In-situ Synthesis Of Nano-silver/Copper-graphene Composites By Electroless Plating And Electrochemical Performance Of Modified Electrodes

Graphene has been used as an excellent carrier for metal nanomaterials because it has unique structure and physical and chemical properties.Metal nanoparticles are often used to construct electrochemical sensors because of its particular catalytic activity.The introduction of metal nanoparticles into graphene can effectively exert the unique advantages of these two materials,which are more concerned in the field of sensing.In this paper,the nano-silver/copper-graphene composite modified glassy carbon electrode was successfully prepared by electroless plating-surface aggregation coating method.The properties of the electrode were characterized by material characterization techniques such as XRD,EDS,XPS,SEM,FT-IR,and electrochemical methods such as CV,EIS,LSV,DPV,and were applied to the detection of ascorbic acid（AA）and hydrogen peroxide.The research contents mainly include the following aspects:In graphene-silver-ammonia mixture solution,nano-silver-graphene composite（Ag/GR）was successfully prepared at low temperature using glucose as the reducing agent.The AgNPs on the graphene surface exists in the elemental form,belonging to the face-centered cubic structure of metallic silver.The grain size was about 21 nm.The electrochemical test results showed that the response peak current of Ag/GR/GCE was the highest,with an oxidation peak current of 212.9 μA,a reduction peak current of 165.1 μA,and a minimum charge transfer resistance of 90.5Ω.Ag/GR/GCE has the maximum electrochemical active area（0.1991 cm2）,which was about 5 times,3 times and 2 times higher than that of bare GCE,AgNPs/GCE and GR/GCE respectively.Under the optimized conditions for the detection of ascorbic acid,Ag/GR/GCE had two optimal linear response ranges of 5 μM～50 μM and 50 μM～120 μM,with the limit of detection as low as 0.06 μM.Ag/GR can maximize the use of ascorbic acid in the limited electrode surface area,provide an electron transfer microenvironment for the electrode reaction,accelerate the generation of dehydroascorbic acid,and achieve the sensitive determination of ascorbic acid.The nano-copper-graphene composite（Cu/GR）was successfully prepared in graphene-copper-ammonia mixture solution at 40℃ under the condition that glucose combined with low-concentration hydrazine hydrate was used as the reducing agent.CuNPs in Cu/GR was metallic Cu0 states,which was uniformly distributed on the surface of graphene,with the average grain size of about 23 nm.The electrochemical test results showed that when Cu/GR/GCE was used as the working electrode,the oxidation peak current was 307.4 μA,the reduction peak current was 252 μA,and the Rct value was 70.08Ω,which was beneficial to the electron transfer process.The order of the ability to accelerate electron transfer was Cu/GR/GCE>GR/GCE>CuNPs/GCE>bare GCE.The parameters of H₂O₂ detection were optimized,the limit of detection of H₂O₂ was 0.006 μM,and the calibration curve had three different linear response regions:0.1μM～5 μM,5 μM～100 μM and 100 μM～2500 μM.Using Cu/GR/GCE to monitor H₂O₂ daily for 2 consecutive weeks,the reduction peak current maintained 94.36%of the initial value with excellent long-term stability.The Cu/GR/GCE electrochemical sensor for H₂O₂ detection in this study has the advantages of multiple amplified electrochemical responses,comparable linear detection range,good accuracy,simple preparation,low detection limit,and so on.It shows great potential in the high sensitivity detection of H₂O₂.