Preparation Of Dawson Polyoxometalate Derivatives Modified Electrode And Detection Of Biological Small Molecules

Objective Designed and synthesized two series of bipyridine-modified Dawson polyoxometalates functionalized derivatives,and constructed an electrochemical biosensor with response to hydrogen peroxide and ascorbic acid by compounding with graphene.Methods Two series of Dawson polyoxometalates functionalized derivatives were synthesized by solvothermal method.Their structures were characterized by X-ray single crystal diffraction,X-ray diffraction,infrared spectroscopy,X-ray photoelectron spectroscopy and elemental analysis.Dawson polyoxometalates functionalized derivatives were compounded with graphene by ultrasonic mixing method and modified on the surface of glassy carbon electrode by dropping coating method.Detection of hydrogen peroxide and ascorbic acid by three-electrode system.Results Dawson polyoxometalates were functionalized by 4,4'-bipyridine compounds and six new Dawson functional compounds 1-6 were successfully designed.On this basis,six new modified electrodes were also prepared by compounding with graphene.The results showed that the current response intensity of compounds 1-3?Mo series?were larged than precursor Dawson polyoxometalates(P₂Mo₁₈).Compounds 1-3 and graphene were combined with each other and their current response intensity were about 6.3 times stronger than that of P₂Mo₁₈.Compound 1-3 showed a good linear relationship with hydrogen peroxide in the detection concentration range of 3.5-500?M,4-500?M and 6.5-500?M,and the detection limits were3.5?M,4?M and 6.5?M,respectively.The optimum electrochemical activity for hydrogen peroxide was pH=2,and have no response to other biological small molecules such as ascorbic acid.The current response intensity of compounds 4-6?W series?were larged than precursor Dawson polyoxometalates(P₂W₁₈),Compounds 4-6 and graphene were combined with each other and their current response intensity were about 15 times stronger than that of P₂W₁₈.Compound 4-6 showed a good linear relationship with ascorbic acid in the detection range of 1-300?M,3.5-300?M and 4.5-300?M,and the detection limits were 1?M,3.5?M and 4.5?M,respectively.It was observed that the optimum electrochemical activity for hydrogen peroxide was pH=3,and no response to other biological small molecules such as hydrogen peroxide.Conclusions Proper material ratio and reaction time,optimal reaction temperature and pH are the key factors in the synthesis process;4,4'-bipyridine compounds can improve Dawson polyoxometalates electrochemical properties,because their rigid conjugated structure is conducive to electron transfer,it is found that the modification effect of W series is better;The electrochemical performance was greatly improved when graphene was compounded with compounds 1-6,which indicated that the graphene could be improved their electrochemical performance;The compounds 1-6 of electrochemical activity is the best when the pH is 2-3.It is interesting that the same bipyridine compounds modify Dawson polyoxometalates with different coordination atoms,which can detect different biological small molecules,indicating the different coordination atoms can influence their the electrochemical properties.Successful preparation of Dawson polyoxometalates functionalized derivatives and graphene composite modified electrodes can provide new structural models and basic data for the development of novel electrochemical biosensors.