Study On The Electrochemical Biosensors Based On Highly Dispersed Nanoplatinum/Graphene

Graphene is a typical two-dimensional inorganic nanomaterial hybridized by sp².It has a series of excellent electrochemical properties,such as:wide electrochemical window,high catalytic activity,small charge transfer resistance,and fast electron transfer rate.Therefore,graphene is an ideal electrode modification material.However,graphene also has some obvious disadvantages.It has poor dispersion stability and is easy to agglomerate.Better performance,especially better dispersion and catalytic activity,can be achieved by preparing graphene-based composites.Noble metals?such as Pt,Au,Ag?play an irreplaceable role in catalysts,fuel cells,etc.Their nanoparticles have been widely used to modify carbon nanotubes to form new composites,and these composites exhibit good performance as biosensors and catalysts.Therefore,the combination of graphene and noble metal is a potential method to further increase its electrical conductivity and catalytic activity.In this paper,two kinds of electrochemical biosensors were prepared based on highly dispersed nanoplatinum/graphene.And their detection performance were studied.At the same time,a carbon paste electrode capable of quantitatively detecting traces of lead was prepared,which utilized a synergistic effect between the ruthenium film and the chelating agent.The specific research work is as follows:Firstly,graphene oxide was synthesized from flake graphite by using the improved Hummers method.Graphene oxide was reduced by solvothermal method and Pt nanoparticles were loaded to prepare highly dispersed nanoplatinum/graphene?GPNs?.The SEM was used to characterize GPNs.It was found that the Pt nanoparticles were uniformly dispersed on the GPNs,and the mass fraction of Pt was 28%by EDS.The H₂O,ethanol,nafion?Naf?and chitosan?CS?solutions were used as dispersing agents.Then the GPNs were dispersed and modify the glassy carbon electrodes?GCE?.The results of cyclic voltammetry?CV?and catalytic test for H₂O₂ showed that the modified electrodes with Naf and CS solution as dispersant were better than others.GPNs were dispered in nafion solution and then modify the glassy carbon electrode.Then lactate oxidase was immobilized on it.And on this basis,the lactic acid biosensor was prepared.The biosensor exhibits good detection performance for lactic acid.The linear range of detection is 0.2-1.2 mM.The linear relationship between response current and lactic acid concentration is:i/?A=0.18+3.32 c/mM,R²=0.996.The detection limit is 8.0?M?S/N=3?.The biosensor has high sensitivity to lactic acid?3.32?A/mM?and low theoretical detection limit?8.0?M?.It has good repeatability and stability,and the lactic acid is tested for 15 consecutive days with a deviation of 2.18%.In addition,it has good anti-interference ability.Next,GPNs were dispered in CS solution and then modify the glassy carbon electrode.Then sarcosine oxidase was immobilized on it.And on this basis,the sarcosine biosensor was prepared.The sensor exhibits good detection performance for sarcosine with a linear range of10-520?M.When the concerntion of sarcosine is between 10-100?M,the linear relationship is:i/?A=0.071+0.011 c/?M,R²=0.999.When the concerntion is between 100-520?M,the linear relationship is:i/?A=0.37+0.008 c/?M,R²=0.999.The detection limit is 1.8?M?S/N=3?.In addition,the sensor has good stability.The response signal loss is 6.8%for 12 consecutive days,and the RSD for repeated measurements is 1.8%.The recovery of sarcosine detection in serum is stable between 73.3%and 73.6%.The reason for the low recovery rate needs further research.Finally,carbon paste electrode was prepared by using cerium oxide and dithizone as modifiers to detect heavy metal lead ions.Compared with a single modifier carbon paste electrode,the composite modifier modified carbon paste electrode has the best detection effect on Pb²⁺and has good electrode reproducibility.The linear range of detection is 5-80?g/L,and the linear regression equation is:i/?A=4.63+0.62 c/??g/L?,R²=0.997.The detection sensitivity of the sensor to Pb²⁺was 0.62?A/??g/L?,the detection limit is 0.1?g/L?S/N=3?,and the carbon paste electrode has good stability and anti-interference ability.