Non enzymatic electrochemical detection of paraoxon methyl using zinc oxide graphene nanocomposite in water and food samples

Abstract

Highly toxic nature of organophosphorous compounds necessitates their sensing for the safety of humans. Non enzymatic electrochemical sensors are advantageous compared to enzymatic ones as they are sensitive, simple, stable and inexpensive. Herein, we have synthesized a nanocomposite of ZnO supported on graphene nanosheets (ZnO-G) and studied its applicability as an electrode material for the electrochemical sensing of organophosphate, paraoxon-methyl. Nanocomposite prepared was characterized for structural and morphological details using X-ray diffraction (XRD), BET surface area analyser and field emission scanning electron microscopic (FESEM) techniques. The sensing applicability was tested using electrochemical techniques like cyclic voltammetry (CV) and differential pulse voltammetry (DPV). Under optimized conditions, peak current was linearly proportional to the concentration of paraoxon-methyl in the range of 0.002–0.04 µg/ml and 0.06–1.0 µg/ml with the sensitivities of 118.0nA/mM.cm2 and 35.7nA/mM.cm2 respectively and detection limit of 1.6 ng/ml. In comparison, solar reduced graphene oxide (SRGO) showed linear range of 0.05–1 µg/ml with the detection limit of 10.2 ng/ml and sensitivity of 55.3nA/mM.cm2. High performance of ZnO-G is attributed to the unique morphology and modified properties of the nanocomposite. The nanocomposite prepared has also been tested for its applicability in real samples of tap water, waste water, cabbage and tomatoes. This study confirms the excellent selectivity, reproducibility, repeatability and stability exhibited by the nanocomposite ZnO-G sample for paraoxon methyl sensing in non-enzymatic mode.