Construction Of Nano - Effect Enhanced Molecular Imprinting Electrochemical Sensor

Molecularly imprinted electrochemical sensors boast the characters of molecularly imprinted polymers(MIPs), sensors and electrochemistry, which have been widely used due to MIPs as a sensitive element. The MIPs have the properties of recognition, stability and selectivity. In this work, we have prepared functionalized graphene composites using surface imprinting technique and reversible addition-fragmentation chain transfer (RAFT) polymerization technique respectively, which can determine target molecules rapidly, sensitively and selectively. And the applications for determination of dibutyl phthalate (DBP) and ractopamine (RAC) in food were investigated. The main contents are as follows:(1) First of all, we prepared the magnetic graphene composites (Fe3O4@RGO) by solvothermal reduction method. Then, gold nanoparticles were doped to the Fe3O4@RGO with different redox methods. We can obtain the strongest composite material of electrochemical response signal and determine the optimal preparation method of Au@Fe3O4@RGO through the measurement and analysis. Finally, we optimized the preparation method and the results showed that:the proportion of solvent is VEG:VDEG=1:1 and the dosage of HAuCl4 is 200 μL.(2) A novel of molecularly imprinted hybrid materials (Au@Fe3O4@RGO-MIP) were prepared with the DBP as the target molecules and Au@Fe3O4@RGO as the support by surface imprinting technique. The results showed that:the adsorption equilibration time of Au@Fe3O4@RGO-MIP is 6 min for DBP and the detection limit reaching 3.049×10-10mol/L(S/N=3).(3) We synthesized another molecular imprinted films on the surface of Au@Fe3O4@RGO with the RAC as the target molecules by RAFT polymerization approach and constructed the corresponding molecular imprinted electrochemical sensor. The results showed that:this sensor [Au@Fe3O4@RGO-MIP(RAFT)] is superior to conventional molecular imprinted polymers in adsorption properties. Moreover, this sensor exhibits high selectivity, recognition and sensitivity towards the target molecule (RAC). The applied potential for RAC in the PBS solution is 0.5 V, the adsorption saturation time for RAC is 7 min, and the limit of detection is 1.745×10-11 mol/L (S/N=3). It showed that RAFT polymerization improved the sensitive of the molecular imprinted electrochemical sensors furtherly.