The Preparation Of Crown Ether Functionlized Graphene Oxide And The Application For Electrochemical Sensors Of Potassium Ions

Potassium ion,the main intracellular cation,plays a significant role in human biological systems,especially in blood pressure regulation and maintenance of muscular strength.The abnormal concentration of potassium ion can result in many diseases.So it's of great significance to detect the concentration of potassium ion.At present,electrode modification materials used for detecting potassium ions based on electrochemical sensing method have a great limitation on the binding strength and selectivity of potassium ions,resulting in relatively high detection limit and narrow detection range.Graphene,a two-dimensional honeycomb lattice structure formed by the close packing of carbon atoms,has attracted widespread attention due to the excellent properties,such as high electrical,good mechanical,outstanding optical and high thermal conductivity.However,it is easy to agglomerate due to the strong Van der Waals forces between the graphene sheets,which hinders the development of graphene.The functionalized graphene composites can be obtained by modifying graphene using other functional materials.This can not only avoid the agglomeration and stacking between the graphene sheets but also can effectively improve the properties of graphene.Graphene oxide,a product obtained by oxidizing and then exfoliating graphite,is a derivative of graphene.Graphene oxide has a two-dimensional structure similar to graphene,but the graphene oxide structure contains a large number of oxygen-containing functional groups.So the functional modification is convenient for graphene oxide.As a host molecule,crown ether has high binding selectivity to alkali metal and alkaline earth metal ions due to the relationship between the diameter of the metal ion and the diameter of the ligand.Based on this,in this thesis,graphene oxide is functionalized by crown ether to obtain new properties to graphene oxide,and then it is applied to electrochemical sensing of potassium ion.Firstly,graphite oxide is prepared by the modified Hummers method,and graphene oxide is prepared by ultrasonic stripping.SEM,TEM,AFM,FT-IR,XPS and XRD analysis methods are used to characterize the composition,structure and surface functional groups of the sample.The results show that graphene oxide is obtained by highly oxidizing graphite,and graphene oxide sheets contain functional groups such as-OH,-COOH,and C-O-C.Due to the insertion of a large number of oxygen-containing functional groups,the graphene oxide layer spacing increases.Then,the crown ether functionalized graphene oxide composite materials is synthesized by nucleophilic addition reaction with the prepared graphene oxide as precursor.The composition,structure and surface functional groups of the composites are characterized by FT-IR,XPS and Raman.The results show that graphene oxide is successfully functionalized by 1-aza-18-crown-6 crown ether.Finally,the prepared crown ether functionalized graphene oxide composite is deposited on a glass carbon electrode,and potassium ions are detected by electrochemical impedance method.The results of electrochemical measurements show that the linear range of potassium ion is 10^-7-10^-13 M on the crown ether functionalized graphene oxide modified electrode.The linear equation is Y=143.928X+2633.857 and the correlation coefficient is R²=0.983,and the detection limit is 10^-15 M,which is much lower than the detection limit obtained by other methods and other materials.In this paper,a new composite of crown functionalized graphene oxide is introduced as electrochemical sensing material of potassium ion detection by EIS method.By suitable choice of specific crown-ether,this strategy can be used to synthesize other crown-ether functionalized graphene oxide nanocomposites for sensing other ions.