Study On Electrochemical Synthesis Of Self-doped Polyaniline And Its Application In The Biosensors

Organic conductive polymers, on account of their excellent physical and chemical properties, are promising in many fields such as electrochemical catalysis, electrochemical capacitor, chemical biosensor and so on. Among conductive polymers, polyaniline (PANI) has attracted considerable interesting due to its availability, simple synthesis, high conductivity and stability. However, a primary limitation of PANI is its instability at basic or neutral pH, it shows electric conductivity only at low pH values. At pH above 3 or 4, PANI shows neither conductivity, nor electrochemical redox processes. To overcome the disadvantages, we have preparated the self-doped polyaniline (SPAN) which is electrochemically active in neutral aqueous solutions by electropolymerization of substituted and unsubstituted aniline. Due to this advantage, it is a great idea to make the SPAN apply in bioelectrochemistry.1. In this paper, SPAN films were prepared by using aniline and p-aminobenzene sulfonic acid (p-ABS). Effects of the factors on the film preparation and conductivity of the film in neutral solution were investigated. The results indicate that the best ratio of aniline and p-ABS is 1:1, and it can avail preparing the film by increasing the concentrations of aniline, p-ABS and sulfate acid. The SPAN films have good conductivity in both weak acidic and neutral solutions. The thicker the SPAN films the higher the conductivity of the films. Further more, the self-doping PANI films may has latent application in sensor, electrochemical catalyst, nanomaterial and so on.2. A new type of amperometric biosensor was prepared by immobilizing horseradish peroxidase (HRP) into SPAN in this paper. SPAN films were fabricated by electrochemical deposition, and the horseradish peroxidase was immobilized by electrostatic interaction with polymer backbone. The effects of the SPAN thickness (number of electropolymerization cycles) and pH value of the supporting solution (phosphate buffer solution) on the response of the biosensor toward H2O2 were investigated. The experimental results demonstrated that the immobilized HRP retained its bioelctrocatalytic activity for the reduction of H2O2 and the glassy carbon (GC)/SPAN-HRP electrode can rapidly respond to the change of the concentration of H2O2. The biosensor provides a linear response to H2O2 over a concentration range of 7.5×10-6 to 1.25×10-3 mol/L, with a sensitivity of 398μA·L/mmol·cm2. The biosensor has a detection minimum limit of 4×10-6 mol/L, and a response time of about 5s. It is hopeful that the modified electrode will be applied for the analysis such as pharmaceutical and daily industries in future.3. A novel method for the fabrication of a hydrogen peroxide sensor was developed by electrodepositing Prussian blue (PB) on the SPAN film modified glassy carbon electrode (GC/SPAN/PB). The factors such as the scan rate, the thickness of SPAN and the applied potential that influencing the voltammetric behavior of PB in the presence of hydrogen peroxide were studied in detail. In 0.067 mol/L phosphate solution (pH 4.5), the sensor exhibited a wide linear range of 8×10-7~5×10-4 mol/L with a correlation coefficient of 0.997. The detection limit of the sensor is 4×10-7 mol/L. Such sensor can be used for enzyme biosensor. Moreover, the sensor exhibits high good repeatability and long-time stability.