Graphene Oxide-Chitosan Composite-Based Flexible Electrochemical Sensors for Lead ION Detection

In this study, a flexible electrochemical sensor based on an environmentally benign organic nanocomposite material was fabricated. Taking advantage of chitosan's affinity towards heavy metal ions and graphene oxide's functional edge characteristics, a nanocomposite material was prepared for highly sensitive heavy metal ion detection. In addition, this framework provided a flexible and robust working electrode as it forms crustacean shell-like coating. Three electrodes - working, counter, and reference - were screen-printed on a flexible PVC substrate. Then, a graphene oxide (GO)-chitosan composite prepared via self-assembly of GO sheets and chitosan chain was drop-casted onto the working electrode surface. A reference electrode was obtained after the electro-chlorination of the printed silver electrode. The SEM image of the organic nanocomposite shows the porous structure with a high surface area that can enhance the adsorption and preconcentration of the lead ions. The electron transfer characteristics of the composite sensing electrode determined by Electrochemical Impedance Spectroscopy (EIS) after surface modifications indicate the enhanced charge transfer efficiency, which improved the sensor response compared to the pure chitosan electrode. The lead ion detection was performed using square wave anodic stripping voltammetry (SWASV). A ppb level detection of lead ions in water was obtained with good linearity and repeatability. The fabricated sensor is promising for lead ion detection because of facile fabrication, low-cost, environmentally benign nature, high surface area, and fast electron transfer ability.