Synthesis Of Crosslinked Conducting Polyaniline And Application In Electrochemical Sensors

Ascorbic acid (AA) is one of the important substances maintaining life activities, which widely exists in food, drug and human body. It has been shown that the disorders of AA content in vivo have been linked to hepatic disease, diabetes and cancer. Therefore, the determination of ascorbic acid (AA) is crucial for the study of human physiology and quality control of medicines. In this paper, crosslinked polyaniline with high conductivity was prepared via chemical oxidation, electrochemical polymerization, which has been used as sensitive materials and applied in sensor. Meanwhile, the structure of crosslinked polyaniline, surface properties, conductivity and the performance of sensor were studied. The main contents were as following:1. The synthesis of A novel nanostructured crosslinked polyaniline by chemical oxidationA novel crosslinked conducting polyaniline (CPAN) has been synthesized via the chemical copolymerization of aniline (AN) and p-phenylenediamine (PPD) with 1,3,5-tris(phenylamino)benzene (1,3,5-TPAB) as a crosslinker. The nanostructured copolymer was confirmed through surface morphology studies (SEM). The structure of linear (LPAN) and crosslinked polyaniline (CPAN) were characterized by FT-IR, pyrolysis-GC/MS. The resulting copolymer showed greater conductivity enhancement than LPAN by four-point probe measurement.2. Ascorbic Acid electrochemical sensor based on nanostructured crosslinked polyaniline A newly crosslinked polyaniline (CPAN) was preliminarily used to fabricate a sensor for determination of ascorbic acid (AA). The amperometric responses of electrodes toward AA based on crosslinked polyaniline (CPAN) is far more than that of linear polyaniline (LPAN), which exhibits improved electrocatalytic oxidation of ascorbic acid (AA). The linear range of the promising sensor is from 5.0×10-6 to 1.13×10-2 M with a lower detection limit of 1.67×10-6 M(S/N=3) as well as good selectivity, stability and reproducibility.3. Electrochemical sensing for ascorbic acid based on electropolymerized crosslinked polyanilineA novel crosslinked polyaniline (CPAN) has been synthesized by electrochemical polymerization with aniline, p-phenylenediamine and 1,3,5-tris(phenylamino)benzene as monomers. The resulting copolymer showed greater conductivity enhancement than the linear polyaniline (LPAN) by electrochemical impedance spectroscopy (EIS) and cyclic voltammetry studies, indicating 1,3,5-TPAB units are successfully included in the copolymer chains and accelerate electronic transport. The crosslinked polyaniline film coated on Au electrode exhibits excellent electrocatalytic responses towards the electro-oxidation of ascorbic acid (AA). Under the optimized conditions, a linear calibration graph is obtained using chronoamperometry over the AA concentration range of 1.0×10～2.O×10-4 M with a lower detection limit of 3.33×10-5 M (S/N=3). Moreover, the sensor shows good stability and selectivity. Also, the determination of AA in actual samples was evaluated and the results are satisfactory.