Electrochemical Sensor Based On Graphene Paper For Rapid Detection Of Harmful Substances In Food

Food safety monitoring is a very important aspect for dealing with threats to human health and well being of the population.It has emerged as one of the most significant public concerns worldwide.Thus,screening of food contaminants is becoming vital for food industries and consumers.Presently,a greater part of food analysis is carried out at the end of the production process using conventional techniques such as chromatography,mass spectrometry,ultraviolet detection,or fluorescence techniques either individually or in combination with other separation techniques.These traditional approaches are laborious,expensive,time consuming,require large sample volumes,and highly trained personnel.Electrochemical sensors provide a possible solution to overcome the limitations of traditional methods by allowing any potential contaminants in food samples,and have been widely used in the detection of heavy metals and pathogenic microorganisms.In order to break through the shortcomings of traditional electrodes in electrochemical sensing system in detection performance and mechanical properties,Au nanoparticles/redox graphene paper(Au NP/r GOP)flexible electrode was prepared by combining the advantages of graphene materials and noble metal nanoparticles.The excellent performance of Au NP/r GOP electrode was proved by experiments.The electrochemical sensor based on Au NP/r GOP electrode was used for rapid detection of harmful substances in food.The main research contents and achievements are as follows:1.Using graphene oxide(GO)as precursor material,graphene oxide paper(r GOP)flexible electrode was prepared by multiple chemical reduction and vacuum filtration,then Au NP/r GOP flexible electrode was prepared by electrochemical one-step reduction modification of gold nanoparticles(Au NP).The preparation conditions were optimized as follows:cyclic voltammetry scanning for 10 cycles,chlorogenic acid concentration of 0.5 mmol/L.Scanning electron microscope was used to prove that the electrode had good surface physical morphology,and the electrode had excellent electrochemical performance through comparative test.2.A novel electrochemical sensor was developed for detection of Pb²⁺based on graphene paper electrode and gold nanoparticles(Au NPs).The sensor possesses an extremely broad detection range of Pb²⁺from 5?55?g/L,with a detection limit of 1.3?g/L.The sensor also demonstrates highly selectivity of Pb²⁺from many other metal ions especially Cu²⁺.This sensing system is simple,low cost,and highly sensitivity and selectivity for determination of Pb²⁺.Experiments are also conducted to access the ion concentration of spiked electrolyte based on the calibrated response curves.For the spiked recovery test,satisfactory accuracy can be attained.Comparisons to various electrochemical detection of heavy metal using anodic stripping voltammetry methods were also discussed,showing the superior performance of our Au NP/r GOP electrochemical sensor.3.A low-cost and robust impedimetric based on gold nanoparticles modified free-standing graphene paper electrode for rapid and sensitive detection of Escherichia coli O157:H7(E.coli O157:H7)was developed.Graphene paper was prepared by chemical reduction of graphene oxide paper obtained from vacuum filtration method.The scanning electron microscopy was employed to investigate the surface morphology of the prepared graphene paper.The gold nanoparticles were grown on the surface of graphene paper electrode by one-step electrodeposition technique.The immobilization of anti-E.coli O157:H7 antibodies on paper electrode were performed via N-(3-dimethylaminopropyl)-N?-ethylcarbodiimide(EDC)and N-hydroxysuccinimide(NHS)system.Results show that the developed paper electrode was used to detect E.coli O157:H7 captured on the paper electrode.Results show that the developed paper immunosensor possesses greatly enhanced sensing performance,such as wide linear range(9.2×10²?9.2×10⁷ CFU/m L),low detection limit(4.6×10² CFU/m L),and excellent specificity.Furthermore,flexible test demonstrate the graphene paper based sensing device has high tolerability to mechanical stress.The strategy of structurally integrating metal nanomaterials,graphene paper,and biorecognition molecules would provide new sight into design of flexible immunosensors for routine sensing applications.