SYNTHESIS AND CHARACTERIZATION OF NANOSTRUCTURED REDUCED GRAPHENE OXIDE/PANI/ZnO ACETYLCHOLINESTRASE BIOSENSOR FOR MALATHION DETECTION

Abstract

PANI and PANI/ZnO were synthesized electrochemically on both glass carbon electrode and reduced graphene oxide modified glass carbon electrode. PANI, PANI/ZnO and PANI/ZnO/RGO nanocomposites were alsosynthesized by in-situ oxidation polymerization method and characterized by UV-visible and FTIR Spectroscopy. The absorption peaks in FTIR spectra of PANI/ZnO/RGO composite film were found to shift to higher wave number when compared with pure PANI and PANI/ZnO nanocomposite.Electrochemically and chemically produced PANI, PANI/ZnO and PANI/ZnO/RGO were characterized by cyclic voltammetry in 1MHCl aqueous solution. The cyclic voltammetry showed that the deposited PANI/ZnO on RGO/ was more electro active due to high surface area of RGO. The estimated electron transfer rate constant (ks) of PANI,PANI/RGO, PANI/ZnO,and PANI/ZnO/RGO 0.123s-1 , 0.144s-1 ,0.1348 s-1and 0.1667s-1respectively. The synthesized PANI/ZnO/RGO with larger estimated electron transfer rate constant (ks) than others.Therefore PANI/ZNO/RGO/GCE was provided an excellent biocompatible environment for AChE and facilitate the electron transfer reaction in malathion detection.The resulting biosensor exhibited alinear response for acetylcholine in a concentration range of 100–1000µL. Under optimum conditions, the biosensor showed the inhibition rates of Malathion proportionalto their concentrations in the range of 10–40 nmol L−1 ,good reproducibility,no interference by heavy metal ions and high recovery values around 99.7.0%. The best electro analytical performances of this synthesized electrode was achieved with the detection limitof 11 nmol L−1 for malathion. The simplicity of preparation, high sensitivity and stability of this nanostructured AChE-PANI/ZnO/RGO/GC electrode should open novel opportunities and applications for fabricating robust sensors for detection of malathion.