Fabrication of Electrochemical Sensors for Dimethyl Methylphosphonate and Ascorbic Acid Determination Based on Novel Graphene/PANI/HfO2 Nanocomposites

Abstract

Different types of pesticides had been widely used during the last several decades to improve the increasing demand of food production for ever increasing human population. The widespread use of these pesticides, under the proverb, ―if little is good, a lot more will be better‖ has wrecked the humans and other forms of life. Organophosphate pesticides are acetylcholinesterase (neurotransmission regulating agent) inhibitors. Several techniques have been established for detection of pesticides in food samples and environment over the last decades. Electrochemical sensing has arisen as a promising tool for detection and estimation of organophosphates because of its cost effectiveness, quick response with accuracy and suitable for in-situ and on-site monitoring with good specificity and sensitivity. We utilized graphene in the preparation of pristine graphene/polyaniline/hafnium oxide based nanocomposites for electrochemical nonenzymatic dimethyl methylphosphonate (DMMP) detection. Binary nanocomposites of PPG with varying ratios of pristine graphene and ternary nanocomposite PPG/HfO2 were prepared for comparative study. We performed cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) studies in order to observe electrochemical response of nanocomposites modified glassy carbon electrode (GCE) towards determination of DMMP. PPG3/HfO2/GCE exhibits highest current response and lowest charge transfer resistance value of 3.92 KΩ ascribed to remarkable conductivity of pristine graphene. The PPG3/HfO2/GCE demonstrated good selectivity for detection of DMMP. Accurate detection of ascorbic acid for food quality and healthcare is very important because of its technological and health significance. Since ascorbic acid is a potent reducing agent and an electroactive compound, its detection by applying electrochemical techniques have received considerable attraction. In this work, a novel electrochemical sensing platform based on reduced graphene oxide/polyaniline nanofibers/hafnium oxide nanoparticles nanocomposites was designed for determination of ascorbic acid. The prepared nanocomposites were characterized with FT-IR spectroscopy, X-ray diffraction, SEM and EDX analysis. Cyclic voltammetric experiments indicated that PRGO1/HfO2/GCE demonstrated good electrocatalytic activity towards ascorbic acid oxidation in neutral solution. The effect of variable scan rate, pH and concentration with PRGO1/HfO2/GCE on electrooxidation of ascorbic acid was also investigated.