Chitosan-Gold Nanocomposite for Copper Ions Detection

Background: The presence of heavy metals in water is very harmful for the environment and the human’s health. Some heavy metals such as copper, at trace levels, are indispensable to preserve the metabolism of the human body. The application of the electrochemical methods (potentiometric and impedimetric) for Cu detection are simple and low cost with short detection times. One of the most important challenges in sensors development is how to increase sensibility and the obtained the best detection limit. The aim of this work is to investigate and compare two different types of electrochemical (potentiometric and impedimetric) methods for detection of Cu2+ ions in aqueous solution using chitosan-gold nanoparticles (CS-AuNPs) membrane. Methods: CS-AuNPs membrane has been prepared by adding of AuNPs obtained using Turkevich method to the CS dispersed in the acid acetic solution. Potentiometric and impedimetric measurements were performed using a graphite-epoxy electrode modified by CS-AuNPs membrane in aqueous solution in the concentration range of 10−9 to 10−1 M of Cu(NO3)2. Results: For the first time, the relation between percolation threshold and detection limit of copper ions has been established. The best detection limit in both methods has been observed when the concentration of AuNPs is near the percolation threshold. Obtained results show that potentiometric method has a detection limit of 2.36 × 10-5 and a linear response range between 2.36 × 10-5 and 4 × 10-2 M of Cu2+. However, impedimetric method shows superior properties: detection limit ca. 10-7 M, linear response range 10-7-10-3 M of Cu2+ ions. Conclusion: The obtained relationship between impedance measurements and critical percolation concentration of AuNPs are of primary importance in the design and optimization of nanocomposite for sensor application. Our results suggest that CS-AuNPs membranes can be used for the development of a low cost sensor for copper detection based upon potentiometric and impedimetric measurements. Keywords: Chitosan nanocomposite, copper ions detection, gold nanoparticles, impedimetric measurements, percolation threshold, potentiometric measurements.