combined with carbon nano-materials which used as a binder of conductive carbon paste to make the working electrode and counter electrode of screen printing electrode.The filling amounts of different conductive carbon material filler used for printing electrodes and additive contents were optimized by cyclic voltammetry.The results revealed that the content of graphite powder,carbon nanomaterials and additives was34%,2.5%and 6%respectively.And the mass ratio of carbon nanotubes to graphene was1:1,the electrochemical performance of the prepared screen-printed electrode was best.2.Nitrogen-doped graphene-modified screen-printed electrode was used to measure the oxidation induction time of vegetable oil by AC impedance methodNitrogen-doped graphene was successfully prepared with graphene oxide as the main component and melamine as nitrogen source by high temperature annealing,reductiom and nitrogen-doping.Then,the nitrogen-doped graphene was characterized.A novel system for measuring the oxidation induction time of oil with nitrogen-doped graphene modified screen-printed electrode by AC impedance methodwas developed.The system consisted of four systems:injection,mixing,extraction/separation and measuring.The ratio of the modified materials for screen printing electrode and the impedance measurement conditions were optimized.The AC impedance behavior of the extraction phase,which was separated after the mixture of the oil and the extractant,on different modified electrodes was also studied.The results showed that when the volume ratio of acetonitrile to phosphate buffer?pH=7.0?was 1:2,the volume ratio of oil to extractant was 1:1,and the flow rate was 1.5mL/min,the polar and weak polar oxidation products produced in the process of oil oxidation could be extracted rapidly and efficiently by the extractant.The established measurement system could sensitively detect the impedance of the extraction phase and its changes to reflect the different oxidation degrees of the oil.The relative deviation between the oxidation induction time obtained from the impedance-time curve and the oxidation induction time determined by the national standard method was less than 4%.The results of the F and t tests showed that there was no systematic error between the two methods.3.Simultaneous determination of hydroquinone isomers in water with nitrogen-doped graphene-gold nanocomposite modified screen printing electrode.The nitrogen-doped graphene-gold nanocomposites were successfully prepared by impregnation method and characterized by SEM,TEM,XRD,EDS,XPS.The nitrogen-doped graphene-gold nanocomposites were modified onto the surface of the screen printing working electrode by drop casting.The results of cyclic voltammetry showed that the electrode had good catalytic activity for electrochemical oxidation of three isomers of hydroquinone.The oxidation peaks of the three isomers could be better divided.The experimental parameters were optimized and the possible reaction mechanism of hydroquinone isomer on the electrode was discussed.The three isomers of hydroquinone?HQ?,catechol?CT?and resorcinol?RS?were sensitively detected simultaneously by differential pulse voltammetry.The results showed that HQ,CT and RS had good linearity in the concentration range of 0.1?M-300?M,0.5?M-300?M and 5?M-500?M,respectively.The detection limit?S/N=3?were 0.03?M,0.15?M and 0.5?M,respectively.The method was used to detect the content of HQ,CT and RS in the actual sample.The recoveries of the spiked sample were in the range of 97.2%-103%.