| 4-nitrophenol is a highly toxic organic pollutant widely present in water,and its trace presence in the water environment will pose a potential threat to the ecosystem and human health.At present,the traditional 4-nitrophenol detection method has many shortcomings,which is difficult to fulfill the demands of rapid,simple and highly selective detection.The molecularly imprinted electrochemical sensor combines the advantages of molecularly imprinted polymer and electrochemical sensors.It has the characteristics of strong selectivity and easy operation.It is a trace of organic pollutant detection technology with broad development prospects.Aimed at major issues including tedious preparation process,high cost and low sensitivity of the molecular imprinting electrochemical sensor（MIECS）for detecting4-nitrophenol,in this paper,the MIECSs are prepared by directly loading polyaniline on the substrate electrode of nickel foam.The preparation method,characterization of the electrode and the performance of detecting 4-nitrophenol in water are studied.Copper nanoparticles（Cu NPs）are used as the sensitizing materials to modify the nickel foam.The method for modifing the sensor using non-precious metal nanomaterials to improve the detecting performance is studied.A MIECS is prepared by an electrochemical method by using aniline,4-nitrophenol and inexpensive nickel foam as the functional monomer,the template molecule,and the substrate electrode,respectively.The results show that the molecularly imprinted polymer film can be directly polymerized one step on nickel foam by a cyclic voltammetry electrochemical polymerization method.This greatly simplifies the preparation process.SEM and FT-IR characterization show that a relatively uniform,dense and complete molecularly imprinted polymer film is formed on the surface of the nickel foam.The film is tightly and firmly combined with the nickel foam,and it is difficult to fall off.Electrochemical impedance spectroscopy（EIS）research shows that the formed molecularly imprinted film had good conductivity and excellent recognition response activity to 4-nitrophenol in water.Electrochemical cyclic voltammetry（CV）studies indicate that the prepared sensor has a significant oxidation peak current for identification response to 4-nitrophenol in water.The preparation parameters and conditions for the sensor have certain impact on the oxidation peak current.With the increase of the ratio of functional monomer to template molecule in the polymerization solution and the number of CV scans,the peak current value tends to increase first and then decrease.It reaches the maximum at the 4:1 ratio of functional monomer to template molecule and with 15 times CV scan.The peak current value tends to stabilize with the increase of elution time.As the p H of the detection solution increases,the peak current value increases first and then decreases.With the increase of adsorption time during the detection,the peak current value first increases and then stabilizes.;As the detection scan rate increases,the peak current value gradually decreases.The linear range of the sensor for detecting 4-nitrophenol in water is 1.0×10-7～2.5×10-6 M,and the detection limit is9.04×10-8 M.The sensor exhibits excellent selectivity to 4-nitrophenol and anti-interference of metal ions in water.Because of the low sensitivity of molecularly imprinted electrochemical sensors,the molecularly imprinted electrochemical sensors are improved by directly depositing a sensitizing material of Cu NPs on the surface of nickel foam using Cu SO4 as the raw material.It shows that Cu NPs was successfully electrodeposited on the nickel foam surface,and presents ellipsoidal nanoparticles with a diameter of 39 nm.The MIP with a 3D structure made of interlaced polyaniline fibers is electropolymerized on the sensitizing material Cu NPs on the surface of the base electrode.It is beneficial to increase the specific surface area of the electrode and improve the mass transfer performance of the electrode.The linear range of detection of 4-nitrophenol in water is 1.0×10-11～2.0×10-10 M,and the detection limit reaches 1.4×10-12 M,being four orders of magnitude lower than that before modification.Reusability and storage stability have also been enhanced.After being reused 10 times and storeing at room temperature for 30 days,The ratio of the peak current value to initial value was increased to 88.0%and 89.0%,respectively.The molecularly imprinted electrochemical sensor developed in this paper has unique advantages of simple preparation without needing a second shaped process,low cost,and easy operation with high sensitivity and good selectivity.It should have a broad developing prospect in the field of detecting trace 4-nitrophenol in water. |
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