Flexible copper-biopolymer nanocomposite sensors for trace level lead detection in water

In this work, a novel copper-chitosan (Cu-chitosan) nanocomposite-based flexible electrochemical sensor with an integrated Ag/AgCl reference electrode is fabricated. The electrochemical sensor is fabricated using low-cost screen-printing technology on a flexible substrate, followed by the electrochlorination of silver to form an integrated Ag/AgCl reference electrode and electrochemical deposition of a Cu-chitosan nanocomposite film to produce a working electrode. The surface chemical analysis of the working and reference electrodes using XPS (X-ray photoelectron spectroscopy) shows the formation of functional layers. The fabricated Cu-chitosan nanocomposite-based sensors are used to determine the trace level lead (Pb2+) ions in real-world water samples (i.e., tap water, mining wastewater, and soil leachate) using square wave anodic stripping voltammetry (SWSAV). A noticeable peak for lead ions is observed at ∼0.46 V vs. integrated Ag/AgCl reference electrode. The limit of detection (LOD) of the developed flexible electrochemical sensor in tap water is 0.72 ppb with the relative standard deviations (n = 10) of 0.65 %. The fabricated electrochemical sensor exhibits a higher response to lead ions (Pb2+) than the previously reported copper-based electrochemical sensor. These results show that chitosan's presence on the composite material enhances the sensitivity and mechanical flexibility.