SYNTHESIS AND CHARACTERIZATION OF POLYANILINE/NiO NANOCOMPOSITE FOR ELECTROCHEMICAL DETERMINATION OF DOPAMINE

Abstract

Polyaniline-nickel(II)oxide (PANI/NiO) nanocomposites was prepared using in-situ polymerization method. The structural properties of as produced PANI, NiO and PANI/NiO nanocmposte were characterized by employing X-ray diffraction (XRD), infrared absorption (FT-IR) and UV–visible spectroscopy (UV–vis). The XRD pattern indicated semi-crystalline phase in PANI but crystalline phase for NiO and PANI/NiO nanocmposite. In addition to this, elelectrochemical behavior of glassy carbon (GC) electrode modified by PANI, NiO and PANI/NiO materials was characterized using cyclic voltammetry (CV and electrochemical impedance spectroscopy (EIS) in 0.1 M phosphate buffer solution. The result showed that the nanocomposite modified electrode was more electrochemically active than the others due to the synergetic effect of the catalytic nature of NiO and high conductivity of PANI. It was also noticed that the electrode revealed a quasi – reversible nature. Moreover, dopamine (DA) electrochemical nature was studied using PANI/NiO/GCE as working electrode in various scan rates (20 -90 mV/s). The DA oxidized at (0.180V ) and its diffusion coefficient estimated was 0.45 and showed a quasi –reversible process. Besides, PANI/NiO/GCE was used as electrochemical sensor for the detection of dopamine in standard solution (1 – 150 µM) at optimum pH =7 using both CV and differential pulse voltammetry (DPV) at scan rate of 50 mV/s. The composite modified electrode exhibited a linear range 1  M to 80 µM (R = 0.996) and 80 µM to 200.0  M (R = 0.996), and good detection limit of 0.016 M (S/N = 3) for DPV measurement. The sensor was also used to detect dopamine in real sample (i.e., human urine and serum). Furthermore, the sensor exhibited good selectivity towards DA since no response to ascorbic acid (AA) and uric acid (UA), repeatability and stability. Therefore PANI/NiO/GCE sensor can be a good candidate for the determination of DA in different samples