SYNTHESIS AND CHARACTERIZATION OF PANI/ZnO/Fe2O3 NANOCOMPOSITE FOR ELECTROCHEMICAL DETECTION OF AMMONIA

Abstract

The PANI/ZnO/Fe2O3 nanocomposites with different weight ratios (1:2, 1:1 and 2:1) were synthesized effectively via in-situ oxidative polymerization method. The structure and morphology of these as synthesized nanomaterials were characterized by X-ray diffraction (XRD), Fourier transform infrared (FTIR) and Uv-vis spectroscopy. The direct electrooxidation behavior of ammonia on the PANI/ZnO/Fe2O3 modified platinum electrode (PtE) as a sensing mechanism was studied via cyclic voltammetry. The oxidation peak current in PANI/ZnO/Fe2O3 (2:1) modified PtE was higher compare to the other modified and bare electrodes. This could be most probably due to the synergistc effect of the high surface area of PANI and the high catalytic property of ZnO. The response profile indicated that the electrooxidation of ammonia on modified PtE was takes place at -0.32 V Vs Ag/AgCl and the process was irreversible. To improve the ammonia sensing performance of PANI/ZnO/Fe2O3, the experimental parameters such as pH and scan rate were optimized. From the linear plot of peak current and square root of scan rate, the excellent linearity indicated the electrochemical oxidation of ammonia was diffusion controlled. At the optimized condition (pH 14), a dynamic linear range of 10- 100 ppm, sensitivity of 0.180 μA/ppm, a detection limit of 17.22 ppm ammonia were established for the sensor system using LSV. While using CV, the sensitivity and detection limit was 0.07μA/ppm and 39.42 ppm respectively. The prepared sensor also exhibited good stability, and reproducibility towards ammonia electrooxidation. Moreover, the interference study result indicated that it can selectivly detect ammonia in the presence of interfering substances such as CH3OH, C2H5OH, and acetone. This electrode was applied to determine the concentration of ammonia in waste water and good percentage recovery was obtained which was between 96.96% and 100.15%. Thus, PANI/ZnO/Fe2O3(2:1) nanocomposites can be a good candidates for electrochemical detection of ammonia in various samples.