Preparation Of Graphene By Liquid-phase Exfoliation Method And Its Application In Electrochemical Sensors

Graphene,a new "member"of carbon family,has been applied in many aspects,including biosensor,fuel cell,and supercapacitor,which is due to its excellent physical and chemical properties.At present,the chemical method(Hummers method)is the major way to prepare graphene.The Hummers method is the most popular strategy owing to its stable great yield.However,the graphene prepared by this method need to be treated with strong acid and then reduced by some chemicals and is therefore often called chemical converted graphene(CCG).The chemical processes definitely cause the irreversible structure destruction of CCG and result in a decline in its conductivity.Recently,high quality pristine graphene(PG)based on liquid phase exfoliation method(high throughput)has become a hot topic.In the thesis,we have developed a method to improve exfoliated efficiency of graphite in ethanol by using organic salts.The contents of this thesis are given as follows:1.PG dispersion was synthesized by sonicating original graphite in ethanol with aid of organic salts(tartaric acid sodium,potassium sodium tartrate,sodium citrate).Typically,graphite powder and potassium sodium tartrate were added in ethanol.The resulting mixture was then placed in an ultrasonic bath with a frequency of 40 KHz for 2 hours at room temperature.TEM,AFM,FTIR,TGA,UV-Vis,Zeta,Raman,and XRD were utilized to characterize morphologies and propertiesof samples.The result shows that the PG has perfect structure and clean surface.2.A novel electrochemical sensor based on high PG(exfoliated in high boiling solvent)is successfully constructed to detect ascorbic acid(AA),dopamine(DA),and uric acid(UA).The linear detection ranges for AA,DA,and UA are 9.00-2314,5.00-710,and 6.00-1330 ?M,respectively,with detection limits of 6.45,2.00,and 4.82?M.This PG based sensor exhibits excellent performance for detection of AA,DA,and UA,which is much better than those electrochemical sensors based on CCG.3.A novel label-free electrochemical immunosensor for rapid determination of ractopamine was constructed by incorporating ractopamine-PG modified on a glassy carbon electrode.Cyclic voltammetry and differentialpulse voltammetry were used to investigate the electrochemical character of the imnunosensor using a redox probe system of K3[Fe(CN)6].A competitiveimmunoreaction system was employed to detect the free ractopamine in phosphate buffer solution.The linear detection range is 10-4000 ng/mL.The selected monoclonalantibody showed very high sensitivity and specificity for ractopamine,and was used for the determination and quantitative determination oftrace amounts of ractopamine in spiked animal feeds.