| Electrochemical sensor is a device which transforms a quantitative or qualitative type of chemical information into an electrical signal based on electrochemical properties of analytes. It has advantages such as remarkable sensitivity, experimental simplicity, easy miniaturization and low cost. Combination of MIPs as recognition element with sensors would enhance the selectivity of sensors. In this paper, atrazine (ATZ) was used as the template molecule, and o-phenylenediamine (o-PD) as the functional monomer. We used electrochemical polymerization to prepare molecularly imprinted sensing films based on the o-phenylenediamine homopolymer. The performance of sensing film was characterized by electrochemical methods.The Density Functional Theory (DFT) method of Gaussian 09 was used to simulate the configuration of template-functional monomer complex. The geometry optimization, the bonding situation and the binding energies of the imprinted molecule with the functional monomer at different ratio were studied, and the NBO charge was analyzed. The optimum ratio of ATZ and o-PD was predicted theoretically. The results indicated that ATZ and o-PD generally form compounds via the hydrogen bonding interactions. The polymer with a ratio of ATZ to o-PD (1:4) had the lowest binding energy and the maximum charge transfer trend.In the presence of ATZ, a sensitive molecularly imprinted polymer film was prepared on the surface of a gold electrode by using cyclic voltammetry to electropolymerize o-PD. Electroactive substances, potassium ferricyanide and potassium ferrocyanide, were chosen as the probe. The relationship between the current signal produced by K3[Fe(CN)6]/K4[Fe(CN)6] and the concentration of ATZ was revealed. The effects of scanning rate, scan cycle and ATZ concentration on the sensitivity and adsorption properties of MIP modified electrode were discussed by differential pulse voltammetry (DPV). The optimum conditions for preparation of sensing films were obtained.The electrochemical properties of MIP modified electrode were characterized indirectly by cyclic voltammetry, differential pulse voltammetry and AC impedance. The response and selective adsorption for analytes on the imprinted electrode were investigated. The reusability, stability and recovery of the imprinted electrode were also studied. The results showed that the imprinted modified electrode had high selectivity and sensitivity for ATZ. The relative current change increased linearly with the concentration of ATZ in the range between 5.0×10-9 and 1.4×10-7 mol/L, and the detection limit was 1.0×10-9 mol/L. The selectivity factors compared to interferents were all larger than 1. The imprinted modified electrode had a good stability and reusability, and the percentage of recovery was obtained in the range of 95.5% to 103.5%.Finally, graphene was prepared by oxidation-reduction method. The product was characterized with X-ray diffraction and Fourier Transform Infrared. Then, the graphene modified electrode was prepared, and o-phenylenediamine was polymerized on the surface of graphene modified electrode in the presence of atrazine. The properties of MIP-graphene modified electrode were characterized by electrochemical method. The results showed that the current responses of the graphene modified electrode were significantly enhanced. The MlP-graphene modified electrode had a higher sensitivity for atrazine. Compared to the modified electrode with poly-o-phenylenediamine imprinted film, it had a wider detection range from 2.0x10"9 to 3.0×10-7 mol/L and a lower detection limit of 0.8×10-9 mol/L. |
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