The Fabrication And Application Of Screen Printed Electrodes Modified By Graphene And Its Composites

Over the last decades,electrochemical sensors have became one of the main research objects of electrochemical researchers and have been widely used in electroanalytical methods.The electrochemical sensors using the method of screen printing technique which have great research value and application prospect are characterized by portable,low cost,sensitive,point-of-care testing and so on.The screen printed work electrodes and reference electrode modified by graphene and its composites was prepared in this paper and used for evaluating the oxidation stability of vegetable oil and detecting the three dihydroxybenzene isomers,simultaneously.The result is satisfactory.The contents include the following three aspects:1 Screen printed electrodes?MSPE?which were modified by reduced graphene oxide?rGO?,BMIMPF₆ and g-C₃N₄ were constructed.The conditions for the electrodes modification and the electrochemical characteristics of MSPE were investigated.The optimal constitutions of MSPE were that carbon paste?rGO?BMIMPF₆=50?1?2?W/W?and the addition amount of g-C₃N₄ were 2 ?L.The parameters for the determination of oil impedance and the impedance behavior of vegetable oils on the modified electrodes were thoroughly studied.It was found that g-C₃N₄/rGO/BMIMPF₆-SPE can be used to sensitively and rapidly determine the oil impedance and the impedance variation in the process of oil oxidation.Therefore,a simple,sensitive and accurate method for the determination of oil's oxidation induction time was established.The oxidative stability of olive oil,almond oil,wheat germ oil and safflower seed oil were evaluated.The order of stability of the four kinds of vegetable oil was olive oil>almond oil>wheat germ oil>safflower oil.There is no statistical error between this method with GB method.2 Using the screen printing technique prepared the planar solid reference electrode.In the experiment,we optimized the concentration of KCl agar solution,the modification of AuNPs/rGO composite and polyvinyl chloride?PVC?membrane solution;compared the different modified materials which impact on the stability of electrode potential,investigated the influence of common inorganic salt,acidity and light on the stability of electrode potential.The results show that the optimal constitutions of the planar solid reference electrode were that drop-coated of KCl agar solution with 1.0 mol/L,the addition amount of AuNPs/rGO composite and PVC solution was 3 ?L,8 ?L,respectively.The electrode potential is relative stable and the time required to stabilize the potential is about 0.05 h.The effect of inorganic salt and pH?p H=3.0⁹.0?on the electrode potential was less than 2 m V/dec or 0.104 mV/pH.The prepared planar solid reference electrode keep stable and the potential change is less than 2.0 mV after three months.3.Graphitic carbon nitride/reduced graphene oxide composite modified screen printed electrodes?g-C₃N₄/rGO/SPE?was prepared Scanning electron microscope?SEM?confirmed that the as-prepared g-C₃N₄/rGO composite presented the lamellar structure.We optimized the modification of g-C₃N₄/rGO composite,the scanning rate of cyclic voltammetry and pH conditions of buffer solution,discussed the electrochemical reaction process and the reaction mechanism of Hydroquinone?HQ?,catechol?CC?and Resorcinol?RC?on g-C₃N₄/rGO/SPE;studied the reproducibility and anti-interference ability of g-C₃N₄/rGO/SPE.The cyclic voltammetry results showed that the obtained g-C₃N₄/rGO/SPE had good catalytic performance for the oxidation of hydroquinone?HQ?,catechol?CC?and resorcinol?RC?and the oxidation potential were 0.18 V,0.29 V and 0.65 V,respectively.The differential pulse vohammetric?DPV?peak current was proportional to the concentration of HQ,CC and RC,respectively.The calibration curves for HQ,CC and RC were obtained in the range of 0.1 ?M³00 ?M,0.5 ?M³00 ?M,1 ?M²00 ?M,respectively and the detection limits were 0.03 ?M,0.07 ?M,0.1 ?M,respectively?S/N=3?.The recoveries of HQ,CC and RC in water samples were 97.2%¹03.8%.